llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp - toolchain/llvm-project - Gitiles

 //=- WebAssemblyISelLowering.cpp - WebAssembly DAG Lowering Implementation -==//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
 /// \brief This file implements the WebAssemblyTargetLowering class.
 ///
 //===----------------------------------------------------------------------===//

 #include "WebAssemblyISelLowering.h"
 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
 #include "WebAssemblyMachineFunctionInfo.h"
 #include "WebAssemblySubtarget.h"
 #include "WebAssemblyTargetMachine.h"
 #include "WebAssemblyTargetObjectFile.h"
 #include "llvm/CodeGen/Analysis.h"
 #include "llvm/CodeGen/CallingConvLower.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/SelectionDAG.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/DiagnosticPrinter.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetOptions.h"

 using namespace llvm;

 #define DEBUG_TYPE "wasm-lower"

 namespace {
 // Diagnostic information for unimplemented or unsupported feature reporting.
 // FIXME copied from BPF and AMDGPU.
 class DiagnosticInfoUnsupported : public DiagnosticInfo {
 private:
   // Debug location where this diagnostic is triggered.
   DebugLoc DLoc;
   const Twine &Description;
   const Function &Fn;
   SDValue Value;

   static int KindID;

   static int getKindID() {
     if (KindID == 0)
       KindID = llvm::getNextAvailablePluginDiagnosticKind();
     return KindID;
   }

 public:
   DiagnosticInfoUnsupported(SDLoc DLoc, const Function &Fn, const Twine &Desc,
                             SDValue Value)
       : DiagnosticInfo(getKindID(), DS_Error), DLoc(DLoc.getDebugLoc()),
         Description(Desc), Fn(Fn), Value(Value) {}

   void print(DiagnosticPrinter &DP) const override {
     std::string Str;
     raw_string_ostream OS(Str);

     if (DLoc) {
       auto DIL = DLoc.get();
       StringRef Filename = DIL->getFilename();
       unsigned Line = DIL->getLine();
       unsigned Column = DIL->getColumn();
       OS << Filename << ':' << Line << ':' << Column << ' ';
     }

     OS << "in function " << Fn.getName() << ' ' << *Fn.getFunctionType() << '\n'
        << Description;
     if (Value)
       Value->print(OS);
     OS << '\n';
     OS.flush();
     DP << Str;
   }

   static bool classof(const DiagnosticInfo *DI) {
     return DI->getKind() == getKindID();
   }
 };

 int DiagnosticInfoUnsupported::KindID = 0;
 } // end anonymous namespace

 WebAssemblyTargetLowering::WebAssemblyTargetLowering(
     const TargetMachine &TM, const WebAssemblySubtarget &STI)
     : TargetLowering(TM), Subtarget(&STI) {
   auto MVTPtr = Subtarget->hasAddr64() ? MVT::i64 : MVT::i32;

   // Booleans always contain 0 or 1.
   setBooleanContents(ZeroOrOneBooleanContent);
   // WebAssembly does not produce floating-point exceptions on normal floating
   // point operations.
   setHasFloatingPointExceptions(false);
   // We don't know the microarchitecture here, so just reduce register pressure.
   setSchedulingPreference(Sched::RegPressure);
   // Tell ISel that we have a stack pointer.
   setStackPointerRegisterToSaveRestore(
       Subtarget->hasAddr64() ? WebAssembly::SP64 : WebAssembly::SP32);
   // Set up the register classes.
   addRegisterClass(MVT::i32, &WebAssembly::Int32RegClass);
   addRegisterClass(MVT::i64, &WebAssembly::Int64RegClass);
   addRegisterClass(MVT::f32, &WebAssembly::Float32RegClass);
   addRegisterClass(MVT::f64, &WebAssembly::Float64RegClass);
   // Compute derived properties from the register classes.
   computeRegisterProperties(Subtarget->getRegisterInfo());

   setOperationAction(ISD::GlobalAddress, MVTPtr, Custom);

   for (auto T : {MVT::f32, MVT::f64}) {
     // Don't expand the floating-point types to constant pools.
     setOperationAction(ISD::ConstantFP, T, Legal);
     // Expand floating-point comparisons.
     for (auto CC : {ISD::SETO, ISD::SETUO, ISD::SETUEQ, ISD::SETONE,
                     ISD::SETULT, ISD::SETULE, ISD::SETUGT, ISD::SETUGE})
       setCondCodeAction(CC, T, Expand);
     // Expand floating-point library function operators.
     for (auto Op : {ISD::FSIN, ISD::FCOS, ISD::FSINCOS, ISD::FPOWI, ISD::FPOW})
       setOperationAction(Op, T, Expand);
     // Note supported floating-point library function operators that otherwise
     // default to expand.
     for (auto Op : {ISD::FCEIL, ISD::FFLOOR, ISD::FTRUNC, ISD::FNEARBYINT,
                     ISD::FRINT})
       setOperationAction(Op, T, Legal);
   }

   for (auto T : {MVT::i32, MVT::i64}) {
     // Expand unavailable integer operations.
     for (auto Op : {ISD::BSWAP, ISD::ROTL, ISD::ROTR,
                     ISD::SMUL_LOHI, ISD::UMUL_LOHI,
                     ISD::MULHS, ISD::MULHU, ISD::SDIVREM, ISD::UDIVREM,
                     ISD::SHL_PARTS, ISD::SRA_PARTS, ISD::SRL_PARTS,
                     ISD::ADDC, ISD::ADDE, ISD::SUBC, ISD::SUBE}) {
       setOperationAction(Op, T, Expand);
     }
   }

   // As a special case, these operators use the type to mean the type to
   // sign-extend from.
   for (auto T : {MVT::i1, MVT::i8, MVT::i16})
     setOperationAction(ISD::SIGN_EXTEND_INREG, T, Expand);

   // Dynamic stack allocation: use the default expansion.
   setOperationAction(ISD::STACKSAVE, MVT::Other, Expand);
   setOperationAction(ISD::STACKRESTORE, MVT::Other, Expand);
   setOperationAction(ISD::DYNAMIC_STACKALLOC, MVTPtr, Expand);

   // WebAssembly doesn't have:
   //  - Floating-point extending loads.
   //  - Floating-point truncating stores.
   //  - i1 extending loads.
   setLoadExtAction(ISD::EXTLOAD, MVT::f32, MVT::f64, Expand);
   setTruncStoreAction(MVT::f64, MVT::f32, Expand);
   for (auto T : MVT::integer_valuetypes())
     for (auto Ext : {ISD::EXTLOAD, ISD::ZEXTLOAD, ISD::SEXTLOAD})
       setLoadExtAction(Ext, T, MVT::i1, Promote);
 }

 FastISel *WebAssemblyTargetLowering::createFastISel(
     FunctionLoweringInfo &FuncInfo, const TargetLibraryInfo *LibInfo) const {
   return WebAssembly::createFastISel(FuncInfo, LibInfo);
 }

 bool WebAssemblyTargetLowering::isOffsetFoldingLegal(
     const GlobalAddressSDNode *GA) const {
   // The WebAssembly target doesn't support folding offsets into global
   // addresses.
   return false;
 }

 MVT WebAssemblyTargetLowering::getScalarShiftAmountTy(const DataLayout &DL,
                                                       EVT VT) const {
   return VT.getSimpleVT();
 }

 const char *
 WebAssemblyTargetLowering::getTargetNodeName(unsigned Opcode) const {
   switch (static_cast<WebAssemblyISD::NodeType>(Opcode)) {
   case WebAssemblyISD::FIRST_NUMBER:
     break;
 #define HANDLE_NODETYPE(NODE)                                                  \
   case WebAssemblyISD::NODE:                                                   \
     return "WebAssemblyISD::" #NODE;
 #include "WebAssemblyISD.def"
 #undef HANDLE_NODETYPE
   }
   return nullptr;
 }

 //===----------------------------------------------------------------------===//
 // WebAssembly Lowering private implementation.
 //===----------------------------------------------------------------------===//

 //===----------------------------------------------------------------------===//
 // Lowering Code
 //===----------------------------------------------------------------------===//

 static void fail(SDLoc DL, SelectionDAG &DAG, const char *msg) {
   MachineFunction &MF = DAG.getMachineFunction();
   DAG.getContext()->diagnose(
       DiagnosticInfoUnsupported(DL, *MF.getFunction(), msg, SDValue()));
 }

 SDValue
 WebAssemblyTargetLowering::LowerCall(CallLoweringInfo &CLI,
                                      SmallVectorImpl<SDValue> &InVals) const {
   SelectionDAG &DAG = CLI.DAG;
   SDLoc DL = CLI.DL;
   SDValue Chain = CLI.Chain;
   SDValue Callee = CLI.Callee;
   MachineFunction &MF = DAG.getMachineFunction();

   CallingConv::ID CallConv = CLI.CallConv;
   if (CallConv != CallingConv::C)
     fail(DL, DAG, "WebAssembly doesn't support non-C calling conventions");
   if (CLI.IsTailCall || MF.getTarget().Options.GuaranteedTailCallOpt)
     fail(DL, DAG, "WebAssembly doesn't support tail call yet");
   if (CLI.IsPatchPoint)
     fail(DL, DAG, "WebAssembly doesn't support patch point yet");

   SmallVectorImpl<ISD::OutputArg> &Outs = CLI.Outs;
   SmallVectorImpl<SDValue> &OutVals = CLI.OutVals;
   bool IsStructRet = (Outs.empty()) ? false : Outs[0].Flags.isSRet();
   if (IsStructRet)
     fail(DL, DAG, "WebAssembly doesn't support struct return yet");
   if (Outs.size() > 1)
     fail(DL, DAG, "WebAssembly doesn't support more than 1 returned value yet");

   SmallVectorImpl<ISD::InputArg> &Ins = CLI.Ins;
   bool IsVarArg = CLI.IsVarArg;
   if (IsVarArg)
     fail(DL, DAG, "WebAssembly doesn't support varargs yet");
   // Analyze operands of the call, assigning locations to each operand.
   SmallVector<CCValAssign, 16> ArgLocs;
   CCState CCInfo(CallConv, IsVarArg, MF, ArgLocs, *DAG.getContext());
   unsigned NumBytes = CCInfo.getNextStackOffset();

   auto PtrVT = getPointerTy(MF.getDataLayout());
   auto Zero = DAG.getConstant(0, DL, PtrVT, true);
   auto NB = DAG.getConstant(NumBytes, DL, PtrVT, true);
   Chain = DAG.getCALLSEQ_START(Chain, NB, DL);

   SmallVector<SDValue, 16> Ops;
   Ops.push_back(Chain);
   Ops.push_back(Callee);
   Ops.append(OutVals.begin(), OutVals.end());

   SmallVector<EVT, 8> Tys;
   for (const auto &In : Ins)
     Tys.push_back(In.VT);
   Tys.push_back(MVT::Other);
   SDVTList TyList = DAG.getVTList(Tys);
   SDValue Res = DAG.getNode(WebAssemblyISD::CALL, DL, TyList, Ops);
   if (Ins.empty()) {
     Chain = Res;
   } else {
     InVals.push_back(Res);
     Chain = Res.getValue(1);
   }

   // FIXME: handle CLI.RetSExt and CLI.RetZExt?

   Chain = DAG.getCALLSEQ_END(Chain, NB, Zero, SDValue(), DL);

   return Chain;
 }

 bool WebAssemblyTargetLowering::CanLowerReturn(
     CallingConv::ID CallConv, MachineFunction &MF, bool IsVarArg,
     const SmallVectorImpl<ISD::OutputArg> &Outs, LLVMContext &Context) const {
   // WebAssembly can't currently handle returning tuples.
   return Outs.size() <= 1;
 }

 SDValue WebAssemblyTargetLowering::LowerReturn(
     SDValue Chain, CallingConv::ID CallConv, bool IsVarArg,
     const SmallVectorImpl<ISD::OutputArg> &Outs,
     const SmallVectorImpl<SDValue> &OutVals, SDLoc DL,
     SelectionDAG &DAG) const {

   assert(Outs.size() <= 1 && "WebAssembly can only return up to one value");
   if (CallConv != CallingConv::C)
     fail(DL, DAG, "WebAssembly doesn't support non-C calling conventions");
   if (IsVarArg)
     fail(DL, DAG, "WebAssembly doesn't support varargs yet");

   SmallVector<SDValue, 4> RetOps(1, Chain);
   RetOps.append(OutVals.begin(), OutVals.end());
   Chain = DAG.getNode(WebAssemblyISD::RETURN, DL, MVT::Other, RetOps);

   return Chain;
 }

 SDValue WebAssemblyTargetLowering::LowerFormalArguments(
     SDValue Chain, CallingConv::ID CallConv, bool IsVarArg,
     const SmallVectorImpl<ISD::InputArg> &Ins, SDLoc DL, SelectionDAG &DAG,
     SmallVectorImpl<SDValue> &InVals) const {
   MachineFunction &MF = DAG.getMachineFunction();

   if (CallConv != CallingConv::C)
     fail(DL, DAG, "WebAssembly doesn't support non-C calling conventions");
   if (IsVarArg)
     fail(DL, DAG, "WebAssembly doesn't support varargs yet");
   if (MF.getFunction()->hasStructRetAttr())
     fail(DL, DAG, "WebAssembly doesn't support struct return yet");

   unsigned ArgNo = 0;
   for (const ISD::InputArg &In : Ins) {
     if (In.Flags.isZExt())
       fail(DL, DAG, "WebAssembly hasn't implemented zext arguments");
     if (In.Flags.isSExt())
       fail(DL, DAG, "WebAssembly hasn't implemented sext arguments");
     if (In.Flags.isInReg())
       fail(DL, DAG, "WebAssembly hasn't implemented inreg arguments");
     if (In.Flags.isSRet())
       fail(DL, DAG, "WebAssembly hasn't implemented sret arguments");
     if (In.Flags.isByVal())
       fail(DL, DAG, "WebAssembly hasn't implemented byval arguments");
     if (In.Flags.isInAlloca())
       fail(DL, DAG, "WebAssembly hasn't implemented inalloca arguments");
     if (In.Flags.isNest())
       fail(DL, DAG, "WebAssembly hasn't implemented nest arguments");
     if (In.Flags.isReturned())
       fail(DL, DAG, "WebAssembly hasn't implemented returned arguments");
     if (In.Flags.isInConsecutiveRegs())
       fail(DL, DAG, "WebAssembly hasn't implemented cons regs arguments");
     if (In.Flags.isInConsecutiveRegsLast())
       fail(DL, DAG, "WebAssembly hasn't implemented cons regs last arguments");
     if (In.Flags.isSplit())
       fail(DL, DAG, "WebAssembly hasn't implemented split arguments");
     // FIXME Do something with In.getOrigAlign()?
     InVals.push_back(
         In.Used
             ? DAG.getNode(WebAssemblyISD::ARGUMENT, DL, In.VT,
                           DAG.getTargetConstant(ArgNo, DL, MVT::i32))
             : DAG.getNode(ISD::UNDEF, DL, In.VT));
     ++ArgNo;
   }

   return Chain;
 }

 //===----------------------------------------------------------------------===//
 //  Custom lowering hooks.
 //===----------------------------------------------------------------------===//

 SDValue WebAssemblyTargetLowering::LowerOperation(SDValue Op,
                                                   SelectionDAG &DAG) const {
   switch (Op.getOpcode()) {
   default:
     llvm_unreachable("unimplemented operation lowering");
     return SDValue();
   case ISD::GlobalAddress:
     return LowerGlobalAddress(Op, DAG);
   }
 }

 SDValue WebAssemblyTargetLowering::LowerGlobalAddress(SDValue Op,
                                                       SelectionDAG &DAG) const {
   SDLoc DL(Op);
   const auto *GA = cast<GlobalAddressSDNode>(Op);
   EVT VT = Op.getValueType();
   assert(GA->getOffset() == 0 &&
          "offsets on global addresses are forbidden by isOffsetFoldingLegal");
   assert(GA->getTargetFlags() == 0 && "WebAssembly doesn't set target flags");
   if (GA->getAddressSpace() != 0)
     fail(DL, DAG, "WebAssembly only expects the 0 address space");
   return DAG.getNode(WebAssemblyISD::Wrapper, DL, VT,
                      DAG.getTargetGlobalAddress(GA->getGlobal(), DL, VT));
 }

 //===----------------------------------------------------------------------===//
 //                          WebAssembly Optimization Hooks
 //===----------------------------------------------------------------------===//

 MCSection *WebAssemblyTargetObjectFile::SelectSectionForGlobal(
     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
     const TargetMachine &TM) const {
   return getDataSection();
 }
	//=- WebAssemblyISelLowering.cpp - WebAssembly DAG Lowering Implementation -==//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	///
	/// \file
	/// \brief This file implements the WebAssemblyTargetLowering class.
	///
	//===----------------------------------------------------------------------===//

	#include "WebAssemblyISelLowering.h"
	#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
	#include "WebAssemblyMachineFunctionInfo.h"
	#include "WebAssemblySubtarget.h"
	#include "WebAssemblyTargetMachine.h"
	#include "WebAssemblyTargetObjectFile.h"
	#include "llvm/CodeGen/Analysis.h"
	#include "llvm/CodeGen/CallingConvLower.h"
	#include "llvm/CodeGen/MachineRegisterInfo.h"
	#include "llvm/CodeGen/SelectionDAG.h"
	#include "llvm/IR/DiagnosticInfo.h"
	#include "llvm/IR/DiagnosticPrinter.h"
	#include "llvm/IR/Function.h"
	#include "llvm/IR/Intrinsics.h"
	#include "llvm/Support/CommandLine.h"
	#include "llvm/Support/Debug.h"
	#include "llvm/Support/ErrorHandling.h"
	#include "llvm/Support/raw_ostream.h"
	#include "llvm/Target/TargetOptions.h"

	using namespace llvm;

	#define DEBUG_TYPE "wasm-lower"

	namespace {
	// Diagnostic information for unimplemented or unsupported feature reporting.
	// FIXME copied from BPF and AMDGPU.
	class DiagnosticInfoUnsupported : public DiagnosticInfo {
	private:
	// Debug location where this diagnostic is triggered.
	DebugLoc DLoc;
	const Twine &Description;
	const Function &Fn;
	SDValue Value;

	static int KindID;

	static int getKindID() {
	if (KindID == 0)
	KindID = llvm::getNextAvailablePluginDiagnosticKind();
	return KindID;
	}

	public:
	DiagnosticInfoUnsupported(SDLoc DLoc, const Function &Fn, const Twine &Desc,
	SDValue Value)
	: DiagnosticInfo(getKindID(), DS_Error), DLoc(DLoc.getDebugLoc()),
	Description(Desc), Fn(Fn), Value(Value) {}

	void print(DiagnosticPrinter &DP) const override {
	std::string Str;
	raw_string_ostream OS(Str);

	if (DLoc) {
	auto DIL = DLoc.get();
	StringRef Filename = DIL->getFilename();
	unsigned Line = DIL->getLine();
	unsigned Column = DIL->getColumn();
	OS << Filename << ':' << Line << ':' << Column << ' ';
	}

	OS << "in function " << Fn.getName() << ' ' << *Fn.getFunctionType() << '\n'
	<< Description;
	if (Value)
	Value->print(OS);
	OS << '\n';
	OS.flush();
	DP << Str;
	}

	static bool classof(const DiagnosticInfo *DI) {
	return DI->getKind() == getKindID();
	}
	};

	int DiagnosticInfoUnsupported::KindID = 0;
	} // end anonymous namespace

	WebAssemblyTargetLowering::WebAssemblyTargetLowering(
	const TargetMachine &TM, const WebAssemblySubtarget &STI)
	: TargetLowering(TM), Subtarget(&STI) {
	auto MVTPtr = Subtarget->hasAddr64() ? MVT::i64 : MVT::i32;

	// Booleans always contain 0 or 1.
	setBooleanContents(ZeroOrOneBooleanContent);
	// WebAssembly does not produce floating-point exceptions on normal floating
	// point operations.
	setHasFloatingPointExceptions(false);
	// We don't know the microarchitecture here, so just reduce register pressure.
	setSchedulingPreference(Sched::RegPressure);
	// Tell ISel that we have a stack pointer.
	setStackPointerRegisterToSaveRestore(
	Subtarget->hasAddr64() ? WebAssembly::SP64 : WebAssembly::SP32);
	// Set up the register classes.
	addRegisterClass(MVT::i32, &WebAssembly::Int32RegClass);
	addRegisterClass(MVT::i64, &WebAssembly::Int64RegClass);
	addRegisterClass(MVT::f32, &WebAssembly::Float32RegClass);
	addRegisterClass(MVT::f64, &WebAssembly::Float64RegClass);
	// Compute derived properties from the register classes.
	computeRegisterProperties(Subtarget->getRegisterInfo());

	setOperationAction(ISD::GlobalAddress, MVTPtr, Custom);

	for (auto T : {MVT::f32, MVT::f64}) {
	// Don't expand the floating-point types to constant pools.
	setOperationAction(ISD::ConstantFP, T, Legal);
	// Expand floating-point comparisons.
	for (auto CC : {ISD::SETO, ISD::SETUO, ISD::SETUEQ, ISD::SETONE,
	ISD::SETULT, ISD::SETULE, ISD::SETUGT, ISD::SETUGE})
	setCondCodeAction(CC, T, Expand);
	// Expand floating-point library function operators.
	for (auto Op : {ISD::FSIN, ISD::FCOS, ISD::FSINCOS, ISD::FPOWI, ISD::FPOW})
	setOperationAction(Op, T, Expand);
	// Note supported floating-point library function operators that otherwise
	// default to expand.
	for (auto Op : {ISD::FCEIL, ISD::FFLOOR, ISD::FTRUNC, ISD::FNEARBYINT,
	ISD::FRINT})
	setOperationAction(Op, T, Legal);
	}

	for (auto T : {MVT::i32, MVT::i64}) {
	// Expand unavailable integer operations.
	for (auto Op : {ISD::BSWAP, ISD::ROTL, ISD::ROTR,
	ISD::SMUL_LOHI, ISD::UMUL_LOHI,
	ISD::MULHS, ISD::MULHU, ISD::SDIVREM, ISD::UDIVREM,
	ISD::SHL_PARTS, ISD::SRA_PARTS, ISD::SRL_PARTS,
	ISD::ADDC, ISD::ADDE, ISD::SUBC, ISD::SUBE}) {
	setOperationAction(Op, T, Expand);
	}
	}

	// As a special case, these operators use the type to mean the type to
	// sign-extend from.
	for (auto T : {MVT::i1, MVT::i8, MVT::i16})
	setOperationAction(ISD::SIGN_EXTEND_INREG, T, Expand);

	// Dynamic stack allocation: use the default expansion.
	setOperationAction(ISD::STACKSAVE, MVT::Other, Expand);
	setOperationAction(ISD::STACKRESTORE, MVT::Other, Expand);
	setOperationAction(ISD::DYNAMIC_STACKALLOC, MVTPtr, Expand);

	// WebAssembly doesn't have:
	// - Floating-point extending loads.
	// - Floating-point truncating stores.
	// - i1 extending loads.
	setLoadExtAction(ISD::EXTLOAD, MVT::f32, MVT::f64, Expand);
	setTruncStoreAction(MVT::f64, MVT::f32, Expand);
	for (auto T : MVT::integer_valuetypes())
	for (auto Ext : {ISD::EXTLOAD, ISD::ZEXTLOAD, ISD::SEXTLOAD})
	setLoadExtAction(Ext, T, MVT::i1, Promote);
	}

	FastISel *WebAssemblyTargetLowering::createFastISel(
	FunctionLoweringInfo &FuncInfo, const TargetLibraryInfo *LibInfo) const {
	return WebAssembly::createFastISel(FuncInfo, LibInfo);
	}

	bool WebAssemblyTargetLowering::isOffsetFoldingLegal(
	const GlobalAddressSDNode *GA) const {
	// The WebAssembly target doesn't support folding offsets into global
	// addresses.
	return false;
	}

	MVT WebAssemblyTargetLowering::getScalarShiftAmountTy(const DataLayout &DL,
	EVT VT) const {
	return VT.getSimpleVT();
	}

	const char *
	WebAssemblyTargetLowering::getTargetNodeName(unsigned Opcode) const {
	switch (static_cast<WebAssemblyISD::NodeType>(Opcode)) {
	case WebAssemblyISD::FIRST_NUMBER:
	break;
	#define HANDLE_NODETYPE(NODE) \
	case WebAssemblyISD::NODE: \
	return "WebAssemblyISD::" #NODE;
	#include "WebAssemblyISD.def"
	#undef HANDLE_NODETYPE
	}
	return nullptr;
	}

	//===----------------------------------------------------------------------===//
	// WebAssembly Lowering private implementation.
	//===----------------------------------------------------------------------===//

	//===----------------------------------------------------------------------===//
	// Lowering Code
	//===----------------------------------------------------------------------===//

	static void fail(SDLoc DL, SelectionDAG &DAG, const char *msg) {
	MachineFunction &MF = DAG.getMachineFunction();
	DAG.getContext()->diagnose(
	DiagnosticInfoUnsupported(DL, *MF.getFunction(), msg, SDValue()));
	}

	SDValue
	WebAssemblyTargetLowering::LowerCall(CallLoweringInfo &CLI,
	SmallVectorImpl<SDValue> &InVals) const {
	SelectionDAG &DAG = CLI.DAG;
	SDLoc DL = CLI.DL;
	SDValue Chain = CLI.Chain;
	SDValue Callee = CLI.Callee;
	MachineFunction &MF = DAG.getMachineFunction();

	CallingConv::ID CallConv = CLI.CallConv;
	if (CallConv != CallingConv::C)
	fail(DL, DAG, "WebAssembly doesn't support non-C calling conventions");
	if (CLI.IsTailCall \|\| MF.getTarget().Options.GuaranteedTailCallOpt)
	fail(DL, DAG, "WebAssembly doesn't support tail call yet");
	if (CLI.IsPatchPoint)
	fail(DL, DAG, "WebAssembly doesn't support patch point yet");

	SmallVectorImpl<ISD::OutputArg> &Outs = CLI.Outs;
	SmallVectorImpl<SDValue> &OutVals = CLI.OutVals;
	bool IsStructRet = (Outs.empty()) ? false : Outs[0].Flags.isSRet();
	if (IsStructRet)
	fail(DL, DAG, "WebAssembly doesn't support struct return yet");
	if (Outs.size() > 1)
	fail(DL, DAG, "WebAssembly doesn't support more than 1 returned value yet");

	SmallVectorImpl<ISD::InputArg> &Ins = CLI.Ins;
	bool IsVarArg = CLI.IsVarArg;
	if (IsVarArg)
	fail(DL, DAG, "WebAssembly doesn't support varargs yet");
	// Analyze operands of the call, assigning locations to each operand.
	SmallVector<CCValAssign, 16> ArgLocs;
	CCState CCInfo(CallConv, IsVarArg, MF, ArgLocs, *DAG.getContext());
	unsigned NumBytes = CCInfo.getNextStackOffset();

	auto PtrVT = getPointerTy(MF.getDataLayout());
	auto Zero = DAG.getConstant(0, DL, PtrVT, true);
	auto NB = DAG.getConstant(NumBytes, DL, PtrVT, true);
	Chain = DAG.getCALLSEQ_START(Chain, NB, DL);

	SmallVector<SDValue, 16> Ops;
	Ops.push_back(Chain);
	Ops.push_back(Callee);
	Ops.append(OutVals.begin(), OutVals.end());

	SmallVector<EVT, 8> Tys;
	for (const auto &In : Ins)
	Tys.push_back(In.VT);
	Tys.push_back(MVT::Other);
	SDVTList TyList = DAG.getVTList(Tys);
	SDValue Res = DAG.getNode(WebAssemblyISD::CALL, DL, TyList, Ops);
	if (Ins.empty()) {
	Chain = Res;
	} else {
	InVals.push_back(Res);
	Chain = Res.getValue(1);
	}

	// FIXME: handle CLI.RetSExt and CLI.RetZExt?

	Chain = DAG.getCALLSEQ_END(Chain, NB, Zero, SDValue(), DL);

	return Chain;
	}

	bool WebAssemblyTargetLowering::CanLowerReturn(
	CallingConv::ID CallConv, MachineFunction &MF, bool IsVarArg,
	const SmallVectorImpl<ISD::OutputArg> &Outs, LLVMContext &Context) const {
	// WebAssembly can't currently handle returning tuples.
	return Outs.size() <= 1;
	}

	SDValue WebAssemblyTargetLowering::LowerReturn(
	SDValue Chain, CallingConv::ID CallConv, bool IsVarArg,
	const SmallVectorImpl<ISD::OutputArg> &Outs,
	const SmallVectorImpl<SDValue> &OutVals, SDLoc DL,
	SelectionDAG &DAG) const {

	assert(Outs.size() <= 1 && "WebAssembly can only return up to one value");
	if (CallConv != CallingConv::C)
	fail(DL, DAG, "WebAssembly doesn't support non-C calling conventions");
	if (IsVarArg)
	fail(DL, DAG, "WebAssembly doesn't support varargs yet");

	SmallVector<SDValue, 4> RetOps(1, Chain);
	RetOps.append(OutVals.begin(), OutVals.end());
	Chain = DAG.getNode(WebAssemblyISD::RETURN, DL, MVT::Other, RetOps);

	return Chain;
	}

	SDValue WebAssemblyTargetLowering::LowerFormalArguments(
	SDValue Chain, CallingConv::ID CallConv, bool IsVarArg,
	const SmallVectorImpl<ISD::InputArg> &Ins, SDLoc DL, SelectionDAG &DAG,
	SmallVectorImpl<SDValue> &InVals) const {
	MachineFunction &MF = DAG.getMachineFunction();

	if (CallConv != CallingConv::C)
	fail(DL, DAG, "WebAssembly doesn't support non-C calling conventions");
	if (IsVarArg)
	fail(DL, DAG, "WebAssembly doesn't support varargs yet");
	if (MF.getFunction()->hasStructRetAttr())
	fail(DL, DAG, "WebAssembly doesn't support struct return yet");

	unsigned ArgNo = 0;
	for (const ISD::InputArg &In : Ins) {
	if (In.Flags.isZExt())
	fail(DL, DAG, "WebAssembly hasn't implemented zext arguments");
	if (In.Flags.isSExt())
	fail(DL, DAG, "WebAssembly hasn't implemented sext arguments");
	if (In.Flags.isInReg())
	fail(DL, DAG, "WebAssembly hasn't implemented inreg arguments");
	if (In.Flags.isSRet())
	fail(DL, DAG, "WebAssembly hasn't implemented sret arguments");
	if (In.Flags.isByVal())
	fail(DL, DAG, "WebAssembly hasn't implemented byval arguments");
	if (In.Flags.isInAlloca())
	fail(DL, DAG, "WebAssembly hasn't implemented inalloca arguments");
	if (In.Flags.isNest())
	fail(DL, DAG, "WebAssembly hasn't implemented nest arguments");
	if (In.Flags.isReturned())
	fail(DL, DAG, "WebAssembly hasn't implemented returned arguments");
	if (In.Flags.isInConsecutiveRegs())
	fail(DL, DAG, "WebAssembly hasn't implemented cons regs arguments");
	if (In.Flags.isInConsecutiveRegsLast())
	fail(DL, DAG, "WebAssembly hasn't implemented cons regs last arguments");
	if (In.Flags.isSplit())
	fail(DL, DAG, "WebAssembly hasn't implemented split arguments");
	// FIXME Do something with In.getOrigAlign()?
	InVals.push_back(
	In.Used
	? DAG.getNode(WebAssemblyISD::ARGUMENT, DL, In.VT,
	DAG.getTargetConstant(ArgNo, DL, MVT::i32))
	: DAG.getNode(ISD::UNDEF, DL, In.VT));
	++ArgNo;
	}

	return Chain;
	}

	//===----------------------------------------------------------------------===//
	// Custom lowering hooks.
	//===----------------------------------------------------------------------===//

	SDValue WebAssemblyTargetLowering::LowerOperation(SDValue Op,
	SelectionDAG &DAG) const {
	switch (Op.getOpcode()) {
	default:
	llvm_unreachable("unimplemented operation lowering");
	return SDValue();
	case ISD::GlobalAddress:
	return LowerGlobalAddress(Op, DAG);
	}
	}

	SDValue WebAssemblyTargetLowering::LowerGlobalAddress(SDValue Op,
	SelectionDAG &DAG) const {
	SDLoc DL(Op);
	const auto *GA = cast<GlobalAddressSDNode>(Op);
	EVT VT = Op.getValueType();
	assert(GA->getOffset() == 0 &&
	"offsets on global addresses are forbidden by isOffsetFoldingLegal");
	assert(GA->getTargetFlags() == 0 && "WebAssembly doesn't set target flags");
	if (GA->getAddressSpace() != 0)
	fail(DL, DAG, "WebAssembly only expects the 0 address space");
	return DAG.getNode(WebAssemblyISD::Wrapper, DL, VT,
	DAG.getTargetGlobalAddress(GA->getGlobal(), DL, VT));
	}

	//===----------------------------------------------------------------------===//
	// WebAssembly Optimization Hooks
	//===----------------------------------------------------------------------===//

	MCSection *WebAssemblyTargetObjectFile::SelectSectionForGlobal(
	const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
	const TargetMachine &TM) const {
	return getDataSection();
	}