clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp

//===---- CGOpenMPRuntimeNVPTX.cpp - Interface to OpenMP NVPTX Runtimes ---===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This provides a class for OpenMP runtime code generation specialized to NVPTX
// targets.
//
//===----------------------------------------------------------------------===//

#include "CGOpenMPRuntimeNVPTX.h"
#include "CodeGenFunction.h"
#include "clang/AST/DeclOpenMP.h"
#include "clang/AST/StmtOpenMP.h"
#include "clang/AST/StmtVisitor.h"
#include "llvm/ADT/SmallPtrSet.h"

using namespace clang;
using namespace CodeGen;

namespace {
enum OpenMPRTLFunctionNVPTX {
  /// Call to void __kmpc_kernel_init(kmp_int32 thread_limit,
  /// int16_t RequiresOMPRuntime);
  OMPRTL_NVPTX__kmpc_kernel_init,
  /// Call to void __kmpc_kernel_deinit(int16_t IsOMPRuntimeInitialized);
  OMPRTL_NVPTX__kmpc_kernel_deinit,
  /// Call to void __kmpc_spmd_kernel_init(kmp_int32 thread_limit,
  /// int16_t RequiresOMPRuntime, int16_t RequiresDataSharing);
  OMPRTL_NVPTX__kmpc_spmd_kernel_init,
  /// Call to void __kmpc_spmd_kernel_deinit();
  OMPRTL_NVPTX__kmpc_spmd_kernel_deinit,
  /// Call to void __kmpc_kernel_prepare_parallel(void
  /// *outlined_function, int16_t
  /// IsOMPRuntimeInitialized);
  OMPRTL_NVPTX__kmpc_kernel_prepare_parallel,
  /// Call to bool __kmpc_kernel_parallel(void **outlined_function,
  /// int16_t IsOMPRuntimeInitialized);
  OMPRTL_NVPTX__kmpc_kernel_parallel,
  /// Call to void __kmpc_kernel_end_parallel();
  OMPRTL_NVPTX__kmpc_kernel_end_parallel,
  /// Call to void __kmpc_serialized_parallel(ident_t *loc, kmp_int32
  /// global_tid);
  OMPRTL_NVPTX__kmpc_serialized_parallel,
  /// Call to void __kmpc_end_serialized_parallel(ident_t *loc, kmp_int32
  /// global_tid);
  OMPRTL_NVPTX__kmpc_end_serialized_parallel,
  /// Call to int32_t __kmpc_shuffle_int32(int32_t element,
  /// int16_t lane_offset, int16_t warp_size);
  OMPRTL_NVPTX__kmpc_shuffle_int32,
  /// Call to int64_t __kmpc_shuffle_int64(int64_t element,
  /// int16_t lane_offset, int16_t warp_size);
  OMPRTL_NVPTX__kmpc_shuffle_int64,
  /// Call to __kmpc_nvptx_parallel_reduce_nowait(kmp_int32
  /// global_tid, kmp_int32 num_vars, size_t reduce_size, void* reduce_data,
  /// void (*kmp_ShuffleReductFctPtr)(void *rhsData, int16_t lane_id, int16_t
  /// lane_offset, int16_t shortCircuit),
  /// void (*kmp_InterWarpCopyFctPtr)(void* src, int32_t warp_num));
  OMPRTL_NVPTX__kmpc_parallel_reduce_nowait,
  /// Call to __kmpc_nvptx_simd_reduce_nowait(kmp_int32
  /// global_tid, kmp_int32 num_vars, size_t reduce_size, void* reduce_data,
  /// void (*kmp_ShuffleReductFctPtr)(void *rhsData, int16_t lane_id, int16_t
  /// lane_offset, int16_t shortCircuit),
  /// void (*kmp_InterWarpCopyFctPtr)(void* src, int32_t warp_num));
  OMPRTL_NVPTX__kmpc_simd_reduce_nowait,
  /// Call to __kmpc_nvptx_teams_reduce_nowait(int32_t global_tid,
  /// int32_t num_vars, size_t reduce_size, void *reduce_data,
  /// void (*kmp_ShuffleReductFctPtr)(void *rhs, int16_t lane_id, int16_t
  /// lane_offset, int16_t shortCircuit),
  /// void (*kmp_InterWarpCopyFctPtr)(void* src, int32_t warp_num),
  /// void (*kmp_CopyToScratchpadFctPtr)(void *reduce_data, void * scratchpad,
  /// int32_t index, int32_t width),
  /// void (*kmp_LoadReduceFctPtr)(void *reduce_data, void * scratchpad, int32_t
  /// index, int32_t width, int32_t reduce))
  OMPRTL_NVPTX__kmpc_teams_reduce_nowait,
  /// Call to __kmpc_nvptx_end_reduce_nowait(int32_t global_tid);
  OMPRTL_NVPTX__kmpc_end_reduce_nowait,
  /// Call to void __kmpc_data_sharing_init_stack();
  OMPRTL_NVPTX__kmpc_data_sharing_init_stack,
  /// Call to void __kmpc_data_sharing_init_stack_spmd();
  OMPRTL_NVPTX__kmpc_data_sharing_init_stack_spmd,
  /// Call to void* __kmpc_data_sharing_push_stack(size_t size,
  /// int16_t UseSharedMemory);
  OMPRTL_NVPTX__kmpc_data_sharing_push_stack,
  /// Call to void __kmpc_data_sharing_pop_stack(void *a);
  OMPRTL_NVPTX__kmpc_data_sharing_pop_stack,
  /// Call to void __kmpc_begin_sharing_variables(void ***args,
  /// size_t n_args);
  OMPRTL_NVPTX__kmpc_begin_sharing_variables,
  /// Call to void __kmpc_end_sharing_variables();
  OMPRTL_NVPTX__kmpc_end_sharing_variables,
  /// Call to void __kmpc_get_shared_variables(void ***GlobalArgs)
  OMPRTL_NVPTX__kmpc_get_shared_variables,
  /// Call to uint16_t __kmpc_parallel_level(ident_t *loc, kmp_int32
  /// global_tid);
  OMPRTL_NVPTX__kmpc_parallel_level,
  /// Call to int8_t __kmpc_is_spmd_exec_mode();
  OMPRTL_NVPTX__kmpc_is_spmd_exec_mode,
};

/// Pre(post)-action for different OpenMP constructs specialized for NVPTX.
class NVPTXActionTy final : public PrePostActionTy {
  llvm::Value *EnterCallee = nullptr;
  ArrayRef<llvm::Value *> EnterArgs;
  llvm::Value *ExitCallee = nullptr;
  ArrayRef<llvm::Value *> ExitArgs;
  bool Conditional = false;
  llvm::BasicBlock *ContBlock = nullptr;

public:
  NVPTXActionTy(llvm::Value *EnterCallee, ArrayRef<llvm::Value *> EnterArgs,
                llvm::Value *ExitCallee, ArrayRef<llvm::Value *> ExitArgs,
                bool Conditional = false)
      : EnterCallee(EnterCallee), EnterArgs(EnterArgs), ExitCallee(ExitCallee),
        ExitArgs(ExitArgs), Conditional(Conditional) {}
  void Enter(CodeGenFunction &CGF) override {
    llvm::Value *EnterRes = CGF.EmitRuntimeCall(EnterCallee, EnterArgs);
    if (Conditional) {
      llvm::Value *CallBool = CGF.Builder.CreateIsNotNull(EnterRes);
      auto *ThenBlock = CGF.createBasicBlock("omp_if.then");
      ContBlock = CGF.createBasicBlock("omp_if.end");
      // Generate the branch (If-stmt)
      CGF.Builder.CreateCondBr(CallBool, ThenBlock, ContBlock);
      CGF.EmitBlock(ThenBlock);
    }
  }
  void Done(CodeGenFunction &CGF) {
    // Emit the rest of blocks/branches
    CGF.EmitBranch(ContBlock);
    CGF.EmitBlock(ContBlock, true);
  }
  void Exit(CodeGenFunction &CGF) override {
    CGF.EmitRuntimeCall(ExitCallee, ExitArgs);
  }
};

/// A class to track the execution mode when codegening directives within
/// a target region. The appropriate mode (SPMD|NON-SPMD) is set on entry
/// to the target region and used by containing directives such as 'parallel'
/// to emit optimized code.
class ExecutionModeRAII {
private:
  CGOpenMPRuntimeNVPTX::ExecutionMode SavedMode;
  CGOpenMPRuntimeNVPTX::ExecutionMode &Mode;

public:
  ExecutionModeRAII(CGOpenMPRuntimeNVPTX::ExecutionMode &Mode, bool IsSPMD)
      : Mode(Mode) {
    SavedMode = Mode;
    Mode = IsSPMD ? CGOpenMPRuntimeNVPTX::EM_SPMD
                  : CGOpenMPRuntimeNVPTX::EM_NonSPMD;
  }
  ~ExecutionModeRAII() { Mode = SavedMode; }
};

/// GPU Configuration:  This information can be derived from cuda registers,
/// however, providing compile time constants helps generate more efficient
/// code.  For all practical purposes this is fine because the configuration
/// is the same for all known NVPTX architectures.
enum MachineConfiguration : unsigned {
  WarpSize = 32,
  /// Number of bits required to represent a lane identifier, which is
  /// computed as log_2(WarpSize).
  LaneIDBits = 5,
  LaneIDMask = WarpSize - 1,

  /// Global memory alignment for performance.
  GlobalMemoryAlignment = 256,
};

enum NamedBarrier : unsigned {
  /// Synchronize on this barrier #ID using a named barrier primitive.
  /// Only the subset of active threads in a parallel region arrive at the
  /// barrier.
  NB_Parallel = 1,
};

/// Get the list of variables that can escape their declaration context.
class CheckVarsEscapingDeclContext final
    : public ConstStmtVisitor<CheckVarsEscapingDeclContext> {
  CodeGenFunction &CGF;
  llvm::SetVector<const ValueDecl *> EscapedDecls;
  llvm::SetVector<const ValueDecl *> EscapedVariableLengthDecls;
  llvm::SmallPtrSet<const Decl *, 4> EscapedParameters;
  RecordDecl *GlobalizedRD = nullptr;
  llvm::SmallDenseMap<const ValueDecl *, const FieldDecl *> MappedDeclsFields;
  bool AllEscaped = false;
  bool IsForCombinedParallelRegion = false;

  void markAsEscaped(const ValueDecl *VD) {
    // Do not globalize declare target variables.
    if (!isa<VarDecl>(VD) ||
        OMPDeclareTargetDeclAttr::isDeclareTargetDeclaration(VD))
      return;
    VD = cast<ValueDecl>(VD->getCanonicalDecl());
    // Variables captured by value must be globalized.
    if (auto *CSI = CGF.CapturedStmtInfo) {
      if (const FieldDecl *FD = CSI->lookup(cast<VarDecl>(VD))) {
        // Check if need to capture the variable that was already captured by
        // value in the outer region.
        if (!IsForCombinedParallelRegion) {
          if (!FD->hasAttrs())
            return;
          const auto *Attr = FD->getAttr<OMPCaptureKindAttr>();
          if (!Attr)
            return;
          if (!isOpenMPPrivate(
                  static_cast<OpenMPClauseKind>(Attr->getCaptureKind())) ||
              Attr->getCaptureKind() == OMPC_map)
            return;
        }
        if (!FD->getType()->isReferenceType()) {
          assert(!VD->getType()->isVariablyModifiedType() &&
                 "Parameter captured by value with variably modified type");
          EscapedParameters.insert(VD);
        } else if (!IsForCombinedParallelRegion) {
          return;
        }
      }
    }
    if ((!CGF.CapturedStmtInfo ||
         (IsForCombinedParallelRegion && CGF.CapturedStmtInfo)) &&
        VD->getType()->isReferenceType())
      // Do not globalize variables with reference type.
      return;
    if (VD->getType()->isVariablyModifiedType())
      EscapedVariableLengthDecls.insert(VD);
    else
      EscapedDecls.insert(VD);
  }

  void VisitValueDecl(const ValueDecl *VD) {
    if (VD->getType()->isLValueReferenceType())
      markAsEscaped(VD);
    if (const auto *VarD = dyn_cast<VarDecl>(VD)) {
      if (!isa<ParmVarDecl>(VarD) && VarD->hasInit()) {
        const bool SavedAllEscaped = AllEscaped;
        AllEscaped = VD->getType()->isLValueReferenceType();
        Visit(VarD->getInit());
        AllEscaped = SavedAllEscaped;
      }
    }
  }
  void VisitOpenMPCapturedStmt(const CapturedStmt *S,
                               ArrayRef<OMPClause *> Clauses,
                               bool IsCombinedParallelRegion) {
    if (!S)
      return;
    for (const CapturedStmt::Capture &C : S->captures()) {
      if (C.capturesVariable() && !C.capturesVariableByCopy()) {
        const ValueDecl *VD = C.getCapturedVar();
        bool SavedIsForCombinedParallelRegion = IsForCombinedParallelRegion;
        if (IsCombinedParallelRegion) {
          // Check if the variable is privatized in the combined construct and
          // those private copies must be shared in the inner parallel
          // directive.
          IsForCombinedParallelRegion = false;
          for (const OMPClause *C : Clauses) {
            if (!isOpenMPPrivate(C->getClauseKind()) ||
                C->getClauseKind() == OMPC_reduction ||
                C->getClauseKind() == OMPC_linear ||
                C->getClauseKind() == OMPC_private)
              continue;
            ArrayRef<const Expr *> Vars;
            if (const auto *PC = dyn_cast<OMPFirstprivateClause>(C))
              Vars = PC->getVarRefs();
            else if (const auto *PC = dyn_cast<OMPLastprivateClause>(C))
              Vars = PC->getVarRefs();
            else
              llvm_unreachable("Unexpected clause.");
            for (const auto *E : Vars) {
              const Decl *D =
                  cast<DeclRefExpr>(E)->getDecl()->getCanonicalDecl();
              if (D == VD->getCanonicalDecl()) {
                IsForCombinedParallelRegion = true;
                break;
              }
            }
            if (IsForCombinedParallelRegion)
              break;
          }
        }
        markAsEscaped(VD);
        if (isa<OMPCapturedExprDecl>(VD))
          VisitValueDecl(VD);
        IsForCombinedParallelRegion = SavedIsForCombinedParallelRegion;
      }
    }
  }

  typedef std::pair<CharUnits /*Align*/, const ValueDecl *> VarsDataTy;
  static bool stable_sort_comparator(const VarsDataTy P1, const VarsDataTy P2) {
    return P1.first > P2.first;
  }

  void buildRecordForGlobalizedVars() {
    assert(!GlobalizedRD &&
           "Record for globalized variables is built already.");
    if (EscapedDecls.empty())
      return;
    ASTContext &C = CGF.getContext();
    SmallVector<VarsDataTy, 4> GlobalizedVars;
    for (const ValueDecl *D : EscapedDecls)
      GlobalizedVars.emplace_back(C.getDeclAlign(D), D);
    std::stable_sort(GlobalizedVars.begin(), GlobalizedVars.end(),
                     stable_sort_comparator);
    // Build struct _globalized_locals_ty {
    //         /*  globalized vars  */
    //       };
    GlobalizedRD = C.buildImplicitRecord("_globalized_locals_ty");
    GlobalizedRD->startDefinition();
    for (const auto &Pair : GlobalizedVars) {
      const ValueDecl *VD = Pair.second;
      QualType Type = VD->getType();
      if (Type->isLValueReferenceType())
        Type = C.getPointerType(Type.getNonReferenceType());
      else
        Type = Type.getNonReferenceType();
      SourceLocation Loc = VD->getLocation();
      auto *Field = FieldDecl::Create(
          C, GlobalizedRD, Loc, Loc, VD->getIdentifier(), Type,
          C.getTrivialTypeSourceInfo(Type, SourceLocation()),
          /*BW=*/nullptr, /*Mutable=*/false,
          /*InitStyle=*/ICIS_NoInit);
      Field->setAccess(AS_public);
      GlobalizedRD->addDecl(Field);
      if (VD->hasAttrs()) {
        for (specific_attr_iterator<AlignedAttr> I(VD->getAttrs().begin()),
             E(VD->getAttrs().end());
             I != E; ++I)
          Field->addAttr(*I);
      }
      MappedDeclsFields.try_emplace(VD, Field);
    }
    GlobalizedRD->completeDefinition();
  }

public:
  CheckVarsEscapingDeclContext(CodeGenFunction &CGF) : CGF(CGF) {}
  virtual ~CheckVarsEscapingDeclContext() = default;
  void VisitDeclStmt(const DeclStmt *S) {
    if (!S)
      return;
    for (const Decl *D : S->decls())
      if (const auto *VD = dyn_cast_or_null<ValueDecl>(D))
        VisitValueDecl(VD);
  }
  void VisitOMPExecutableDirective(const OMPExecutableDirective *D) {
    if (!D)
      return;
    if (!D->hasAssociatedStmt())
      return;
    if (const auto *S =
            dyn_cast_or_null<CapturedStmt>(D->getAssociatedStmt())) {
      // Do not analyze directives that do not actually require capturing,
      // like `omp for` or `omp simd` directives.
      llvm::SmallVector<OpenMPDirectiveKind, 4> CaptureRegions;
      getOpenMPCaptureRegions(CaptureRegions, D->getDirectiveKind());
      if (CaptureRegions.size() == 1 && CaptureRegions.back() == OMPD_unknown) {
        VisitStmt(S->getCapturedStmt());
        return;
      }
      VisitOpenMPCapturedStmt(
          S, D->clauses(),
          CaptureRegions.back() == OMPD_parallel &&
              isOpenMPDistributeDirective(D->getDirectiveKind()));
    }
  }
  void VisitCapturedStmt(const CapturedStmt *S) {
    if (!S)
      return;
    for (const CapturedStmt::Capture &C : S->captures()) {
      if (C.capturesVariable() && !C.capturesVariableByCopy()) {
        const ValueDecl *VD = C.getCapturedVar();
        markAsEscaped(VD);
        if (isa<OMPCapturedExprDecl>(VD))
          VisitValueDecl(VD);
      }
    }
  }
  void VisitLambdaExpr(const LambdaExpr *E) {
    if (!E)
      return;
    for (const LambdaCapture &C : E->captures()) {
      if (C.capturesVariable()) {
        if (C.getCaptureKind() == LCK_ByRef) {
          const ValueDecl *VD = C.getCapturedVar();
          markAsEscaped(VD);
          if (E->isInitCapture(&C) || isa<OMPCapturedExprDecl>(VD))
            VisitValueDecl(VD);
        }
      }
    }
  }
  void VisitBlockExpr(const BlockExpr *E) {
    if (!E)
      return;
    for (const BlockDecl::Capture &C : E->getBlockDecl()->captures()) {
      if (C.isByRef()) {
        const VarDecl *VD = C.getVariable();
        markAsEscaped(VD);
        if (isa<OMPCapturedExprDecl>(VD) || VD->isInitCapture())
          VisitValueDecl(VD);
      }
    }
  }
  void VisitCallExpr(const CallExpr *E) {
    if (!E)
      return;
    for (const Expr *Arg : E->arguments()) {
      if (!Arg)
        continue;
      if (Arg->isLValue()) {
        const bool SavedAllEscaped = AllEscaped;
        AllEscaped = true;
        Visit(Arg);
        AllEscaped = SavedAllEscaped;
      } else {
        Visit(Arg);
      }
    }
    Visit(E->getCallee());
  }
  void VisitDeclRefExpr(const DeclRefExpr *E) {
    if (!E)
      return;
    const ValueDecl *VD = E->getDecl();
    if (AllEscaped)
      markAsEscaped(VD);
    if (isa<OMPCapturedExprDecl>(VD))
      VisitValueDecl(VD);
    else if (const auto *VarD = dyn_cast<VarDecl>(VD))
      if (VarD->isInitCapture())
        VisitValueDecl(VD);
  }
  void VisitUnaryOperator(const UnaryOperator *E) {
    if (!E)
      return;
    if (E->getOpcode() == UO_AddrOf) {
      const bool SavedAllEscaped = AllEscaped;
      AllEscaped = true;
      Visit(E->getSubExpr());
      AllEscaped = SavedAllEscaped;
    } else {
      Visit(E->getSubExpr());
    }
  }
  void VisitImplicitCastExpr(const ImplicitCastExpr *E) {
    if (!E)
      return;
    if (E->getCastKind() == CK_ArrayToPointerDecay) {
      const bool SavedAllEscaped = AllEscaped;
      AllEscaped = true;
      Visit(E->getSubExpr());
      AllEscaped = SavedAllEscaped;
    } else {
      Visit(E->getSubExpr());
    }
  }
  void VisitExpr(const Expr *E) {
    if (!E)
      return;
    bool SavedAllEscaped = AllEscaped;
    if (!E->isLValue())
      AllEscaped = false;
    for (const Stmt *Child : E->children())
      if (Child)
        Visit(Child);
    AllEscaped = SavedAllEscaped;
  }
  void VisitStmt(const Stmt *S) {
    if (!S)
      return;
    for (const Stmt *Child : S->children())
      if (Child)
        Visit(Child);
  }

  /// Returns the record that handles all the escaped local variables and used
  /// instead of their original storage.
  const RecordDecl *getGlobalizedRecord() {
    if (!GlobalizedRD)
      buildRecordForGlobalizedVars();
    return GlobalizedRD;
  }

  /// Returns the field in the globalized record for the escaped variable.
  const FieldDecl *getFieldForGlobalizedVar(const ValueDecl *VD) const {
    assert(GlobalizedRD &&
           "Record for globalized variables must be generated already.");
    auto I = MappedDeclsFields.find(VD);
    if (I == MappedDeclsFields.end())
      return nullptr;
    return I->getSecond();
  }

  /// Returns the list of the escaped local variables/parameters.
  ArrayRef<const ValueDecl *> getEscapedDecls() const {
    return EscapedDecls.getArrayRef();
  }

  /// Checks if the escaped local variable is actually a parameter passed by
  /// value.
  const llvm::SmallPtrSetImpl<const Decl *> &getEscapedParameters() const {
    return EscapedParameters;
  }

  /// Returns the list of the escaped variables with the variably modified
  /// types.
  ArrayRef<const ValueDecl *> getEscapedVariableLengthDecls() const {
    return EscapedVariableLengthDecls.getArrayRef();
  }
};
} // anonymous namespace

/// Get the GPU warp size.
static llvm::Value *getNVPTXWarpSize(CodeGenFunction &CGF) {
  return CGF.EmitRuntimeCall(
      llvm::Intrinsic::getDeclaration(
          &CGF.CGM.getModule(), llvm::Intrinsic::nvvm_read_ptx_sreg_warpsize),
      "nvptx_warp_size");
}

/// Get the id of the current thread on the GPU.
static llvm::Value *getNVPTXThreadID(CodeGenFunction &CGF) {
  return CGF.EmitRuntimeCall(
      llvm::Intrinsic::getDeclaration(
          &CGF.CGM.getModule(), llvm::Intrinsic::nvvm_read_ptx_sreg_tid_x),
      "nvptx_tid");
}

/// Get the id of the warp in the block.
/// We assume that the warp size is 32, which is always the case
/// on the NVPTX device, to generate more efficient code.
static llvm::Value *getNVPTXWarpID(CodeGenFunction &CGF) {
  CGBuilderTy &Bld = CGF.Builder;
  return Bld.CreateAShr(getNVPTXThreadID(CGF), LaneIDBits, "nvptx_warp_id");
}

/// Get the id of the current lane in the Warp.
/// We assume that the warp size is 32, which is always the case
/// on the NVPTX device, to generate more efficient code.
static llvm::Value *getNVPTXLaneID(CodeGenFunction &CGF) {
  CGBuilderTy &Bld = CGF.Builder;
  return Bld.CreateAnd(getNVPTXThreadID(CGF), Bld.getInt32(LaneIDMask),
                       "nvptx_lane_id");
}

/// Get the maximum number of threads in a block of the GPU.
static llvm::Value *getNVPTXNumThreads(CodeGenFunction &CGF) {
  return CGF.EmitRuntimeCall(
      llvm::Intrinsic::getDeclaration(
          &CGF.CGM.getModule(), llvm::Intrinsic::nvvm_read_ptx_sreg_ntid_x),
      "nvptx_num_threads");
}

/// Get barrier to synchronize all threads in a block.
static void getNVPTXCTABarrier(CodeGenFunction &CGF) {
  CGF.EmitRuntimeCall(llvm::Intrinsic::getDeclaration(
      &CGF.CGM.getModule(), llvm::Intrinsic::nvvm_barrier0));
}

/// Get barrier #ID to synchronize selected (multiple of warp size) threads in
/// a CTA.
static void getNVPTXBarrier(CodeGenFunction &CGF, int ID,
                            llvm::Value *NumThreads) {
  CGBuilderTy &Bld = CGF.Builder;
  llvm::Value *Args[] = {Bld.getInt32(ID), NumThreads};
  CGF.EmitRuntimeCall(llvm::Intrinsic::getDeclaration(
                          &CGF.CGM.getModule(), llvm::Intrinsic::nvvm_barrier),
                      Args);
}

/// Synchronize all GPU threads in a block.
static void syncCTAThreads(CodeGenFunction &CGF) { getNVPTXCTABarrier(CGF); }

/// Synchronize worker threads in a parallel region.
static void syncParallelThreads(CodeGenFunction &CGF, llvm::Value *NumThreads) {
  return getNVPTXBarrier(CGF, NB_Parallel, NumThreads);
}

/// Get the value of the thread_limit clause in the teams directive.
/// For the 'generic' execution mode, the runtime encodes thread_limit in
/// the launch parameters, always starting thread_limit+warpSize threads per
/// CTA. The threads in the last warp are reserved for master execution.
/// For the 'spmd' execution mode, all threads in a CTA are part of the team.
static llvm::Value *getThreadLimit(CodeGenFunction &CGF,
                                   bool IsInSPMDExecutionMode = false) {
  CGBuilderTy &Bld = CGF.Builder;
  return IsInSPMDExecutionMode
             ? getNVPTXNumThreads(CGF)
             : Bld.CreateNUWSub(getNVPTXNumThreads(CGF), getNVPTXWarpSize(CGF),
                                "thread_limit");
}

/// Get the thread id of the OMP master thread.
/// The master thread id is the first thread (lane) of the last warp in the
/// GPU block.  Warp size is assumed to be some power of 2.
/// Thread id is 0 indexed.
/// E.g: If NumThreads is 33, master id is 32.
///      If NumThreads is 64, master id is 32.
///      If NumThreads is 1024, master id is 992.
static llvm::Value *getMasterThreadID(CodeGenFunction &CGF) {
  CGBuilderTy &Bld = CGF.Builder;
  llvm::Value *NumThreads = getNVPTXNumThreads(CGF);

  // We assume that the warp size is a power of 2.
  llvm::Value *Mask = Bld.CreateNUWSub(getNVPTXWarpSize(CGF), Bld.getInt32(1));

  return Bld.CreateAnd(Bld.CreateNUWSub(NumThreads, Bld.getInt32(1)),
                       Bld.CreateNot(Mask), "master_tid");
}

CGOpenMPRuntimeNVPTX::WorkerFunctionState::WorkerFunctionState(
    CodeGenModule &CGM, SourceLocation Loc)
    : WorkerFn(nullptr), CGFI(CGM.getTypes().arrangeNullaryFunction()),
      Loc(Loc) {
  createWorkerFunction(CGM);
}

void CGOpenMPRuntimeNVPTX::WorkerFunctionState::createWorkerFunction(
    CodeGenModule &CGM) {
  // Create an worker function with no arguments.

  WorkerFn = llvm::Function::Create(
      CGM.getTypes().GetFunctionType(CGFI), llvm::GlobalValue::InternalLinkage,
      /*placeholder=*/"_worker", &CGM.getModule());
  CGM.SetInternalFunctionAttributes(GlobalDecl(), WorkerFn, CGFI);
  WorkerFn->setDoesNotRecurse();
}

CGOpenMPRuntimeNVPTX::ExecutionMode
CGOpenMPRuntimeNVPTX::getExecutionMode() const {
  return CurrentExecutionMode;
}

static CGOpenMPRuntimeNVPTX::DataSharingMode
getDataSharingMode(CodeGenModule &CGM) {
  return CGM.getLangOpts().OpenMPCUDAMode ? CGOpenMPRuntimeNVPTX::CUDA
                                          : CGOpenMPRuntimeNVPTX::Generic;
}

/// Checks if the \p Body is the \a CompoundStmt and returns its child statement
/// iff there is only one.
static const Stmt *getSingleCompoundChild(const Stmt *Body) {
  if (const auto *C = dyn_cast<CompoundStmt>(Body))
    if (C->size() == 1)
      return C->body_front();
  return Body;
}

/// Check if the parallel directive has an 'if' clause with non-constant or
/// false condition. Also, check if the number of threads is strictly specified
/// and run those directives in non-SPMD mode.
static bool hasParallelIfNumThreadsClause(ASTContext &Ctx,
                                          const OMPExecutableDirective &D) {
  if (D.hasClausesOfKind<OMPNumThreadsClause>())
    return true;
  for (const auto *C : D.getClausesOfKind<OMPIfClause>()) {
    OpenMPDirectiveKind NameModifier = C->getNameModifier();
    if (NameModifier != OMPD_parallel && NameModifier != OMPD_unknown)
      continue;
    const Expr *Cond = C->getCondition();
    bool Result;
    if (!Cond->EvaluateAsBooleanCondition(Result, Ctx) || !Result)
      return true;
  }
  return false;
}

/// Checks if the directive is the distribute clause with the lastprivate
/// clauses. This construct does not support SPMD execution mode.
static bool hasDistributeWithLastprivateClauses(const OMPExecutableDirective &D) {
  return isOpenMPDistributeDirective(D.getDirectiveKind()) &&
         D.hasClausesOfKind<OMPLastprivateClause>();
}

/// Check for inner (nested) SPMD construct, if any
static bool hasNestedSPMDDirective(ASTContext &Ctx,
                                   const OMPExecutableDirective &D) {
  const auto *CS = D.getInnermostCapturedStmt();
  const auto *Body =
      CS->getCapturedStmt()->IgnoreContainers(/*IgnoreCaptured=*/true);
  const Stmt *ChildStmt = getSingleCompoundChild(Body);

  if (const auto *NestedDir = dyn_cast<OMPExecutableDirective>(ChildStmt)) {
    OpenMPDirectiveKind DKind = NestedDir->getDirectiveKind();
    switch (D.getDirectiveKind()) {
    case OMPD_target:
      if (isOpenMPParallelDirective(DKind) &&
          !hasParallelIfNumThreadsClause(Ctx, *NestedDir) &&
          !hasDistributeWithLastprivateClauses(*NestedDir))
        return true;
      if (DKind == OMPD_teams) {
        Body = NestedDir->getInnermostCapturedStmt()->IgnoreContainers(
            /*IgnoreCaptured=*/true);
        if (!Body)
          return false;
        ChildStmt = getSingleCompoundChild(Body);
        if (const auto *NND = dyn_cast<OMPExecutableDirective>(ChildStmt)) {
          DKind = NND->getDirectiveKind();
          if (isOpenMPParallelDirective(DKind) &&
              !hasParallelIfNumThreadsClause(Ctx, *NND) &&
              !hasDistributeWithLastprivateClauses(*NND))
            return true;
        }
      }
      return false;
    case OMPD_target_teams:
      return isOpenMPParallelDirective(DKind) &&
             !hasParallelIfNumThreadsClause(Ctx, *NestedDir) &&
             !hasDistributeWithLastprivateClauses(*NestedDir);
    case OMPD_target_simd:
    case OMPD_target_parallel:
    case OMPD_target_parallel_for:
    case OMPD_target_parallel_for_simd:
    case OMPD_target_teams_distribute:
    case OMPD_target_teams_distribute_simd:
    case OMPD_target_teams_distribute_parallel_for:
    case OMPD_target_teams_distribute_parallel_for_simd:
    case OMPD_parallel:
    case OMPD_for:
    case OMPD_parallel_for:
    case OMPD_parallel_sections:
    case OMPD_for_simd:
    case OMPD_parallel_for_simd:
    case OMPD_cancel:
    case OMPD_cancellation_point:
    case OMPD_ordered:
    case OMPD_threadprivate:
    case OMPD_task:
    case OMPD_simd:
    case OMPD_sections:
    case OMPD_section:
    case OMPD_single:
    case OMPD_master:
    case OMPD_critical:
    case OMPD_taskyield:
    case OMPD_barrier:
    case OMPD_taskwait:
    case OMPD_taskgroup:
    case OMPD_atomic:
    case OMPD_flush:
    case OMPD_teams:
    case OMPD_target_data:
    case OMPD_target_exit_data:
    case OMPD_target_enter_data:
    case OMPD_distribute:
    case OMPD_distribute_simd:
    case OMPD_distribute_parallel_for:
    case OMPD_distribute_parallel_for_simd:
    case OMPD_teams_distribute:
    case OMPD_teams_distribute_simd:
    case OMPD_teams_distribute_parallel_for:
    case OMPD_teams_distribute_parallel_for_simd:
    case OMPD_target_update:
    case OMPD_declare_simd:
    case OMPD_declare_target:
    case OMPD_end_declare_target:
    case OMPD_declare_reduction:
    case OMPD_taskloop:
    case OMPD_taskloop_simd:
    case OMPD_unknown:
      llvm_unreachable("Unexpected directive.");
    }
  }

  return false;
}

static bool supportsSPMDExecutionMode(ASTContext &Ctx,
                                      const OMPExecutableDirective &D) {
  OpenMPDirectiveKind DirectiveKind = D.getDirectiveKind();
  switch (DirectiveKind) {
  case OMPD_target:
  case OMPD_target_teams:
    return hasNestedSPMDDirective(Ctx, D);
  case OMPD_target_parallel:
  case OMPD_target_parallel_for:
  case OMPD_target_parallel_for_simd:
    return !hasParallelIfNumThreadsClause(Ctx, D);
  case OMPD_target_teams_distribute_parallel_for:
  case OMPD_target_teams_distribute_parallel_for_simd:
    // Distribute with lastprivates requires non-SPMD execution mode.
    return !hasParallelIfNumThreadsClause(Ctx, D) &&
           !hasDistributeWithLastprivateClauses(D);
  case OMPD_target_simd:
  case OMPD_target_teams_distribute:
  case OMPD_target_teams_distribute_simd:
    return false;
  case OMPD_parallel:
  case OMPD_for:
  case OMPD_parallel_for:
  case OMPD_parallel_sections:
  case OMPD_for_simd:
  case OMPD_parallel_for_simd:
  case OMPD_cancel:
  case OMPD_cancellation_point:
  case OMPD_ordered:
  case OMPD_threadprivate:
  case OMPD_task:
  case OMPD_simd:
  case OMPD_sections:
  case OMPD_section:
  case OMPD_single:
  case OMPD_master:
  case OMPD_critical:
  case OMPD_taskyield:
  case OMPD_barrier:
  case OMPD_taskwait:
  case OMPD_taskgroup:
  case OMPD_atomic:
  case OMPD_flush:
  case OMPD_teams:
  case OMPD_target_data:
  case OMPD_target_exit_data:
  case OMPD_target_enter_data:
  case OMPD_distribute:
  case OMPD_distribute_simd:
  case OMPD_distribute_parallel_for:
  case OMPD_distribute_parallel_for_simd:
  case OMPD_teams_distribute:
  case OMPD_teams_distribute_simd:
  case OMPD_teams_distribute_parallel_for:
  case OMPD_teams_distribute_parallel_for_simd:
  case OMPD_target_update:
  case OMPD_declare_simd:
  case OMPD_declare_target:
  case OMPD_end_declare_target:
  case OMPD_declare_reduction:
  case OMPD_taskloop:
  case OMPD_taskloop_simd:
  case OMPD_unknown:
    break;
  }
  llvm_unreachable(
      "Unknown programming model for OpenMP directive on NVPTX target.");
}

/// Check if the directive is loops based and has schedule clause at all or has
/// static scheduling.
static bool hasStaticScheduling(const OMPExecutableDirective &D) {
  assert(isOpenMPWorksharingDirective(D.getDirectiveKind()) &&
         isOpenMPLoopDirective(D.getDirectiveKind()) &&
         "Expected loop-based directive.");
  return !D.hasClausesOfKind<OMPOrderedClause>() &&
         (!D.hasClausesOfKind<OMPScheduleClause>() ||
          llvm::any_of(D.getClausesOfKind<OMPScheduleClause>(),
                       [](const OMPScheduleClause *C) {
                         return C->getScheduleKind() == OMPC_SCHEDULE_static;
                       }));
}

/// Check for inner (nested) lightweight runtime construct, if any
static bool hasNestedLightweightDirective(ASTContext &Ctx,
                                          const OMPExecutableDirective &D) {
  assert(supportsSPMDExecutionMode(Ctx, D) && "Expected SPMD mode directive.");
  const auto *CS = D.getInnermostCapturedStmt();
  const auto *Body =
      CS->getCapturedStmt()->IgnoreContainers(/*IgnoreCaptured=*/true);
  const Stmt *ChildStmt = getSingleCompoundChild(Body);

  if (const auto *NestedDir = dyn_cast<OMPExecutableDirective>(ChildStmt)) {
    OpenMPDirectiveKind DKind = NestedDir->getDirectiveKind();
    switch (D.getDirectiveKind()) {
    case OMPD_target:
      if (isOpenMPParallelDirective(DKind) &&
          isOpenMPWorksharingDirective(DKind) && isOpenMPLoopDirective(DKind) &&
          hasStaticScheduling(*NestedDir))
        return true;
      if (DKind == OMPD_parallel) {
        Body = NestedDir->getInnermostCapturedStmt()->IgnoreContainers(
            /*IgnoreCaptured=*/true);
        if (!Body)
          return false;
        ChildStmt = getSingleCompoundChild(Body);
        if (const auto *NND = dyn_cast<OMPExecutableDirective>(ChildStmt)) {
          DKind = NND->getDirectiveKind();
          if (isOpenMPWorksharingDirective(DKind) &&
              isOpenMPLoopDirective(DKind) && hasStaticScheduling(*NND))
            return true;
        }
      } else if (DKind == OMPD_teams) {
        Body = NestedDir->getInnermostCapturedStmt()->IgnoreContainers(
            /*IgnoreCaptured=*/true);
        if (!Body)
          return false;
        ChildStmt = getSingleCompoundChild(Body);
        if (const auto *NND = dyn_cast<OMPExecutableDirective>(ChildStmt)) {
          DKind = NND->getDirectiveKind();
          if (isOpenMPParallelDirective(DKind) &&
              isOpenMPWorksharingDirective(DKind) &&
              isOpenMPLoopDirective(DKind) && hasStaticScheduling(*NND))
            return true;
          if (DKind == OMPD_parallel) {
            Body = NND->getInnermostCapturedStmt()->IgnoreContainers(
                /*IgnoreCaptured=*/true);
            if (!Body)
              return false;
            ChildStmt = getSingleCompoundChild(Body);
            if (const auto *NND = dyn_cast<OMPExecutableDirective>(ChildStmt)) {
              DKind = NND->getDirectiveKind();
              if (isOpenMPWorksharingDirective(DKind) &&
                  isOpenMPLoopDirective(DKind) && hasStaticScheduling(*NND))
                return true;
            }
          }
        }
      }
      return false;
    case OMPD_target_teams:
      if (isOpenMPParallelDirective(DKind) &&
          isOpenMPWorksharingDirective(DKind) && isOpenMPLoopDirective(DKind) &&
          hasStaticScheduling(*NestedDir))
        return true;
      if (DKind == OMPD_parallel) {
        Body = NestedDir->getInnermostCapturedStmt()->IgnoreContainers(
            /*IgnoreCaptured=*/true);
        if (!Body)
          return false;
        ChildStmt = getSingleCompoundChild(Body);
        if (const auto *NND = dyn_cast<OMPExecutableDirective>(ChildStmt)) {
          DKind = NND->getDirectiveKind();
          if (isOpenMPWorksharingDirective(DKind) &&
              isOpenMPLoopDirective(DKind) && hasStaticScheduling(*NND))
            return true;
        }
      }
      return false;
    case OMPD_target_parallel:
      return isOpenMPWorksharingDirective(DKind) &&
             isOpenMPLoopDirective(DKind) && hasStaticScheduling(*NestedDir);
    case OMPD_target_teams_distribute:
    case OMPD_target_simd:
    case OMPD_target_parallel_for:
    case OMPD_target_parallel_for_simd:
    case OMPD_target_teams_distribute_simd:
    case OMPD_target_teams_distribute_parallel_for:
    case OMPD_target_teams_distribute_parallel_for_simd:
    case OMPD_parallel:
    case OMPD_for:
    case OMPD_parallel_for:
    case OMPD_parallel_sections:
    case OMPD_for_simd:
    case OMPD_parallel_for_simd:
    case OMPD_cancel:
    case OMPD_cancellation_point:
    case OMPD_ordered:
    case OMPD_threadprivate:
    case OMPD_task:
    case OMPD_simd:
    case OMPD_sections:
    case OMPD_section:
    case OMPD_single:
    case OMPD_master:
    case OMPD_critical:
    case OMPD_taskyield:
    case OMPD_barrier:
    case OMPD_taskwait:
    case OMPD_taskgroup:
    case OMPD_atomic:
    case OMPD_flush:
    case OMPD_teams:
    case OMPD_target_data:
    case OMPD_target_exit_data:
    case OMPD_target_enter_data:
    case OMPD_distribute:
    case OMPD_distribute_simd:
    case OMPD_distribute_parallel_for:
    case OMPD_distribute_parallel_for_simd:
    case OMPD_teams_distribute:
    case OMPD_teams_distribute_simd:
    case OMPD_teams_distribute_parallel_for:
    case OMPD_teams_distribute_parallel_for_simd:
    case OMPD_target_update:
    case OMPD_declare_simd:
    case OMPD_declare_target:
    case OMPD_end_declare_target:
    case OMPD_declare_reduction:
    case OMPD_taskloop:
    case OMPD_taskloop_simd:
    case OMPD_unknown:
      llvm_unreachable("Unexpected directive.");
    }
  }

  return false;
}

/// Checks if the construct supports lightweight runtime. It must be SPMD
/// construct + inner loop-based construct with static scheduling.
static bool supportsLightweightRuntime(ASTContext &Ctx,
                                       const OMPExecutableDirective &D) {
  if (!supportsSPMDExecutionMode(Ctx, D))
    return false;
  OpenMPDirectiveKind DirectiveKind = D.getDirectiveKind();
  switch (DirectiveKind) {
  case OMPD_target:
  case OMPD_target_teams:
  case OMPD_target_parallel:
    return hasNestedLightweightDirective(Ctx, D);
  case OMPD_target_parallel_for:
  case OMPD_target_parallel_for_simd:
  case OMPD_target_teams_distribute_parallel_for:
  case OMPD_target_teams_distribute_parallel_for_simd:
    // (Last|First)-privates must be shared in parallel region.
    return hasStaticScheduling(D);
  case OMPD_target_simd:
  case OMPD_target_teams_distribute:
  case OMPD_target_teams_distribute_simd:
    return false;
  case OMPD_parallel:
  case OMPD_for:
  case OMPD_parallel_for:
  case OMPD_parallel_sections:
  case OMPD_for_simd:
  case OMPD_parallel_for_simd:
  case OMPD_cancel:
  case OMPD_cancellation_point:
  case OMPD_ordered:
  case OMPD_threadprivate:
  case OMPD_task:
  case OMPD_simd:
  case OMPD_sections:
  case OMPD_section:
  case OMPD_single:
  case OMPD_master:
  case OMPD_critical:
  case OMPD_taskyield:
  case OMPD_barrier:
  case OMPD_taskwait:
  case OMPD_taskgroup:
  case OMPD_atomic:
  case OMPD_flush:
  case OMPD_teams:
  case OMPD_target_data:
  case OMPD_target_exit_data:
  case OMPD_target_enter_data:
  case OMPD_distribute:
  case OMPD_distribute_simd:
  case OMPD_distribute_parallel_for:
  case OMPD_distribute_parallel_for_simd:
  case OMPD_teams_distribute:
  case OMPD_teams_distribute_simd:
  case OMPD_teams_distribute_parallel_for:
  case OMPD_teams_distribute_parallel_for_simd:
  case OMPD_target_update:
  case OMPD_declare_simd:
  case OMPD_declare_target:
  case OMPD_end_declare_target:
  case OMPD_declare_reduction:
  case OMPD_taskloop:
  case OMPD_taskloop_simd:
  case OMPD_unknown:
    break;
  }
  llvm_unreachable(
      "Unknown programming model for OpenMP directive on NVPTX target.");
}

void CGOpenMPRuntimeNVPTX::emitNonSPMDKernel(const OMPExecutableDirective &D,
                                             StringRef ParentName,
                                             llvm::Function *&OutlinedFn,
                                             llvm::Constant *&OutlinedFnID,
                                             bool IsOffloadEntry,
                                             const RegionCodeGenTy &CodeGen) {
  ExecutionModeRAII ModeRAII(CurrentExecutionMode, /*IsSPMD=*/false);
  EntryFunctionState EST;
  WorkerFunctionState WST(CGM, D.getBeginLoc());
  Work.clear();
  WrapperFunctionsMap.clear();

  // Emit target region as a standalone region.
  class NVPTXPrePostActionTy : public PrePostActionTy {
    CGOpenMPRuntimeNVPTX::EntryFunctionState &EST;
    CGOpenMPRuntimeNVPTX::WorkerFunctionState &WST;

  public:
    NVPTXPrePostActionTy(CGOpenMPRuntimeNVPTX::EntryFunctionState &EST,
                         CGOpenMPRuntimeNVPTX::WorkerFunctionState &WST)
        : EST(EST), WST(WST) {}
    void Enter(CodeGenFunction &CGF) override {
      static_cast<CGOpenMPRuntimeNVPTX &>(CGF.CGM.getOpenMPRuntime())
          .emitNonSPMDEntryHeader(CGF, EST, WST);
    }
    void Exit(CodeGenFunction &CGF) override {
      static_cast<CGOpenMPRuntimeNVPTX &>(CGF.CGM.getOpenMPRuntime())
          .emitNonSPMDEntryFooter(CGF, EST);
    }
  } Action(EST, WST);
  CodeGen.setAction(Action);
  emitTargetOutlinedFunctionHelper(D, ParentName, OutlinedFn, OutlinedFnID,
                                   IsOffloadEntry, CodeGen);

  // Now change the name of the worker function to correspond to this target
  // region's entry function.
  WST.WorkerFn->setName(Twine(OutlinedFn->getName(), "_worker"));

  // Create the worker function
  emitWorkerFunction(WST);
}

// Setup NVPTX threads for master-worker OpenMP scheme.
void CGOpenMPRuntimeNVPTX::emitNonSPMDEntryHeader(CodeGenFunction &CGF,
                                                  EntryFunctionState &EST,
                                                  WorkerFunctionState &WST) {
  CGBuilderTy &Bld = CGF.Builder;

  llvm::BasicBlock *WorkerBB = CGF.createBasicBlock(".worker");
  llvm::BasicBlock *MasterCheckBB = CGF.createBasicBlock(".mastercheck");
  llvm::BasicBlock *MasterBB = CGF.createBasicBlock(".master");
  EST.ExitBB = CGF.createBasicBlock(".exit");

  llvm::Value *IsWorker =
      Bld.CreateICmpULT(getNVPTXThreadID(CGF), getThreadLimit(CGF));
  Bld.CreateCondBr(IsWorker, WorkerBB, MasterCheckBB);

  CGF.EmitBlock(WorkerBB);
  emitCall(CGF, WST.Loc, WST.WorkerFn);
  CGF.EmitBranch(EST.ExitBB);

  CGF.EmitBlock(MasterCheckBB);
  llvm::Value *IsMaster =
      Bld.CreateICmpEQ(getNVPTXThreadID(CGF), getMasterThreadID(CGF));
  Bld.CreateCondBr(IsMaster, MasterBB, EST.ExitBB);

  CGF.EmitBlock(MasterBB);
  IsInTargetMasterThreadRegion = true;
  // SEQUENTIAL (MASTER) REGION START
  // First action in sequential region:
  // Initialize the state of the OpenMP runtime library on the GPU.
  // TODO: Optimize runtime initialization and pass in correct value.
  llvm::Value *Args[] = {getThreadLimit(CGF),
                         Bld.getInt16(/*RequiresOMPRuntime=*/1)};
  CGF.EmitRuntimeCall(
      createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_kernel_init), Args);

  // For data sharing, we need to initialize the stack.
  CGF.EmitRuntimeCall(
      createNVPTXRuntimeFunction(
          OMPRTL_NVPTX__kmpc_data_sharing_init_stack));

  emitGenericVarsProlog(CGF, WST.Loc);
}

void CGOpenMPRuntimeNVPTX::emitNonSPMDEntryFooter(CodeGenFunction &CGF,
                                                  EntryFunctionState &EST) {
  IsInTargetMasterThreadRegion = false;
  if (!CGF.HaveInsertPoint())
    return;

  emitGenericVarsEpilog(CGF);

  if (!EST.ExitBB)
    EST.ExitBB = CGF.createBasicBlock(".exit");

  llvm::BasicBlock *TerminateBB = CGF.createBasicBlock(".termination.notifier");
  CGF.EmitBranch(TerminateBB);

  CGF.EmitBlock(TerminateBB);
  // Signal termination condition.
  // TODO: Optimize runtime initialization and pass in correct value.
  llvm::Value *Args[] = {CGF.Builder.getInt16(/*IsOMPRuntimeInitialized=*/1)};
  CGF.EmitRuntimeCall(
      createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_kernel_deinit), Args);
  // Barrier to terminate worker threads.
  syncCTAThreads(CGF);
  // Master thread jumps to exit point.
  CGF.EmitBranch(EST.ExitBB);

  CGF.EmitBlock(EST.ExitBB);
  EST.ExitBB = nullptr;
}

void CGOpenMPRuntimeNVPTX::emitSPMDKernel(const OMPExecutableDirective &D,
                                          StringRef ParentName,
                                          llvm::Function *&OutlinedFn,
                                          llvm::Constant *&OutlinedFnID,
                                          bool IsOffloadEntry,
                                          const RegionCodeGenTy &CodeGen) {
  ExecutionModeRAII ModeRAII(CurrentExecutionMode, /*IsSPMD=*/true);
  EntryFunctionState EST;

  // Emit target region as a standalone region.
  class NVPTXPrePostActionTy : public PrePostActionTy {
    CGOpenMPRuntimeNVPTX &RT;
    CGOpenMPRuntimeNVPTX::EntryFunctionState &EST;
    const OMPExecutableDirective &D;

  public:
    NVPTXPrePostActionTy(CGOpenMPRuntimeNVPTX &RT,
                         CGOpenMPRuntimeNVPTX::EntryFunctionState &EST,
                         const OMPExecutableDirective &D)
        : RT(RT), EST(EST), D(D) {}
    void Enter(CodeGenFunction &CGF) override {
      RT.emitSPMDEntryHeader(CGF, EST, D);
    }
    void Exit(CodeGenFunction &CGF) override {
      RT.emitSPMDEntryFooter(CGF, EST);
    }
  } Action(*this, EST, D);
  CodeGen.setAction(Action);
  emitTargetOutlinedFunctionHelper(D, ParentName, OutlinedFn, OutlinedFnID,
                                   IsOffloadEntry, CodeGen);
}

void CGOpenMPRuntimeNVPTX::emitSPMDEntryHeader(
    CodeGenFunction &CGF, EntryFunctionState &EST,
    const OMPExecutableDirective &D) {
  CGBuilderTy &Bld = CGF.Builder;

  // Setup BBs in entry function.
  llvm::BasicBlock *ExecuteBB = CGF.createBasicBlock(".execute");
  EST.ExitBB = CGF.createBasicBlock(".exit");

  // Initialize the OMP state in the runtime; called by all active threads.
  bool RequiresFullRuntime = CGM.getLangOpts().OpenMPCUDAForceFullRuntime ||
                             !supportsLightweightRuntime(CGF.getContext(), D);
  llvm::Value *Args[] = {
      getThreadLimit(CGF, /*IsInSPMDExecutionMode=*/true),
      /*RequiresOMPRuntime=*/
      Bld.getInt16(RequiresFullRuntime ? 1 : 0),
      /*RequiresDataSharing=*/Bld.getInt16(RequiresFullRuntime ? 1 : 0)};
  CGF.EmitRuntimeCall(
      createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_spmd_kernel_init), Args);

  if (RequiresFullRuntime) {
    // For data sharing, we need to initialize the stack.
    CGF.EmitRuntimeCall(createNVPTXRuntimeFunction(
        OMPRTL_NVPTX__kmpc_data_sharing_init_stack_spmd));
  }

  CGF.EmitBranch(ExecuteBB);

  CGF.EmitBlock(ExecuteBB);

  IsInTargetMasterThreadRegion = true;
}

void CGOpenMPRuntimeNVPTX::emitSPMDEntryFooter(CodeGenFunction &CGF,
                                               EntryFunctionState &EST) {
  IsInTargetMasterThreadRegion = false;
  if (!CGF.HaveInsertPoint())
    return;

  if (!EST.ExitBB)
    EST.ExitBB = CGF.createBasicBlock(".exit");

  llvm::BasicBlock *OMPDeInitBB = CGF.createBasicBlock(".omp.deinit");
  CGF.EmitBranch(OMPDeInitBB);

  CGF.EmitBlock(OMPDeInitBB);
  // DeInitialize the OMP state in the runtime; called by all active threads.
  CGF.EmitRuntimeCall(
      createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_spmd_kernel_deinit), None);
  CGF.EmitBranch(EST.ExitBB);

  CGF.EmitBlock(EST.ExitBB);
  EST.ExitBB = nullptr;
}

// Create a unique global variable to indicate the execution mode of this target
// region. The execution mode is either 'generic', or 'spmd' depending on the
// target directive. This variable is picked up by the offload library to setup
// the device appropriately before kernel launch. If the execution mode is
// 'generic', the runtime reserves one warp for the master, otherwise, all
// warps participate in parallel work.
static void setPropertyExecutionMode(CodeGenModule &CGM, StringRef Name,
                                     bool Mode) {
  auto *GVMode =
      new llvm::GlobalVariable(CGM.getModule(), CGM.Int8Ty, /*isConstant=*/true,
                               llvm::GlobalValue::WeakAnyLinkage,
                               llvm::ConstantInt::get(CGM.Int8Ty, Mode ? 0 : 1),
                               Twine(Name, "_exec_mode"));
  CGM.addCompilerUsedGlobal(GVMode);
}

void CGOpenMPRuntimeNVPTX::emitWorkerFunction(WorkerFunctionState &WST) {
  ASTContext &Ctx = CGM.getContext();

  CodeGenFunction CGF(CGM, /*suppressNewContext=*/true);
  CGF.StartFunction(GlobalDecl(), Ctx.VoidTy, WST.WorkerFn, WST.CGFI, {},
                    WST.Loc, WST.Loc);
  emitWorkerLoop(CGF, WST);
  CGF.FinishFunction();
}

void CGOpenMPRuntimeNVPTX::emitWorkerLoop(CodeGenFunction &CGF,
                                          WorkerFunctionState &WST) {
  //
  // The workers enter this loop and wait for parallel work from the master.
  // When the master encounters a parallel region it sets up the work + variable
  // arguments, and wakes up the workers.  The workers first check to see if
  // they are required for the parallel region, i.e., within the # of requested
  // parallel threads.  The activated workers load the variable arguments and
  // execute the parallel work.
  //

  CGBuilderTy &Bld = CGF.Builder;

  llvm::BasicBlock *AwaitBB = CGF.createBasicBlock(".await.work");
  llvm::BasicBlock *SelectWorkersBB = CGF.createBasicBlock(".select.workers");
  llvm::BasicBlock *ExecuteBB = CGF.createBasicBlock(".execute.parallel");
  llvm::BasicBlock *TerminateBB = CGF.createBasicBlock(".terminate.parallel");
  llvm::BasicBlock *BarrierBB = CGF.createBasicBlock(".barrier.parallel");
  llvm::BasicBlock *ExitBB = CGF.createBasicBlock(".exit");

  CGF.EmitBranch(AwaitBB);

  // Workers wait for work from master.
  CGF.EmitBlock(AwaitBB);
  // Wait for parallel work
  syncCTAThreads(CGF);

  Address WorkFn =
      CGF.CreateDefaultAlignTempAlloca(CGF.Int8PtrTy, /*Name=*/"work_fn");
  Address ExecStatus =
      CGF.CreateDefaultAlignTempAlloca(CGF.Int8Ty, /*Name=*/"exec_status");
  CGF.InitTempAlloca(ExecStatus, Bld.getInt8(/*C=*/0));
  CGF.InitTempAlloca(WorkFn, llvm::Constant::getNullValue(CGF.Int8PtrTy));

  // TODO: Optimize runtime initialization and pass in correct value.
  llvm::Value *Args[] = {WorkFn.getPointer(),
                         /*RequiresOMPRuntime=*/Bld.getInt16(1)};
  llvm::Value *Ret = CGF.EmitRuntimeCall(
      createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_kernel_parallel), Args);
  Bld.CreateStore(Bld.CreateZExt(Ret, CGF.Int8Ty), ExecStatus);

  // On termination condition (workid == 0), exit loop.
  llvm::Value *WorkID = Bld.CreateLoad(WorkFn);
  llvm::Value *ShouldTerminate = Bld.CreateIsNull(WorkID, "should_terminate");
  Bld.CreateCondBr(ShouldTerminate, ExitBB, SelectWorkersBB);

  // Activate requested workers.
  CGF.EmitBlock(SelectWorkersBB);
  llvm::Value *IsActive =
      Bld.CreateIsNotNull(Bld.CreateLoad(ExecStatus), "is_active");
  Bld.CreateCondBr(IsActive, ExecuteBB, BarrierBB);

  // Signal start of parallel region.
  CGF.EmitBlock(ExecuteBB);

  // Process work items: outlined parallel functions.
  for (llvm::Function *W : Work) {
    // Try to match this outlined function.
    llvm::Value *ID = Bld.CreatePointerBitCastOrAddrSpaceCast(W, CGM.Int8PtrTy);

    llvm::Value *WorkFnMatch =
        Bld.CreateICmpEQ(Bld.CreateLoad(WorkFn), ID, "work_match");

    llvm::BasicBlock *ExecuteFNBB = CGF.createBasicBlock(".execute.fn");
    llvm::BasicBlock *CheckNextBB = CGF.createBasicBlock(".check.next");
    Bld.CreateCondBr(WorkFnMatch, ExecuteFNBB, CheckNextBB);

    // Execute this outlined function.
    CGF.EmitBlock(ExecuteFNBB);

    // Insert call to work function via shared wrapper. The shared
    // wrapper takes two arguments:
    //   - the parallelism level;
    //   - the thread ID;
    emitCall(CGF, WST.Loc, W,
             {Bld.getInt16(/*ParallelLevel=*/0), getThreadID(CGF, WST.Loc)});

    // Go to end of parallel region.
    CGF.EmitBranch(TerminateBB);

    CGF.EmitBlock(CheckNextBB);
  }
  // Default case: call to outlined function through pointer if the target
  // region makes a declare target call that may contain an orphaned parallel
  // directive.
  auto *ParallelFnTy =
      llvm::FunctionType::get(CGM.VoidTy, {CGM.Int16Ty, CGM.Int32Ty},
                              /*isVarArg=*/false)
          ->getPointerTo();
  llvm::Value *WorkFnCast = Bld.CreateBitCast(WorkID, ParallelFnTy);
  // Insert call to work function via shared wrapper. The shared
  // wrapper takes two arguments:
  //   - the parallelism level;
  //   - the thread ID;
  emitCall(CGF, WST.Loc, WorkFnCast,
           {Bld.getInt16(/*ParallelLevel=*/0), getThreadID(CGF, WST.Loc)});
  // Go to end of parallel region.
  CGF.EmitBranch(TerminateBB);

  // Signal end of parallel region.
  CGF.EmitBlock(TerminateBB);
  CGF.EmitRuntimeCall(
      createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_kernel_end_parallel),
      llvm::None);
  CGF.EmitBranch(BarrierBB);

  // All active and inactive workers wait at a barrier after parallel region.
  CGF.EmitBlock(BarrierBB);
  // Barrier after parallel region.
  syncCTAThreads(CGF);
  CGF.EmitBranch(AwaitBB);

  // Exit target region.
  CGF.EmitBlock(ExitBB);
}

/// Returns specified OpenMP runtime function for the current OpenMP
/// implementation.  Specialized for the NVPTX device.
/// \param Function OpenMP runtime function.
/// \return Specified function.
llvm::Constant *
CGOpenMPRuntimeNVPTX::createNVPTXRuntimeFunction(unsigned Function) {
  llvm::Constant *RTLFn = nullptr;
  switch (static_cast<OpenMPRTLFunctionNVPTX>(Function)) {
  case OMPRTL_NVPTX__kmpc_kernel_init: {
    // Build void __kmpc_kernel_init(kmp_int32 thread_limit, int16_t
    // RequiresOMPRuntime);
    llvm::Type *TypeParams[] = {CGM.Int32Ty, CGM.Int16Ty};
    auto *FnTy =
        llvm::FunctionType::get(CGM.VoidTy, TypeParams, /*isVarArg*/ false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_kernel_init");
    break;
  }
  case OMPRTL_NVPTX__kmpc_kernel_deinit: {
    // Build void __kmpc_kernel_deinit(int16_t IsOMPRuntimeInitialized);
    llvm::Type *TypeParams[] = {CGM.Int16Ty};
    auto *FnTy =
        llvm::FunctionType::get(CGM.VoidTy, TypeParams, /*isVarArg*/ false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_kernel_deinit");
    break;
  }
  case OMPRTL_NVPTX__kmpc_spmd_kernel_init: {
    // Build void __kmpc_spmd_kernel_init(kmp_int32 thread_limit,
    // int16_t RequiresOMPRuntime, int16_t RequiresDataSharing);
    llvm::Type *TypeParams[] = {CGM.Int32Ty, CGM.Int16Ty, CGM.Int16Ty};
    auto *FnTy =
        llvm::FunctionType::get(CGM.VoidTy, TypeParams, /*isVarArg*/ false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_spmd_kernel_init");
    break;
  }
  case OMPRTL_NVPTX__kmpc_spmd_kernel_deinit: {
    // Build void __kmpc_spmd_kernel_deinit();
    auto *FnTy =
        llvm::FunctionType::get(CGM.VoidTy, llvm::None, /*isVarArg*/ false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_spmd_kernel_deinit");
    break;
  }
  case OMPRTL_NVPTX__kmpc_kernel_prepare_parallel: {
    /// Build void __kmpc_kernel_prepare_parallel(
    /// void *outlined_function, int16_t IsOMPRuntimeInitialized);
    llvm::Type *TypeParams[] = {CGM.Int8PtrTy, CGM.Int16Ty};
    auto *FnTy =
        llvm::FunctionType::get(CGM.VoidTy, TypeParams, /*isVarArg*/ false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_kernel_prepare_parallel");
    break;
  }
  case OMPRTL_NVPTX__kmpc_kernel_parallel: {
    /// Build bool __kmpc_kernel_parallel(void **outlined_function,
    /// int16_t IsOMPRuntimeInitialized);
    llvm::Type *TypeParams[] = {CGM.Int8PtrPtrTy, CGM.Int16Ty};
    llvm::Type *RetTy = CGM.getTypes().ConvertType(CGM.getContext().BoolTy);
    auto *FnTy =
        llvm::FunctionType::get(RetTy, TypeParams, /*isVarArg*/ false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_kernel_parallel");
    break;
  }
  case OMPRTL_NVPTX__kmpc_kernel_end_parallel: {
    /// Build void __kmpc_kernel_end_parallel();
    auto *FnTy =
        llvm::FunctionType::get(CGM.VoidTy, llvm::None, /*isVarArg*/ false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_kernel_end_parallel");
    break;
  }
  case OMPRTL_NVPTX__kmpc_serialized_parallel: {
    // Build void __kmpc_serialized_parallel(ident_t *loc, kmp_int32
    // global_tid);
    llvm::Type *TypeParams[] = {getIdentTyPointerTy(), CGM.Int32Ty};
    auto *FnTy =
        llvm::FunctionType::get(CGM.VoidTy, TypeParams, /*isVarArg*/ false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_serialized_parallel");
    break;
  }
  case OMPRTL_NVPTX__kmpc_end_serialized_parallel: {
    // Build void __kmpc_end_serialized_parallel(ident_t *loc, kmp_int32
    // global_tid);
    llvm::Type *TypeParams[] = {getIdentTyPointerTy(), CGM.Int32Ty};
    auto *FnTy =
        llvm::FunctionType::get(CGM.VoidTy, TypeParams, /*isVarArg*/ false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_end_serialized_parallel");
    break;
  }
  case OMPRTL_NVPTX__kmpc_shuffle_int32: {
    // Build int32_t __kmpc_shuffle_int32(int32_t element,
    // int16_t lane_offset, int16_t warp_size);
    llvm::Type *TypeParams[] = {CGM.Int32Ty, CGM.Int16Ty, CGM.Int16Ty};
    auto *FnTy =
        llvm::FunctionType::get(CGM.Int32Ty, TypeParams, /*isVarArg*/ false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_shuffle_int32");
    break;
  }
  case OMPRTL_NVPTX__kmpc_shuffle_int64: {
    // Build int64_t __kmpc_shuffle_int64(int64_t element,
    // int16_t lane_offset, int16_t warp_size);
    llvm::Type *TypeParams[] = {CGM.Int64Ty, CGM.Int16Ty, CGM.Int16Ty};
    auto *FnTy =
        llvm::FunctionType::get(CGM.Int64Ty, TypeParams, /*isVarArg*/ false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_shuffle_int64");
    break;
  }
  case OMPRTL_NVPTX__kmpc_parallel_reduce_nowait: {
    // Build int32_t kmpc_nvptx_parallel_reduce_nowait(kmp_int32 global_tid,
    // kmp_int32 num_vars, size_t reduce_size, void* reduce_data,
    // void (*kmp_ShuffleReductFctPtr)(void *rhsData, int16_t lane_id, int16_t
    // lane_offset, int16_t Algorithm Version),
    // void (*kmp_InterWarpCopyFctPtr)(void* src, int warp_num));
    llvm::Type *ShuffleReduceTypeParams[] = {CGM.VoidPtrTy, CGM.Int16Ty,
                                             CGM.Int16Ty, CGM.Int16Ty};
    auto *ShuffleReduceFnTy =
        llvm::FunctionType::get(CGM.VoidTy, ShuffleReduceTypeParams,
                                /*isVarArg=*/false);
    llvm::Type *InterWarpCopyTypeParams[] = {CGM.VoidPtrTy, CGM.Int32Ty};
    auto *InterWarpCopyFnTy =
        llvm::FunctionType::get(CGM.VoidTy, InterWarpCopyTypeParams,
                                /*isVarArg=*/false);
    llvm::Type *TypeParams[] = {CGM.Int32Ty,
                                CGM.Int32Ty,
                                CGM.SizeTy,
                                CGM.VoidPtrTy,
                                ShuffleReduceFnTy->getPointerTo(),
                                InterWarpCopyFnTy->getPointerTo()};
    auto *FnTy =
        llvm::FunctionType::get(CGM.Int32Ty, TypeParams, /*isVarArg=*/false);
    RTLFn = CGM.CreateRuntimeFunction(
        FnTy, /*Name=*/"__kmpc_nvptx_parallel_reduce_nowait");
    break;
  }
  case OMPRTL_NVPTX__kmpc_simd_reduce_nowait: {
    // Build int32_t kmpc_nvptx_simd_reduce_nowait(kmp_int32 global_tid,
    // kmp_int32 num_vars, size_t reduce_size, void* reduce_data,
    // void (*kmp_ShuffleReductFctPtr)(void *rhsData, int16_t lane_id, int16_t
    // lane_offset, int16_t Algorithm Version),
    // void (*kmp_InterWarpCopyFctPtr)(void* src, int warp_num));
    llvm::Type *ShuffleReduceTypeParams[] = {CGM.VoidPtrTy, CGM.Int16Ty,
                                             CGM.Int16Ty, CGM.Int16Ty};
    auto *ShuffleReduceFnTy =
        llvm::FunctionType::get(CGM.VoidTy, ShuffleReduceTypeParams,
                                /*isVarArg=*/false);
    llvm::Type *InterWarpCopyTypeParams[] = {CGM.VoidPtrTy, CGM.Int32Ty};
    auto *InterWarpCopyFnTy =
        llvm::FunctionType::get(CGM.VoidTy, InterWarpCopyTypeParams,
                                /*isVarArg=*/false);
    llvm::Type *TypeParams[] = {CGM.Int32Ty,
                                CGM.Int32Ty,
                                CGM.SizeTy,
                                CGM.VoidPtrTy,
                                ShuffleReduceFnTy->getPointerTo(),
                                InterWarpCopyFnTy->getPointerTo()};
    auto *FnTy =
        llvm::FunctionType::get(CGM.Int32Ty, TypeParams, /*isVarArg=*/false);
    RTLFn = CGM.CreateRuntimeFunction(
        FnTy, /*Name=*/"__kmpc_nvptx_simd_reduce_nowait");
    break;
  }
  case OMPRTL_NVPTX__kmpc_teams_reduce_nowait: {
    // Build int32_t __kmpc_nvptx_teams_reduce_nowait(int32_t global_tid,
    // int32_t num_vars, size_t reduce_size, void *reduce_data,
    // void (*kmp_ShuffleReductFctPtr)(void *rhsData, int16_t lane_id, int16_t
    // lane_offset, int16_t shortCircuit),
    // void (*kmp_InterWarpCopyFctPtr)(void* src, int32_t warp_num),
    // void (*kmp_CopyToScratchpadFctPtr)(void *reduce_data, void * scratchpad,
    // int32_t index, int32_t width),
    // void (*kmp_LoadReduceFctPtr)(void *reduce_data, void * scratchpad,
    // int32_t index, int32_t width, int32_t reduce))
    llvm::Type *ShuffleReduceTypeParams[] = {CGM.VoidPtrTy, CGM.Int16Ty,
                                             CGM.Int16Ty, CGM.Int16Ty};
    auto *ShuffleReduceFnTy =
        llvm::FunctionType::get(CGM.VoidTy, ShuffleReduceTypeParams,
                                /*isVarArg=*/false);
    llvm::Type *InterWarpCopyTypeParams[] = {CGM.VoidPtrTy, CGM.Int32Ty};
    auto *InterWarpCopyFnTy =
        llvm::FunctionType::get(CGM.VoidTy, InterWarpCopyTypeParams,
                                /*isVarArg=*/false);
    llvm::Type *CopyToScratchpadTypeParams[] = {CGM.VoidPtrTy, CGM.VoidPtrTy,
                                                CGM.Int32Ty, CGM.Int32Ty};
    auto *CopyToScratchpadFnTy =
        llvm::FunctionType::get(CGM.VoidTy, CopyToScratchpadTypeParams,
                                /*isVarArg=*/false);
    llvm::Type *LoadReduceTypeParams[] = {
        CGM.VoidPtrTy, CGM.VoidPtrTy, CGM.Int32Ty, CGM.Int32Ty, CGM.Int32Ty};
    auto *LoadReduceFnTy =
        llvm::FunctionType::get(CGM.VoidTy, LoadReduceTypeParams,
                                /*isVarArg=*/false);
    llvm::Type *TypeParams[] = {CGM.Int32Ty,
                                CGM.Int32Ty,
                                CGM.SizeTy,
                                CGM.VoidPtrTy,
                                ShuffleReduceFnTy->getPointerTo(),
                                InterWarpCopyFnTy->getPointerTo(),
                                CopyToScratchpadFnTy->getPointerTo(),
                                LoadReduceFnTy->getPointerTo()};
    auto *FnTy =
        llvm::FunctionType::get(CGM.Int32Ty, TypeParams, /*isVarArg=*/false);
    RTLFn = CGM.CreateRuntimeFunction(
        FnTy, /*Name=*/"__kmpc_nvptx_teams_reduce_nowait");
    break;
  }
  case OMPRTL_NVPTX__kmpc_end_reduce_nowait: {
    // Build __kmpc_end_reduce_nowait(kmp_int32 global_tid);
    llvm::Type *TypeParams[] = {CGM.Int32Ty};
    auto *FnTy =
        llvm::FunctionType::get(CGM.VoidTy, TypeParams, /*isVarArg=*/false);
    RTLFn = CGM.CreateRuntimeFunction(
        FnTy, /*Name=*/"__kmpc_nvptx_end_reduce_nowait");
    break;
  }
  case OMPRTL_NVPTX__kmpc_data_sharing_init_stack: {
    /// Build void __kmpc_data_sharing_init_stack();
    auto *FnTy =
        llvm::FunctionType::get(CGM.VoidTy, llvm::None, /*isVarArg*/ false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_data_sharing_init_stack");
    break;
  }
  case OMPRTL_NVPTX__kmpc_data_sharing_init_stack_spmd: {
    /// Build void __kmpc_data_sharing_init_stack_spmd();
    auto *FnTy =
        llvm::FunctionType::get(CGM.VoidTy, llvm::None, /*isVarArg*/ false);
    RTLFn =
        CGM.CreateRuntimeFunction(FnTy, "__kmpc_data_sharing_init_stack_spmd");
    break;
  }
  case OMPRTL_NVPTX__kmpc_data_sharing_push_stack: {
    // Build void *__kmpc_data_sharing_push_stack(size_t size,
    // int16_t UseSharedMemory);
    llvm::Type *TypeParams[] = {CGM.SizeTy, CGM.Int16Ty};
    auto *FnTy =
        llvm::FunctionType::get(CGM.VoidPtrTy, TypeParams, /*isVarArg=*/false);
    RTLFn = CGM.CreateRuntimeFunction(
        FnTy, /*Name=*/"__kmpc_data_sharing_push_stack");
    break;
  }
  case OMPRTL_NVPTX__kmpc_data_sharing_pop_stack: {
    // Build void __kmpc_data_sharing_pop_stack(void *a);
    llvm::Type *TypeParams[] = {CGM.VoidPtrTy};
    auto *FnTy =
        llvm::FunctionType::get(CGM.VoidTy, TypeParams, /*isVarArg=*/false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy,
                                      /*Name=*/"__kmpc_data_sharing_pop_stack");
    break;
  }
  case OMPRTL_NVPTX__kmpc_begin_sharing_variables: {
    /// Build void __kmpc_begin_sharing_variables(void ***args,
    /// size_t n_args);
    llvm::Type *TypeParams[] = {CGM.Int8PtrPtrTy->getPointerTo(), CGM.SizeTy};
    auto *FnTy =
        llvm::FunctionType::get(CGM.VoidTy, TypeParams, /*isVarArg*/ false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_begin_sharing_variables");
    break;
  }
  case OMPRTL_NVPTX__kmpc_end_sharing_variables: {
    /// Build void __kmpc_end_sharing_variables();
    auto *FnTy =
        llvm::FunctionType::get(CGM.VoidTy, llvm::None, /*isVarArg*/ false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_end_sharing_variables");
    break;
  }
  case OMPRTL_NVPTX__kmpc_get_shared_variables: {
    /// Build void __kmpc_get_shared_variables(void ***GlobalArgs);
    llvm::Type *TypeParams[] = {CGM.Int8PtrPtrTy->getPointerTo()};
    auto *FnTy =
        llvm::FunctionType::get(CGM.VoidTy, TypeParams, /*isVarArg*/ false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_get_shared_variables");
    break;
  }
  case OMPRTL_NVPTX__kmpc_parallel_level: {
    // Build uint16_t __kmpc_parallel_level(ident_t *loc, kmp_int32 global_tid);
    llvm::Type *TypeParams[] = {getIdentTyPointerTy(), CGM.Int32Ty};
    auto *FnTy =
        llvm::FunctionType::get(CGM.Int16Ty, TypeParams, /*isVarArg*/ false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_parallel_level");
    break;
  }
  case OMPRTL_NVPTX__kmpc_is_spmd_exec_mode: {
    // Build int8_t __kmpc_is_spmd_exec_mode();
    auto *FnTy = llvm::FunctionType::get(CGM.Int8Ty, /*isVarArg=*/false);
    RTLFn = CGM.CreateRuntimeFunction(FnTy, "__kmpc_is_spmd_exec_mode");
    break;
  }
  }
  return RTLFn;
}

void CGOpenMPRuntimeNVPTX::createOffloadEntry(llvm::Constant *ID,
                                              llvm::Constant *Addr,
                                              uint64_t Size, int32_t,
                                              llvm::GlobalValue::LinkageTypes) {
  // TODO: Add support for global variables on the device after declare target
  // support.
  if (!isa<llvm::Function>(Addr))
    return;
  llvm::Module &M = CGM.getModule();
  llvm::LLVMContext &Ctx = CGM.getLLVMContext();

  // Get "nvvm.annotations" metadata node
  llvm::NamedMDNode *MD = M.getOrInsertNamedMetadata("nvvm.annotations");

  llvm::Metadata *MDVals[] = {
      llvm::ConstantAsMetadata::get(Addr), llvm::MDString::get(Ctx, "kernel"),
      llvm::ConstantAsMetadata::get(
          llvm::ConstantInt::get(llvm::Type::getInt32Ty(Ctx), 1))};
  // Append metadata to nvvm.annotations
  MD->addOperand(llvm::MDNode::get(Ctx, MDVals));
}

void CGOpenMPRuntimeNVPTX::emitTargetOutlinedFunction(
    const OMPExecutableDirective &D, StringRef ParentName,
    llvm::Function *&OutlinedFn, llvm::Constant *&OutlinedFnID,
    bool IsOffloadEntry, const RegionCodeGenTy &CodeGen) {
  if (!IsOffloadEntry) // Nothing to do.
    return;

  assert(!ParentName.empty() && "Invalid target region parent name!");

  bool Mode = supportsSPMDExecutionMode(CGM.getContext(), D);
  if (Mode)
    emitSPMDKernel(D, ParentName, OutlinedFn, OutlinedFnID, IsOffloadEntry,
                   CodeGen);
  else
    emitNonSPMDKernel(D, ParentName, OutlinedFn, OutlinedFnID, IsOffloadEntry,
                      CodeGen);

  setPropertyExecutionMode(CGM, OutlinedFn->getName(), Mode);
}

CGOpenMPRuntimeNVPTX::CGOpenMPRuntimeNVPTX(CodeGenModule &CGM)
    : CGOpenMPRuntime(CGM, "_", "$") {
  if (!CGM.getLangOpts().OpenMPIsDevice)
    llvm_unreachable("OpenMP NVPTX can only handle device code.");
}

void CGOpenMPRuntimeNVPTX::emitProcBindClause(CodeGenFunction &CGF,
                                              OpenMPProcBindClauseKind ProcBind,
                                              SourceLocation Loc) {
  // Do nothing in case of SPMD mode and L0 parallel.
  if (getExecutionMode() == CGOpenMPRuntimeNVPTX::EM_SPMD)
    return;

  CGOpenMPRuntime::emitProcBindClause(CGF, ProcBind, Loc);
}

void CGOpenMPRuntimeNVPTX::emitNumThreadsClause(CodeGenFunction &CGF,
                                                llvm::Value *NumThreads,
                                                SourceLocation Loc) {
  // Do nothing in case of SPMD mode and L0 parallel.
  if (getExecutionMode() == CGOpenMPRuntimeNVPTX::EM_SPMD)
    return;

  CGOpenMPRuntime::emitNumThreadsClause(CGF, NumThreads, Loc);
}

void CGOpenMPRuntimeNVPTX::emitNumTeamsClause(CodeGenFunction &CGF,
                                              const Expr *NumTeams,
                                              const Expr *ThreadLimit,
                                              SourceLocation Loc) {}

llvm::Value *CGOpenMPRuntimeNVPTX::emitParallelOutlinedFunction(
    const OMPExecutableDirective &D, const VarDecl *ThreadIDVar,
    OpenMPDirectiveKind InnermostKind, const RegionCodeGenTy &CodeGen) {
  // Emit target region as a standalone region.
  class NVPTXPrePostActionTy : public PrePostActionTy {
    bool &IsInParallelRegion;
    bool PrevIsInParallelRegion;

  public:
    NVPTXPrePostActionTy(bool &IsInParallelRegion)
        : IsInParallelRegion(IsInParallelRegion) {}
    void Enter(CodeGenFunction &CGF) override {
      PrevIsInParallelRegion = IsInParallelRegion;
      IsInParallelRegion = true;
    }
    void Exit(CodeGenFunction &CGF) override {
      IsInParallelRegion = PrevIsInParallelRegion;
    }
  } Action(IsInParallelRegion);
  CodeGen.setAction(Action);
  bool PrevIsInTargetMasterThreadRegion = IsInTargetMasterThreadRegion;
  IsInTargetMasterThreadRegion = false;
  auto *OutlinedFun =
      cast<llvm::Function>(CGOpenMPRuntime::emitParallelOutlinedFunction(
          D, ThreadIDVar, InnermostKind, CodeGen));
  IsInTargetMasterThreadRegion = PrevIsInTargetMasterThreadRegion;
  if (getExecutionMode() != CGOpenMPRuntimeNVPTX::EM_SPMD &&
      !IsInParallelRegion) {
    llvm::Function *WrapperFun =
        createParallelDataSharingWrapper(OutlinedFun, D);
    WrapperFunctionsMap[OutlinedFun] = WrapperFun;
  }

  return OutlinedFun;
}

llvm::Value *CGOpenMPRuntimeNVPTX::emitTeamsOutlinedFunction(
    const OMPExecutableDirective &D, const VarDecl *ThreadIDVar,
    OpenMPDirectiveKind InnermostKind, const RegionCodeGenTy &CodeGen) {
  SourceLocation Loc = D.getBeginLoc();

  // Emit target region as a standalone region.
  class NVPTXPrePostActionTy : public PrePostActionTy {
    SourceLocation &Loc;

  public:
    NVPTXPrePostActionTy(SourceLocation &Loc) : Loc(Loc) {}
    void Enter(CodeGenFunction &CGF) override {
      static_cast<CGOpenMPRuntimeNVPTX &>(CGF.CGM.getOpenMPRuntime())
          .emitGenericVarsProlog(CGF, Loc);
    }
    void Exit(CodeGenFunction &CGF) override {
      static_cast<CGOpenMPRuntimeNVPTX &>(CGF.CGM.getOpenMPRuntime())
          .emitGenericVarsEpilog(CGF);
    }
  } Action(Loc);
  if (getExecutionMode() != CGOpenMPRuntimeNVPTX::EM_SPMD)
    CodeGen.setAction(Action);
  llvm::Value *OutlinedFunVal = CGOpenMPRuntime::emitTeamsOutlinedFunction(
      D, ThreadIDVar, InnermostKind, CodeGen);
  llvm::Function *OutlinedFun = cast<llvm::Function>(OutlinedFunVal);
  OutlinedFun->removeFnAttr(llvm::Attribute::NoInline);
  OutlinedFun->removeFnAttr(llvm::Attribute::OptimizeNone);
  OutlinedFun->addFnAttr(llvm::Attribute::AlwaysInline);

  return OutlinedFun;
}

void CGOpenMPRuntimeNVPTX::emitGenericVarsProlog(CodeGenFunction &CGF,
                                                 SourceLocation Loc) {
  if (getDataSharingMode(CGM) != CGOpenMPRuntimeNVPTX::Generic)
    return;

  CGBuilderTy &Bld = CGF.Builder;

  const auto I = FunctionGlobalizedDecls.find(CGF.CurFn);
  if (I == FunctionGlobalizedDecls.end())
    return;
  if (const RecordDecl *GlobalizedVarsRecord = I->getSecond().GlobalRecord) {
    QualType RecTy = CGM.getContext().getRecordType(GlobalizedVarsRecord);

    // Recover pointer to this function's global record. The runtime will
    // handle the specifics of the allocation of the memory.
    // Use actual memory size of the record including the padding
    // for alignment purposes.
    unsigned Alignment =
        CGM.getContext().getTypeAlignInChars(RecTy).getQuantity();
    unsigned GlobalRecordSize =
        CGM.getContext().getTypeSizeInChars(RecTy).getQuantity();
    GlobalRecordSize = llvm::alignTo(GlobalRecordSize, Alignment);

    llvm::Value *GlobalRecCastAddr;
    if (getExecutionMode() == CGOpenMPRuntimeNVPTX::EM_Unknown) {
      llvm::BasicBlock *ExitBB = CGF.createBasicBlock(".exit");
      llvm::BasicBlock *SPMDBB = CGF.createBasicBlock(".spmd");
      llvm::BasicBlock *NonSPMDBB = CGF.createBasicBlock(".non-spmd");
      llvm::Value *IsSPMD = Bld.CreateIsNotNull(CGF.EmitNounwindRuntimeCall(
          createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_is_spmd_exec_mode)));
      Bld.CreateCondBr(IsSPMD, SPMDBB, NonSPMDBB);
      // There is no need to emit line number for unconditional branch.
      (void)ApplyDebugLocation::CreateEmpty(CGF);
      CGF.EmitBlock(SPMDBB);
      Address RecPtr = CGF.CreateMemTemp(RecTy, "_local_stack");
      CGF.EmitBranch(ExitBB);
      // There is no need to emit line number for unconditional branch.
      (void)ApplyDebugLocation::CreateEmpty(CGF);
      CGF.EmitBlock(NonSPMDBB);
      // TODO: allow the usage of shared memory to be controlled by
      // the user, for now, default to global.
      llvm::Value *GlobalRecordSizeArg[] = {
          llvm::ConstantInt::get(CGM.SizeTy, GlobalRecordSize),
          CGF.Builder.getInt16(/*UseSharedMemory=*/0)};
      llvm::Value *GlobalRecValue =
          CGF.EmitRuntimeCall(createNVPTXRuntimeFunction(
                                  OMPRTL_NVPTX__kmpc_data_sharing_push_stack),
                              GlobalRecordSizeArg);
      GlobalRecCastAddr = Bld.CreatePointerBitCastOrAddrSpaceCast(
          GlobalRecValue, CGF.ConvertTypeForMem(RecTy)->getPointerTo());
      CGF.EmitBlock(ExitBB);
      auto *Phi = Bld.CreatePHI(GlobalRecCastAddr->getType(),
                                /*NumReservedValues=*/2, "_select_stack");
      Phi->addIncoming(RecPtr.getPointer(), SPMDBB);
      Phi->addIncoming(GlobalRecCastAddr, NonSPMDBB);
      GlobalRecCastAddr = Phi;
      I->getSecond().GlobalRecordAddr = Phi;
      I->getSecond().IsInSPMDModeFlag = IsSPMD;
    } else {
      assert(getExecutionMode() == CGOpenMPRuntimeNVPTX::EM_NonSPMD &&
             "Expected Non-SPMD construct.");
      // TODO: allow the usage of shared memory to be controlled by
      // the user, for now, default to global.
      llvm::Value *GlobalRecordSizeArg[] = {
          llvm::ConstantInt::get(CGM.SizeTy, GlobalRecordSize),
          CGF.Builder.getInt16(/*UseSharedMemory=*/0)};
      llvm::Value *GlobalRecValue =
          CGF.EmitRuntimeCall(createNVPTXRuntimeFunction(
                                  OMPRTL_NVPTX__kmpc_data_sharing_push_stack),
                              GlobalRecordSizeArg);
      GlobalRecCastAddr = Bld.CreatePointerBitCastOrAddrSpaceCast(
          GlobalRecValue, CGF.ConvertTypeForMem(RecTy)->getPointerTo());
      I->getSecond().GlobalRecordAddr = GlobalRecValue;
      I->getSecond().IsInSPMDModeFlag = nullptr;
    }
    LValue Base =
        CGF.MakeNaturalAlignPointeeAddrLValue(GlobalRecCastAddr, RecTy);

    // Emit the "global alloca" which is a GEP from the global declaration
    // record using the pointer returned by the runtime.
    for (auto &Rec : I->getSecond().LocalVarData) {
      bool EscapedParam = I->getSecond().EscapedParameters.count(Rec.first);
      llvm::Value *ParValue;
      if (EscapedParam) {
        const auto *VD = cast<VarDecl>(Rec.first);
        LValue ParLVal =
            CGF.MakeAddrLValue(CGF.GetAddrOfLocalVar(VD), VD->getType());
        ParValue = CGF.EmitLoadOfScalar(ParLVal, Loc);
      }
      const FieldDecl *FD = Rec.second.first;
      LValue VarAddr = CGF.EmitLValueForField(Base, FD);
      Rec.second.second = VarAddr.getAddress();
      if (EscapedParam) {
        const auto *VD = cast<VarDecl>(Rec.first);
        CGF.EmitStoreOfScalar(ParValue, VarAddr);
        I->getSecond().MappedParams->setVarAddr(CGF, VD, VarAddr.getAddress());
      }
    }
  }
  for (const ValueDecl *VD : I->getSecond().EscapedVariableLengthDecls) {
    // Recover pointer to this function's global record. The runtime will
    // handle the specifics of the allocation of the memory.
    // Use actual memory size of the record including the padding
    // for alignment purposes.
    CGBuilderTy &Bld = CGF.Builder;
    llvm::Value *Size = CGF.getTypeSize(VD->getType());
    CharUnits Align = CGM.getContext().getDeclAlign(VD);
    Size = Bld.CreateNUWAdd(
        Size, llvm::ConstantInt::get(CGF.SizeTy, Align.getQuantity() - 1));
    llvm::Value *AlignVal =
        llvm::ConstantInt::get(CGF.SizeTy, Align.getQuantity());
    Size = Bld.CreateUDiv(Size, AlignVal);
    Size = Bld.CreateNUWMul(Size, AlignVal);
    // TODO: allow the usage of shared memory to be controlled by
    // the user, for now, default to global.
    llvm::Value *GlobalRecordSizeArg[] = {
        Size, CGF.Builder.getInt16(/*UseSharedMemory=*/0)};
    llvm::Value *GlobalRecValue = CGF.EmitRuntimeCall(
        createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_data_sharing_push_stack),
        GlobalRecordSizeArg);
    llvm::Value *GlobalRecCastAddr = Bld.CreatePointerBitCastOrAddrSpaceCast(
        GlobalRecValue, CGF.ConvertTypeForMem(VD->getType())->getPointerTo());
    LValue Base = CGF.MakeAddrLValue(GlobalRecCastAddr, VD->getType(),
                                     CGM.getContext().getDeclAlign(VD),
                                     AlignmentSource::Decl);
    I->getSecond().MappedParams->setVarAddr(CGF, cast<VarDecl>(VD),
                                            Base.getAddress());
    I->getSecond().EscapedVariableLengthDeclsAddrs.emplace_back(GlobalRecValue);
  }
  I->getSecond().MappedParams->apply(CGF);
}

void CGOpenMPRuntimeNVPTX::emitGenericVarsEpilog(CodeGenFunction &CGF) {
  if (getDataSharingMode(CGM) != CGOpenMPRuntimeNVPTX::Generic)
    return;

  const auto I = FunctionGlobalizedDecls.find(CGF.CurFn);
  if (I != FunctionGlobalizedDecls.end()) {
    I->getSecond().MappedParams->restore(CGF);
    if (!CGF.HaveInsertPoint())
      return;
    for (llvm::Value *Addr :
         llvm::reverse(I->getSecond().EscapedVariableLengthDeclsAddrs)) {
      CGF.EmitRuntimeCall(
          createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_data_sharing_pop_stack),
          Addr);
    }
    if (I->getSecond().GlobalRecordAddr) {
      if (getExecutionMode() == CGOpenMPRuntimeNVPTX::EM_Unknown) {
        CGBuilderTy &Bld = CGF.Builder;
        llvm::BasicBlock *ExitBB = CGF.createBasicBlock(".exit");
        llvm::BasicBlock *NonSPMDBB = CGF.createBasicBlock(".non-spmd");
        Bld.CreateCondBr(I->getSecond().IsInSPMDModeFlag, ExitBB, NonSPMDBB);
        // There is no need to emit line number for unconditional branch.
        (void)ApplyDebugLocation::CreateEmpty(CGF);
        CGF.EmitBlock(NonSPMDBB);
        CGF.EmitRuntimeCall(
            createNVPTXRuntimeFunction(
                OMPRTL_NVPTX__kmpc_data_sharing_pop_stack),
            CGF.EmitCastToVoidPtr(I->getSecond().GlobalRecordAddr));
        CGF.EmitBlock(ExitBB);
      } else {
        assert(getExecutionMode() == CGOpenMPRuntimeNVPTX::EM_NonSPMD &&
               "Expected Non-SPMD mode.");
        CGF.EmitRuntimeCall(createNVPTXRuntimeFunction(
                                OMPRTL_NVPTX__kmpc_data_sharing_pop_stack),
                            I->getSecond().GlobalRecordAddr);
      }
    }
  }
}

void CGOpenMPRuntimeNVPTX::emitTeamsCall(CodeGenFunction &CGF,
                                         const OMPExecutableDirective &D,
                                         SourceLocation Loc,
                                         llvm::Value *OutlinedFn,
                                         ArrayRef<llvm::Value *> CapturedVars) {
  if (!CGF.HaveInsertPoint())
    return;

  Address ZeroAddr = CGF.CreateMemTemp(
      CGF.getContext().getIntTypeForBitwidth(/*DestWidth=*/32, /*Signed=*/1),
      /*Name*/ ".zero.addr");
  CGF.InitTempAlloca(ZeroAddr, CGF.Builder.getInt32(/*C*/ 0));
  llvm::SmallVector<llvm::Value *, 16> OutlinedFnArgs;
  OutlinedFnArgs.push_back(emitThreadIDAddress(CGF, Loc).getPointer());
  OutlinedFnArgs.push_back(ZeroAddr.getPointer());
  OutlinedFnArgs.append(CapturedVars.begin(), CapturedVars.end());
  emitOutlinedFunctionCall(CGF, Loc, OutlinedFn, OutlinedFnArgs);
}

void CGOpenMPRuntimeNVPTX::emitParallelCall(
    CodeGenFunction &CGF, SourceLocation Loc, llvm::Value *OutlinedFn,
    ArrayRef<llvm::Value *> CapturedVars, const Expr *IfCond) {
  if (!CGF.HaveInsertPoint())
    return;

  if (getExecutionMode() == CGOpenMPRuntimeNVPTX::EM_SPMD)
    emitSPMDParallelCall(CGF, Loc, OutlinedFn, CapturedVars, IfCond);
  else
    emitNonSPMDParallelCall(CGF, Loc, OutlinedFn, CapturedVars, IfCond);
}

void CGOpenMPRuntimeNVPTX::emitNonSPMDParallelCall(
    CodeGenFunction &CGF, SourceLocation Loc, llvm::Value *OutlinedFn,
    ArrayRef<llvm::Value *> CapturedVars, const Expr *IfCond) {
  llvm::Function *Fn = cast<llvm::Function>(OutlinedFn);

  // Force inline this outlined function at its call site.
  Fn->setLinkage(llvm::GlobalValue::InternalLinkage);

  Address ZeroAddr = CGF.CreateMemTemp(CGF.getContext().getIntTypeForBitwidth(
                                           /*DestWidth=*/32, /*Signed=*/1),
                                       ".zero.addr");
  CGF.InitTempAlloca(ZeroAddr, CGF.Builder.getInt32(/*C*/ 0));
  // ThreadId for serialized parallels is 0.
  Address ThreadIDAddr = ZeroAddr;
  auto &&CodeGen = [this, Fn, CapturedVars, Loc, ZeroAddr, &ThreadIDAddr](
                       CodeGenFunction &CGF, PrePostActionTy &Action) {
    Action.Enter(CGF);

    llvm::SmallVector<llvm::Value *, 16> OutlinedFnArgs;
    OutlinedFnArgs.push_back(ThreadIDAddr.getPointer());
    OutlinedFnArgs.push_back(ZeroAddr.getPointer());
    OutlinedFnArgs.append(CapturedVars.begin(), CapturedVars.end());
    emitOutlinedFunctionCall(CGF, Loc, Fn, OutlinedFnArgs);
  };
  auto &&SeqGen = [this, &CodeGen, Loc](CodeGenFunction &CGF,
                                        PrePostActionTy &) {

    RegionCodeGenTy RCG(CodeGen);
    llvm::Value *RTLoc = emitUpdateLocation(CGF, Loc);
    llvm::Value *ThreadID = getThreadID(CGF, Loc);
    llvm::Value *Args[] = {RTLoc, ThreadID};

    NVPTXActionTy Action(
        createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_serialized_parallel),
        Args,
        createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_end_serialized_parallel),
        Args);
    RCG.setAction(Action);
    RCG(CGF);
  };

  auto &&L0ParallelGen = [this, CapturedVars, Fn](CodeGenFunction &CGF,
                                                  PrePostActionTy &Action) {
    CGBuilderTy &Bld = CGF.Builder;
    llvm::Function *WFn = WrapperFunctionsMap[Fn];
    assert(WFn && "Wrapper function does not exist!");
    llvm::Value *ID = Bld.CreateBitOrPointerCast(WFn, CGM.Int8PtrTy);

    // Prepare for parallel region. Indicate the outlined function.
    llvm::Value *Args[] = {ID, /*RequiresOMPRuntime=*/Bld.getInt16(1)};
    CGF.EmitRuntimeCall(
        createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_kernel_prepare_parallel),
        Args);

    // Create a private scope that will globalize the arguments
    // passed from the outside of the target region.
    CodeGenFunction::OMPPrivateScope PrivateArgScope(CGF);

    // There's somehting to share.
    if (!CapturedVars.empty()) {
      // Prepare for parallel region. Indicate the outlined function.
      Address SharedArgs =
          CGF.CreateDefaultAlignTempAlloca(CGF.VoidPtrPtrTy, "shared_arg_refs");
      llvm::Value *SharedArgsPtr = SharedArgs.getPointer();

      llvm::Value *DataSharingArgs[] = {
          SharedArgsPtr,
          llvm::ConstantInt::get(CGM.SizeTy, CapturedVars.size())};
      CGF.EmitRuntimeCall(createNVPTXRuntimeFunction(
                              OMPRTL_NVPTX__kmpc_begin_sharing_variables),
                          DataSharingArgs);

      // Store variable address in a list of references to pass to workers.
      unsigned Idx = 0;
      ASTContext &Ctx = CGF.getContext();
      Address SharedArgListAddress = CGF.EmitLoadOfPointer(
          SharedArgs, Ctx.getPointerType(Ctx.getPointerType(Ctx.VoidPtrTy))
                          .castAs<PointerType>());
      for (llvm::Value *V : CapturedVars) {
        Address Dst = Bld.CreateConstInBoundsGEP(SharedArgListAddress, Idx,
                                                 CGF.getPointerSize());
        llvm::Value *PtrV;
        if (V->getType()->isIntegerTy())
          PtrV = Bld.CreateIntToPtr(V, CGF.VoidPtrTy);
        else
          PtrV = Bld.CreatePointerBitCastOrAddrSpaceCast(V, CGF.VoidPtrTy);
        CGF.EmitStoreOfScalar(PtrV, Dst, /*Volatile=*/false,
                              Ctx.getPointerType(Ctx.VoidPtrTy));
        ++Idx;
      }
    }

    // Activate workers. This barrier is used by the master to signal
    // work for the workers.
    syncCTAThreads(CGF);

    // OpenMP [2.5, Parallel Construct, p.49]
    // There is an implied barrier at the end of a parallel region. After the
    // end of a parallel region, only the master thread of the team resumes
    // execution of the enclosing task region.
    //
    // The master waits at this barrier until all workers are done.
    syncCTAThreads(CGF);

    if (!CapturedVars.empty())
      CGF.EmitRuntimeCall(
          createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_end_sharing_variables));

    // Remember for post-processing in worker loop.
    Work.emplace_back(WFn);
  };

  auto &&LNParallelGen = [this, Loc, &SeqGen, &L0ParallelGen, &CodeGen,
                          &ThreadIDAddr](CodeGenFunction &CGF,
                                         PrePostActionTy &Action) {
    RegionCodeGenTy RCG(CodeGen);
    if (IsInParallelRegion) {
      SeqGen(CGF, Action);
    } else if (IsInTargetMasterThreadRegion) {
      L0ParallelGen(CGF, Action);
    } else if (getExecutionMode() == CGOpenMPRuntimeNVPTX::EM_NonSPMD) {
      RCG(CGF);
    } else {
      // Check for master and then parallelism:
      // if (__kmpc_is_spmd_exec_mode() || __kmpc_parallel_level(loc, gtid)) {
      //  Serialized execution.
      // } else if (master) {
      //   Worker call.
      // } else {
      //   Outlined function call.
      // }
      CGBuilderTy &Bld = CGF.Builder;
      llvm::BasicBlock *ExitBB = CGF.createBasicBlock(".exit");
      llvm::BasicBlock *SeqBB = CGF.createBasicBlock(".sequential");
      llvm::BasicBlock *ParallelCheckBB = CGF.createBasicBlock(".parcheck");
      llvm::BasicBlock *MasterCheckBB = CGF.createBasicBlock(".mastercheck");
      llvm::Value *IsSPMD = Bld.CreateIsNotNull(CGF.EmitNounwindRuntimeCall(
          createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_is_spmd_exec_mode)));
      Bld.CreateCondBr(IsSPMD, SeqBB, ParallelCheckBB);
      // There is no need to emit line number for unconditional branch.
      (void)ApplyDebugLocation::CreateEmpty(CGF);
      CGF.EmitBlock(ParallelCheckBB);
      llvm::Value *RTLoc = emitUpdateLocation(CGF, Loc);
      llvm::Value *ThreadID = getThreadID(CGF, Loc);
      llvm::Value *PL = CGF.EmitRuntimeCall(
          createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_parallel_level),
          {RTLoc, ThreadID});
      llvm::Value *Res = Bld.CreateIsNotNull(PL);
      Bld.CreateCondBr(Res, SeqBB, MasterCheckBB);
      CGF.EmitBlock(SeqBB);
      SeqGen(CGF, Action);
      CGF.EmitBranch(ExitBB);
      // There is no need to emit line number for unconditional branch.
      (void)ApplyDebugLocation::CreateEmpty(CGF);
      CGF.EmitBlock(MasterCheckBB);
      llvm::BasicBlock *MasterThenBB = CGF.createBasicBlock("master.then");
      llvm::BasicBlock *ElseBlock = CGF.createBasicBlock("omp_if.else");
      llvm::Value *IsMaster =
          Bld.CreateICmpEQ(getNVPTXThreadID(CGF), getMasterThreadID(CGF));
      Bld.CreateCondBr(IsMaster, MasterThenBB, ElseBlock);
      CGF.EmitBlock(MasterThenBB);
      L0ParallelGen(CGF, Action);
      CGF.EmitBranch(ExitBB);
      // There is no need to emit line number for unconditional branch.
      (void)ApplyDebugLocation::CreateEmpty(CGF);
      CGF.EmitBlock(ElseBlock);
      // In the worker need to use the real thread id.
      ThreadIDAddr = emitThreadIDAddress(CGF, Loc);
      RCG(CGF);
      // There is no need to emit line number for unconditional branch.
      (void)ApplyDebugLocation::CreateEmpty(CGF);
      // Emit the continuation block for code after the if.
      CGF.EmitBlock(ExitBB, /*IsFinished=*/true);
    }
  };

  if (IfCond) {
    emitOMPIfClause(CGF, IfCond, LNParallelGen, SeqGen);
  } else {
    CodeGenFunction::RunCleanupsScope Scope(CGF);
    RegionCodeGenTy ThenRCG(LNParallelGen);
    ThenRCG(CGF);
  }
}

void CGOpenMPRuntimeNVPTX::emitSPMDParallelCall(
    CodeGenFunction &CGF, SourceLocation Loc, llvm::Value *OutlinedFn,
    ArrayRef<llvm::Value *> CapturedVars, const Expr *IfCond) {
  // Just call the outlined function to execute the parallel region.
  // OutlinedFn(&GTid, &zero, CapturedStruct);
  //
  llvm::SmallVector<llvm::Value *, 16> OutlinedFnArgs;

  Address ZeroAddr = CGF.CreateMemTemp(CGF.getContext().getIntTypeForBitwidth(
                                           /*DestWidth=*/32, /*Signed=*/1),
                                       ".zero.addr");
  CGF.InitTempAlloca(ZeroAddr, CGF.Builder.getInt32(/*C*/ 0));
  // ThreadId for serialized parallels is 0.
  Address ThreadIDAddr = ZeroAddr;
  auto &&CodeGen = [this, OutlinedFn, CapturedVars, Loc, ZeroAddr,
                    &ThreadIDAddr](CodeGenFunction &CGF,
                                   PrePostActionTy &Action) {
    Action.Enter(CGF);

    llvm::SmallVector<llvm::Value *, 16> OutlinedFnArgs;
    OutlinedFnArgs.push_back(ThreadIDAddr.getPointer());
    OutlinedFnArgs.push_back(ZeroAddr.getPointer());
    OutlinedFnArgs.append(CapturedVars.begin(), CapturedVars.end());
    emitOutlinedFunctionCall(CGF, Loc, OutlinedFn, OutlinedFnArgs);
  };
  auto &&SeqGen = [this, &CodeGen, Loc](CodeGenFunction &CGF,
                                        PrePostActionTy &) {

    RegionCodeGenTy RCG(CodeGen);
    llvm::Value *RTLoc = emitUpdateLocation(CGF, Loc);
    llvm::Value *ThreadID = getThreadID(CGF, Loc);
    llvm::Value *Args[] = {RTLoc, ThreadID};

    NVPTXActionTy Action(
        createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_serialized_parallel),
        Args,
        createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_end_serialized_parallel),
        Args);
    RCG.setAction(Action);
    RCG(CGF);
  };

  if (IsInTargetMasterThreadRegion) {
    // In the worker need to use the real thread id.
    ThreadIDAddr = emitThreadIDAddress(CGF, Loc);
    RegionCodeGenTy RCG(CodeGen);
    RCG(CGF);
  } else {
    // If we are not in the target region, it is definitely L2 parallelism or
    // more, because for SPMD mode we always has L1 parallel level, sowe don't
    // need to check for orphaned directives.
    RegionCodeGenTy RCG(SeqGen);
    RCG(CGF);
  }
}

void CGOpenMPRuntimeNVPTX::emitCriticalRegion(
    CodeGenFunction &CGF, StringRef CriticalName,
    const RegionCodeGenTy &CriticalOpGen, SourceLocation Loc,
    const Expr *Hint) {
  llvm::BasicBlock *LoopBB = CGF.createBasicBlock("omp.critical.loop");
  llvm::BasicBlock *TestBB = CGF.createBasicBlock("omp.critical.test");
  llvm::BasicBlock *SyncBB = CGF.createBasicBlock("omp.critical.sync");
  llvm::BasicBlock *BodyBB = CGF.createBasicBlock("omp.critical.body");
  llvm::BasicBlock *ExitBB = CGF.createBasicBlock("omp.critical.exit");

  // Fetch team-local id of the thread.
  llvm::Value *ThreadID = getNVPTXThreadID(CGF);

  // Get the width of the team.
  llvm::Value *TeamWidth = getNVPTXNumThreads(CGF);

  // Initialize the counter variable for the loop.
  QualType Int32Ty =
      CGF.getContext().getIntTypeForBitwidth(/*DestWidth=*/32, /*Signed=*/0);
  Address Counter = CGF.CreateMemTemp(Int32Ty, "critical_counter");
  LValue CounterLVal = CGF.MakeAddrLValue(Counter, Int32Ty);
  CGF.EmitStoreOfScalar(llvm::Constant::getNullValue(CGM.Int32Ty), CounterLVal,
                        /*isInit=*/true);

  // Block checks if loop counter exceeds upper bound.
  CGF.EmitBlock(LoopBB);
  llvm::Value *CounterVal = CGF.EmitLoadOfScalar(CounterLVal, Loc);
  llvm::Value *CmpLoopBound = CGF.Builder.CreateICmpSLT(CounterVal, TeamWidth);
  CGF.Builder.CreateCondBr(CmpLoopBound, TestBB, ExitBB);

  // Block tests which single thread should execute region, and which threads
  // should go straight to synchronisation point.
  CGF.EmitBlock(TestBB);
  CounterVal = CGF.EmitLoadOfScalar(CounterLVal, Loc);
  llvm::Value *CmpThreadToCounter =
      CGF.Builder.CreateICmpEQ(ThreadID, CounterVal);
  CGF.Builder.CreateCondBr(CmpThreadToCounter, BodyBB, SyncBB);

  // Block emits the body of the critical region.
  CGF.EmitBlock(BodyBB);

  // Output the critical statement.
  CriticalOpGen(CGF);

  // After the body surrounded by the critical region, the single executing
  // thread will jump to the synchronisation point.
  // Block waits for all threads in current team to finish then increments the
  // counter variable and returns to the loop.
  CGF.EmitBlock(SyncBB);
  getNVPTXCTABarrier(CGF);

  llvm::Value *IncCounterVal =
      CGF.Builder.CreateNSWAdd(CounterVal, CGF.Builder.getInt32(1));
  CGF.EmitStoreOfScalar(IncCounterVal, CounterLVal);
  CGF.EmitBranch(LoopBB);

  // Block that is reached when  all threads in the team complete the region.
  CGF.EmitBlock(ExitBB, /*IsFinished=*/true);
}

/// Cast value to the specified type.
static llvm::Value *castValueToType(CodeGenFunction &CGF, llvm::Value *Val,
                                    QualType ValTy, QualType CastTy,
                                    SourceLocation Loc) {
  assert(!CGF.getContext().getTypeSizeInChars(CastTy).isZero() &&
         "Cast type must sized.");
  assert(!CGF.getContext().getTypeSizeInChars(ValTy).isZero() &&
         "Val type must sized.");
  llvm::Type *LLVMCastTy = CGF.ConvertTypeForMem(CastTy);
  if (ValTy == CastTy)
    return Val;
  if (CGF.getContext().getTypeSizeInChars(ValTy) ==
      CGF.getContext().getTypeSizeInChars(CastTy))
    return CGF.Builder.CreateBitCast(Val, LLVMCastTy);
  if (CastTy->isIntegerType() && ValTy->isIntegerType())
    return CGF.Builder.CreateIntCast(Val, LLVMCastTy,
                                     CastTy->hasSignedIntegerRepresentation());
  Address CastItem = CGF.CreateMemTemp(CastTy);
  Address ValCastItem = CGF.Builder.CreatePointerBitCastOrAddrSpaceCast(
      CastItem, Val->getType()->getPointerTo(CastItem.getAddressSpace()));
  CGF.EmitStoreOfScalar(Val, ValCastItem, /*Volatile=*/false, ValTy);
  return CGF.EmitLoadOfScalar(CastItem, /*Volatile=*/false, CastTy, Loc);
}

/// This function creates calls to one of two shuffle functions to copy
/// variables between lanes in a warp.
static llvm::Value *createRuntimeShuffleFunction(CodeGenFunction &CGF,
                                                 llvm::Value *Elem,
                                                 QualType ElemType,
                                                 llvm::Value *Offset,
                                                 SourceLocation Loc) {
  CodeGenModule &CGM = CGF.CGM;
  CGBuilderTy &Bld = CGF.Builder;
  CGOpenMPRuntimeNVPTX &RT =
      *(static_cast<CGOpenMPRuntimeNVPTX *>(&CGM.getOpenMPRuntime()));

  CharUnits Size = CGF.getContext().getTypeSizeInChars(ElemType);
  assert(Size.getQuantity() <= 8 &&
         "Unsupported bitwidth in shuffle instruction.");

  OpenMPRTLFunctionNVPTX ShuffleFn = Size.getQuantity() <= 4
                                         ? OMPRTL_NVPTX__kmpc_shuffle_int32
                                         : OMPRTL_NVPTX__kmpc_shuffle_int64;

  // Cast all types to 32- or 64-bit values before calling shuffle routines.
  QualType CastTy = CGF.getContext().getIntTypeForBitwidth(
      Size.getQuantity() <= 4 ? 32 : 64, /*Signed=*/1);
  llvm::Value *ElemCast = castValueToType(CGF, Elem, ElemType, CastTy, Loc);
  llvm::Value *WarpSize =
      Bld.CreateIntCast(getNVPTXWarpSize(CGF), CGM.Int16Ty, /*isSigned=*/true);

  llvm::Value *ShuffledVal = CGF.EmitRuntimeCall(
      RT.createNVPTXRuntimeFunction(ShuffleFn), {ElemCast, Offset, WarpSize});

  return castValueToType(CGF, ShuffledVal, CastTy, ElemType, Loc);
}

static void shuffleAndStore(CodeGenFunction &CGF, Address SrcAddr,
                            Address DestAddr, QualType ElemType,
                            llvm::Value *Offset, SourceLocation Loc) {
  CGBuilderTy &Bld = CGF.Builder;

  CharUnits Size = CGF.getContext().getTypeSizeInChars(ElemType);
  // Create the loop over the big sized data.
  // ptr = (void*)Elem;
  // ptrEnd = (void*) Elem + 1;
  // Step = 8;
  // while (ptr + Step < ptrEnd)
  //   shuffle((int64_t)*ptr);
  // Step = 4;
  // while (ptr + Step < ptrEnd)
  //   shuffle((int32_t)*ptr);
  // ...
  Address ElemPtr = DestAddr;
  Address Ptr = SrcAddr;
  Address PtrEnd = Bld.CreatePointerBitCastOrAddrSpaceCast(
      Bld.CreateConstGEP(SrcAddr, 1, Size), CGF.VoidPtrTy);
  for (int IntSize = 8; IntSize >= 1; IntSize /= 2) {
    if (Size < CharUnits::fromQuantity(IntSize))
      continue;
    QualType IntType = CGF.getContext().getIntTypeForBitwidth(
        CGF.getContext().toBits(CharUnits::fromQuantity(IntSize)),
        /*Signed=*/1);
    llvm::Type *IntTy = CGF.ConvertTypeForMem(IntType);
    Ptr = Bld.CreatePointerBitCastOrAddrSpaceCast(Ptr, IntTy->getPointerTo());
    ElemPtr =
        Bld.CreatePointerBitCastOrAddrSpaceCast(ElemPtr, IntTy->getPointerTo());
    if (Size.getQuantity() / IntSize > 1) {
      llvm::BasicBlock *PreCondBB = CGF.createBasicBlock(".shuffle.pre_cond");
      llvm::BasicBlock *ThenBB = CGF.createBasicBlock(".shuffle.then");
      llvm::BasicBlock *ExitBB = CGF.createBasicBlock(".shuffle.exit");
      llvm::BasicBlock *CurrentBB = Bld.GetInsertBlock();
      CGF.EmitBlock(PreCondBB);
      llvm::PHINode *PhiSrc =
          Bld.CreatePHI(Ptr.getType(), /*NumReservedValues=*/2);
      PhiSrc->addIncoming(Ptr.getPointer(), CurrentBB);
      llvm::PHINode *PhiDest =
          Bld.CreatePHI(ElemPtr.getType(), /*NumReservedValues=*/2);
      PhiDest->addIncoming(ElemPtr.getPointer(), CurrentBB);
      Ptr = Address(PhiSrc, Ptr.getAlignment());
      ElemPtr = Address(PhiDest, ElemPtr.getAlignment());
      llvm::Value *PtrDiff = Bld.CreatePtrDiff(
          PtrEnd.getPointer(), Bld.CreatePointerBitCastOrAddrSpaceCast(
                                   Ptr.getPointer(), CGF.VoidPtrTy));
      Bld.CreateCondBr(Bld.CreateICmpSGT(PtrDiff, Bld.getInt64(IntSize - 1)),
                       ThenBB, ExitBB);
      CGF.EmitBlock(ThenBB);
      llvm::Value *Res = createRuntimeShuffleFunction(
          CGF, CGF.EmitLoadOfScalar(Ptr, /*Volatile=*/false, IntType, Loc),
          IntType, Offset, Loc);
      CGF.EmitStoreOfScalar(Res, ElemPtr, /*Volatile=*/false, IntType);
      Ptr = Bld.CreateConstGEP(Ptr, 1, CharUnits::fromQuantity(IntSize));
      ElemPtr =
          Bld.CreateConstGEP(ElemPtr, 1, CharUnits::fromQuantity(IntSize));
      PhiSrc->addIncoming(Ptr.getPointer(), ThenBB);
      PhiDest->addIncoming(ElemPtr.getPointer(), ThenBB);
      CGF.EmitBranch(PreCondBB);
      CGF.EmitBlock(ExitBB);
    } else {
      llvm::Value *Res = createRuntimeShuffleFunction(
          CGF, CGF.EmitLoadOfScalar(Ptr, /*Volatile=*/false, IntType, Loc),
          IntType, Offset, Loc);
      CGF.EmitStoreOfScalar(Res, ElemPtr, /*Volatile=*/false, IntType);
      Ptr = Bld.CreateConstGEP(Ptr, 1, CharUnits::fromQuantity(IntSize));
      ElemPtr =
          Bld.CreateConstGEP(ElemPtr, 1, CharUnits::fromQuantity(IntSize));
    }
    Size = Size % IntSize;
  }
}

namespace {
enum CopyAction : unsigned {
  // RemoteLaneToThread: Copy over a Reduce list from a remote lane in
  // the warp using shuffle instructions.
  RemoteLaneToThread,
  // ThreadCopy: Make a copy of a Reduce list on the thread's stack.
  ThreadCopy,
  // ThreadToScratchpad: Copy a team-reduced array to the scratchpad.
  ThreadToScratchpad,
  // ScratchpadToThread: Copy from a scratchpad array in global memory
  // containing team-reduced data to a thread's stack.
  ScratchpadToThread,
};
} // namespace

struct CopyOptionsTy {
  llvm::Value *RemoteLaneOffset;
  llvm::Value *ScratchpadIndex;
  llvm::Value *ScratchpadWidth;
};

/// Emit instructions to copy a Reduce list, which contains partially
/// aggregated values, in the specified direction.
static void emitReductionListCopy(
    CopyAction Action, CodeGenFunction &CGF, QualType ReductionArrayTy,
    ArrayRef<const Expr *> Privates, Address SrcBase, Address DestBase,
    CopyOptionsTy CopyOptions = {nullptr, nullptr, nullptr}) {

  CodeGenModule &CGM = CGF.CGM;
  ASTContext &C = CGM.getContext();
  CGBuilderTy &Bld = CGF.Builder;

  llvm::Value *RemoteLaneOffset = CopyOptions.RemoteLaneOffset;
  llvm::Value *ScratchpadIndex = CopyOptions.ScratchpadIndex;
  llvm::Value *ScratchpadWidth = CopyOptions.ScratchpadWidth;

  // Iterates, element-by-element, through the source Reduce list and
  // make a copy.
  unsigned Idx = 0;
  unsigned Size = Privates.size();
  for (const Expr *Private : Privates) {
    Address SrcElementAddr = Address::invalid();
    Address DestElementAddr = Address::invalid();
    Address DestElementPtrAddr = Address::invalid();
    // Should we shuffle in an element from a remote lane?
    bool ShuffleInElement = false;
    // Set to true to update the pointer in the dest Reduce list to a
    // newly created element.
    bool UpdateDestListPtr = false;
    // Increment the src or dest pointer to the scratchpad, for each
    // new element.
    bool IncrScratchpadSrc = false;
    bool IncrScratchpadDest = false;

    switch (Action) {
    case RemoteLaneToThread: {
      // Step 1.1: Get the address for the src element in the Reduce list.
      Address SrcElementPtrAddr =
          Bld.CreateConstArrayGEP(SrcBase, Idx, CGF.getPointerSize());
      SrcElementAddr = CGF.EmitLoadOfPointer(
          SrcElementPtrAddr,
          C.getPointerType(Private->getType())->castAs<PointerType>());

      // Step 1.2: Create a temporary to store the element in the destination
      // Reduce list.
      DestElementPtrAddr =
          Bld.CreateConstArrayGEP(DestBase, Idx, CGF.getPointerSize());
      DestElementAddr =
          CGF.CreateMemTemp(Private->getType(), ".omp.reduction.element");
      ShuffleInElement = true;
      UpdateDestListPtr = true;
      break;
    }
    case ThreadCopy: {
      // Step 1.1: Get the address for the src element in the Reduce list.
      Address SrcElementPtrAddr =
          Bld.CreateConstArrayGEP(SrcBase, Idx, CGF.getPointerSize());
      SrcElementAddr = CGF.EmitLoadOfPointer(
          SrcElementPtrAddr,
          C.getPointerType(Private->getType())->castAs<PointerType>());

      // Step 1.2: Get the address for dest element.  The destination
      // element has already been created on the thread's stack.
      DestElementPtrAddr =
          Bld.CreateConstArrayGEP(DestBase, Idx, CGF.getPointerSize());
      DestElementAddr = CGF.EmitLoadOfPointer(
          DestElementPtrAddr,
          C.getPointerType(Private->getType())->castAs<PointerType>());
      break;
    }
    case ThreadToScratchpad: {
      // Step 1.1: Get the address for the src element in the Reduce list.
      Address SrcElementPtrAddr =
          Bld.CreateConstArrayGEP(SrcBase, Idx, CGF.getPointerSize());
      SrcElementAddr = CGF.EmitLoadOfPointer(
          SrcElementPtrAddr,
          C.getPointerType(Private->getType())->castAs<PointerType>());

      // Step 1.2: Get the address for dest element:
      // address = base + index * ElementSizeInChars.
      llvm::Value *ElementSizeInChars = CGF.getTypeSize(Private->getType());
      llvm::Value *CurrentOffset =
          Bld.CreateNUWMul(ElementSizeInChars, ScratchpadIndex);
      llvm::Value *ScratchPadElemAbsolutePtrVal =
          Bld.CreateNUWAdd(DestBase.getPointer(), CurrentOffset);
      ScratchPadElemAbsolutePtrVal =
          Bld.CreateIntToPtr(ScratchPadElemAbsolutePtrVal, CGF.VoidPtrTy);
      DestElementAddr = Address(ScratchPadElemAbsolutePtrVal,
                                C.getTypeAlignInChars(Private->getType()));
      IncrScratchpadDest = true;
      break;
    }
    case ScratchpadToThread: {
      // Step 1.1: Get the address for the src element in the scratchpad.
      // address = base + index * ElementSizeInChars.
      llvm::Value *ElementSizeInChars = CGF.getTypeSize(Private->getType());
      llvm::Value *CurrentOffset =
          Bld.CreateNUWMul(ElementSizeInChars, ScratchpadIndex);
      llvm::Value *ScratchPadElemAbsolutePtrVal =
          Bld.CreateNUWAdd(SrcBase.getPointer(), CurrentOffset);
      ScratchPadElemAbsolutePtrVal =
          Bld.CreateIntToPtr(ScratchPadElemAbsolutePtrVal, CGF.VoidPtrTy);
      SrcElementAddr = Address(ScratchPadElemAbsolutePtrVal,
                               C.getTypeAlignInChars(Private->getType()));
      IncrScratchpadSrc = true;

      // Step 1.2: Create a temporary to store the element in the destination
      // Reduce list.
      DestElementPtrAddr =
          Bld.CreateConstArrayGEP(DestBase, Idx, CGF.getPointerSize());
      DestElementAddr =
          CGF.CreateMemTemp(Private->getType(), ".omp.reduction.element");
      UpdateDestListPtr = true;
      break;
    }
    }

    // Regardless of src and dest of copy, we emit the load of src
    // element as this is required in all directions
    SrcElementAddr = Bld.CreateElementBitCast(
        SrcElementAddr, CGF.ConvertTypeForMem(Private->getType()));
    DestElementAddr = Bld.CreateElementBitCast(DestElementAddr,
                                               SrcElementAddr.getElementType());

    // Now that all active lanes have read the element in the
    // Reduce list, shuffle over the value from the remote lane.
    if (ShuffleInElement) {
      shuffleAndStore(CGF, SrcElementAddr, DestElementAddr, Private->getType(),
                      RemoteLaneOffset, Private->getExprLoc());
    } else {
      if (Private->getType()->isScalarType()) {
        llvm::Value *Elem =
            CGF.EmitLoadOfScalar(SrcElementAddr, /*Volatile=*/false,
                                 Private->getType(), Private->getExprLoc());
        // Store the source element value to the dest element address.
        CGF.EmitStoreOfScalar(Elem, DestElementAddr, /*Volatile=*/false,
                              Private->getType());
      } else {
        CGF.EmitAggregateCopy(
            CGF.MakeAddrLValue(DestElementAddr, Private->getType()),
            CGF.MakeAddrLValue(SrcElementAddr, Private->getType()),
            Private->getType(), AggValueSlot::DoesNotOverlap);
      }
    }

    // Step 3.1: Modify reference in dest Reduce list as needed.
    // Modifying the reference in Reduce list to point to the newly
    // created element.  The element is live in the current function
    // scope and that of functions it invokes (i.e., reduce_function).
    // RemoteReduceData[i] = (void*)&RemoteElem
    if (UpdateDestListPtr) {
      CGF.EmitStoreOfScalar(Bld.CreatePointerBitCastOrAddrSpaceCast(
                                DestElementAddr.getPointer(), CGF.VoidPtrTy),
                            DestElementPtrAddr, /*Volatile=*/false,
                            C.VoidPtrTy);
    }

    // Step 4.1: Increment SrcBase/DestBase so that it points to the starting
    // address of the next element in scratchpad memory, unless we're currently
    // processing the last one.  Memory alignment is also taken care of here.
    if ((IncrScratchpadDest || IncrScratchpadSrc) && (Idx + 1 < Size)) {
      llvm::Value *ScratchpadBasePtr =
          IncrScratchpadDest ? DestBase.getPointer() : SrcBase.getPointer();
      llvm::Value *ElementSizeInChars = CGF.getTypeSize(Private->getType());
      ScratchpadBasePtr = Bld.CreateNUWAdd(
          ScratchpadBasePtr,
          Bld.CreateNUWMul(ScratchpadWidth, ElementSizeInChars));

      // Take care of global memory alignment for performance
      ScratchpadBasePtr = Bld.CreateNUWSub(
          ScratchpadBasePtr, llvm::ConstantInt::get(CGM.SizeTy, 1));
      ScratchpadBasePtr = Bld.CreateUDiv(
          ScratchpadBasePtr,
          llvm::ConstantInt::get(CGM.SizeTy, GlobalMemoryAlignment));
      ScratchpadBasePtr = Bld.CreateNUWAdd(
          ScratchpadBasePtr, llvm::ConstantInt::get(CGM.SizeTy, 1));
      ScratchpadBasePtr = Bld.CreateNUWMul(
          ScratchpadBasePtr,
          llvm::ConstantInt::get(CGM.SizeTy, GlobalMemoryAlignment));

      if (IncrScratchpadDest)
        DestBase = Address(ScratchpadBasePtr, CGF.getPointerAlign());
      else /* IncrScratchpadSrc = true */
        SrcBase = Address(ScratchpadBasePtr, CGF.getPointerAlign());
    }

    ++Idx;
  }
}

/// This function emits a helper that loads data from the scratchpad array
/// and (optionally) reduces it with the input operand.
///
///  load_and_reduce(local, scratchpad, index, width, should_reduce)
///  reduce_data remote;
///  for elem in remote:
///    remote.elem = Scratchpad[elem_id][index]
///  if (should_reduce)
///    local = local @ remote
///  else
///    local = remote
static llvm::Value *emitReduceScratchpadFunction(
    CodeGenModule &CGM, ArrayRef<const Expr *> Privates,
    QualType ReductionArrayTy, llvm::Value *ReduceFn, SourceLocation Loc) {
  ASTContext &C = CGM.getContext();
  QualType Int32Ty = C.getIntTypeForBitwidth(32, /*Signed=*/1);

  // Destination of the copy.
  ImplicitParamDecl ReduceListArg(C, /*DC=*/nullptr, Loc, /*Id=*/nullptr,
                                  C.VoidPtrTy, ImplicitParamDecl::Other);
  // Base address of the scratchpad array, with each element storing a
  // Reduce list per team.
  ImplicitParamDecl ScratchPadArg(C, /*DC=*/nullptr, Loc, /*Id=*/nullptr,
                                  C.VoidPtrTy, ImplicitParamDecl::Other);
  // A source index into the scratchpad array.
  ImplicitParamDecl IndexArg(C, /*DC=*/nullptr, Loc, /*Id=*/nullptr, Int32Ty,
                             ImplicitParamDecl::Other);
  // Row width of an element in the scratchpad array, typically
  // the number of teams.
  ImplicitParamDecl WidthArg(C, /*DC=*/nullptr, Loc, /*Id=*/nullptr, Int32Ty,
                             ImplicitParamDecl::Other);
  // If should_reduce == 1, then it's load AND reduce,
  // If should_reduce == 0 (or otherwise), then it only loads (+ copy).
  // The latter case is used for initialization.
  ImplicitParamDecl ShouldReduceArg(C, /*DC=*/nullptr, Loc, /*Id=*/nullptr,
                                    Int32Ty, ImplicitParamDecl::Other);

  FunctionArgList Args;
  Args.push_back(&ReduceListArg);
  Args.push_back(&ScratchPadArg);
  Args.push_back(&IndexArg);
  Args.push_back(&WidthArg);
  Args.push_back(&ShouldReduceArg);

  const CGFunctionInfo &CGFI =
      CGM.getTypes().arrangeBuiltinFunctionDeclaration(C.VoidTy, Args);
  auto *Fn = llvm::Function::Create(
      CGM.getTypes().GetFunctionType(CGFI), llvm::GlobalValue::InternalLinkage,
      "_omp_reduction_load_and_reduce", &CGM.getModule());
  CGM.SetInternalFunctionAttributes(GlobalDecl(), Fn, CGFI);
  Fn->setDoesNotRecurse();
  CodeGenFunction CGF(CGM);
  CGF.StartFunction(GlobalDecl(), C.VoidTy, Fn, CGFI, Args, Loc, Loc);

  CGBuilderTy &Bld = CGF.Builder;

  // Get local Reduce list pointer.
  Address AddrReduceListArg = CGF.GetAddrOfLocalVar(&ReduceListArg);
  Address ReduceListAddr(
      Bld.CreatePointerBitCastOrAddrSpaceCast(
          CGF.EmitLoadOfScalar(AddrReduceListArg, /*Volatile=*/false,
                               C.VoidPtrTy, Loc),
          CGF.ConvertTypeForMem(ReductionArrayTy)->getPointerTo()),
      CGF.getPointerAlign());

  Address AddrScratchPadArg = CGF.GetAddrOfLocalVar(&ScratchPadArg);
  llvm::Value *ScratchPadBase = CGF.EmitLoadOfScalar(
      AddrScratchPadArg, /*Volatile=*/false, C.VoidPtrTy, Loc);

  Address AddrIndexArg = CGF.GetAddrOfLocalVar(&IndexArg);
  llvm::Value *IndexVal = Bld.CreateIntCast(
      CGF.EmitLoadOfScalar(AddrIndexArg, /*Volatile=*/false, Int32Ty, Loc),
      CGM.SizeTy, /*isSigned=*/true);

  Address AddrWidthArg = CGF.GetAddrOfLocalVar(&WidthArg);
  llvm::Value *WidthVal = Bld.CreateIntCast(
      CGF.EmitLoadOfScalar(AddrWidthArg, /*Volatile=*/false, Int32Ty, Loc),
      CGM.SizeTy, /*isSigned=*/true);

  Address AddrShouldReduceArg = CGF.GetAddrOfLocalVar(&ShouldReduceArg);
  llvm::Value *ShouldReduceVal = CGF.EmitLoadOfScalar(
      AddrShouldReduceArg, /*Volatile=*/false, Int32Ty, Loc);

  // The absolute ptr address to the base addr of the next element to copy.
  llvm::Value *CumulativeElemBasePtr =
      Bld.CreatePtrToInt(ScratchPadBase, CGM.SizeTy);
  Address SrcDataAddr(CumulativeElemBasePtr, CGF.getPointerAlign());

  // Create a Remote Reduce list to store the elements read from the
  // scratchpad array.
  Address RemoteReduceList =
      CGF.CreateMemTemp(ReductionArrayTy, ".omp.reduction.remote_red_list");

  // Assemble remote Reduce list from scratchpad array.
  emitReductionListCopy(ScratchpadToThread, CGF, ReductionArrayTy, Privates,
                        SrcDataAddr, RemoteReduceList,
                        {/*RemoteLaneOffset=*/nullptr,
                         /*ScratchpadIndex=*/IndexVal,
                         /*ScratchpadWidth=*/WidthVal});

  llvm::BasicBlock *ThenBB = CGF.createBasicBlock("then");
  llvm::BasicBlock *ElseBB = CGF.createBasicBlock("else");
  llvm::BasicBlock *MergeBB = CGF.createBasicBlock("ifcont");

  llvm::Value *CondReduce = Bld.CreateIsNotNull(ShouldReduceVal);
  Bld.CreateCondBr(CondReduce, ThenBB, ElseBB);

  CGF.EmitBlock(ThenBB);
  // We should reduce with the local Reduce list.
  // reduce_function(LocalReduceList, RemoteReduceList)
  llvm::Value *LocalDataPtr = Bld.CreatePointerBitCastOrAddrSpaceCast(
      ReduceListAddr.getPointer(), CGF.VoidPtrTy);
  llvm::Value *RemoteDataPtr = Bld.CreatePointerBitCastOrAddrSpaceCast(
      RemoteReduceList.getPointer(), CGF.VoidPtrTy);
  CGM.getOpenMPRuntime().emitOutlinedFunctionCall(
      CGF, Loc, ReduceFn, {LocalDataPtr, RemoteDataPtr});
  Bld.CreateBr(MergeBB);

  CGF.EmitBlock(ElseBB);
  // No reduction; just copy:
  // Local Reduce list = Remote Reduce list.
  emitReductionListCopy(ThreadCopy, CGF, ReductionArrayTy, Privates,
                        RemoteReduceList, ReduceListAddr);
  Bld.CreateBr(MergeBB);

  CGF.EmitBlock(MergeBB);

  CGF.FinishFunction();
  return Fn;
}

/// This function emits a helper that stores reduced data from the team
/// master to a scratchpad array in global memory.
///
///  for elem in Reduce List:
///    scratchpad[elem_id][index] = elem
///
static llvm::Value *emitCopyToScratchpad(CodeGenModule &CGM,
                                         ArrayRef<const Expr *> Privates,
                                         QualType ReductionArrayTy,
                                         SourceLocation Loc) {

  ASTContext &C = CGM.getContext();
  QualType Int32Ty = C.getIntTypeForBitwidth(32, /*Signed=*/1);

  // Source of the copy.
  ImplicitParamDecl ReduceListArg(C, /*DC=*/nullptr, Loc, /*Id=*/nullptr,
                                  C.VoidPtrTy, ImplicitParamDecl::Other);
  // Base address of the scratchpad array, with each element storing a
  // Reduce list per team.
  ImplicitParamDecl ScratchPadArg(C, /*DC=*/nullptr, Loc, /*Id=*/nullptr,
                                  C.VoidPtrTy, ImplicitParamDecl::Other);
  // A destination index into the scratchpad array, typically the team
  // identifier.
  ImplicitParamDecl IndexArg(C, /*DC=*/nullptr, Loc, /*Id=*/nullptr, Int32Ty,
                             ImplicitParamDecl::Other);
  // Row width of an element in the scratchpad array, typically
  // the number of teams.
  ImplicitParamDecl WidthArg(C, /*DC=*/nullptr, Loc, /*Id=*/nullptr, Int32Ty,
                             ImplicitParamDecl::Other);

  FunctionArgList Args;
  Args.push_back(&ReduceListArg);
  Args.push_back(&ScratchPadArg);
  Args.push_back(&IndexArg);
  Args.push_back(&WidthArg);

  const CGFunctionInfo &CGFI =
      CGM.getTypes().arrangeBuiltinFunctionDeclaration(C.VoidTy, Args);
  auto *Fn = llvm::Function::Create(
      CGM.getTypes().GetFunctionType(CGFI), llvm::GlobalValue::InternalLinkage,
      "_omp_reduction_copy_to_scratchpad", &CGM.getModule());
  CGM.SetInternalFunctionAttributes(GlobalDecl(), Fn, CGFI);
  Fn->setDoesNotRecurse();
  CodeGenFunction CGF(CGM);
  CGF.StartFunction(GlobalDecl(), C.VoidTy, Fn, CGFI, Args, Loc, Loc);

  CGBuilderTy &Bld = CGF.Builder;

  Address AddrReduceListArg = CGF.GetAddrOfLocalVar(&ReduceListArg);
  Address SrcDataAddr(
      Bld.CreatePointerBitCastOrAddrSpaceCast(
          CGF.EmitLoadOfScalar(AddrReduceListArg, /*Volatile=*/false,
                               C.VoidPtrTy, Loc),
          CGF.ConvertTypeForMem(ReductionArrayTy)->getPointerTo()),
      CGF.getPointerAlign());

  Address AddrScratchPadArg = CGF.GetAddrOfLocalVar(&ScratchPadArg);
  llvm::Value *ScratchPadBase = CGF.EmitLoadOfScalar(
      AddrScratchPadArg, /*Volatile=*/false, C.VoidPtrTy, Loc);

  Address AddrIndexArg = CGF.GetAddrOfLocalVar(&IndexArg);
  llvm::Value *IndexVal = Bld.CreateIntCast(
      CGF.EmitLoadOfScalar(AddrIndexArg, /*Volatile=*/false, Int32Ty, Loc),
      CGF.SizeTy, /*isSigned=*/true);

  Address AddrWidthArg = CGF.GetAddrOfLocalVar(&WidthArg);
  llvm::Value *WidthVal =
      Bld.CreateIntCast(CGF.EmitLoadOfScalar(AddrWidthArg, /*Volatile=*/false,
                                             Int32Ty, SourceLocation()),
                        CGF.SizeTy, /*isSigned=*/true);

  // The absolute ptr address to the base addr of the next element to copy.
  llvm::Value *CumulativeElemBasePtr =
      Bld.CreatePtrToInt(ScratchPadBase, CGM.SizeTy);
  Address DestDataAddr(CumulativeElemBasePtr, CGF.getPointerAlign());

  emitReductionListCopy(ThreadToScratchpad, CGF, ReductionArrayTy, Privates,
                        SrcDataAddr, DestDataAddr,
                        {/*RemoteLaneOffset=*/nullptr,
                         /*ScratchpadIndex=*/IndexVal,
                         /*ScratchpadWidth=*/WidthVal});

  CGF.FinishFunction();
  return Fn;
}

/// This function emits a helper that gathers Reduce lists from the first
/// lane of every active warp to lanes in the first warp.
///
/// void inter_warp_copy_func(void* reduce_data, num_warps)
///   shared smem[warp_size];
///   For all data entries D in reduce_data:
///     If (I am the first lane in each warp)
///       Copy my local D to smem[warp_id]
///     sync
///     if (I am the first warp)
///       Copy smem[thread_id] to my local D
///     sync
static llvm::Value *emitInterWarpCopyFunction(CodeGenModule &CGM,
                                              ArrayRef<const Expr *> Privates,
                                              QualType ReductionArrayTy,
                                              SourceLocation Loc) {
  ASTContext &C = CGM.getContext();
  llvm::Module &M = CGM.getModule();

  // ReduceList: thread local Reduce list.
  // At the stage of the computation when this function is called, partially
  // aggregated values reside in the first lane of every active warp.
  ImplicitParamDecl ReduceListArg(C, /*DC=*/nullptr, Loc, /*Id=*/nullptr,
                                  C.VoidPtrTy, ImplicitParamDecl::Other);
  // NumWarps: number of warps active in the parallel region.  This could
  // be smaller than 32 (max warps in a CTA) for partial block reduction.
  ImplicitParamDecl NumWarpsArg(C, /*DC=*/nullptr, Loc, /*Id=*/nullptr,
                                C.getIntTypeForBitwidth(32, /* Signed */ true),
                                ImplicitParamDecl::Other);
  FunctionArgList Args;
  Args.push_back(&ReduceListArg);
  Args.push_back(&NumWarpsArg);

  const CGFunctionInfo &CGFI =
      CGM.getTypes().arrangeBuiltinFunctionDeclaration(C.VoidTy, Args);
  auto *Fn = llvm::Function::Create(
      CGM.getTypes().GetFunctionType(CGFI), llvm::GlobalValue::InternalLinkage,
      "_omp_reduction_inter_warp_copy_func", &CGM.getModule());
  CGM.SetInternalFunctionAttributes(GlobalDecl(), Fn, CGFI);
  Fn->setDoesNotRecurse();
  CodeGenFunction CGF(CGM);
  CGF.StartFunction(GlobalDecl(), C.VoidTy, Fn, CGFI, Args, Loc, Loc);

  CGBuilderTy &Bld = CGF.Builder;

  // This array is used as a medium to transfer, one reduce element at a time,
  // the data from the first lane of every warp to lanes in the first warp
  // in order to perform the final step of a reduction in a parallel region
  // (reduction across warps).  The array is placed in NVPTX __shared__ memory
  // for reduced latency, as well as to have a distinct copy for concurrently
  // executing target regions.  The array is declared with common linkage so
  // as to be shared across compilation units.
  StringRef TransferMediumName =
      "__openmp_nvptx_data_transfer_temporary_storage";
  llvm::GlobalVariable *TransferMedium =
      M.getGlobalVariable(TransferMediumName);
  if (!TransferMedium) {
    auto *Ty = llvm::ArrayType::get(CGM.Int64Ty, WarpSize);
    unsigned SharedAddressSpace = C.getTargetAddressSpace(LangAS::cuda_shared);
    TransferMedium = new llvm::GlobalVariable(
        M, Ty,
        /*isConstant=*/false, llvm::GlobalVariable::CommonLinkage,
        llvm::Constant::getNullValue(Ty), TransferMediumName,
        /*InsertBefore=*/nullptr, llvm::GlobalVariable::NotThreadLocal,
        SharedAddressSpace);
    CGM.addCompilerUsedGlobal(TransferMedium);
  }

  // Get the CUDA thread id of the current OpenMP thread on the GPU.
  llvm::Value *ThreadID = getNVPTXThreadID(CGF);
  // nvptx_lane_id = nvptx_id % warpsize
  llvm::Value *LaneID = getNVPTXLaneID(CGF);
  // nvptx_warp_id = nvptx_id / warpsize
  llvm::Value *WarpID = getNVPTXWarpID(CGF);

  Address AddrReduceListArg = CGF.GetAddrOfLocalVar(&ReduceListArg);
  Address LocalReduceList(
      Bld.CreatePointerBitCastOrAddrSpaceCast(
          CGF.EmitLoadOfScalar(AddrReduceListArg, /*Volatile=*/false,
                               C.VoidPtrTy, SourceLocation()),
          CGF.ConvertTypeForMem(ReductionArrayTy)->getPointerTo()),
      CGF.getPointerAlign());

  unsigned Idx = 0;
  for (const Expr *Private : Privates) {
    //
    // Warp master copies reduce element to transfer medium in __shared__
    // memory.
    //
    llvm::BasicBlock *ThenBB = CGF.createBasicBlock("then");
    llvm::BasicBlock *ElseBB = CGF.createBasicBlock("else");
    llvm::BasicBlock *MergeBB = CGF.createBasicBlock("ifcont");

    // if (lane_id == 0)
    llvm::Value *IsWarpMaster = Bld.CreateIsNull(LaneID, "warp_master");
    Bld.CreateCondBr(IsWarpMaster, ThenBB, ElseBB);
    CGF.EmitBlock(ThenBB);

    // Reduce element = LocalReduceList[i]
    Address ElemPtrPtrAddr =
        Bld.CreateConstArrayGEP(LocalReduceList, Idx, CGF.getPointerSize());
    llvm::Value *ElemPtrPtr = CGF.EmitLoadOfScalar(
        ElemPtrPtrAddr, /*Volatile=*/false, C.VoidPtrTy, SourceLocation());
    // elemptr = (type[i]*)(elemptrptr)
    Address ElemPtr =
        Address(ElemPtrPtr, C.getTypeAlignInChars(Private->getType()));
    ElemPtr = Bld.CreateElementBitCast(
        ElemPtr, CGF.ConvertTypeForMem(Private->getType()));

    // Get pointer to location in transfer medium.
    // MediumPtr = &medium[warp_id]
    llvm::Value *MediumPtrVal = Bld.CreateInBoundsGEP(
        TransferMedium, {llvm::Constant::getNullValue(CGM.Int64Ty), WarpID});
    Address MediumPtr(MediumPtrVal, C.getTypeAlignInChars(Private->getType()));
    // Casting to actual data type.
    // MediumPtr = (type[i]*)MediumPtrAddr;
    MediumPtr = Bld.CreateElementBitCast(
        MediumPtr, CGF.ConvertTypeForMem(Private->getType()));

    // elem = *elemptr
    //*MediumPtr = elem
    if (Private->getType()->isScalarType()) {
      llvm::Value *Elem = CGF.EmitLoadOfScalar(ElemPtr, /*Volatile=*/false,
                                               Private->getType(), Loc);
      // Store the source element value to the dest element address.
      CGF.EmitStoreOfScalar(Elem, MediumPtr, /*Volatile=*/false,
                            Private->getType());
    } else {
      CGF.EmitAggregateCopy(CGF.MakeAddrLValue(ElemPtr, Private->getType()),
                            CGF.MakeAddrLValue(MediumPtr, Private->getType()),
                            Private->getType(), AggValueSlot::DoesNotOverlap);
    }

    Bld.CreateBr(MergeBB);

    CGF.EmitBlock(ElseBB);
    Bld.CreateBr(MergeBB);

    CGF.EmitBlock(MergeBB);

    Address AddrNumWarpsArg = CGF.GetAddrOfLocalVar(&NumWarpsArg);
    llvm::Value *NumWarpsVal = CGF.EmitLoadOfScalar(
        AddrNumWarpsArg, /*Volatile=*/false, C.IntTy, SourceLocation());

    llvm::Value *NumActiveThreads = Bld.CreateNSWMul(
        NumWarpsVal, getNVPTXWarpSize(CGF), "num_active_threads");
    // named_barrier_sync(ParallelBarrierID, num_active_threads)
    syncParallelThreads(CGF, NumActiveThreads);

    //
    // Warp 0 copies reduce element from transfer medium.
    //
    llvm::BasicBlock *W0ThenBB = CGF.createBasicBlock("then");
    llvm::BasicBlock *W0ElseBB = CGF.createBasicBlock("else");
    llvm::BasicBlock *W0MergeBB = CGF.createBasicBlock("ifcont");

    // Up to 32 threads in warp 0 are active.
    llvm::Value *IsActiveThread =
        Bld.CreateICmpULT(ThreadID, NumWarpsVal, "is_active_thread");
    Bld.CreateCondBr(IsActiveThread, W0ThenBB, W0ElseBB);

    CGF.EmitBlock(W0ThenBB);

    // SrcMediumPtr = &medium[tid]
    llvm::Value *SrcMediumPtrVal = Bld.CreateInBoundsGEP(
        TransferMedium, {llvm::Constant::getNullValue(CGM.Int64Ty), ThreadID});
    Address SrcMediumPtr(SrcMediumPtrVal,
                         C.getTypeAlignInChars(Private->getType()));
    // SrcMediumVal = *SrcMediumPtr;
    SrcMediumPtr = Bld.CreateElementBitCast(
        SrcMediumPtr, CGF.ConvertTypeForMem(Private->getType()));

    // TargetElemPtr = (type[i]*)(SrcDataAddr[i])
    Address TargetElemPtrPtr =
        Bld.CreateConstArrayGEP(LocalReduceList, Idx, CGF.getPointerSize());
    llvm::Value *TargetElemPtrVal = CGF.EmitLoadOfScalar(
        TargetElemPtrPtr, /*Volatile=*/false, C.VoidPtrTy, SourceLocation());
    Address TargetElemPtr =
        Address(TargetElemPtrVal, C.getTypeAlignInChars(Private->getType()));
    TargetElemPtr = Bld.CreateElementBitCast(
        TargetElemPtr, CGF.ConvertTypeForMem(Private->getType()));

    // *TargetElemPtr = SrcMediumVal;
    if (Private->getType()->isScalarType()) {
      llvm::Value *SrcMediumValue = CGF.EmitLoadOfScalar(
          SrcMediumPtr, /*Volatile=*/false, Private->getType(), Loc);
      CGF.EmitStoreOfScalar(SrcMediumValue, TargetElemPtr, /*Volatile=*/false,
                            Private->getType());
    } else {
      CGF.EmitAggregateCopy(
          CGF.MakeAddrLValue(SrcMediumPtr, Private->getType()),
          CGF.MakeAddrLValue(TargetElemPtr, Private->getType()),
          Private->getType(), AggValueSlot::DoesNotOverlap);
    }
    Bld.CreateBr(W0MergeBB);

    CGF.EmitBlock(W0ElseBB);
    Bld.CreateBr(W0MergeBB);

    CGF.EmitBlock(W0MergeBB);

    // While warp 0 copies values from transfer medium, all other warps must
    // wait.
    syncParallelThreads(CGF, NumActiveThreads);
    ++Idx;
  }

  CGF.FinishFunction();
  return Fn;
}

/// Emit a helper that reduces data across two OpenMP threads (lanes)
/// in the same warp.  It uses shuffle instructions to copy over data from
/// a remote lane's stack.  The reduction algorithm performed is specified
/// by the fourth parameter.
///
/// Algorithm Versions.
/// Full Warp Reduce (argument value 0):
///   This algorithm assumes that all 32 lanes are active and gathers
///   data from these 32 lanes, producing a single resultant value.
/// Contiguous Partial Warp Reduce (argument value 1):
///   This algorithm assumes that only a *contiguous* subset of lanes
///   are active.  This happens for the last warp in a parallel region
///   when the user specified num_threads is not an integer multiple of
///   32.  This contiguous subset always starts with the zeroth lane.
/// Partial Warp Reduce (argument value 2):
///   This algorithm gathers data from any number of lanes at any position.
/// All reduced values are stored in the lowest possible lane.  The set
/// of problems every algorithm addresses is a super set of those
/// addressable by algorithms with a lower version number.  Overhead
/// increases as algorithm version increases.
///
/// Terminology
/// Reduce element:
///   Reduce element refers to the individual data field with primitive
///   data types to be combined and reduced across threads.
/// Reduce list:
///   Reduce list refers to a collection of local, thread-private
///   reduce elements.
/// Remote Reduce list:
///   Remote Reduce list refers to a collection of remote (relative to
///   the current thread) reduce elements.
///
/// We distinguish between three states of threads that are important to
/// the implementation of this function.
/// Alive threads:
///   Threads in a warp executing the SIMT instruction, as distinguished from
///   threads that are inactive due to divergent control flow.
/// Active threads:
///   The minimal set of threads that has to be alive upon entry to this
///   function.  The computation is correct iff active threads are alive.
///   Some threads are alive but they are not active because they do not
///   contribute to the computation in any useful manner.  Turning them off
///   may introduce control flow overheads without any tangible benefits.
/// Effective threads:
///   In order to comply with the argument requirements of the shuffle
///   function, we must keep all lanes holding data alive.  But at most
///   half of them perform value aggregation; we refer to this half of
///   threads as effective. The other half is simply handing off their
///   data.
///
/// Procedure
/// Value shuffle:
///   In this step active threads transfer data from higher lane positions
///   in the warp to lower lane positions, creating Remote Reduce list.
/// Value aggregation:
///   In this step, effective threads combine their thread local Reduce list
///   with Remote Reduce list and store the result in the thread local
///   Reduce list.
/// Value copy:
///   In this step, we deal with the assumption made by algorithm 2
///   (i.e. contiguity assumption).  When we have an odd number of lanes
///   active, say 2k+1, only k threads will be effective and therefore k
///   new values will be produced.  However, the Reduce list owned by the
///   (2k+1)th thread is ignored in the value aggregation.  Therefore
///   we copy the Reduce list from the (2k+1)th lane to (k+1)th lane so
///   that the contiguity assumption still holds.
static llvm::Value *emitShuffleAndReduceFunction(
    CodeGenModule &CGM, ArrayRef<const Expr *> Privates,
    QualType ReductionArrayTy, llvm::Value *ReduceFn, SourceLocation Loc) {
  ASTContext &C = CGM.getContext();

  // Thread local Reduce list used to host the values of data to be reduced.
  ImplicitParamDecl ReduceListArg(C, /*DC=*/nullptr, Loc, /*Id=*/nullptr,
                                  C.VoidPtrTy, ImplicitParamDecl::Other);
  // Current lane id; could be logical.
  ImplicitParamDecl LaneIDArg(C, /*DC=*/nullptr, Loc, /*Id=*/nullptr, C.ShortTy,
                              ImplicitParamDecl::Other);
  // Offset of the remote source lane relative to the current lane.
  ImplicitParamDecl RemoteLaneOffsetArg(C, /*DC=*/nullptr, Loc, /*Id=*/nullptr,
                                        C.ShortTy, ImplicitParamDecl::Other);
  // Algorithm version.  This is expected to be known at compile time.
  ImplicitParamDecl AlgoVerArg(C, /*DC=*/nullptr, Loc, /*Id=*/nullptr,
                               C.ShortTy, ImplicitParamDecl::Other);
  FunctionArgList Args;
  Args.push_back(&ReduceListArg);
  Args.push_back(&LaneIDArg);
  Args.push_back(&RemoteLaneOffsetArg);
  Args.push_back(&AlgoVerArg);

  const CGFunctionInfo &CGFI =
      CGM.getTypes().arrangeBuiltinFunctionDeclaration(C.VoidTy, Args);
  auto *Fn = llvm::Function::Create(
      CGM.getTypes().GetFunctionType(CGFI), llvm::GlobalValue::InternalLinkage,
      "_omp_reduction_shuffle_and_reduce_func", &CGM.getModule());
  CGM.SetInternalFunctionAttributes(GlobalDecl(), Fn, CGFI);
  Fn->setDoesNotRecurse();
  CodeGenFunction CGF(CGM);
  CGF.StartFunction(GlobalDecl(), C.VoidTy, Fn, CGFI, Args, Loc, Loc);

  CGBuilderTy &Bld = CGF.Builder;

  Address AddrReduceListArg = CGF.GetAddrOfLocalVar(&ReduceListArg);
  Address LocalReduceList(
      Bld.CreatePointerBitCastOrAddrSpaceCast(
          CGF.EmitLoadOfScalar(AddrReduceListArg, /*Volatile=*/false,
                               C.VoidPtrTy, SourceLocation()),
          CGF.ConvertTypeForMem(ReductionArrayTy)->getPointerTo()),
      CGF.getPointerAlign());

  Address AddrLaneIDArg = CGF.GetAddrOfLocalVar(&LaneIDArg);
  llvm::Value *LaneIDArgVal = CGF.EmitLoadOfScalar(
      AddrLaneIDArg, /*Volatile=*/false, C.ShortTy, SourceLocation());

  Address AddrRemoteLaneOffsetArg = CGF.GetAddrOfLocalVar(&RemoteLaneOffsetArg);
  llvm::Value *RemoteLaneOffsetArgVal = CGF.EmitLoadOfScalar(
      AddrRemoteLaneOffsetArg, /*Volatile=*/false, C.ShortTy, SourceLocation());

  Address AddrAlgoVerArg = CGF.GetAddrOfLocalVar(&AlgoVerArg);
  llvm::Value *AlgoVerArgVal = CGF.EmitLoadOfScalar(
      AddrAlgoVerArg, /*Volatile=*/false, C.ShortTy, SourceLocation());

  // Create a local thread-private variable to host the Reduce list
  // from a remote lane.
  Address RemoteReduceList =
      CGF.CreateMemTemp(ReductionArrayTy, ".omp.reduction.remote_reduce_list");

  // This loop iterates through the list of reduce elements and copies,
  // element by element, from a remote lane in the warp to RemoteReduceList,
  // hosted on the thread's stack.
  emitReductionListCopy(RemoteLaneToThread, CGF, ReductionArrayTy, Privates,
                        LocalReduceList, RemoteReduceList,
                        {/*RemoteLaneOffset=*/RemoteLaneOffsetArgVal,
                         /*ScratchpadIndex=*/nullptr,
                         /*ScratchpadWidth=*/nullptr});

  // The actions to be performed on the Remote Reduce list is dependent
  // on the algorithm version.
  //
  //  if (AlgoVer==0) || (AlgoVer==1 && (LaneId < Offset)) || (AlgoVer==2 &&
  //  LaneId % 2 == 0 && Offset > 0):
  //    do the reduction value aggregation
  //
  //  The thread local variable Reduce list is mutated in place to host the
  //  reduced data, which is the aggregated value produced from local and
  //  remote lanes.
  //
  //  Note that AlgoVer is expected to be a constant integer known at compile
  //  time.
  //  When AlgoVer==0, the first conjunction evaluates to true, making
  //    the entire predicate true during compile time.
  //  When AlgoVer==1, the second conjunction has only the second part to be
  //    evaluated during runtime.  Other conjunctions evaluates to false
  //    during compile time.
  //  When AlgoVer==2, the third conjunction has only the second part to be
  //    evaluated during runtime.  Other conjunctions evaluates to false
  //    during compile time.
  llvm::Value *CondAlgo0 = Bld.CreateIsNull(AlgoVerArgVal);

  llvm::Value *Algo1 = Bld.CreateICmpEQ(AlgoVerArgVal, Bld.getInt16(1));
  llvm::Value *CondAlgo1 = Bld.CreateAnd(
      Algo1, Bld.CreateICmpULT(LaneIDArgVal, RemoteLaneOffsetArgVal));

  llvm::Value *Algo2 = Bld.CreateICmpEQ(AlgoVerArgVal, Bld.getInt16(2));
  llvm::Value *CondAlgo2 = Bld.CreateAnd(
      Algo2, Bld.CreateIsNull(Bld.CreateAnd(LaneIDArgVal, Bld.getInt16(1))));
  CondAlgo2 = Bld.CreateAnd(
      CondAlgo2, Bld.CreateICmpSGT(RemoteLaneOffsetArgVal, Bld.getInt16(0)));

  llvm::Value *CondReduce = Bld.CreateOr(CondAlgo0, CondAlgo1);
  CondReduce = Bld.CreateOr(CondReduce, CondAlgo2);

  llvm::BasicBlock *ThenBB = CGF.createBasicBlock("then");
  llvm::BasicBlock *ElseBB = CGF.createBasicBlock("else");
  llvm::BasicBlock *MergeBB = CGF.createBasicBlock("ifcont");
  Bld.CreateCondBr(CondReduce, ThenBB, ElseBB);

  CGF.EmitBlock(ThenBB);
  // reduce_function(LocalReduceList, RemoteReduceList)
  llvm::Value *LocalReduceListPtr = Bld.CreatePointerBitCastOrAddrSpaceCast(
      LocalReduceList.getPointer(), CGF.VoidPtrTy);
  llvm::Value *RemoteReduceListPtr = Bld.CreatePointerBitCastOrAddrSpaceCast(
      RemoteReduceList.getPointer(), CGF.VoidPtrTy);
  CGM.getOpenMPRuntime().emitOutlinedFunctionCall(
      CGF, Loc, ReduceFn, {LocalReduceListPtr, RemoteReduceListPtr});
  Bld.CreateBr(MergeBB);

  CGF.EmitBlock(ElseBB);
  Bld.CreateBr(MergeBB);

  CGF.EmitBlock(MergeBB);

  // if (AlgoVer==1 && (LaneId >= Offset)) copy Remote Reduce list to local
  // Reduce list.
  Algo1 = Bld.CreateICmpEQ(AlgoVerArgVal, Bld.getInt16(1));
  llvm::Value *CondCopy = Bld.CreateAnd(
      Algo1, Bld.CreateICmpUGE(LaneIDArgVal, RemoteLaneOffsetArgVal));

  llvm::BasicBlock *CpyThenBB = CGF.createBasicBlock("then");
  llvm::BasicBlock *CpyElseBB = CGF.createBasicBlock("else");
  llvm::BasicBlock *CpyMergeBB = CGF.createBasicBlock("ifcont");
  Bld.CreateCondBr(CondCopy, CpyThenBB, CpyElseBB);

  CGF.EmitBlock(CpyThenBB);
  emitReductionListCopy(ThreadCopy, CGF, ReductionArrayTy, Privates,
                        RemoteReduceList, LocalReduceList);
  Bld.CreateBr(CpyMergeBB);

  CGF.EmitBlock(CpyElseBB);
  Bld.CreateBr(CpyMergeBB);

  CGF.EmitBlock(CpyMergeBB);

  CGF.FinishFunction();
  return Fn;
}

///
/// Design of OpenMP reductions on the GPU
///
/// Consider a typical OpenMP program with one or more reduction
/// clauses:
///
/// float foo;
/// double bar;
/// #pragma omp target teams distribute parallel for \
///             reduction(+:foo) reduction(*:bar)
/// for (int i = 0; i < N; i++) {
///   foo += A[i]; bar *= B[i];
/// }
///
/// where 'foo' and 'bar' are reduced across all OpenMP threads in
/// all teams.  In our OpenMP implementation on the NVPTX device an
/// OpenMP team is mapped to a CUDA threadblock and OpenMP threads
/// within a team are mapped to CUDA threads within a threadblock.
/// Our goal is to efficiently aggregate values across all OpenMP
/// threads such that:
///
///   - the compiler and runtime are logically concise, and
///   - the reduction is performed efficiently in a hierarchical
///     manner as follows: within OpenMP threads in the same warp,
///     across warps in a threadblock, and finally across teams on
///     the NVPTX device.
///
/// Introduction to Decoupling
///
/// We would like to decouple the compiler and the runtime so that the
/// latter is ignorant of the reduction variables (number, data types)
/// and the reduction operators.  This allows a simpler interface
/// and implementation while still attaining good performance.
///
/// Pseudocode for the aforementioned OpenMP program generated by the
/// compiler is as follows:
///
/// 1. Create private copies of reduction variables on each OpenMP
///    thread: 'foo_private', 'bar_private'
/// 2. Each OpenMP thread reduces the chunk of 'A' and 'B' assigned
///    to it and writes the result in 'foo_private' and 'bar_private'
///    respectively.
/// 3. Call the OpenMP runtime on the GPU to reduce within a team
///    and store the result on the team master:
///
///     __kmpc_nvptx_parallel_reduce_nowait(...,
///        reduceData, shuffleReduceFn, interWarpCpyFn)
///
///     where:
///       struct ReduceData {
///         double *foo;
///         double *bar;
///       } reduceData
///       reduceData.foo = &foo_private
///       reduceData.bar = &bar_private
///
///     'shuffleReduceFn' and 'interWarpCpyFn' are pointers to two
///     auxiliary functions generated by the compiler that operate on
///     variables of type 'ReduceData'.  They aid the runtime perform
///     algorithmic steps in a data agnostic manner.
///
///     'shuffleReduceFn' is a pointer to a function that reduces data
///     of type 'ReduceData' across two OpenMP threads (lanes) in the
///     same warp.  It takes the following arguments as input:
///
///     a. variable of type 'ReduceData' on the calling lane,
///     b. its lane_id,
///     c. an offset relative to the current lane_id to generate a
///        remote_lane_id.  The remote lane contains the second
///        variable of type 'ReduceData' that is to be reduced.
///     d. an algorithm version parameter determining which reduction
///        algorithm to use.
///
///     'shuffleReduceFn' retrieves data from the remote lane using
///     efficient GPU shuffle intrinsics and reduces, using the
///     algorithm specified by the 4th parameter, the two operands
///     element-wise.  The result is written to the first operand.
///
///     Different reduction algorithms are implemented in different
///     runtime functions, all calling 'shuffleReduceFn' to perform
///     the essential reduction step.  Therefore, based on the 4th
///     parameter, this function behaves slightly differently to
///     cooperate with the runtime to ensure correctness under
///     different circumstances.
///
///     'InterWarpCpyFn' is a pointer to a function that transfers
///     reduced variables across warps.  It tunnels, through CUDA
///     shared memory, the thread-private data of type 'ReduceData'
///     from lane 0 of each warp to a lane in the first warp.
/// 4. Call the OpenMP runtime on the GPU to reduce across teams.
///    The last team writes the global reduced value to memory.
///
///     ret = __kmpc_nvptx_teams_reduce_nowait(...,
///             reduceData, shuffleReduceFn, interWarpCpyFn,
///             scratchpadCopyFn, loadAndReduceFn)
///
///     'scratchpadCopyFn' is a helper that stores reduced
///     data from the team master to a scratchpad array in
///     global memory.
///
///     'loadAndReduceFn' is a helper that loads data from
///     the scratchpad array and reduces it with the input
///     operand.
///
///     These compiler generated functions hide address
///     calculation and alignment information from the runtime.
/// 5. if ret == 1:
///     The team master of the last team stores the reduced
///     result to the globals in memory.
///     foo += reduceData.foo; bar *= reduceData.bar
///
///
/// Warp Reduction Algorithms
///
/// On the warp level, we have three algorithms implemented in the
/// OpenMP runtime depending on the number of active lanes:
///
/// Full Warp Reduction
///
/// The reduce algorithm within a warp where all lanes are active
/// is implemented in the runtime as follows:
///
/// full_warp_reduce(void *reduce_data,
///                  kmp_ShuffleReductFctPtr ShuffleReduceFn) {
///   for (int offset = WARPSIZE/2; offset > 0; offset /= 2)
///     ShuffleReduceFn(reduce_data, 0, offset, 0);
/// }
///
/// The algorithm completes in log(2, WARPSIZE) steps.
///
/// 'ShuffleReduceFn' is used here with lane_id set to 0 because it is
/// not used therefore we save instructions by not retrieving lane_id
/// from the corresponding special registers.  The 4th parameter, which
/// represents the version of the algorithm being used, is set to 0 to
/// signify full warp reduction.
///
/// In this version, 'ShuffleReduceFn' behaves, per element, as follows:
///
/// #reduce_elem refers to an element in the local lane's data structure
/// #remote_elem is retrieved from a remote lane
/// remote_elem = shuffle_down(reduce_elem, offset, WARPSIZE);
/// reduce_elem = reduce_elem REDUCE_OP remote_elem;
///
/// Contiguous Partial Warp Reduction
///
/// This reduce algorithm is used within a warp where only the first
/// 'n' (n <= WARPSIZE) lanes are active.  It is typically used when the
/// number of OpenMP threads in a parallel region is not a multiple of
/// WARPSIZE.  The algorithm is implemented in the runtime as follows:
///
/// void
/// contiguous_partial_reduce(void *reduce_data,
///                           kmp_ShuffleReductFctPtr ShuffleReduceFn,
///                           int size, int lane_id) {
///   int curr_size;
///   int offset;
///   curr_size = size;
///   mask = curr_size/2;
///   while (offset>0) {
///     ShuffleReduceFn(reduce_data, lane_id, offset, 1);
///     curr_size = (curr_size+1)/2;
///     offset = curr_size/2;
///   }
/// }
///
/// In this version, 'ShuffleReduceFn' behaves, per element, as follows:
///
/// remote_elem = shuffle_down(reduce_elem, offset, WARPSIZE);
/// if (lane_id < offset)
///     reduce_elem = reduce_elem REDUCE_OP remote_elem
/// else
///     reduce_elem = remote_elem
///
/// This algorithm assumes that the data to be reduced are located in a
/// contiguous subset of lanes starting from the first.  When there is
/// an odd number of active lanes, the data in the last lane is not
/// aggregated with any other lane's dat but is instead copied over.
///
/// Dispersed Partial Warp Reduction
///
/// This algorithm is used within a warp when any discontiguous subset of
/// lanes are active.  It is used to implement the reduction operation
/// across lanes in an OpenMP simd region or in a nested parallel region.
///
/// void
/// dispersed_partial_reduce(void *reduce_data,
///                          kmp_ShuffleReductFctPtr ShuffleReduceFn) {
///   int size, remote_id;
///   int logical_lane_id = number_of_active_lanes_before_me() * 2;
///   do {
///       remote_id = next_active_lane_id_right_after_me();
///       # the above function returns 0 of no active lane
///       # is present right after the current lane.
///       size = number_of_active_lanes_in_this_warp();
///       logical_lane_id /= 2;
///       ShuffleReduceFn(reduce_data, logical_lane_id,
///                       remote_id-1-threadIdx.x, 2);
///   } while (logical_lane_id % 2 == 0 && size > 1);
/// }
///
/// There is no assumption made about the initial state of the reduction.
/// Any number of lanes (>=1) could be active at any position.  The reduction
/// result is returned in the first active lane.
///
/// In this version, 'ShuffleReduceFn' behaves, per element, as follows:
///
/// remote_elem = shuffle_down(reduce_elem, offset, WARPSIZE);
/// if (lane_id % 2 == 0 && offset > 0)
///     reduce_elem = reduce_elem REDUCE_OP remote_elem
/// else
///     reduce_elem = remote_elem
///
///
/// Intra-Team Reduction
///
/// This function, as implemented in the runtime call
/// '__kmpc_nvptx_parallel_reduce_nowait', aggregates data across OpenMP
/// threads in a team.  It first reduces within a warp using the
/// aforementioned algorithms.  We then proceed to gather all such
/// reduced values at the first warp.
///
/// The runtime makes use of the function 'InterWarpCpyFn', which copies
/// data from each of the "warp master" (zeroth lane of each warp, where
/// warp-reduced data is held) to the zeroth warp.  This step reduces (in
/// a mathematical sense) the problem of reduction across warp masters in
/// a block to the problem of warp reduction.
///
///
/// Inter-Team Reduction
///
/// Once a team has reduced its data to a single value, it is stored in
/// a global scratchpad array.  Since each team has a distinct slot, this
/// can be done without locking.
///
/// The last team to write to the scratchpad array proceeds to reduce the
/// scratchpad array.  One or more workers in the last team use the helper
/// 'loadAndReduceDataFn' to load and reduce values from the array, i.e.,
/// the k'th worker reduces every k'th element.
///
/// Finally, a call is made to '__kmpc_nvptx_parallel_reduce_nowait' to
/// reduce across workers and compute a globally reduced value.
///
void CGOpenMPRuntimeNVPTX::emitReduction(
    CodeGenFunction &CGF, SourceLocation Loc, ArrayRef<const Expr *> Privates,
    ArrayRef<const Expr *> LHSExprs, ArrayRef<const Expr *> RHSExprs,
    ArrayRef<const Expr *> ReductionOps, ReductionOptionsTy Options) {
  if (!CGF.HaveInsertPoint())
    return;

  bool ParallelReduction = isOpenMPParallelDirective(Options.ReductionKind);
  bool TeamsReduction = isOpenMPTeamsDirective(Options.ReductionKind);
  bool SimdReduction = isOpenMPSimdDirective(Options.ReductionKind);
  assert((TeamsReduction || ParallelReduction || SimdReduction) &&
         "Invalid reduction selection in emitReduction.");

  if (Options.SimpleReduction) {
    CGOpenMPRuntime::emitReduction(CGF, Loc, Privates, LHSExprs, RHSExprs,
                                   ReductionOps, Options);
    return;
  }

  ASTContext &C = CGM.getContext();

  // 1. Build a list of reduction variables.
  // void *RedList[<n>] = {<ReductionVars>[0], ..., <ReductionVars>[<n>-1]};
  auto Size = RHSExprs.size();
  for (const Expr *E : Privates) {
    if (E->getType()->isVariablyModifiedType())
      // Reserve place for array size.
      ++Size;
  }
  llvm::APInt ArraySize(/*unsigned int numBits=*/32, Size);
  QualType ReductionArrayTy =
      C.getConstantArrayType(C.VoidPtrTy, ArraySize, ArrayType::Normal,
                             /*IndexTypeQuals=*/0);
  Address ReductionList =
      CGF.CreateMemTemp(ReductionArrayTy, ".omp.reduction.red_list");
  auto IPriv = Privates.begin();
  unsigned Idx = 0;
  for (unsigned I = 0, E = RHSExprs.size(); I < E; ++I, ++IPriv, ++Idx) {
    Address Elem = CGF.Builder.CreateConstArrayGEP(ReductionList, Idx,
                                                   CGF.getPointerSize());
    CGF.Builder.CreateStore(
        CGF.Builder.CreatePointerBitCastOrAddrSpaceCast(
            CGF.EmitLValue(RHSExprs[I]).getPointer(), CGF.VoidPtrTy),
        Elem);
    if ((*IPriv)->getType()->isVariablyModifiedType()) {
      // Store array size.
      ++Idx;
      Elem = CGF.Builder.CreateConstArrayGEP(ReductionList, Idx,
                                             CGF.getPointerSize());
      llvm::Value *Size = CGF.Builder.CreateIntCast(
          CGF.getVLASize(
                 CGF.getContext().getAsVariableArrayType((*IPriv)->getType()))
              .NumElts,
          CGF.SizeTy, /*isSigned=*/false);
      CGF.Builder.CreateStore(CGF.Builder.CreateIntToPtr(Size, CGF.VoidPtrTy),
                              Elem);
    }
  }

  // 2. Emit reduce_func().
  llvm::Value *ReductionFn = emitReductionFunction(
      CGM, Loc, CGF.ConvertTypeForMem(ReductionArrayTy)->getPointerTo(),
      Privates, LHSExprs, RHSExprs, ReductionOps);

  // 4. Build res = __kmpc_reduce{_nowait}(<gtid>, <n>, sizeof(RedList),
  // RedList, shuffle_reduce_func, interwarp_copy_func);
  llvm::Value *ThreadId = getThreadID(CGF, Loc);
  llvm::Value *ReductionArrayTySize = CGF.getTypeSize(ReductionArrayTy);
  llvm::Value *RL = CGF.Builder.CreatePointerBitCastOrAddrSpaceCast(
      ReductionList.getPointer(), CGF.VoidPtrTy);

  llvm::Value *ShuffleAndReduceFn = emitShuffleAndReduceFunction(
      CGM, Privates, ReductionArrayTy, ReductionFn, Loc);
  llvm::Value *InterWarpCopyFn =
      emitInterWarpCopyFunction(CGM, Privates, ReductionArrayTy, Loc);

  llvm::Value *Args[] = {ThreadId,
                         CGF.Builder.getInt32(RHSExprs.size()),
                         ReductionArrayTySize,
                         RL,
                         ShuffleAndReduceFn,
                         InterWarpCopyFn};

  llvm::Value *Res = nullptr;
  if (ParallelReduction)
    Res = CGF.EmitRuntimeCall(
        createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_parallel_reduce_nowait),
        Args);
  else if (SimdReduction)
    Res = CGF.EmitRuntimeCall(
        createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_simd_reduce_nowait),
        Args);

  if (TeamsReduction) {
    llvm::Value *ScratchPadCopyFn =
        emitCopyToScratchpad(CGM, Privates, ReductionArrayTy, Loc);
    llvm::Value *LoadAndReduceFn = emitReduceScratchpadFunction(
        CGM, Privates, ReductionArrayTy, ReductionFn, Loc);

    llvm::Value *Args[] = {ThreadId,
                           CGF.Builder.getInt32(RHSExprs.size()),
                           ReductionArrayTySize,
                           RL,
                           ShuffleAndReduceFn,
                           InterWarpCopyFn,
                           ScratchPadCopyFn,
                           LoadAndReduceFn};
    Res = CGF.EmitRuntimeCall(
        createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_teams_reduce_nowait),
        Args);
  }

  // 5. Build switch(res)
  llvm::BasicBlock *DefaultBB = CGF.createBasicBlock(".omp.reduction.default");
  llvm::SwitchInst *SwInst =
      CGF.Builder.CreateSwitch(Res, DefaultBB, /*NumCases=*/1);

  // 6. Build case 1: where we have reduced values in the master
  //    thread in each team.
  //    __kmpc_end_reduce{_nowait}(<gtid>);
  //    break;
  llvm::BasicBlock *Case1BB = CGF.createBasicBlock(".omp.reduction.case1");
  SwInst->addCase(CGF.Builder.getInt32(1), Case1BB);
  CGF.EmitBlock(Case1BB);

  // Add emission of __kmpc_end_reduce{_nowait}(<gtid>);
  llvm::Value *EndArgs[] = {ThreadId};
  auto &&CodeGen = [Privates, LHSExprs, RHSExprs, ReductionOps,
                    this](CodeGenFunction &CGF, PrePostActionTy &Action) {
    auto IPriv = Privates.begin();
    auto ILHS = LHSExprs.begin();
    auto IRHS = RHSExprs.begin();
    for (const Expr *E : ReductionOps) {
      emitSingleReductionCombiner(CGF, E, *IPriv, cast<DeclRefExpr>(*ILHS),
                                  cast<DeclRefExpr>(*IRHS));
      ++IPriv;
      ++ILHS;
      ++IRHS;
    }
  };
  RegionCodeGenTy RCG(CodeGen);
  NVPTXActionTy Action(
      nullptr, llvm::None,
      createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_end_reduce_nowait),
      EndArgs);
  RCG.setAction(Action);
  RCG(CGF);
  CGF.EmitBranch(DefaultBB);
  CGF.EmitBlock(DefaultBB, /*IsFinished=*/true);
}

const VarDecl *
CGOpenMPRuntimeNVPTX::translateParameter(const FieldDecl *FD,
                                         const VarDecl *NativeParam) const {
  if (!NativeParam->getType()->isReferenceType())
    return NativeParam;
  QualType ArgType = NativeParam->getType();
  QualifierCollector QC;
  const Type *NonQualTy = QC.strip(ArgType);
  QualType PointeeTy = cast<ReferenceType>(NonQualTy)->getPointeeType();
  if (const auto *Attr = FD->getAttr<OMPCaptureKindAttr>()) {
    if (Attr->getCaptureKind() == OMPC_map) {
      PointeeTy = CGM.getContext().getAddrSpaceQualType(PointeeTy,
                                                        LangAS::opencl_global);
    }
  }
  ArgType = CGM.getContext().getPointerType(PointeeTy);
  QC.addRestrict();
  enum { NVPTX_local_addr = 5 };
  QC.addAddressSpace(getLangASFromTargetAS(NVPTX_local_addr));
  ArgType = QC.apply(CGM.getContext(), ArgType);
  if (isa<ImplicitParamDecl>(NativeParam))
    return ImplicitParamDecl::Create(
        CGM.getContext(), /*DC=*/nullptr, NativeParam->getLocation(),
        NativeParam->getIdentifier(), ArgType, ImplicitParamDecl::Other);
  return ParmVarDecl::Create(
      CGM.getContext(),
      const_cast<DeclContext *>(NativeParam->getDeclContext()),
      NativeParam->getBeginLoc(), NativeParam->getLocation(),
      NativeParam->getIdentifier(), ArgType,
      /*TInfo=*/nullptr, SC_None, /*DefArg=*/nullptr);
}

Address
CGOpenMPRuntimeNVPTX::getParameterAddress(CodeGenFunction &CGF,
                                          const VarDecl *NativeParam,
                                          const VarDecl *TargetParam) const {
  assert(NativeParam != TargetParam &&
         NativeParam->getType()->isReferenceType() &&
         "Native arg must not be the same as target arg.");
  Address LocalAddr = CGF.GetAddrOfLocalVar(TargetParam);
  QualType NativeParamType = NativeParam->getType();
  QualifierCollector QC;
  const Type *NonQualTy = QC.strip(NativeParamType);
  QualType NativePointeeTy = cast<ReferenceType>(NonQualTy)->getPointeeType();
  unsigned NativePointeeAddrSpace =
      CGF.getContext().getTargetAddressSpace(NativePointeeTy);
  QualType TargetTy = TargetParam->getType();
  llvm::Value *TargetAddr = CGF.EmitLoadOfScalar(
      LocalAddr, /*Volatile=*/false, TargetTy, SourceLocation());
  // First cast to generic.
  TargetAddr = CGF.Builder.CreatePointerBitCastOrAddrSpaceCast(
      TargetAddr, TargetAddr->getType()->getPointerElementType()->getPointerTo(
                      /*AddrSpace=*/0));
  // Cast from generic to native address space.
  TargetAddr = CGF.Builder.CreatePointerBitCastOrAddrSpaceCast(
      TargetAddr, TargetAddr->getType()->getPointerElementType()->getPointerTo(
                      NativePointeeAddrSpace));
  Address NativeParamAddr = CGF.CreateMemTemp(NativeParamType);
  CGF.EmitStoreOfScalar(TargetAddr, NativeParamAddr, /*Volatile=*/false,
                        NativeParamType);
  return NativeParamAddr;
}

void CGOpenMPRuntimeNVPTX::emitOutlinedFunctionCall(
    CodeGenFunction &CGF, SourceLocation Loc, llvm::Value *OutlinedFn,
    ArrayRef<llvm::Value *> Args) const {
  SmallVector<llvm::Value *, 4> TargetArgs;
  TargetArgs.reserve(Args.size());
  auto *FnType =
      cast<llvm::FunctionType>(OutlinedFn->getType()->getPointerElementType());
  for (unsigned I = 0, E = Args.size(); I < E; ++I) {
    if (FnType->isVarArg() && FnType->getNumParams() <= I) {
      TargetArgs.append(std::next(Args.begin(), I), Args.end());
      break;
    }
    llvm::Type *TargetType = FnType->getParamType(I);
    llvm::Value *NativeArg = Args[I];
    if (!TargetType->isPointerTy()) {
      TargetArgs.emplace_back(NativeArg);
      continue;
    }
    llvm::Value *TargetArg = CGF.Builder.CreatePointerBitCastOrAddrSpaceCast(
        NativeArg,
        NativeArg->getType()->getPointerElementType()->getPointerTo());
    TargetArgs.emplace_back(
        CGF.Builder.CreatePointerBitCastOrAddrSpaceCast(TargetArg, TargetType));
  }
  CGOpenMPRuntime::emitOutlinedFunctionCall(CGF, Loc, OutlinedFn, TargetArgs);
}

/// Emit function which wraps the outline parallel region
/// and controls the arguments which are passed to this function.
/// The wrapper ensures that the outlined function is called
/// with the correct arguments when data is shared.
llvm::Function *CGOpenMPRuntimeNVPTX::createParallelDataSharingWrapper(
    llvm::Function *OutlinedParallelFn, const OMPExecutableDirective &D) {
  ASTContext &Ctx = CGM.getContext();
  const auto &CS = *D.getCapturedStmt(OMPD_parallel);

  // Create a function that takes as argument the source thread.
  FunctionArgList WrapperArgs;
  QualType Int16QTy =
      Ctx.getIntTypeForBitwidth(/*DestWidth=*/16, /*Signed=*/false);
  QualType Int32QTy =
      Ctx.getIntTypeForBitwidth(/*DestWidth=*/32, /*Signed=*/false);
  ImplicitParamDecl ParallelLevelArg(Ctx, /*DC=*/nullptr, D.getBeginLoc(),
                                     /*Id=*/nullptr, Int16QTy,
                                     ImplicitParamDecl::Other);
  ImplicitParamDecl WrapperArg(Ctx, /*DC=*/nullptr, D.getBeginLoc(),
                               /*Id=*/nullptr, Int32QTy,
                               ImplicitParamDecl::Other);
  WrapperArgs.emplace_back(&ParallelLevelArg);
  WrapperArgs.emplace_back(&WrapperArg);

  const CGFunctionInfo &CGFI =
      CGM.getTypes().arrangeBuiltinFunctionDeclaration(Ctx.VoidTy, WrapperArgs);

  auto *Fn = llvm::Function::Create(
      CGM.getTypes().GetFunctionType(CGFI), llvm::GlobalValue::InternalLinkage,
      Twine(OutlinedParallelFn->getName(), "_wrapper"), &CGM.getModule());
  CGM.SetInternalFunctionAttributes(GlobalDecl(), Fn, CGFI);
  Fn->setLinkage(llvm::GlobalValue::InternalLinkage);
  Fn->setDoesNotRecurse();

  CodeGenFunction CGF(CGM, /*suppressNewContext=*/true);
  CGF.StartFunction(GlobalDecl(), Ctx.VoidTy, Fn, CGFI, WrapperArgs,
                    D.getBeginLoc(), D.getBeginLoc());

  const auto *RD = CS.getCapturedRecordDecl();
  auto CurField = RD->field_begin();

  Address ZeroAddr = CGF.CreateMemTemp(
      CGF.getContext().getIntTypeForBitwidth(/*DestWidth=*/32, /*Signed=*/1),
      /*Name*/ ".zero.addr");
  CGF.InitTempAlloca(ZeroAddr, CGF.Builder.getInt32(/*C*/ 0));
  // Get the array of arguments.
  SmallVector<llvm::Value *, 8> Args;

  Args.emplace_back(CGF.GetAddrOfLocalVar(&WrapperArg).getPointer());
  Args.emplace_back(ZeroAddr.getPointer());

  CGBuilderTy &Bld = CGF.Builder;
  auto CI = CS.capture_begin();

  // Use global memory for data sharing.
  // Handle passing of global args to workers.
  Address GlobalArgs =
      CGF.CreateDefaultAlignTempAlloca(CGF.VoidPtrPtrTy, "global_args");
  llvm::Value *GlobalArgsPtr = GlobalArgs.getPointer();
  llvm::Value *DataSharingArgs[] = {GlobalArgsPtr};
  CGF.EmitRuntimeCall(
      createNVPTXRuntimeFunction(OMPRTL_NVPTX__kmpc_get_shared_variables),
      DataSharingArgs);

  // Retrieve the shared variables from the list of references returned
  // by the runtime. Pass the variables to the outlined function.
  Address SharedArgListAddress = Address::invalid();
  if (CS.capture_size() > 0 ||
      isOpenMPLoopBoundSharingDirective(D.getDirectiveKind())) {
    SharedArgListAddress = CGF.EmitLoadOfPointer(
        GlobalArgs, CGF.getContext()
                        .getPointerType(CGF.getContext().getPointerType(
                            CGF.getContext().VoidPtrTy))
                        .castAs<PointerType>());
  }
  unsigned Idx = 0;
  if (isOpenMPLoopBoundSharingDirective(D.getDirectiveKind())) {
    Address Src = Bld.CreateConstInBoundsGEP(SharedArgListAddress, Idx,
                                             CGF.getPointerSize());
    Address TypedAddress = Bld.CreatePointerBitCastOrAddrSpaceCast(
        Src, CGF.SizeTy->getPointerTo());
    llvm::Value *LB = CGF.EmitLoadOfScalar(
        TypedAddress,
        /*Volatile=*/false,
        CGF.getContext().getPointerType(CGF.getContext().getSizeType()),
        cast<OMPLoopDirective>(D).getLowerBoundVariable()->getExprLoc());
    Args.emplace_back(LB);
    ++Idx;
    Src = Bld.CreateConstInBoundsGEP(SharedArgListAddress, Idx,
                                     CGF.getPointerSize());
    TypedAddress = Bld.CreatePointerBitCastOrAddrSpaceCast(
        Src, CGF.SizeTy->getPointerTo());
    llvm::Value *UB = CGF.EmitLoadOfScalar(
        TypedAddress,
        /*Volatile=*/false,
        CGF.getContext().getPointerType(CGF.getContext().getSizeType()),
        cast<OMPLoopDirective>(D).getUpperBoundVariable()->getExprLoc());
    Args.emplace_back(UB);
    ++Idx;
  }
  if (CS.capture_size() > 0) {
    ASTContext &CGFContext = CGF.getContext();
    for (unsigned I = 0, E = CS.capture_size(); I < E; ++I, ++CI, ++CurField) {
      QualType ElemTy = CurField->getType();
      Address Src = Bld.CreateConstInBoundsGEP(SharedArgListAddress, I + Idx,
                                               CGF.getPointerSize());
      Address TypedAddress = Bld.CreatePointerBitCastOrAddrSpaceCast(
          Src, CGF.ConvertTypeForMem(CGFContext.getPointerType(ElemTy)));
      llvm::Value *Arg = CGF.EmitLoadOfScalar(TypedAddress,
                                              /*Volatile=*/false,
                                              CGFContext.getPointerType(ElemTy),
                                              CI->getLocation());
      if (CI->capturesVariableByCopy() &&
          !CI->getCapturedVar()->getType()->isAnyPointerType()) {
        Arg = castValueToType(CGF, Arg, ElemTy, CGFContext.getUIntPtrType(),
                              CI->getLocation());
      }
      Args.emplace_back(Arg);
    }
  }

  emitOutlinedFunctionCall(CGF, D.getBeginLoc(), OutlinedParallelFn, Args);
  CGF.FinishFunction();
  return Fn;
}

void CGOpenMPRuntimeNVPTX::emitFunctionProlog(CodeGenFunction &CGF,
                                              const Decl *D) {
  if (getDataSharingMode(CGM) != CGOpenMPRuntimeNVPTX::Generic)
    return;

  assert(D && "Expected function or captured|block decl.");
  assert(FunctionGlobalizedDecls.count(CGF.CurFn) == 0 &&
         "Function is registered already.");
  const Stmt *Body = nullptr;
  bool NeedToDelayGlobalization = false;
  if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
    Body = FD->getBody();
  } else if (const auto *BD = dyn_cast<BlockDecl>(D)) {
    Body = BD->getBody();
  } else if (const auto *CD = dyn_cast<CapturedDecl>(D)) {
    Body = CD->getBody();
    NeedToDelayGlobalization = CGF.CapturedStmtInfo->getKind() == CR_OpenMP;
  }
  if (!Body)
    return;
  CheckVarsEscapingDeclContext VarChecker(CGF);
  VarChecker.Visit(Body);
  const RecordDecl *GlobalizedVarsRecord = VarChecker.getGlobalizedRecord();
  ArrayRef<const ValueDecl *> EscapedVariableLengthDecls =
      VarChecker.getEscapedVariableLengthDecls();
  if (!GlobalizedVarsRecord && EscapedVariableLengthDecls.empty())
    return;
  auto I = FunctionGlobalizedDecls.try_emplace(CGF.CurFn).first;
  I->getSecond().MappedParams =
      llvm::make_unique<CodeGenFunction::OMPMapVars>();
  I->getSecond().GlobalRecord = GlobalizedVarsRecord;
  I->getSecond().EscapedParameters.insert(
      VarChecker.getEscapedParameters().begin(),
      VarChecker.getEscapedParameters().end());
  I->getSecond().EscapedVariableLengthDecls.append(
      EscapedVariableLengthDecls.begin(), EscapedVariableLengthDecls.end());
  DeclToAddrMapTy &Data = I->getSecond().LocalVarData;
  for (const ValueDecl *VD : VarChecker.getEscapedDecls()) {
    assert(VD->isCanonicalDecl() && "Expected canonical declaration");
    const FieldDecl *FD = VarChecker.getFieldForGlobalizedVar(VD);
    Data.insert(std::make_pair(VD, std::make_pair(FD, Address::invalid())));
  }
  if (!NeedToDelayGlobalization) {
    emitGenericVarsProlog(CGF, D->getBeginLoc());
    struct GlobalizationScope final : EHScopeStack::Cleanup {
      GlobalizationScope() = default;

      void Emit(CodeGenFunction &CGF, Flags flags) override {
        static_cast<CGOpenMPRuntimeNVPTX &>(CGF.CGM.getOpenMPRuntime())
            .emitGenericVarsEpilog(CGF);
      }
    };
    CGF.EHStack.pushCleanup<GlobalizationScope>(NormalAndEHCleanup);
  }
}

Address CGOpenMPRuntimeNVPTX::getAddressOfLocalVariable(CodeGenFunction &CGF,
                                                        const VarDecl *VD) {
  if (getDataSharingMode(CGM) != CGOpenMPRuntimeNVPTX::Generic)
    return Address::invalid();

  VD = VD->getCanonicalDecl();
  auto I = FunctionGlobalizedDecls.find(CGF.CurFn);
  if (I == FunctionGlobalizedDecls.end())
    return Address::invalid();
  auto VDI = I->getSecond().LocalVarData.find(VD);
  if (VDI != I->getSecond().LocalVarData.end())
    return VDI->second.second;
  if (VD->hasAttrs()) {
    for (specific_attr_iterator<OMPReferencedVarAttr> IT(VD->attr_begin()),
         E(VD->attr_end());
         IT != E; ++IT) {
      auto VDI = I->getSecond().LocalVarData.find(
          cast<VarDecl>(cast<DeclRefExpr>(IT->getRef())->getDecl())
              ->getCanonicalDecl());
      if (VDI != I->getSecond().LocalVarData.end())
        return VDI->second.second;
    }
  }
  return Address::invalid();
}

void CGOpenMPRuntimeNVPTX::functionFinished(CodeGenFunction &CGF) {
  FunctionGlobalizedDecls.erase(CGF.CurFn);
  CGOpenMPRuntime::functionFinished(CGF);
}