llvm/lib/Target/AMDGPU/AMDGPUMCInstLower.cpp - toolchain/llvm-project - Gitiles

 //===- AMDGPUMCInstLower.cpp - Lower AMDGPU MachineInstr to an MCInst -----===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 /// \file
 /// Code to lower AMDGPU MachineInstrs to their corresponding MCInst.
 //
 //===----------------------------------------------------------------------===//
 //

 #include "AMDGPUAsmPrinter.h"
 #include "AMDGPUSubtarget.h"
 #include "AMDGPUTargetMachine.h"
 #include "MCTargetDesc/AMDGPUInstPrinter.h"
 #include "MCTargetDesc/AMDGPUMCTargetDesc.h"
 #include "R600AsmPrinter.h"
 #include "SIInstrInfo.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/MachineInstr.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/MC/MCCodeEmitter.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCInst.h"
 #include "llvm/MC/MCObjectStreamer.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Format.h"
 #include <algorithm>

 using namespace llvm;

 namespace {

 class AMDGPUMCInstLower {
   MCContext &Ctx;
   const TargetSubtargetInfo &ST;
   const AsmPrinter &AP;

   const MCExpr *getLongBranchBlockExpr(const MachineBasicBlock &SrcBB,
                                        const MachineOperand &MO) const;

 public:
   AMDGPUMCInstLower(MCContext &ctx, const TargetSubtargetInfo &ST,
                     const AsmPrinter &AP);

   bool lowerOperand(const MachineOperand &MO, MCOperand &MCOp) const;

   /// Lower a MachineInstr to an MCInst
   void lower(const MachineInstr *MI, MCInst &OutMI) const;

 };

 class R600MCInstLower : public AMDGPUMCInstLower {
 public:
   R600MCInstLower(MCContext &ctx, const R600Subtarget &ST,
                   const AsmPrinter &AP);

   /// Lower a MachineInstr to an MCInst
   void lower(const MachineInstr *MI, MCInst &OutMI) const;
 };


 } // End anonymous namespace

 #include "AMDGPUGenMCPseudoLowering.inc"

 AMDGPUMCInstLower::AMDGPUMCInstLower(MCContext &ctx,
                                      const TargetSubtargetInfo &st,
                                      const AsmPrinter &ap):
   Ctx(ctx), ST(st), AP(ap) { }

 static MCSymbolRefExpr::VariantKind getVariantKind(unsigned MOFlags) {
   switch (MOFlags) {
   default:
     return MCSymbolRefExpr::VK_None;
   case SIInstrInfo::MO_GOTPCREL:
     return MCSymbolRefExpr::VK_GOTPCREL;
   case SIInstrInfo::MO_GOTPCREL32_LO:
     return MCSymbolRefExpr::VK_AMDGPU_GOTPCREL32_LO;
   case SIInstrInfo::MO_GOTPCREL32_HI:
     return MCSymbolRefExpr::VK_AMDGPU_GOTPCREL32_HI;
   case SIInstrInfo::MO_REL32_LO:
     return MCSymbolRefExpr::VK_AMDGPU_REL32_LO;
   case SIInstrInfo::MO_REL32_HI:
     return MCSymbolRefExpr::VK_AMDGPU_REL32_HI;
   }
 }

 const MCExpr *AMDGPUMCInstLower::getLongBranchBlockExpr(
   const MachineBasicBlock &SrcBB,
   const MachineOperand &MO) const {
   const MCExpr *DestBBSym
     = MCSymbolRefExpr::create(MO.getMBB()->getSymbol(), Ctx);
   const MCExpr *SrcBBSym = MCSymbolRefExpr::create(SrcBB.getSymbol(), Ctx);

   // FIXME: The first half of this assert should be removed. This should
   // probably be PC relative instead of using the source block symbol, and
   // therefore the indirect branch expansion should use a bundle.
   assert(
       skipDebugInstructionsForward(SrcBB.begin(), SrcBB.end())->getOpcode() ==
           AMDGPU::S_GETPC_B64 &&
       ST.getInstrInfo()->get(AMDGPU::S_GETPC_B64).Size == 4);

   // s_getpc_b64 returns the address of next instruction.
   const MCConstantExpr *One = MCConstantExpr::create(4, Ctx);
   SrcBBSym = MCBinaryExpr::createAdd(SrcBBSym, One, Ctx);

   if (MO.getTargetFlags() == AMDGPU::TF_LONG_BRANCH_FORWARD)
     return MCBinaryExpr::createSub(DestBBSym, SrcBBSym, Ctx);

   assert(MO.getTargetFlags() == AMDGPU::TF_LONG_BRANCH_BACKWARD);
   return MCBinaryExpr::createSub(SrcBBSym, DestBBSym, Ctx);
 }

 bool AMDGPUMCInstLower::lowerOperand(const MachineOperand &MO,
                                      MCOperand &MCOp) const {
   switch (MO.getType()) {
   default:
     llvm_unreachable("unknown operand type");
   case MachineOperand::MO_Immediate:
     MCOp = MCOperand::createImm(MO.getImm());
     return true;
   case MachineOperand::MO_Register:
     MCOp = MCOperand::createReg(AMDGPU::getMCReg(MO.getReg(), ST));
     return true;
   case MachineOperand::MO_MachineBasicBlock: {
     if (MO.getTargetFlags() != 0) {
       MCOp = MCOperand::createExpr(
         getLongBranchBlockExpr(*MO.getParent()->getParent(), MO));
     } else {
       MCOp = MCOperand::createExpr(
         MCSymbolRefExpr::create(MO.getMBB()->getSymbol(), Ctx));
     }

     return true;
   }
   case MachineOperand::MO_GlobalAddress: {
     const GlobalValue *GV = MO.getGlobal();
     SmallString<128> SymbolName;
     AP.getNameWithPrefix(SymbolName, GV);
     MCSymbol *Sym = Ctx.getOrCreateSymbol(SymbolName);
     const MCExpr *SymExpr =
       MCSymbolRefExpr::create(Sym, getVariantKind(MO.getTargetFlags()),Ctx);
     const MCExpr *Expr = MCBinaryExpr::createAdd(SymExpr,
       MCConstantExpr::create(MO.getOffset(), Ctx), Ctx);
     MCOp = MCOperand::createExpr(Expr);
     return true;
   }
   case MachineOperand::MO_ExternalSymbol: {
     MCSymbol *Sym = Ctx.getOrCreateSymbol(StringRef(MO.getSymbolName()));
     Sym->setExternal(true);
     const MCSymbolRefExpr *Expr = MCSymbolRefExpr::create(Sym, Ctx);
     MCOp = MCOperand::createExpr(Expr);
     return true;
   }
   case MachineOperand::MO_RegisterMask:
     // Regmasks are like implicit defs.
     return false;
   }
 }

 void AMDGPUMCInstLower::lower(const MachineInstr *MI, MCInst &OutMI) const {
   unsigned Opcode = MI->getOpcode();
   const auto *TII = static_cast<const SIInstrInfo*>(ST.getInstrInfo());

   // FIXME: Should be able to handle this with emitPseudoExpansionLowering. We
   // need to select it to the subtarget specific version, and there's no way to
   // do that with a single pseudo source operation.
   if (Opcode == AMDGPU::S_SETPC_B64_return)
     Opcode = AMDGPU::S_SETPC_B64;
   else if (Opcode == AMDGPU::SI_CALL) {
     // SI_CALL is just S_SWAPPC_B64 with an additional operand to track the
     // called function (which we need to remove here).
     OutMI.setOpcode(TII->pseudoToMCOpcode(AMDGPU::S_SWAPPC_B64));
     MCOperand Dest, Src;
     lowerOperand(MI->getOperand(0), Dest);
     lowerOperand(MI->getOperand(1), Src);
     OutMI.addOperand(Dest);
     OutMI.addOperand(Src);
     return;
   } else if (Opcode == AMDGPU::SI_TCRETURN) {
     // TODO: How to use branch immediate and avoid register+add?
     Opcode = AMDGPU::S_SETPC_B64;
   }

   int MCOpcode = TII->pseudoToMCOpcode(Opcode);
   if (MCOpcode == -1) {
     LLVMContext &C = MI->getParent()->getParent()->getFunction().getContext();
     C.emitError("AMDGPUMCInstLower::lower - Pseudo instruction doesn't have "
                 "a target-specific version: " + Twine(MI->getOpcode()));
   }

   OutMI.setOpcode(MCOpcode);

   for (const MachineOperand &MO : MI->explicit_operands()) {
     MCOperand MCOp;
     lowerOperand(MO, MCOp);
     OutMI.addOperand(MCOp);
   }
 }

 bool AMDGPUAsmPrinter::lowerOperand(const MachineOperand &MO,
                                     MCOperand &MCOp) const {
   const GCNSubtarget &STI = MF->getSubtarget<GCNSubtarget>();
   AMDGPUMCInstLower MCInstLowering(OutContext, STI, *this);
   return MCInstLowering.lowerOperand(MO, MCOp);
 }

 static const MCExpr *lowerAddrSpaceCast(const TargetMachine &TM,
                                         const Constant *CV,
                                         MCContext &OutContext) {
   // TargetMachine does not support llvm-style cast. Use C++-style cast.
   // This is safe since TM is always of type AMDGPUTargetMachine or its
   // derived class.
   auto &AT = static_cast<const AMDGPUTargetMachine&>(TM);
   auto *CE = dyn_cast<ConstantExpr>(CV);

   // Lower null pointers in private and local address space.
   // Clang generates addrspacecast for null pointers in private and local
   // address space, which needs to be lowered.
   if (CE && CE->getOpcode() == Instruction::AddrSpaceCast) {
     auto Op = CE->getOperand(0);
     auto SrcAddr = Op->getType()->getPointerAddressSpace();
     if (Op->isNullValue() && AT.getNullPointerValue(SrcAddr) == 0) {
       auto DstAddr = CE->getType()->getPointerAddressSpace();
       return MCConstantExpr::create(AT.getNullPointerValue(DstAddr),
         OutContext);
     }
   }
   return nullptr;
 }

 const MCExpr *AMDGPUAsmPrinter::lowerConstant(const Constant *CV) {
   if (const MCExpr *E = lowerAddrSpaceCast(TM, CV, OutContext))
     return E;
   return AsmPrinter::lowerConstant(CV);
 }

 void AMDGPUAsmPrinter::EmitInstruction(const MachineInstr *MI) {
   if (emitPseudoExpansionLowering(*OutStreamer, MI))
     return;

   const GCNSubtarget &STI = MF->getSubtarget<GCNSubtarget>();
   AMDGPUMCInstLower MCInstLowering(OutContext, STI, *this);

   StringRef Err;
   if (!STI.getInstrInfo()->verifyInstruction(*MI, Err)) {
     LLVMContext &C = MI->getParent()->getParent()->getFunction().getContext();
     C.emitError("Illegal instruction detected: " + Err);
     MI->print(errs());
   }

   if (MI->isBundle()) {
     const MachineBasicBlock *MBB = MI->getParent();
     MachineBasicBlock::const_instr_iterator I = ++MI->getIterator();
     while (I != MBB->instr_end() && I->isInsideBundle()) {
       EmitInstruction(&*I);
       ++I;
     }
   } else {
     // We don't want SI_MASK_BRANCH/SI_RETURN_TO_EPILOG encoded. They are
     // placeholder terminator instructions and should only be printed as
     // comments.
     if (MI->getOpcode() == AMDGPU::SI_MASK_BRANCH) {
       if (isVerbose()) {
         SmallVector<char, 16> BBStr;
         raw_svector_ostream Str(BBStr);

         const MachineBasicBlock *MBB = MI->getOperand(0).getMBB();
         const MCSymbolRefExpr *Expr
           = MCSymbolRefExpr::create(MBB->getSymbol(), OutContext);
         Expr->print(Str, MAI);
         OutStreamer->emitRawComment(Twine(" mask branch ") + BBStr);
       }

       return;
     }

     if (MI->getOpcode() == AMDGPU::SI_RETURN_TO_EPILOG) {
       if (isVerbose())
         OutStreamer->emitRawComment(" return to shader part epilog");
       return;
     }

     if (MI->getOpcode() == AMDGPU::WAVE_BARRIER) {
       if (isVerbose())
         OutStreamer->emitRawComment(" wave barrier");
       return;
     }

     if (MI->getOpcode() == AMDGPU::SI_MASKED_UNREACHABLE) {
       if (isVerbose())
         OutStreamer->emitRawComment(" divergent unreachable");
       return;
     }

     MCInst TmpInst;
     MCInstLowering.lower(MI, TmpInst);
     EmitToStreamer(*OutStreamer, TmpInst);

 #ifdef EXPENSIVE_CHECKS
     // Sanity-check getInstSizeInBytes on explicitly specified CPUs (it cannot
     // work correctly for the generic CPU).
     //
     // The isPseudo check really shouldn't be here, but unfortunately there are
     // some negative lit tests that depend on being able to continue through
     // here even when pseudo instructions haven't been lowered.
     if (!MI->isPseudo() && STI.isCPUStringValid(STI.getCPU())) {
       SmallVector<MCFixup, 4> Fixups;
       SmallVector<char, 16> CodeBytes;
       raw_svector_ostream CodeStream(CodeBytes);

       std::unique_ptr<MCCodeEmitter> InstEmitter(createSIMCCodeEmitter(
           *STI.getInstrInfo(), *OutContext.getRegisterInfo(), OutContext));
       InstEmitter->encodeInstruction(TmpInst, CodeStream, Fixups, STI);

       assert(CodeBytes.size() == STI.getInstrInfo()->getInstSizeInBytes(*MI));
     }
 #endif

     if (STI.dumpCode()) {
       // Disassemble instruction/operands to text.
       DisasmLines.resize(DisasmLines.size() + 1);
       std::string &DisasmLine = DisasmLines.back();
       raw_string_ostream DisasmStream(DisasmLine);

       AMDGPUInstPrinter InstPrinter(*TM.getMCAsmInfo(),
                                     *STI.getInstrInfo(),
                                     *STI.getRegisterInfo());
       InstPrinter.printInst(&TmpInst, DisasmStream, StringRef(), STI);

       // Disassemble instruction/operands to hex representation.
       SmallVector<MCFixup, 4> Fixups;
       SmallVector<char, 16> CodeBytes;
       raw_svector_ostream CodeStream(CodeBytes);

       auto &ObjStreamer = static_cast<MCObjectStreamer&>(*OutStreamer);
       MCCodeEmitter &InstEmitter = ObjStreamer.getAssembler().getEmitter();
       InstEmitter.encodeInstruction(TmpInst, CodeStream, Fixups,
                                     MF->getSubtarget<MCSubtargetInfo>());
       HexLines.resize(HexLines.size() + 1);
       std::string &HexLine = HexLines.back();
       raw_string_ostream HexStream(HexLine);

       for (size_t i = 0; i < CodeBytes.size(); i += 4) {
         unsigned int CodeDWord = *(unsigned int *)&CodeBytes[i];
         HexStream << format("%s%08X", (i > 0 ? " " : ""), CodeDWord);
       }

       DisasmStream.flush();
       DisasmLineMaxLen = std::max(DisasmLineMaxLen, DisasmLine.size());
     }
   }
 }

 R600MCInstLower::R600MCInstLower(MCContext &Ctx, const R600Subtarget &ST,
                                  const AsmPrinter &AP) :
         AMDGPUMCInstLower(Ctx, ST, AP) { }

 void R600MCInstLower::lower(const MachineInstr *MI, MCInst &OutMI) const {
   OutMI.setOpcode(MI->getOpcode());
   for (const MachineOperand &MO : MI->explicit_operands()) {
     MCOperand MCOp;
     lowerOperand(MO, MCOp);
     OutMI.addOperand(MCOp);
   }
 }

 void R600AsmPrinter::EmitInstruction(const MachineInstr *MI) {
   const R600Subtarget &STI = MF->getSubtarget<R600Subtarget>();
   R600MCInstLower MCInstLowering(OutContext, STI, *this);

   StringRef Err;
   if (!STI.getInstrInfo()->verifyInstruction(*MI, Err)) {
     LLVMContext &C = MI->getParent()->getParent()->getFunction().getContext();
     C.emitError("Illegal instruction detected: " + Err);
     MI->print(errs());
   }

   if (MI->isBundle()) {
     const MachineBasicBlock *MBB = MI->getParent();
     MachineBasicBlock::const_instr_iterator I = ++MI->getIterator();
     while (I != MBB->instr_end() && I->isInsideBundle()) {
       EmitInstruction(&*I);
       ++I;
     }
   } else {
     MCInst TmpInst;
     MCInstLowering.lower(MI, TmpInst);
     EmitToStreamer(*OutStreamer, TmpInst);
  }
 }

 const MCExpr *R600AsmPrinter::lowerConstant(const Constant *CV) {
   if (const MCExpr *E = lowerAddrSpaceCast(TM, CV, OutContext))
     return E;
   return AsmPrinter::lowerConstant(CV);
 }
	//===- AMDGPUMCInstLower.cpp - Lower AMDGPU MachineInstr to an MCInst -----===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//
	//
	/// \file
	/// Code to lower AMDGPU MachineInstrs to their corresponding MCInst.
	//
	//===----------------------------------------------------------------------===//
	//

	#include "AMDGPUAsmPrinter.h"
	#include "AMDGPUSubtarget.h"
	#include "AMDGPUTargetMachine.h"
	#include "MCTargetDesc/AMDGPUInstPrinter.h"
	#include "MCTargetDesc/AMDGPUMCTargetDesc.h"
	#include "R600AsmPrinter.h"
	#include "SIInstrInfo.h"
	#include "llvm/CodeGen/MachineBasicBlock.h"
	#include "llvm/CodeGen/MachineInstr.h"
	#include "llvm/IR/Constants.h"
	#include "llvm/IR/Function.h"
	#include "llvm/IR/GlobalVariable.h"
	#include "llvm/MC/MCCodeEmitter.h"
	#include "llvm/MC/MCContext.h"
	#include "llvm/MC/MCExpr.h"
	#include "llvm/MC/MCInst.h"
	#include "llvm/MC/MCObjectStreamer.h"
	#include "llvm/MC/MCStreamer.h"
	#include "llvm/Support/ErrorHandling.h"
	#include "llvm/Support/Format.h"
	#include <algorithm>

	using namespace llvm;

	namespace {

	class AMDGPUMCInstLower {
	MCContext &Ctx;
	const TargetSubtargetInfo &ST;
	const AsmPrinter &AP;

	const MCExpr *getLongBranchBlockExpr(const MachineBasicBlock &SrcBB,
	const MachineOperand &MO) const;

	public:
	AMDGPUMCInstLower(MCContext &ctx, const TargetSubtargetInfo &ST,
	const AsmPrinter &AP);

	bool lowerOperand(const MachineOperand &MO, MCOperand &MCOp) const;

	/// Lower a MachineInstr to an MCInst
	void lower(const MachineInstr *MI, MCInst &OutMI) const;

	};

	class R600MCInstLower : public AMDGPUMCInstLower {
	public:
	R600MCInstLower(MCContext &ctx, const R600Subtarget &ST,
	const AsmPrinter &AP);

	/// Lower a MachineInstr to an MCInst
	void lower(const MachineInstr *MI, MCInst &OutMI) const;
	};


	} // End anonymous namespace

	#include "AMDGPUGenMCPseudoLowering.inc"

	AMDGPUMCInstLower::AMDGPUMCInstLower(MCContext &ctx,
	const TargetSubtargetInfo &st,
	const AsmPrinter &ap):
	Ctx(ctx), ST(st), AP(ap) { }

	static MCSymbolRefExpr::VariantKind getVariantKind(unsigned MOFlags) {
	switch (MOFlags) {
	default:
	return MCSymbolRefExpr::VK_None;
	case SIInstrInfo::MO_GOTPCREL:
	return MCSymbolRefExpr::VK_GOTPCREL;
	case SIInstrInfo::MO_GOTPCREL32_LO:
	return MCSymbolRefExpr::VK_AMDGPU_GOTPCREL32_LO;
	case SIInstrInfo::MO_GOTPCREL32_HI:
	return MCSymbolRefExpr::VK_AMDGPU_GOTPCREL32_HI;
	case SIInstrInfo::MO_REL32_LO:
	return MCSymbolRefExpr::VK_AMDGPU_REL32_LO;
	case SIInstrInfo::MO_REL32_HI:
	return MCSymbolRefExpr::VK_AMDGPU_REL32_HI;
	}
	}

	const MCExpr *AMDGPUMCInstLower::getLongBranchBlockExpr(
	const MachineBasicBlock &SrcBB,
	const MachineOperand &MO) const {
	const MCExpr *DestBBSym
	= MCSymbolRefExpr::create(MO.getMBB()->getSymbol(), Ctx);
	const MCExpr *SrcBBSym = MCSymbolRefExpr::create(SrcBB.getSymbol(), Ctx);

	// FIXME: The first half of this assert should be removed. This should
	// probably be PC relative instead of using the source block symbol, and
	// therefore the indirect branch expansion should use a bundle.
	assert(
	skipDebugInstructionsForward(SrcBB.begin(), SrcBB.end())->getOpcode() ==
	AMDGPU::S_GETPC_B64 &&
	ST.getInstrInfo()->get(AMDGPU::S_GETPC_B64).Size == 4);

	// s_getpc_b64 returns the address of next instruction.
	const MCConstantExpr *One = MCConstantExpr::create(4, Ctx);
	SrcBBSym = MCBinaryExpr::createAdd(SrcBBSym, One, Ctx);

	if (MO.getTargetFlags() == AMDGPU::TF_LONG_BRANCH_FORWARD)
	return MCBinaryExpr::createSub(DestBBSym, SrcBBSym, Ctx);

	assert(MO.getTargetFlags() == AMDGPU::TF_LONG_BRANCH_BACKWARD);
	return MCBinaryExpr::createSub(SrcBBSym, DestBBSym, Ctx);
	}

	bool AMDGPUMCInstLower::lowerOperand(const MachineOperand &MO,
	MCOperand &MCOp) const {
	switch (MO.getType()) {
	default:
	llvm_unreachable("unknown operand type");
	case MachineOperand::MO_Immediate:
	MCOp = MCOperand::createImm(MO.getImm());
	return true;
	case MachineOperand::MO_Register:
	MCOp = MCOperand::createReg(AMDGPU::getMCReg(MO.getReg(), ST));
	return true;
	case MachineOperand::MO_MachineBasicBlock: {
	if (MO.getTargetFlags() != 0) {
	MCOp = MCOperand::createExpr(
	getLongBranchBlockExpr(*MO.getParent()->getParent(), MO));
	} else {
	MCOp = MCOperand::createExpr(
	MCSymbolRefExpr::create(MO.getMBB()->getSymbol(), Ctx));
	}

	return true;
	}
	case MachineOperand::MO_GlobalAddress: {
	const GlobalValue *GV = MO.getGlobal();
	SmallString<128> SymbolName;
	AP.getNameWithPrefix(SymbolName, GV);
	MCSymbol *Sym = Ctx.getOrCreateSymbol(SymbolName);
	const MCExpr *SymExpr =
	MCSymbolRefExpr::create(Sym, getVariantKind(MO.getTargetFlags()),Ctx);
	const MCExpr *Expr = MCBinaryExpr::createAdd(SymExpr,
	MCConstantExpr::create(MO.getOffset(), Ctx), Ctx);
	MCOp = MCOperand::createExpr(Expr);
	return true;
	}
	case MachineOperand::MO_ExternalSymbol: {
	MCSymbol *Sym = Ctx.getOrCreateSymbol(StringRef(MO.getSymbolName()));
	Sym->setExternal(true);
	const MCSymbolRefExpr *Expr = MCSymbolRefExpr::create(Sym, Ctx);
	MCOp = MCOperand::createExpr(Expr);
	return true;
	}
	case MachineOperand::MO_RegisterMask:
	// Regmasks are like implicit defs.
	return false;
	}
	}

	void AMDGPUMCInstLower::lower(const MachineInstr *MI, MCInst &OutMI) const {
	unsigned Opcode = MI->getOpcode();
	const auto TII = static_cast<const SIInstrInfo>(ST.getInstrInfo());

	// FIXME: Should be able to handle this with emitPseudoExpansionLowering. We
	// need to select it to the subtarget specific version, and there's no way to
	// do that with a single pseudo source operation.
	if (Opcode == AMDGPU::S_SETPC_B64_return)
	Opcode = AMDGPU::S_SETPC_B64;
	else if (Opcode == AMDGPU::SI_CALL) {
	// SI_CALL is just S_SWAPPC_B64 with an additional operand to track the
	// called function (which we need to remove here).
	OutMI.setOpcode(TII->pseudoToMCOpcode(AMDGPU::S_SWAPPC_B64));
	MCOperand Dest, Src;
	lowerOperand(MI->getOperand(0), Dest);
	lowerOperand(MI->getOperand(1), Src);
	OutMI.addOperand(Dest);
	OutMI.addOperand(Src);
	return;
	} else if (Opcode == AMDGPU::SI_TCRETURN) {
	// TODO: How to use branch immediate and avoid register+add?
	Opcode = AMDGPU::S_SETPC_B64;
	}

	int MCOpcode = TII->pseudoToMCOpcode(Opcode);
	if (MCOpcode == -1) {
	LLVMContext &C = MI->getParent()->getParent()->getFunction().getContext();
	C.emitError("AMDGPUMCInstLower::lower - Pseudo instruction doesn't have "
	"a target-specific version: " + Twine(MI->getOpcode()));
	}

	OutMI.setOpcode(MCOpcode);

	for (const MachineOperand &MO : MI->explicit_operands()) {
	MCOperand MCOp;
	lowerOperand(MO, MCOp);
	OutMI.addOperand(MCOp);
	}
	}

	bool AMDGPUAsmPrinter::lowerOperand(const MachineOperand &MO,
	MCOperand &MCOp) const {
	const GCNSubtarget &STI = MF->getSubtarget<GCNSubtarget>();
	AMDGPUMCInstLower MCInstLowering(OutContext, STI, *this);
	return MCInstLowering.lowerOperand(MO, MCOp);
	}

	static const MCExpr *lowerAddrSpaceCast(const TargetMachine &TM,
	const Constant *CV,
	MCContext &OutContext) {
	// TargetMachine does not support llvm-style cast. Use C++-style cast.
	// This is safe since TM is always of type AMDGPUTargetMachine or its
	// derived class.
	auto &AT = static_cast<const AMDGPUTargetMachine&>(TM);
	auto *CE = dyn_cast<ConstantExpr>(CV);

	// Lower null pointers in private and local address space.
	// Clang generates addrspacecast for null pointers in private and local
	// address space, which needs to be lowered.
	if (CE && CE->getOpcode() == Instruction::AddrSpaceCast) {
	auto Op = CE->getOperand(0);
	auto SrcAddr = Op->getType()->getPointerAddressSpace();
	if (Op->isNullValue() && AT.getNullPointerValue(SrcAddr) == 0) {
	auto DstAddr = CE->getType()->getPointerAddressSpace();
	return MCConstantExpr::create(AT.getNullPointerValue(DstAddr),
	OutContext);
	}
	}
	return nullptr;
	}

	const MCExpr AMDGPUAsmPrinter::lowerConstant(const Constant CV) {
	if (const MCExpr *E = lowerAddrSpaceCast(TM, CV, OutContext))
	return E;
	return AsmPrinter::lowerConstant(CV);
	}

	void AMDGPUAsmPrinter::EmitInstruction(const MachineInstr *MI) {
	if (emitPseudoExpansionLowering(*OutStreamer, MI))
	return;

	const GCNSubtarget &STI = MF->getSubtarget<GCNSubtarget>();
	AMDGPUMCInstLower MCInstLowering(OutContext, STI, *this);

	StringRef Err;
	if (!STI.getInstrInfo()->verifyInstruction(*MI, Err)) {
	LLVMContext &C = MI->getParent()->getParent()->getFunction().getContext();
	C.emitError("Illegal instruction detected: " + Err);
	MI->print(errs());
	}

	if (MI->isBundle()) {
	const MachineBasicBlock *MBB = MI->getParent();
	MachineBasicBlock::const_instr_iterator I = ++MI->getIterator();
	while (I != MBB->instr_end() && I->isInsideBundle()) {
	EmitInstruction(&*I);
	++I;
	}
	} else {
	// We don't want SI_MASK_BRANCH/SI_RETURN_TO_EPILOG encoded. They are
	// placeholder terminator instructions and should only be printed as
	// comments.
	if (MI->getOpcode() == AMDGPU::SI_MASK_BRANCH) {
	if (isVerbose()) {
	SmallVector<char, 16> BBStr;
	raw_svector_ostream Str(BBStr);

	const MachineBasicBlock *MBB = MI->getOperand(0).getMBB();
	const MCSymbolRefExpr *Expr
	= MCSymbolRefExpr::create(MBB->getSymbol(), OutContext);
	Expr->print(Str, MAI);
	OutStreamer->emitRawComment(Twine(" mask branch ") + BBStr);
	}

	return;
	}

	if (MI->getOpcode() == AMDGPU::SI_RETURN_TO_EPILOG) {
	if (isVerbose())
	OutStreamer->emitRawComment(" return to shader part epilog");
	return;
	}

	if (MI->getOpcode() == AMDGPU::WAVE_BARRIER) {
	if (isVerbose())
	OutStreamer->emitRawComment(" wave barrier");
	return;
	}

	if (MI->getOpcode() == AMDGPU::SI_MASKED_UNREACHABLE) {
	if (isVerbose())
	OutStreamer->emitRawComment(" divergent unreachable");
	return;
	}

	MCInst TmpInst;
	MCInstLowering.lower(MI, TmpInst);
	EmitToStreamer(*OutStreamer, TmpInst);

	#ifdef EXPENSIVE_CHECKS
	// Sanity-check getInstSizeInBytes on explicitly specified CPUs (it cannot
	// work correctly for the generic CPU).
	//
	// The isPseudo check really shouldn't be here, but unfortunately there are
	// some negative lit tests that depend on being able to continue through
	// here even when pseudo instructions haven't been lowered.
	if (!MI->isPseudo() && STI.isCPUStringValid(STI.getCPU())) {
	SmallVector<MCFixup, 4> Fixups;
	SmallVector<char, 16> CodeBytes;
	raw_svector_ostream CodeStream(CodeBytes);

	std::unique_ptr<MCCodeEmitter> InstEmitter(createSIMCCodeEmitter(
	STI.getInstrInfo(), OutContext.getRegisterInfo(), OutContext));
	InstEmitter->encodeInstruction(TmpInst, CodeStream, Fixups, STI);

	assert(CodeBytes.size() == STI.getInstrInfo()->getInstSizeInBytes(*MI));
	}
	#endif

	if (STI.dumpCode()) {
	// Disassemble instruction/operands to text.
	DisasmLines.resize(DisasmLines.size() + 1);
	std::string &DisasmLine = DisasmLines.back();
	raw_string_ostream DisasmStream(DisasmLine);

	AMDGPUInstPrinter InstPrinter(*TM.getMCAsmInfo(),
	*STI.getInstrInfo(),
	*STI.getRegisterInfo());
	InstPrinter.printInst(&TmpInst, DisasmStream, StringRef(), STI);

	// Disassemble instruction/operands to hex representation.
	SmallVector<MCFixup, 4> Fixups;
	SmallVector<char, 16> CodeBytes;
	raw_svector_ostream CodeStream(CodeBytes);

	auto &ObjStreamer = static_cast<MCObjectStreamer&>(*OutStreamer);
	MCCodeEmitter &InstEmitter = ObjStreamer.getAssembler().getEmitter();
	InstEmitter.encodeInstruction(TmpInst, CodeStream, Fixups,
	MF->getSubtarget<MCSubtargetInfo>());
	HexLines.resize(HexLines.size() + 1);
	std::string &HexLine = HexLines.back();
	raw_string_ostream HexStream(HexLine);

	for (size_t i = 0; i < CodeBytes.size(); i += 4) {
	unsigned int CodeDWord = (unsigned int )&CodeBytes[i];
	HexStream << format("%s%08X", (i > 0 ? " " : ""), CodeDWord);
	}

	DisasmStream.flush();
	DisasmLineMaxLen = std::max(DisasmLineMaxLen, DisasmLine.size());
	}
	}
	}

	R600MCInstLower::R600MCInstLower(MCContext &Ctx, const R600Subtarget &ST,
	const AsmPrinter &AP) :
	AMDGPUMCInstLower(Ctx, ST, AP) { }

	void R600MCInstLower::lower(const MachineInstr *MI, MCInst &OutMI) const {
	OutMI.setOpcode(MI->getOpcode());
	for (const MachineOperand &MO : MI->explicit_operands()) {
	MCOperand MCOp;
	lowerOperand(MO, MCOp);
	OutMI.addOperand(MCOp);
	}
	}

	void R600AsmPrinter::EmitInstruction(const MachineInstr *MI) {
	const R600Subtarget &STI = MF->getSubtarget<R600Subtarget>();
	R600MCInstLower MCInstLowering(OutContext, STI, *this);

	StringRef Err;
	if (!STI.getInstrInfo()->verifyInstruction(*MI, Err)) {
	LLVMContext &C = MI->getParent()->getParent()->getFunction().getContext();
	C.emitError("Illegal instruction detected: " + Err);
	MI->print(errs());
	}

	if (MI->isBundle()) {
	const MachineBasicBlock *MBB = MI->getParent();
	MachineBasicBlock::const_instr_iterator I = ++MI->getIterator();
	while (I != MBB->instr_end() && I->isInsideBundle()) {
	EmitInstruction(&*I);
	++I;
	}
	} else {
	MCInst TmpInst;
	MCInstLowering.lower(MI, TmpInst);
	EmitToStreamer(*OutStreamer, TmpInst);
	}
	}

	const MCExpr R600AsmPrinter::lowerConstant(const Constant CV) {
	if (const MCExpr *E = lowerAddrSpaceCast(TM, CV, OutContext))
	return E;
	return AsmPrinter::lowerConstant(CV);
	}