clang/lib/CodeGen/CGOpenMPRuntime.h

//===----- CGOpenMPRuntime.h - Interface to OpenMP Runtimes -----*- C++ -*-===//
//
//                     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.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_LIB_CODEGEN_CGOPENMPRUNTIME_H
#define LLVM_CLANG_LIB_CODEGEN_CGOPENMPRUNTIME_H

#include "clang/AST/Type.h"
#include "clang/Basic/OpenMPKinds.h"
#include "clang/Basic/SourceLocation.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/IR/ValueHandle.h"

namespace llvm {
class ArrayType;
class Constant;
class Function;
class FunctionType;
class GlobalVariable;
class StructType;
class Type;
class Value;
} // namespace llvm

namespace clang {
class Expr;
class OMPExecutableDirective;
class VarDecl;

namespace CodeGen {

class CodeGenFunction;
class CodeGenModule;

typedef llvm::function_ref<void(CodeGenFunction &)> RegionCodeGenTy;

class CGOpenMPRuntime {
private:
  enum OpenMPRTLFunction {
    /// \brief Call to void __kmpc_fork_call(ident_t *loc, kmp_int32 argc,
    /// kmpc_micro microtask, ...);
    OMPRTL__kmpc_fork_call,
    /// \brief Call to void *__kmpc_threadprivate_cached(ident_t *loc,
    /// kmp_int32 global_tid, void *data, size_t size, void ***cache);
    OMPRTL__kmpc_threadprivate_cached,
    /// \brief Call to void __kmpc_threadprivate_register( ident_t *,
    /// void *data, kmpc_ctor ctor, kmpc_cctor cctor, kmpc_dtor dtor);
    OMPRTL__kmpc_threadprivate_register,
    // Call to __kmpc_int32 kmpc_global_thread_num(ident_t *loc);
    OMPRTL__kmpc_global_thread_num,
    // Call to void __kmpc_critical(ident_t *loc, kmp_int32 global_tid,
    // kmp_critical_name *crit);
    OMPRTL__kmpc_critical,
    // Call to void __kmpc_end_critical(ident_t *loc, kmp_int32 global_tid,
    // kmp_critical_name *crit);
    OMPRTL__kmpc_end_critical,
    // Call to kmp_int32 __kmpc_cancel_barrier(ident_t *loc, kmp_int32
    // global_tid);
    OMPRTL__kmpc_cancel_barrier,
    // Call to void __kmpc_for_static_fini(ident_t *loc, kmp_int32 global_tid);
    OMPRTL__kmpc_for_static_fini,
    // Call to void __kmpc_serialized_parallel(ident_t *loc, kmp_int32
    // global_tid);
    OMPRTL__kmpc_serialized_parallel,
    // Call to void __kmpc_end_serialized_parallel(ident_t *loc, kmp_int32
    // global_tid);
    OMPRTL__kmpc_end_serialized_parallel,
    // Call to void __kmpc_push_num_threads(ident_t *loc, kmp_int32 global_tid,
    // kmp_int32 num_threads);
    OMPRTL__kmpc_push_num_threads,
    // Call to void __kmpc_flush(ident_t *loc);
    OMPRTL__kmpc_flush,
    // Call to kmp_int32 __kmpc_master(ident_t *, kmp_int32 global_tid);
    OMPRTL__kmpc_master,
    // Call to void __kmpc_end_master(ident_t *, kmp_int32 global_tid);
    OMPRTL__kmpc_end_master,
    // Call to kmp_int32 __kmpc_omp_taskyield(ident_t *, kmp_int32 global_tid,
    // int end_part);
    OMPRTL__kmpc_omp_taskyield,
    // Call to kmp_int32 __kmpc_single(ident_t *, kmp_int32 global_tid);
    OMPRTL__kmpc_single,
    // Call to void __kmpc_end_single(ident_t *, kmp_int32 global_tid);
    OMPRTL__kmpc_end_single,
    // Call to kmp_task_t * __kmpc_omp_task_alloc(ident_t *, kmp_int32 gtid,
    // kmp_int32 flags, size_t sizeof_kmp_task_t, size_t sizeof_shareds,
    // kmp_routine_entry_t *task_entry);
    OMPRTL__kmpc_omp_task_alloc,
    // Call to kmp_int32 __kmpc_omp_task(ident_t *, kmp_int32 gtid, kmp_task_t *
    // new_task);
    OMPRTL__kmpc_omp_task,
    // Call to void __kmpc_copyprivate(ident_t *loc, kmp_int32 global_tid,
    // kmp_int32 cpy_size, void *cpy_data, void(*cpy_func)(void *, void *),
    // kmp_int32 didit);
    OMPRTL__kmpc_copyprivate,
    // Call to kmp_int32 __kmpc_reduce(ident_t *loc, kmp_int32 global_tid,
    // kmp_int32 num_vars, size_t reduce_size, void *reduce_data, void
    // (*reduce_func)(void *lhs_data, void *rhs_data), kmp_critical_name *lck);
    OMPRTL__kmpc_reduce,
    // Call to kmp_int32 __kmpc_reduce_nowait(ident_t *loc, kmp_int32
    // global_tid, kmp_int32 num_vars, size_t reduce_size, void *reduce_data,
    // void (*reduce_func)(void *lhs_data, void *rhs_data), kmp_critical_name
    // *lck);
    OMPRTL__kmpc_reduce_nowait,
    // Call to void __kmpc_end_reduce(ident_t *loc, kmp_int32 global_tid,
    // kmp_critical_name *lck);
    OMPRTL__kmpc_end_reduce,
    // Call to void __kmpc_end_reduce_nowait(ident_t *loc, kmp_int32 global_tid,
    // kmp_critical_name *lck);
    OMPRTL__kmpc_end_reduce_nowait,
  };

  /// \brief Values for bit flags used in the ident_t to describe the fields.
  /// All enumeric elements are named and described in accordance with the code
  /// from http://llvm.org/svn/llvm-project/openmp/trunk/runtime/src/kmp.h
  enum OpenMPLocationFlags {
    /// \brief Use trampoline for internal microtask.
    OMP_IDENT_IMD = 0x01,
    /// \brief Use c-style ident structure.
    OMP_IDENT_KMPC = 0x02,
    /// \brief Atomic reduction option for kmpc_reduce.
    OMP_ATOMIC_REDUCE = 0x10,
    /// \brief Explicit 'barrier' directive.
    OMP_IDENT_BARRIER_EXPL = 0x20,
    /// \brief Implicit barrier in code.
    OMP_IDENT_BARRIER_IMPL = 0x40,
    /// \brief Implicit barrier in 'for' directive.
    OMP_IDENT_BARRIER_IMPL_FOR = 0x40,
    /// \brief Implicit barrier in 'sections' directive.
    OMP_IDENT_BARRIER_IMPL_SECTIONS = 0xC0,
    /// \brief Implicit barrier in 'single' directive.
    OMP_IDENT_BARRIER_IMPL_SINGLE = 0x140
  };
  CodeGenModule &CGM;
  /// \brief Default const ident_t object used for initialization of all other
  /// ident_t objects.
  llvm::Constant *DefaultOpenMPPSource;
  /// \brief Map of flags and corresponding default locations.
  typedef llvm::DenseMap<unsigned, llvm::Value *> OpenMPDefaultLocMapTy;
  OpenMPDefaultLocMapTy OpenMPDefaultLocMap;
  llvm::Value *getOrCreateDefaultLocation(OpenMPLocationFlags Flags);
  /// \brief Describes ident structure that describes a source location.
  /// All descriptions are taken from
  /// http://llvm.org/svn/llvm-project/openmp/trunk/runtime/src/kmp.h
  /// Original structure:
  /// typedef struct ident {
  ///    kmp_int32 reserved_1;   /**<  might be used in Fortran;
  ///                                  see above  */
  ///    kmp_int32 flags;        /**<  also f.flags; KMP_IDENT_xxx flags;
  ///                                  KMP_IDENT_KMPC identifies this union
  ///                                  member  */
  ///    kmp_int32 reserved_2;   /**<  not really used in Fortran any more;
  ///                                  see above */
  ///#if USE_ITT_BUILD
  ///                            /*  but currently used for storing
  ///                                region-specific ITT */
  ///                            /*  contextual information. */
  ///#endif /* USE_ITT_BUILD */
  ///    kmp_int32 reserved_3;   /**< source[4] in Fortran, do not use for
  ///                                 C++  */
  ///    char const *psource;    /**< String describing the source location.
  ///                            The string is composed of semi-colon separated
  //                             fields which describe the source file,
  ///                            the function and a pair of line numbers that
  ///                            delimit the construct.
  ///                             */
  /// } ident_t;
  enum IdentFieldIndex {
    /// \brief might be used in Fortran
    IdentField_Reserved_1,
    /// \brief OMP_IDENT_xxx flags; OMP_IDENT_KMPC identifies this union member.
    IdentField_Flags,
    /// \brief Not really used in Fortran any more
    IdentField_Reserved_2,
    /// \brief Source[4] in Fortran, do not use for C++
    IdentField_Reserved_3,
    /// \brief String describing the source location. The string is composed of
    /// semi-colon separated fields which describe the source file, the function
    /// and a pair of line numbers that delimit the construct.
    IdentField_PSource
  };
  llvm::StructType *IdentTy;
  /// \brief Map for SourceLocation and OpenMP runtime library debug locations.
  typedef llvm::DenseMap<unsigned, llvm::Value *> OpenMPDebugLocMapTy;
  OpenMPDebugLocMapTy OpenMPDebugLocMap;
  /// \brief The type for a microtask which gets passed to __kmpc_fork_call().
  /// Original representation is:
  /// typedef void (kmpc_micro)(kmp_int32 global_tid, kmp_int32 bound_tid,...);
  llvm::FunctionType *Kmpc_MicroTy;
  /// \brief Stores debug location and ThreadID for the function.
  struct DebugLocThreadIdTy {
    llvm::Value *DebugLoc;
    llvm::Value *ThreadID;
  };
  /// \brief Map of local debug location, ThreadId and functions.
  typedef llvm::DenseMap<llvm::Function *, DebugLocThreadIdTy>
      OpenMPLocThreadIDMapTy;
  OpenMPLocThreadIDMapTy OpenMPLocThreadIDMap;
  /// \brief Type kmp_critical_name, originally defined as typedef kmp_int32
  /// kmp_critical_name[8];
  llvm::ArrayType *KmpCriticalNameTy;
  /// \brief An ordered map of auto-generated variables to their unique names.
  /// It stores variables with the following names: 1) ".gomp_critical_user_" +
  /// <critical_section_name> + ".var" for "omp critical" directives; 2)
  /// <mangled_name_for_global_var> + ".cache." for cache for threadprivate
  /// variables.
  llvm::StringMap<llvm::AssertingVH<llvm::Constant>, llvm::BumpPtrAllocator>
      InternalVars;
  /// \brief Type typedef kmp_int32 (* kmp_routine_entry_t)(kmp_int32, void *);
  llvm::Type *KmpRoutineEntryPtrTy;
  QualType KmpRoutineEntryPtrQTy;

  /// \brief Build type kmp_routine_entry_t (if not built yet).
  void emitKmpRoutineEntryT(QualType KmpInt32Ty);

  /// \brief Emits object of ident_t type with info for source location.
  /// \param Flags Flags for OpenMP location.
  ///
  llvm::Value *emitUpdateLocation(CodeGenFunction &CGF, SourceLocation Loc,
                                  OpenMPLocationFlags Flags = OMP_IDENT_KMPC);

  /// \brief Returns pointer to ident_t type.
  llvm::Type *getIdentTyPointerTy();

  /// \brief Returns pointer to kmpc_micro type.
  llvm::Type *getKmpc_MicroPointerTy();

  /// \brief Returns specified OpenMP runtime function.
  /// \param Function OpenMP runtime function.
  /// \return Specified function.
  llvm::Constant *createRuntimeFunction(OpenMPRTLFunction Function);

  /// \brief Returns __kmpc_for_static_init_* runtime function for the specified
  /// size \a IVSize and sign \a IVSigned.
  llvm::Constant *createForStaticInitFunction(unsigned IVSize, bool IVSigned);

  /// \brief Returns __kmpc_dispatch_init_* runtime function for the specified
  /// size \a IVSize and sign \a IVSigned.
  llvm::Constant *createDispatchInitFunction(unsigned IVSize, bool IVSigned);

  /// \brief Returns __kmpc_dispatch_next_* runtime function for the specified
  /// size \a IVSize and sign \a IVSigned.
  llvm::Constant *createDispatchNextFunction(unsigned IVSize, bool IVSigned);

  /// \brief If the specified mangled name is not in the module, create and
  /// return threadprivate cache object. This object is a pointer's worth of
  /// storage that's reserved for use by the OpenMP runtime.
  /// \param VD Threadprivate variable.
  /// \return Cache variable for the specified threadprivate.
  llvm::Constant *getOrCreateThreadPrivateCache(const VarDecl *VD);

  /// \brief Emits address of the word in a memory where current thread id is
  /// stored.
  virtual llvm::Value *emitThreadIDAddress(CodeGenFunction &CGF,
                                           SourceLocation Loc);

  /// \brief Gets thread id value for the current thread.
  ///
  llvm::Value *getThreadID(CodeGenFunction &CGF, SourceLocation Loc);

  /// \brief Gets (if variable with the given name already exist) or creates
  /// internal global variable with the specified Name. The created variable has
  /// linkage CommonLinkage by default and is initialized by null value.
  /// \param Ty Type of the global variable. If it is exist already the type
  /// must be the same.
  /// \param Name Name of the variable.
  llvm::Constant *getOrCreateInternalVariable(llvm::Type *Ty,
                                              const llvm::Twine &Name);

  /// \brief Set of threadprivate variables with the generated initializer.
  llvm::DenseSet<const VarDecl *> ThreadPrivateWithDefinition;

  /// \brief Emits initialization code for the threadprivate variables.
  /// \param VDAddr Address of the global variable \a VD.
  /// \param Ctor Pointer to a global init function for \a VD.
  /// \param CopyCtor Pointer to a global copy function for \a VD.
  /// \param Dtor Pointer to a global destructor function for \a VD.
  /// \param Loc Location of threadprivate declaration.
  void emitThreadPrivateVarInit(CodeGenFunction &CGF, llvm::Value *VDAddr,
                                llvm::Value *Ctor, llvm::Value *CopyCtor,
                                llvm::Value *Dtor, SourceLocation Loc);

  /// \brief Returns corresponding lock object for the specified critical region
  /// name. If the lock object does not exist it is created, otherwise the
  /// reference to the existing copy is returned.
  /// \param CriticalName Name of the critical region.
  ///
  llvm::Value *getCriticalRegionLock(StringRef CriticalName);

public:
  explicit CGOpenMPRuntime(CodeGenModule &CGM);
  virtual ~CGOpenMPRuntime() {}
  virtual void clear();

  /// \brief Emits outlined function for the specified OpenMP parallel directive
  /// \a D. This outlined function has type void(*)(kmp_int32 *ThreadID,
  /// kmp_int32 BoundID, struct context_vars*).
  /// \param D OpenMP directive.
  /// \param ThreadIDVar Variable for thread id in the current OpenMP region.
  /// \param CodeGen Code generation sequence for the \a D directive.
  virtual llvm::Value *
  emitParallelOutlinedFunction(const OMPExecutableDirective &D,
                               const VarDecl *ThreadIDVar,
                               const RegionCodeGenTy &CodeGen);

  /// \brief Emits outlined function for the OpenMP task directive \a D. This
  /// outlined function has type void(*)(kmp_int32 ThreadID, kmp_int32
  /// PartID, struct context_vars*).
  /// \param D OpenMP directive.
  /// \param ThreadIDVar Variable for thread id in the current OpenMP region.
  /// \param CodeGen Code generation sequence for the \a D directive.
  ///
  virtual llvm::Value *emitTaskOutlinedFunction(const OMPExecutableDirective &D,
                                                const VarDecl *ThreadIDVar,
                                                const RegionCodeGenTy &CodeGen);

  /// \brief Cleans up references to the objects in finished function.
  ///
  void functionFinished(CodeGenFunction &CGF);

  /// \brief Emits code for parallel call of the \a OutlinedFn with variables
  /// captured in a record which address is stored in \a CapturedStruct.
  /// \param OutlinedFn Outlined function to be run in parallel threads. Type of
  /// this function is void(*)(kmp_int32 *, kmp_int32, struct context_vars*).
  /// \param CapturedStruct A pointer to the record with the references to
  /// variables used in \a OutlinedFn function.
  ///
  virtual void emitParallelCall(CodeGenFunction &CGF, SourceLocation Loc,
                                llvm::Value *OutlinedFn,
                                llvm::Value *CapturedStruct);

  /// \brief Emits code for serial call of the \a OutlinedFn with variables
  /// captured in a record which address is stored in \a CapturedStruct.
  /// \param OutlinedFn Outlined function to be run in serial mode.
  /// \param CapturedStruct A pointer to the record with the references to
  /// variables used in \a OutlinedFn function.
  ///
  virtual void emitSerialCall(CodeGenFunction &CGF, SourceLocation Loc,
                              llvm::Value *OutlinedFn,
                              llvm::Value *CapturedStruct);

  /// \brief Emits a critical region.
  /// \param CriticalName Name of the critical region.
  /// \param CriticalOpGen Generator for the statement associated with the given
  /// critical region.
  virtual void emitCriticalRegion(CodeGenFunction &CGF, StringRef CriticalName,
                                  const RegionCodeGenTy &CriticalOpGen,
                                  SourceLocation Loc);

  /// \brief Emits a master region.
  /// \param MasterOpGen Generator for the statement associated with the given
  /// master region.
  virtual void emitMasterRegion(CodeGenFunction &CGF,
                                const RegionCodeGenTy &MasterOpGen,
                                SourceLocation Loc);

  /// \brief Emits code for a taskyield directive.
  virtual void emitTaskyieldCall(CodeGenFunction &CGF, SourceLocation Loc);

  /// \brief Emits a single region.
  /// \param SingleOpGen Generator for the statement associated with the given
  /// single region.
  virtual void emitSingleRegion(CodeGenFunction &CGF,
                                const RegionCodeGenTy &SingleOpGen,
                                SourceLocation Loc,
                                ArrayRef<const Expr *> CopyprivateVars,
                                ArrayRef<const Expr *> DestExprs,
                                ArrayRef<const Expr *> SrcExprs,
                                ArrayRef<const Expr *> AssignmentOps);

  /// \brief Emit an implicit/explicit barrier for OpenMP threads.
  /// \param Kind Directive for which this implicit barrier call must be
  /// generated. Must be OMPD_barrier for explicit barrier generation.
  ///
  virtual void emitBarrierCall(CodeGenFunction &CGF, SourceLocation Loc,
                               OpenMPDirectiveKind Kind);

  /// \brief Check if the specified \a ScheduleKind is static non-chunked.
  /// This kind of worksharing directive is emitted without outer loop.
  /// \param ScheduleKind Schedule kind specified in the 'schedule' clause.
  /// \param Chunked True if chunk is specified in the clause.
  ///
  virtual bool isStaticNonchunked(OpenMPScheduleClauseKind ScheduleKind,
                                  bool Chunked) const;

  /// \brief Check if the specified \a ScheduleKind is dynamic.
  /// This kind of worksharing directive is emitted without outer loop.
  /// \param ScheduleKind Schedule Kind specified in the 'schedule' clause.
  ///
  virtual bool isDynamic(OpenMPScheduleClauseKind ScheduleKind) const;

  /// \brief Call the appropriate runtime routine to initialize it before start
  /// of loop.
  ///
  /// Depending on the loop schedule, it is nesessary to call some runtime
  /// routine before start of the OpenMP loop to get the loop upper / lower
  /// bounds \a LB and \a UB and stride \a ST.
  ///
  /// \param CGF Reference to current CodeGenFunction.
  /// \param Loc Clang source location.
  /// \param SchedKind Schedule kind, specified by the 'schedule' clause.
  /// \param IVSize Size of the iteration variable in bits.
  /// \param IVSigned Sign of the interation variable.
  /// \param IL Address of the output variable in which the flag of the
  /// last iteration is returned.
  /// \param LB Address of the output variable in which the lower iteration
  /// number is returned.
  /// \param UB Address of the output variable in which the upper iteration
  /// number is returned.
  /// \param ST Address of the output variable in which the stride value is
  /// returned nesessary to generated the static_chunked scheduled loop.
  /// \param Chunk Value of the chunk for the static_chunked scheduled loop.
  /// For the default (nullptr) value, the chunk 1 will be used.
  ///
  virtual void emitForInit(CodeGenFunction &CGF, SourceLocation Loc,
                           OpenMPScheduleClauseKind SchedKind, unsigned IVSize,
                           bool IVSigned, llvm::Value *IL, llvm::Value *LB,
                           llvm::Value *UB, llvm::Value *ST,
                           llvm::Value *Chunk = nullptr);

  /// \brief Call the appropriate runtime routine to notify that we finished
  /// all the work with current loop.
  ///
  /// \param CGF Reference to current CodeGenFunction.
  /// \param Loc Clang source location.
  /// \param ScheduleKind Schedule kind, specified by the 'schedule' clause.
  ///
  virtual void emitForFinish(CodeGenFunction &CGF, SourceLocation Loc,
                             OpenMPScheduleClauseKind ScheduleKind);

  /// Call __kmpc_dispatch_next(
  ///          ident_t *loc, kmp_int32 tid, kmp_int32 *p_lastiter,
  ///          kmp_int[32|64] *p_lower, kmp_int[32|64] *p_upper,
  ///          kmp_int[32|64] *p_stride);
  /// \param IVSize Size of the iteration variable in bits.
  /// \param IVSigned Sign of the interation variable.
  /// \param IL Address of the output variable in which the flag of the
  /// last iteration is returned.
  /// \param LB Address of the output variable in which the lower iteration
  /// number is returned.
  /// \param UB Address of the output variable in which the upper iteration
  /// number is returned.
  /// \param ST Address of the output variable in which the stride value is
  /// returned.
  virtual llvm::Value *emitForNext(CodeGenFunction &CGF, SourceLocation Loc,
                                   unsigned IVSize, bool IVSigned,
                                   llvm::Value *IL, llvm::Value *LB,
                                   llvm::Value *UB, llvm::Value *ST);

  /// \brief Emits call to void __kmpc_push_num_threads(ident_t *loc, kmp_int32
  /// global_tid, kmp_int32 num_threads) to generate code for 'num_threads'
  /// clause.
  /// \param NumThreads An integer value of threads.
  virtual void emitNumThreadsClause(CodeGenFunction &CGF,
                                    llvm::Value *NumThreads,
                                    SourceLocation Loc);

  /// \brief Returns address of the threadprivate variable for the current
  /// thread.
  /// \param VD Threadprivate variable.
  /// \param VDAddr Address of the global variable \a VD.
  /// \param Loc Location of the reference to threadprivate var.
  /// \return Address of the threadprivate variable for the current thread.
  virtual llvm::Value *getAddrOfThreadPrivate(CodeGenFunction &CGF,
                                              const VarDecl *VD,
                                              llvm::Value *VDAddr,
                                              SourceLocation Loc);

  /// \brief Emit a code for initialization of threadprivate variable. It emits
  /// a call to runtime library which adds initial value to the newly created
  /// threadprivate variable (if it is not constant) and registers destructor
  /// for the variable (if any).
  /// \param VD Threadprivate variable.
  /// \param VDAddr Address of the global variable \a VD.
  /// \param Loc Location of threadprivate declaration.
  /// \param PerformInit true if initialization expression is not constant.
  virtual llvm::Function *
  emitThreadPrivateVarDefinition(const VarDecl *VD, llvm::Value *VDAddr,
                                 SourceLocation Loc, bool PerformInit,
                                 CodeGenFunction *CGF = nullptr);

  /// \brief Emit flush of the variables specified in 'omp flush' directive.
  /// \param Vars List of variables to flush.
  virtual void emitFlush(CodeGenFunction &CGF, ArrayRef<const Expr *> Vars,
                         SourceLocation Loc);

  /// \brief Emit task region for the task directive. The task region is
  /// emmitted in several steps:
  /// 1. Emit a call to kmp_task_t *__kmpc_omp_task_alloc(ident_t *, kmp_int32
  /// gtid, kmp_int32 flags, size_t sizeof_kmp_task_t, size_t sizeof_shareds,
  /// kmp_routine_entry_t *task_entry). Here task_entry is a pointer to the
  /// function:
  /// kmp_int32 .omp_task_entry.(kmp_int32 gtid, kmp_task_t *tt) {
  ///   TaskFunction(gtid, tt->part_id, tt->shareds);
  ///   return 0;
  /// }
  /// 2. Copy a list of shared variables to field shareds of the resulting
  /// structure kmp_task_t returned by the previous call (if any).
  /// 3. Copy a pointer to destructions function to field destructions of the
  /// resulting structure kmp_task_t.
  /// 4. Emit a call to kmp_int32 __kmpc_omp_task(ident_t *, kmp_int32 gtid,
  /// kmp_task_t *new_task), where new_task is a resulting structure from
  /// previous items.
  /// \param Tied true if the task is tied (the task is tied to the thread that
  /// can suspend its task region), false - untied (the task is not tied to any
  /// thread).
  /// \param Final Contains either constant bool value, or llvm::Value * of i1
  /// type for final clause. If the value is true, the task forces all of its
  /// child tasks to become final and included tasks.
  /// \param TaskFunction An LLVM function with type void (*)(i32 /*gtid*/, i32
  /// /*part_id*/, captured_struct */*__context*/);
  /// \param SharedsTy A type which contains references the shared variables.
  /// \param Shareds Context with the list of shared variables from the \a
  /// TaskFunction.
  virtual void emitTaskCall(CodeGenFunction &CGF, SourceLocation Loc, bool Tied,
                            llvm::PointerIntPair<llvm::Value *, 1, bool> Final,
                            llvm::Value *TaskFunction, QualType SharedsTy,
                            llvm::Value *Shareds);

  /// \brief Emit code for the directive that does not require outlining.
  ///
  /// \param CodeGen Code generation sequence for the \a D directive.
  virtual void emitInlinedDirective(CodeGenFunction &CGF,
                                    const RegionCodeGenTy &CodeGen);
  /// \brief Emit a code for reduction clause. Next code should be emitted for
  /// reduction:
  /// \code
  ///
  /// static kmp_critical_name lock = { 0 };
  ///
  /// void reduce_func(void *lhs[<n>], void *rhs[<n>]) {
  ///  ...
  ///  *(Type<i>*)lhs[i] = RedOp<i>(*(Type<i>*)lhs[i], *(Type<i>*)rhs[i]);
  ///  ...
  /// }
  ///
  /// ...
  /// void *RedList[<n>] = {&<RHSExprs>[0], ..., &<RHSExprs>[<n>-1]};
  /// switch (__kmpc_reduce{_nowait}(<loc>, <gtid>, <n>, sizeof(RedList),
  /// RedList, reduce_func, &<lock>)) {
  /// case 1:
  ///  ...
  ///  <LHSExprs>[i] = RedOp<i>(*<LHSExprs>[i], *<RHSExprs>[i]);
  ///  ...
  /// __kmpc_end_reduce{_nowait}(<loc>, <gtid>, &<lock>);
  /// break;
  /// case 2:
  ///  ...
  ///  Atomic(<LHSExprs>[i] = RedOp<i>(*<LHSExprs>[i], *<RHSExprs>[i]));
  ///  ...
  /// break;
  /// default:;
  /// }
  /// \endcode
  ///
  /// \param LHSExprs List of LHS in \a ReductionOps reduction operations.
  /// \param RHSExprs List of RHS in \a ReductionOps reduction operations.
  /// \param ReductionOps List of reduction operations in form 'LHS binop RHS'
  /// or 'operator binop(LHS, RHS)'.
  /// \param WithNowait true if parent directive has also nowait clause, false
  /// otherwise.
  virtual void emitReduction(CodeGenFunction &CGF, SourceLocation Loc,
                             ArrayRef<const Expr *> LHSExprs,
                             ArrayRef<const Expr *> RHSExprs,
                             ArrayRef<const Expr *> ReductionOps,
                             bool WithNowait);
};

} // namespace CodeGen
} // namespace clang

#endif