lib/Target/SystemZ/SystemZShortenInst.cpp - llvm - Git at Google

 //===-- SystemZShortenInst.cpp - Instruction-shortening pass --------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 //
 // This pass tries to replace instructions with shorter forms.  For example,
 // IILF can be replaced with LLILL or LLILH if the constant fits and if the
 // other 32 bits of the GR64 destination are not live.
 //
 //===----------------------------------------------------------------------===//

 #include "SystemZTargetMachine.h"
 #include "llvm/CodeGen/LivePhysRegs.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"

 using namespace llvm;

 #define DEBUG_TYPE "systemz-shorten-inst"

 namespace {
 class SystemZShortenInst : public MachineFunctionPass {
 public:
   static char ID;
   SystemZShortenInst(const SystemZTargetMachine &tm);

   StringRef getPassName() const override {
     return "SystemZ Instruction Shortening";
   }

   bool processBlock(MachineBasicBlock &MBB);
   bool runOnMachineFunction(MachineFunction &F) override;
   MachineFunctionProperties getRequiredProperties() const override {
     return MachineFunctionProperties().set(
         MachineFunctionProperties::Property::NoVRegs);
   }

 private:
   bool shortenIIF(MachineInstr &MI, unsigned LLIxL, unsigned LLIxH);
   bool shortenOn0(MachineInstr &MI, unsigned Opcode);
   bool shortenOn01(MachineInstr &MI, unsigned Opcode);
   bool shortenOn001(MachineInstr &MI, unsigned Opcode);
   bool shortenOn001AddCC(MachineInstr &MI, unsigned Opcode);
   bool shortenFPConv(MachineInstr &MI, unsigned Opcode);

   const SystemZInstrInfo *TII;
   const TargetRegisterInfo *TRI;
   LivePhysRegs LiveRegs;
 };

 char SystemZShortenInst::ID = 0;
 } // end anonymous namespace

 FunctionPass *llvm::createSystemZShortenInstPass(SystemZTargetMachine &TM) {
   return new SystemZShortenInst(TM);
 }

 SystemZShortenInst::SystemZShortenInst(const SystemZTargetMachine &tm)
   : MachineFunctionPass(ID), TII(nullptr) {}

 // Tie operands if MI has become a two-address instruction.
 static void tieOpsIfNeeded(MachineInstr &MI) {
   if (MI.getDesc().getOperandConstraint(0, MCOI::TIED_TO) &&
       !MI.getOperand(0).isTied())
     MI.tieOperands(0, 1);
 }

 // MI loads one word of a GPR using an IIxF instruction and LLIxL and LLIxH
 // are the halfword immediate loads for the same word.  Try to use one of them
 // instead of IIxF.
 bool SystemZShortenInst::shortenIIF(MachineInstr &MI, unsigned LLIxL,
                                     unsigned LLIxH) {
   unsigned Reg = MI.getOperand(0).getReg();
   // The new opcode will clear the other half of the GR64 reg, so
   // cancel if that is live.
   unsigned thisSubRegIdx =
       (SystemZ::GRH32BitRegClass.contains(Reg) ? SystemZ::subreg_h32
                                                : SystemZ::subreg_l32);
   unsigned otherSubRegIdx =
       (thisSubRegIdx == SystemZ::subreg_l32 ? SystemZ::subreg_h32
                                             : SystemZ::subreg_l32);
   unsigned GR64BitReg =
       TRI->getMatchingSuperReg(Reg, thisSubRegIdx, &SystemZ::GR64BitRegClass);
   unsigned OtherReg = TRI->getSubReg(GR64BitReg, otherSubRegIdx);
   if (LiveRegs.contains(OtherReg))
     return false;

   uint64_t Imm = MI.getOperand(1).getImm();
   if (SystemZ::isImmLL(Imm)) {
     MI.setDesc(TII->get(LLIxL));
     MI.getOperand(0).setReg(SystemZMC::getRegAsGR64(Reg));
     return true;
   }
   if (SystemZ::isImmLH(Imm)) {
     MI.setDesc(TII->get(LLIxH));
     MI.getOperand(0).setReg(SystemZMC::getRegAsGR64(Reg));
     MI.getOperand(1).setImm(Imm >> 16);
     return true;
   }
   return false;
 }

 // Change MI's opcode to Opcode if register operand 0 has a 4-bit encoding.
 bool SystemZShortenInst::shortenOn0(MachineInstr &MI, unsigned Opcode) {
   if (SystemZMC::getFirstReg(MI.getOperand(0).getReg()) < 16) {
     MI.setDesc(TII->get(Opcode));
     return true;
   }
   return false;
 }

 // Change MI's opcode to Opcode if register operands 0 and 1 have a
 // 4-bit encoding.
 bool SystemZShortenInst::shortenOn01(MachineInstr &MI, unsigned Opcode) {
   if (SystemZMC::getFirstReg(MI.getOperand(0).getReg()) < 16 &&
       SystemZMC::getFirstReg(MI.getOperand(1).getReg()) < 16) {
     MI.setDesc(TII->get(Opcode));
     return true;
   }
   return false;
 }

 // Change MI's opcode to Opcode if register operands 0, 1 and 2 have a
 // 4-bit encoding and if operands 0 and 1 are tied. Also ties op 0
 // with op 1, if MI becomes 2-address.
 bool SystemZShortenInst::shortenOn001(MachineInstr &MI, unsigned Opcode) {
   if (SystemZMC::getFirstReg(MI.getOperand(0).getReg()) < 16 &&
       MI.getOperand(1).getReg() == MI.getOperand(0).getReg() &&
       SystemZMC::getFirstReg(MI.getOperand(2).getReg()) < 16) {
     MI.setDesc(TII->get(Opcode));
     tieOpsIfNeeded(MI);
     return true;
   }
   return false;
 }

 // Calls shortenOn001 if CCLive is false. CC def operand is added in
 // case of success.
 bool SystemZShortenInst::shortenOn001AddCC(MachineInstr &MI, unsigned Opcode) {
   if (!LiveRegs.contains(SystemZ::CC) && shortenOn001(MI, Opcode)) {
     MachineInstrBuilder(*MI.getParent()->getParent(), &MI)
       .addReg(SystemZ::CC, RegState::ImplicitDefine | RegState::Dead);
     return true;
   }
   return false;
 }

 // MI is a vector-style conversion instruction with the operand order:
 // destination, source, exact-suppress, rounding-mode.  If both registers
 // have a 4-bit encoding then change it to Opcode, which has operand order:
 // destination, rouding-mode, source, exact-suppress.
 bool SystemZShortenInst::shortenFPConv(MachineInstr &MI, unsigned Opcode) {
   if (SystemZMC::getFirstReg(MI.getOperand(0).getReg()) < 16 &&
       SystemZMC::getFirstReg(MI.getOperand(1).getReg()) < 16) {
     MachineOperand Dest(MI.getOperand(0));
     MachineOperand Src(MI.getOperand(1));
     MachineOperand Suppress(MI.getOperand(2));
     MachineOperand Mode(MI.getOperand(3));
     MI.RemoveOperand(3);
     MI.RemoveOperand(2);
     MI.RemoveOperand(1);
     MI.RemoveOperand(0);
     MI.setDesc(TII->get(Opcode));
     MachineInstrBuilder(*MI.getParent()->getParent(), &MI)
         .add(Dest)
         .add(Mode)
         .add(Src)
         .add(Suppress);
     return true;
   }
   return false;
 }

 // Process all instructions in MBB.  Return true if something changed.
 bool SystemZShortenInst::processBlock(MachineBasicBlock &MBB) {
   bool Changed = false;

   // Set up the set of live registers at the end of MBB (live out)
   LiveRegs.clear();
   LiveRegs.addLiveOuts(MBB);

   // Iterate backwards through the block looking for instructions to change.
   for (auto MBBI = MBB.rbegin(), MBBE = MBB.rend(); MBBI != MBBE; ++MBBI) {
     MachineInstr &MI = *MBBI;
     switch (MI.getOpcode()) {
     case SystemZ::IILF:
       Changed |= shortenIIF(MI, SystemZ::LLILL, SystemZ::LLILH);
       break;

     case SystemZ::IIHF:
       Changed |= shortenIIF(MI, SystemZ::LLIHL, SystemZ::LLIHH);
       break;

     case SystemZ::WFADB:
       Changed |= shortenOn001AddCC(MI, SystemZ::ADBR);
       break;

     case SystemZ::WFASB:
       Changed |= shortenOn001AddCC(MI, SystemZ::AEBR);
       break;

     case SystemZ::WFDDB:
       Changed |= shortenOn001(MI, SystemZ::DDBR);
       break;

     case SystemZ::WFDSB:
       Changed |= shortenOn001(MI, SystemZ::DEBR);
       break;

     case SystemZ::WFIDB:
       Changed |= shortenFPConv(MI, SystemZ::FIDBRA);
       break;

     case SystemZ::WFISB:
       Changed |= shortenFPConv(MI, SystemZ::FIEBRA);
       break;

     case SystemZ::WLDEB:
       Changed |= shortenOn01(MI, SystemZ::LDEBR);
       break;

     case SystemZ::WLEDB:
       Changed |= shortenFPConv(MI, SystemZ::LEDBRA);
       break;

     case SystemZ::WFMDB:
       Changed |= shortenOn001(MI, SystemZ::MDBR);
       break;

     case SystemZ::WFMSB:
       Changed |= shortenOn001(MI, SystemZ::MEEBR);
       break;

     case SystemZ::WFLCDB:
       Changed |= shortenOn01(MI, SystemZ::LCDFR);
       break;

     case SystemZ::WFLCSB:
       Changed |= shortenOn01(MI, SystemZ::LCDFR_32);
       break;

     case SystemZ::WFLNDB:
       Changed |= shortenOn01(MI, SystemZ::LNDFR);
       break;

     case SystemZ::WFLNSB:
       Changed |= shortenOn01(MI, SystemZ::LNDFR_32);
       break;

     case SystemZ::WFLPDB:
       Changed |= shortenOn01(MI, SystemZ::LPDFR);
       break;

     case SystemZ::WFLPSB:
       Changed |= shortenOn01(MI, SystemZ::LPDFR_32);
       break;

     case SystemZ::WFSQDB:
       Changed |= shortenOn01(MI, SystemZ::SQDBR);
       break;

     case SystemZ::WFSQSB:
       Changed |= shortenOn01(MI, SystemZ::SQEBR);
       break;

     case SystemZ::WFSDB:
       Changed |= shortenOn001AddCC(MI, SystemZ::SDBR);
       break;

     case SystemZ::WFSSB:
       Changed |= shortenOn001AddCC(MI, SystemZ::SEBR);
       break;

     case SystemZ::WFCDB:
       Changed |= shortenOn01(MI, SystemZ::CDBR);
       break;

     case SystemZ::WFCSB:
       Changed |= shortenOn01(MI, SystemZ::CEBR);
       break;

     case SystemZ::VL32:
       // For z13 we prefer LDE over LE to avoid partial register dependencies.
       Changed |= shortenOn0(MI, SystemZ::LDE32);
       break;

     case SystemZ::VST32:
       Changed |= shortenOn0(MI, SystemZ::STE);
       break;

     case SystemZ::VL64:
       Changed |= shortenOn0(MI, SystemZ::LD);
       break;

     case SystemZ::VST64:
       Changed |= shortenOn0(MI, SystemZ::STD);
       break;
     }

     LiveRegs.stepBackward(MI);
   }

   return Changed;
 }

 bool SystemZShortenInst::runOnMachineFunction(MachineFunction &F) {
   if (skipFunction(F.getFunction()))
     return false;

   const SystemZSubtarget &ST = F.getSubtarget<SystemZSubtarget>();
   TII = ST.getInstrInfo();
   TRI = ST.getRegisterInfo();
   LiveRegs.init(*TRI);

   bool Changed = false;
   for (auto &MBB : F)
     Changed |= processBlock(MBB);

   return Changed;
 }
	//===-- SystemZShortenInst.cpp - Instruction-shortening pass --------------===//
	//
	// 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
	//
	//===----------------------------------------------------------------------===//
	//
	// This pass tries to replace instructions with shorter forms. For example,
	// IILF can be replaced with LLILL or LLILH if the constant fits and if the
	// other 32 bits of the GR64 destination are not live.
	//
	//===----------------------------------------------------------------------===//

	#include "SystemZTargetMachine.h"
	#include "llvm/CodeGen/LivePhysRegs.h"
	#include "llvm/CodeGen/MachineFunctionPass.h"
	#include "llvm/CodeGen/MachineInstrBuilder.h"
	#include "llvm/CodeGen/TargetRegisterInfo.h"

	using namespace llvm;

	#define DEBUG_TYPE "systemz-shorten-inst"

	namespace {
	class SystemZShortenInst : public MachineFunctionPass {
	public:
	static char ID;
	SystemZShortenInst(const SystemZTargetMachine &tm);

	StringRef getPassName() const override {
	return "SystemZ Instruction Shortening";
	}

	bool processBlock(MachineBasicBlock &MBB);
	bool runOnMachineFunction(MachineFunction &F) override;
	MachineFunctionProperties getRequiredProperties() const override {
	return MachineFunctionProperties().set(
	MachineFunctionProperties::Property::NoVRegs);
	}

	private:
	bool shortenIIF(MachineInstr &MI, unsigned LLIxL, unsigned LLIxH);
	bool shortenOn0(MachineInstr &MI, unsigned Opcode);
	bool shortenOn01(MachineInstr &MI, unsigned Opcode);
	bool shortenOn001(MachineInstr &MI, unsigned Opcode);
	bool shortenOn001AddCC(MachineInstr &MI, unsigned Opcode);
	bool shortenFPConv(MachineInstr &MI, unsigned Opcode);

	const SystemZInstrInfo *TII;
	const TargetRegisterInfo *TRI;
	LivePhysRegs LiveRegs;
	};

	char SystemZShortenInst::ID = 0;
	} // end anonymous namespace

	FunctionPass *llvm::createSystemZShortenInstPass(SystemZTargetMachine &TM) {
	return new SystemZShortenInst(TM);
	}

	SystemZShortenInst::SystemZShortenInst(const SystemZTargetMachine &tm)
	: MachineFunctionPass(ID), TII(nullptr) {}

	// Tie operands if MI has become a two-address instruction.
	static void tieOpsIfNeeded(MachineInstr &MI) {
	if (MI.getDesc().getOperandConstraint(0, MCOI::TIED_TO) &&
	!MI.getOperand(0).isTied())
	MI.tieOperands(0, 1);
	}

	// MI loads one word of a GPR using an IIxF instruction and LLIxL and LLIxH
	// are the halfword immediate loads for the same word. Try to use one of them
	// instead of IIxF.
	bool SystemZShortenInst::shortenIIF(MachineInstr &MI, unsigned LLIxL,
	unsigned LLIxH) {
	unsigned Reg = MI.getOperand(0).getReg();
	// The new opcode will clear the other half of the GR64 reg, so
	// cancel if that is live.
	unsigned thisSubRegIdx =
	(SystemZ::GRH32BitRegClass.contains(Reg) ? SystemZ::subreg_h32
	: SystemZ::subreg_l32);
	unsigned otherSubRegIdx =
	(thisSubRegIdx == SystemZ::subreg_l32 ? SystemZ::subreg_h32
	: SystemZ::subreg_l32);
	unsigned GR64BitReg =
	TRI->getMatchingSuperReg(Reg, thisSubRegIdx, &SystemZ::GR64BitRegClass);
	unsigned OtherReg = TRI->getSubReg(GR64BitReg, otherSubRegIdx);
	if (LiveRegs.contains(OtherReg))
	return false;

	uint64_t Imm = MI.getOperand(1).getImm();
	if (SystemZ::isImmLL(Imm)) {
	MI.setDesc(TII->get(LLIxL));
	MI.getOperand(0).setReg(SystemZMC::getRegAsGR64(Reg));
	return true;
	}
	if (SystemZ::isImmLH(Imm)) {
	MI.setDesc(TII->get(LLIxH));
	MI.getOperand(0).setReg(SystemZMC::getRegAsGR64(Reg));
	MI.getOperand(1).setImm(Imm >> 16);
	return true;
	}
	return false;
	}

	// Change MI's opcode to Opcode if register operand 0 has a 4-bit encoding.
	bool SystemZShortenInst::shortenOn0(MachineInstr &MI, unsigned Opcode) {
	if (SystemZMC::getFirstReg(MI.getOperand(0).getReg()) < 16) {
	MI.setDesc(TII->get(Opcode));
	return true;
	}
	return false;
	}

	// Change MI's opcode to Opcode if register operands 0 and 1 have a
	// 4-bit encoding.
	bool SystemZShortenInst::shortenOn01(MachineInstr &MI, unsigned Opcode) {
	if (SystemZMC::getFirstReg(MI.getOperand(0).getReg()) < 16 &&
	SystemZMC::getFirstReg(MI.getOperand(1).getReg()) < 16) {
	MI.setDesc(TII->get(Opcode));
	return true;
	}
	return false;
	}

	// Change MI's opcode to Opcode if register operands 0, 1 and 2 have a
	// 4-bit encoding and if operands 0 and 1 are tied. Also ties op 0
	// with op 1, if MI becomes 2-address.
	bool SystemZShortenInst::shortenOn001(MachineInstr &MI, unsigned Opcode) {
	if (SystemZMC::getFirstReg(MI.getOperand(0).getReg()) < 16 &&
	MI.getOperand(1).getReg() == MI.getOperand(0).getReg() &&
	SystemZMC::getFirstReg(MI.getOperand(2).getReg()) < 16) {
	MI.setDesc(TII->get(Opcode));
	tieOpsIfNeeded(MI);
	return true;
	}
	return false;
	}

	// Calls shortenOn001 if CCLive is false. CC def operand is added in
	// case of success.
	bool SystemZShortenInst::shortenOn001AddCC(MachineInstr &MI, unsigned Opcode) {
	if (!LiveRegs.contains(SystemZ::CC) && shortenOn001(MI, Opcode)) {
	MachineInstrBuilder(*MI.getParent()->getParent(), &MI)
	.addReg(SystemZ::CC, RegState::ImplicitDefine \| RegState::Dead);
	return true;
	}
	return false;
	}

	// MI is a vector-style conversion instruction with the operand order:
	// destination, source, exact-suppress, rounding-mode. If both registers
	// have a 4-bit encoding then change it to Opcode, which has operand order:
	// destination, rouding-mode, source, exact-suppress.
	bool SystemZShortenInst::shortenFPConv(MachineInstr &MI, unsigned Opcode) {
	if (SystemZMC::getFirstReg(MI.getOperand(0).getReg()) < 16 &&
	SystemZMC::getFirstReg(MI.getOperand(1).getReg()) < 16) {
	MachineOperand Dest(MI.getOperand(0));
	MachineOperand Src(MI.getOperand(1));
	MachineOperand Suppress(MI.getOperand(2));
	MachineOperand Mode(MI.getOperand(3));
	MI.RemoveOperand(3);
	MI.RemoveOperand(2);
	MI.RemoveOperand(1);
	MI.RemoveOperand(0);
	MI.setDesc(TII->get(Opcode));
	MachineInstrBuilder(*MI.getParent()->getParent(), &MI)
	.add(Dest)
	.add(Mode)
	.add(Src)
	.add(Suppress);
	return true;
	}
	return false;
	}

	// Process all instructions in MBB. Return true if something changed.
	bool SystemZShortenInst::processBlock(MachineBasicBlock &MBB) {
	bool Changed = false;

	// Set up the set of live registers at the end of MBB (live out)
	LiveRegs.clear();
	LiveRegs.addLiveOuts(MBB);

	// Iterate backwards through the block looking for instructions to change.
	for (auto MBBI = MBB.rbegin(), MBBE = MBB.rend(); MBBI != MBBE; ++MBBI) {
	MachineInstr &MI = *MBBI;
	switch (MI.getOpcode()) {
	case SystemZ::IILF:
	Changed \|= shortenIIF(MI, SystemZ::LLILL, SystemZ::LLILH);
	break;

	case SystemZ::IIHF:
	Changed \|= shortenIIF(MI, SystemZ::LLIHL, SystemZ::LLIHH);
	break;

	case SystemZ::WFADB:
	Changed \|= shortenOn001AddCC(MI, SystemZ::ADBR);
	break;

	case SystemZ::WFASB:
	Changed \|= shortenOn001AddCC(MI, SystemZ::AEBR);
	break;

	case SystemZ::WFDDB:
	Changed \|= shortenOn001(MI, SystemZ::DDBR);
	break;

	case SystemZ::WFDSB:
	Changed \|= shortenOn001(MI, SystemZ::DEBR);
	break;

	case SystemZ::WFIDB:
	Changed \|= shortenFPConv(MI, SystemZ::FIDBRA);
	break;

	case SystemZ::WFISB:
	Changed \|= shortenFPConv(MI, SystemZ::FIEBRA);
	break;

	case SystemZ::WLDEB:
	Changed \|= shortenOn01(MI, SystemZ::LDEBR);
	break;

	case SystemZ::WLEDB:
	Changed \|= shortenFPConv(MI, SystemZ::LEDBRA);
	break;

	case SystemZ::WFMDB:
	Changed \|= shortenOn001(MI, SystemZ::MDBR);
	break;

	case SystemZ::WFMSB:
	Changed \|= shortenOn001(MI, SystemZ::MEEBR);
	break;

	case SystemZ::WFLCDB:
	Changed \|= shortenOn01(MI, SystemZ::LCDFR);
	break;

	case SystemZ::WFLCSB:
	Changed \|= shortenOn01(MI, SystemZ::LCDFR_32);
	break;

	case SystemZ::WFLNDB:
	Changed \|= shortenOn01(MI, SystemZ::LNDFR);
	break;

	case SystemZ::WFLNSB:
	Changed \|= shortenOn01(MI, SystemZ::LNDFR_32);
	break;

	case SystemZ::WFLPDB:
	Changed \|= shortenOn01(MI, SystemZ::LPDFR);
	break;

	case SystemZ::WFLPSB:
	Changed \|= shortenOn01(MI, SystemZ::LPDFR_32);
	break;

	case SystemZ::WFSQDB:
	Changed \|= shortenOn01(MI, SystemZ::SQDBR);
	break;

	case SystemZ::WFSQSB:
	Changed \|= shortenOn01(MI, SystemZ::SQEBR);
	break;

	case SystemZ::WFSDB:
	Changed \|= shortenOn001AddCC(MI, SystemZ::SDBR);
	break;

	case SystemZ::WFSSB:
	Changed \|= shortenOn001AddCC(MI, SystemZ::SEBR);
	break;

	case SystemZ::WFCDB:
	Changed \|= shortenOn01(MI, SystemZ::CDBR);
	break;

	case SystemZ::WFCSB:
	Changed \|= shortenOn01(MI, SystemZ::CEBR);
	break;

	case SystemZ::VL32:
	// For z13 we prefer LDE over LE to avoid partial register dependencies.
	Changed \|= shortenOn0(MI, SystemZ::LDE32);
	break;

	case SystemZ::VST32:
	Changed \|= shortenOn0(MI, SystemZ::STE);
	break;

	case SystemZ::VL64:
	Changed \|= shortenOn0(MI, SystemZ::LD);
	break;

	case SystemZ::VST64:
	Changed \|= shortenOn0(MI, SystemZ::STD);
	break;
	}

	LiveRegs.stepBackward(MI);
	}

	return Changed;
	}

	bool SystemZShortenInst::runOnMachineFunction(MachineFunction &F) {
	if (skipFunction(F.getFunction()))
	return false;

	const SystemZSubtarget &ST = F.getSubtarget<SystemZSubtarget>();
	TII = ST.getInstrInfo();
	TRI = ST.getRegisterInfo();
	LiveRegs.init(*TRI);

	bool Changed = false;
	for (auto &MBB : F)
	Changed \|= processBlock(MBB);

	return Changed;
	}