llvm/lib/Target/SystemZ/SystemZPostRewrite.cpp - llvm-project - Git at Google

 //==---- SystemZPostRewrite.cpp - Select pseudos after RegAlloc ---*- C++ -*-=//
 //
 // 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 file contains a pass that is run immediately after VirtRegRewriter
 // but before MachineCopyPropagation. The purpose is to lower pseudos to
 // target instructions before any later pass might substitute a register for
 // another.
 //
 //===----------------------------------------------------------------------===//

 #include "SystemZ.h"
 #include "SystemZInstrInfo.h"
 #include "SystemZSubtarget.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 using namespace llvm;

 #define SYSTEMZ_POSTREWRITE_NAME "SystemZ Post Rewrite pass"

 #define DEBUG_TYPE "systemz-postrewrite"
 STATISTIC(MemFoldCopies, "Number of copies inserted before folded mem ops.");
 STATISTIC(LOCRMuxJumps, "Number of LOCRMux jump-sequences (lower is better)");

 namespace llvm {
   void initializeSystemZPostRewritePass(PassRegistry&);
 }

 namespace {

 class SystemZPostRewrite : public MachineFunctionPass {
 public:
   static char ID;
   SystemZPostRewrite() : MachineFunctionPass(ID) {
     initializeSystemZPostRewritePass(*PassRegistry::getPassRegistry());
   }

   const SystemZInstrInfo *TII;

   bool runOnMachineFunction(MachineFunction &Fn) override;

   StringRef getPassName() const override { return SYSTEMZ_POSTREWRITE_NAME; }

 private:
   void selectLOCRMux(MachineBasicBlock &MBB,
                      MachineBasicBlock::iterator MBBI,
                      MachineBasicBlock::iterator &NextMBBI,
                      unsigned LowOpcode,
                      unsigned HighOpcode);
   void selectSELRMux(MachineBasicBlock &MBB,
                      MachineBasicBlock::iterator MBBI,
                      MachineBasicBlock::iterator &NextMBBI,
                      unsigned LowOpcode,
                      unsigned HighOpcode);
   bool expandCondMove(MachineBasicBlock &MBB,
                       MachineBasicBlock::iterator MBBI,
                       MachineBasicBlock::iterator &NextMBBI);
   bool selectMI(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
                 MachineBasicBlock::iterator &NextMBBI);
   bool selectMBB(MachineBasicBlock &MBB);
 };

 char SystemZPostRewrite::ID = 0;

 } // end anonymous namespace

 INITIALIZE_PASS(SystemZPostRewrite, "systemz-post-rewrite",
                 SYSTEMZ_POSTREWRITE_NAME, false, false)

 /// Returns an instance of the Post Rewrite pass.
 FunctionPass *llvm::createSystemZPostRewritePass(SystemZTargetMachine &TM) {
   return new SystemZPostRewrite();
 }

 // MI is a load-register-on-condition pseudo instruction.  Replace it with
 // LowOpcode if source and destination are both low GR32s and HighOpcode if
 // source and destination are both high GR32s. Otherwise, a branch sequence
 // is created.
 void SystemZPostRewrite::selectLOCRMux(MachineBasicBlock &MBB,
                                        MachineBasicBlock::iterator MBBI,
                                        MachineBasicBlock::iterator &NextMBBI,
                                        unsigned LowOpcode,
                                        unsigned HighOpcode) {
   Register DestReg = MBBI->getOperand(0).getReg();
   Register SrcReg = MBBI->getOperand(2).getReg();
   bool DestIsHigh = SystemZ::isHighReg(DestReg);
   bool SrcIsHigh = SystemZ::isHighReg(SrcReg);

   if (!DestIsHigh && !SrcIsHigh)
     MBBI->setDesc(TII->get(LowOpcode));
   else if (DestIsHigh && SrcIsHigh)
     MBBI->setDesc(TII->get(HighOpcode));
   else
     expandCondMove(MBB, MBBI, NextMBBI);
 }

 // MI is a select pseudo instruction.  Replace it with LowOpcode if source
 // and destination are all low GR32s and HighOpcode if source and destination
 // are all high GR32s. Otherwise, a branch sequence is created.
 void SystemZPostRewrite::selectSELRMux(MachineBasicBlock &MBB,
                                        MachineBasicBlock::iterator MBBI,
                                        MachineBasicBlock::iterator &NextMBBI,
                                        unsigned LowOpcode,
                                        unsigned HighOpcode) {
   Register DestReg = MBBI->getOperand(0).getReg();
   Register Src1Reg = MBBI->getOperand(1).getReg();
   Register Src2Reg = MBBI->getOperand(2).getReg();
   bool DestIsHigh = SystemZ::isHighReg(DestReg);
   bool Src1IsHigh = SystemZ::isHighReg(Src1Reg);
   bool Src2IsHigh = SystemZ::isHighReg(Src2Reg);

   // If sources and destination aren't all high or all low, we may be able to
   // simplify the operation by moving one of the sources to the destination
   // first.  But only if this doesn't clobber the other source.
   if (DestReg != Src1Reg && DestReg != Src2Reg) {
     if (DestIsHigh != Src1IsHigh) {
       BuildMI(*MBBI->getParent(), MBBI, MBBI->getDebugLoc(),
               TII->get(SystemZ::COPY), DestReg)
         .addReg(MBBI->getOperand(1).getReg(), getRegState(MBBI->getOperand(1)));
       MBBI->getOperand(1).setReg(DestReg);
       Src1Reg = DestReg;
       Src1IsHigh = DestIsHigh;
     } else if (DestIsHigh != Src2IsHigh) {
       BuildMI(*MBBI->getParent(), MBBI, MBBI->getDebugLoc(),
               TII->get(SystemZ::COPY), DestReg)
         .addReg(MBBI->getOperand(2).getReg(), getRegState(MBBI->getOperand(2)));
       MBBI->getOperand(2).setReg(DestReg);
       Src2Reg = DestReg;
       Src2IsHigh = DestIsHigh;
     }
   }

   // If the destination (now) matches one source, prefer this to be first.
   if (DestReg != Src1Reg && DestReg == Src2Reg) {
     TII->commuteInstruction(*MBBI, false, 1, 2);
     std::swap(Src1Reg, Src2Reg);
     std::swap(Src1IsHigh, Src2IsHigh);
   }

   if (!DestIsHigh && !Src1IsHigh && !Src2IsHigh)
     MBBI->setDesc(TII->get(LowOpcode));
   else if (DestIsHigh && Src1IsHigh && Src2IsHigh)
     MBBI->setDesc(TII->get(HighOpcode));
   else
     // Given the simplification above, we must already have a two-operand case.
     expandCondMove(MBB, MBBI, NextMBBI);
 }

 // Replace MBBI by a branch sequence that performs a conditional move of
 // operand 2 to the destination register. Operand 1 is expected to be the
 // same register as the destination.
 bool SystemZPostRewrite::expandCondMove(MachineBasicBlock &MBB,
                                         MachineBasicBlock::iterator MBBI,
                                         MachineBasicBlock::iterator &NextMBBI) {
   MachineFunction &MF = *MBB.getParent();
   const BasicBlock *BB = MBB.getBasicBlock();
   MachineInstr &MI = *MBBI;
   DebugLoc DL = MI.getDebugLoc();
   Register DestReg = MI.getOperand(0).getReg();
   Register SrcReg = MI.getOperand(2).getReg();
   unsigned CCValid = MI.getOperand(3).getImm();
   unsigned CCMask = MI.getOperand(4).getImm();
   assert(DestReg == MI.getOperand(1).getReg() &&
          "Expected destination and first source operand to be the same.");

   LivePhysRegs LiveRegs(TII->getRegisterInfo());
   LiveRegs.addLiveOuts(MBB);
   for (auto I = std::prev(MBB.end()); I != MBBI; --I)
     LiveRegs.stepBackward(*I);

   // Splice MBB at MI, moving the rest of the block into RestMBB.
   MachineBasicBlock *RestMBB = MF.CreateMachineBasicBlock(BB);
   MF.insert(std::next(MachineFunction::iterator(MBB)), RestMBB);
   RestMBB->splice(RestMBB->begin(), &MBB, MI, MBB.end());
   RestMBB->transferSuccessors(&MBB);
   for (auto I = LiveRegs.begin(); I != LiveRegs.end(); ++I)
     RestMBB->addLiveIn(*I);

   // Create a new block MoveMBB to hold the move instruction.
   MachineBasicBlock *MoveMBB = MF.CreateMachineBasicBlock(BB);
   MF.insert(std::next(MachineFunction::iterator(MBB)), MoveMBB);
   MoveMBB->addLiveIn(SrcReg);
   for (auto I = LiveRegs.begin(); I != LiveRegs.end(); ++I)
     MoveMBB->addLiveIn(*I);

   // At the end of MBB, create a conditional branch to RestMBB if the
   // condition is false, otherwise fall through to MoveMBB.
   BuildMI(&MBB, DL, TII->get(SystemZ::BRC))
     .addImm(CCValid).addImm(CCMask ^ CCValid).addMBB(RestMBB);
   MBB.addSuccessor(RestMBB);
   MBB.addSuccessor(MoveMBB);

   // In MoveMBB, emit an instruction to move SrcReg into DestReg,
   // then fall through to RestMBB.
   BuildMI(*MoveMBB, MoveMBB->end(), DL, TII->get(SystemZ::COPY), DestReg)
       .addReg(MI.getOperand(2).getReg(), getRegState(MI.getOperand(2)));
   MoveMBB->addSuccessor(RestMBB);

   NextMBBI = MBB.end();
   MI.eraseFromParent();
   LOCRMuxJumps++;
   return true;
 }

 /// If MBBI references a pseudo instruction that should be selected here,
 /// do it and return true.  Otherwise return false.
 bool SystemZPostRewrite::selectMI(MachineBasicBlock &MBB,
                                   MachineBasicBlock::iterator MBBI,
                                   MachineBasicBlock::iterator &NextMBBI) {
   MachineInstr &MI = *MBBI;
   unsigned Opcode = MI.getOpcode();

   // Note: If this could be done during regalloc in foldMemoryOperandImpl()
   // while also updating the LiveIntervals, there would be no need for the
   // MemFoldPseudo to begin with.
   int TargetMemOpcode = SystemZ::getTargetMemOpcode(Opcode);
   if (TargetMemOpcode != -1) {
     MI.setDesc(TII->get(TargetMemOpcode));
     MI.tieOperands(0, 1);
     Register DstReg = MI.getOperand(0).getReg();
     MachineOperand &SrcMO = MI.getOperand(1);
     if (DstReg != SrcMO.getReg()) {
       BuildMI(MBB, &MI, MI.getDebugLoc(), TII->get(SystemZ::COPY), DstReg)
         .addReg(SrcMO.getReg());
       SrcMO.setReg(DstReg);
       MemFoldCopies++;
     }
     return true;
   }

   switch (Opcode) {
   case SystemZ::LOCRMux:
     selectLOCRMux(MBB, MBBI, NextMBBI, SystemZ::LOCR, SystemZ::LOCFHR);
     return true;
   case SystemZ::SELRMux:
     selectSELRMux(MBB, MBBI, NextMBBI, SystemZ::SELR, SystemZ::SELFHR);
     return true;
   }

   return false;
 }

 /// Iterate over the instructions in basic block MBB and select any
 /// pseudo instructions.  Return true if anything was modified.
 bool SystemZPostRewrite::selectMBB(MachineBasicBlock &MBB) {
   bool Modified = false;

   MachineBasicBlock::iterator MBBI = MBB.begin(), E = MBB.end();
   while (MBBI != E) {
     MachineBasicBlock::iterator NMBBI = std::next(MBBI);
     Modified |= selectMI(MBB, MBBI, NMBBI);
     MBBI = NMBBI;
   }

   return Modified;
 }

 bool SystemZPostRewrite::runOnMachineFunction(MachineFunction &MF) {
   TII = static_cast<const SystemZInstrInfo *>(MF.getSubtarget().getInstrInfo());

   bool Modified = false;
   for (auto &MBB : MF)
     Modified |= selectMBB(MBB);

   return Modified;
 }
	//==---- SystemZPostRewrite.cpp - Select pseudos after RegAlloc ---- C++ --=//
	//
	// 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 file contains a pass that is run immediately after VirtRegRewriter
	// but before MachineCopyPropagation. The purpose is to lower pseudos to
	// target instructions before any later pass might substitute a register for
	// another.
	//
	//===----------------------------------------------------------------------===//

	#include "SystemZ.h"
	#include "SystemZInstrInfo.h"
	#include "SystemZSubtarget.h"
	#include "llvm/ADT/Statistic.h"
	#include "llvm/CodeGen/MachineFunctionPass.h"
	#include "llvm/CodeGen/MachineInstrBuilder.h"
	using namespace llvm;

	#define SYSTEMZ_POSTREWRITE_NAME "SystemZ Post Rewrite pass"

	#define DEBUG_TYPE "systemz-postrewrite"
	STATISTIC(MemFoldCopies, "Number of copies inserted before folded mem ops.");
	STATISTIC(LOCRMuxJumps, "Number of LOCRMux jump-sequences (lower is better)");

	namespace llvm {
	void initializeSystemZPostRewritePass(PassRegistry&);
	}

	namespace {

	class SystemZPostRewrite : public MachineFunctionPass {
	public:
	static char ID;
	SystemZPostRewrite() : MachineFunctionPass(ID) {
	initializeSystemZPostRewritePass(*PassRegistry::getPassRegistry());
	}

	const SystemZInstrInfo *TII;

	bool runOnMachineFunction(MachineFunction &Fn) override;

	StringRef getPassName() const override { return SYSTEMZ_POSTREWRITE_NAME; }

	private:
	void selectLOCRMux(MachineBasicBlock &MBB,
	MachineBasicBlock::iterator MBBI,
	MachineBasicBlock::iterator &NextMBBI,
	unsigned LowOpcode,
	unsigned HighOpcode);
	void selectSELRMux(MachineBasicBlock &MBB,
	MachineBasicBlock::iterator MBBI,
	MachineBasicBlock::iterator &NextMBBI,
	unsigned LowOpcode,
	unsigned HighOpcode);
	bool expandCondMove(MachineBasicBlock &MBB,
	MachineBasicBlock::iterator MBBI,
	MachineBasicBlock::iterator &NextMBBI);
	bool selectMI(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
	MachineBasicBlock::iterator &NextMBBI);
	bool selectMBB(MachineBasicBlock &MBB);
	};

	char SystemZPostRewrite::ID = 0;

	} // end anonymous namespace

	INITIALIZE_PASS(SystemZPostRewrite, "systemz-post-rewrite",
	SYSTEMZ_POSTREWRITE_NAME, false, false)

	/// Returns an instance of the Post Rewrite pass.
	FunctionPass *llvm::createSystemZPostRewritePass(SystemZTargetMachine &TM) {
	return new SystemZPostRewrite();
	}

	// MI is a load-register-on-condition pseudo instruction. Replace it with
	// LowOpcode if source and destination are both low GR32s and HighOpcode if
	// source and destination are both high GR32s. Otherwise, a branch sequence
	// is created.
	void SystemZPostRewrite::selectLOCRMux(MachineBasicBlock &MBB,
	MachineBasicBlock::iterator MBBI,
	MachineBasicBlock::iterator &NextMBBI,
	unsigned LowOpcode,
	unsigned HighOpcode) {
	Register DestReg = MBBI->getOperand(0).getReg();
	Register SrcReg = MBBI->getOperand(2).getReg();
	bool DestIsHigh = SystemZ::isHighReg(DestReg);
	bool SrcIsHigh = SystemZ::isHighReg(SrcReg);

	if (!DestIsHigh && !SrcIsHigh)
	MBBI->setDesc(TII->get(LowOpcode));
	else if (DestIsHigh && SrcIsHigh)
	MBBI->setDesc(TII->get(HighOpcode));
	else
	expandCondMove(MBB, MBBI, NextMBBI);
	}

	// MI is a select pseudo instruction. Replace it with LowOpcode if source
	// and destination are all low GR32s and HighOpcode if source and destination
	// are all high GR32s. Otherwise, a branch sequence is created.
	void SystemZPostRewrite::selectSELRMux(MachineBasicBlock &MBB,
	MachineBasicBlock::iterator MBBI,
	MachineBasicBlock::iterator &NextMBBI,
	unsigned LowOpcode,
	unsigned HighOpcode) {
	Register DestReg = MBBI->getOperand(0).getReg();
	Register Src1Reg = MBBI->getOperand(1).getReg();
	Register Src2Reg = MBBI->getOperand(2).getReg();
	bool DestIsHigh = SystemZ::isHighReg(DestReg);
	bool Src1IsHigh = SystemZ::isHighReg(Src1Reg);
	bool Src2IsHigh = SystemZ::isHighReg(Src2Reg);

	// If sources and destination aren't all high or all low, we may be able to
	// simplify the operation by moving one of the sources to the destination
	// first. But only if this doesn't clobber the other source.
	if (DestReg != Src1Reg && DestReg != Src2Reg) {
	if (DestIsHigh != Src1IsHigh) {
	BuildMI(*MBBI->getParent(), MBBI, MBBI->getDebugLoc(),
	TII->get(SystemZ::COPY), DestReg)
	.addReg(MBBI->getOperand(1).getReg(), getRegState(MBBI->getOperand(1)));
	MBBI->getOperand(1).setReg(DestReg);
	Src1Reg = DestReg;
	Src1IsHigh = DestIsHigh;
	} else if (DestIsHigh != Src2IsHigh) {
	BuildMI(*MBBI->getParent(), MBBI, MBBI->getDebugLoc(),
	TII->get(SystemZ::COPY), DestReg)
	.addReg(MBBI->getOperand(2).getReg(), getRegState(MBBI->getOperand(2)));
	MBBI->getOperand(2).setReg(DestReg);
	Src2Reg = DestReg;
	Src2IsHigh = DestIsHigh;
	}
	}

	// If the destination (now) matches one source, prefer this to be first.
	if (DestReg != Src1Reg && DestReg == Src2Reg) {
	TII->commuteInstruction(*MBBI, false, 1, 2);
	std::swap(Src1Reg, Src2Reg);
	std::swap(Src1IsHigh, Src2IsHigh);
	}

	if (!DestIsHigh && !Src1IsHigh && !Src2IsHigh)
	MBBI->setDesc(TII->get(LowOpcode));
	else if (DestIsHigh && Src1IsHigh && Src2IsHigh)
	MBBI->setDesc(TII->get(HighOpcode));
	else
	// Given the simplification above, we must already have a two-operand case.
	expandCondMove(MBB, MBBI, NextMBBI);
	}

	// Replace MBBI by a branch sequence that performs a conditional move of
	// operand 2 to the destination register. Operand 1 is expected to be the
	// same register as the destination.
	bool SystemZPostRewrite::expandCondMove(MachineBasicBlock &MBB,
	MachineBasicBlock::iterator MBBI,
	MachineBasicBlock::iterator &NextMBBI) {
	MachineFunction &MF = *MBB.getParent();
	const BasicBlock *BB = MBB.getBasicBlock();
	MachineInstr &MI = *MBBI;
	DebugLoc DL = MI.getDebugLoc();
	Register DestReg = MI.getOperand(0).getReg();
	Register SrcReg = MI.getOperand(2).getReg();
	unsigned CCValid = MI.getOperand(3).getImm();
	unsigned CCMask = MI.getOperand(4).getImm();
	assert(DestReg == MI.getOperand(1).getReg() &&
	"Expected destination and first source operand to be the same.");

	LivePhysRegs LiveRegs(TII->getRegisterInfo());
	LiveRegs.addLiveOuts(MBB);
	for (auto I = std::prev(MBB.end()); I != MBBI; --I)
	LiveRegs.stepBackward(*I);

	// Splice MBB at MI, moving the rest of the block into RestMBB.
	MachineBasicBlock *RestMBB = MF.CreateMachineBasicBlock(BB);
	MF.insert(std::next(MachineFunction::iterator(MBB)), RestMBB);
	RestMBB->splice(RestMBB->begin(), &MBB, MI, MBB.end());
	RestMBB->transferSuccessors(&MBB);
	for (auto I = LiveRegs.begin(); I != LiveRegs.end(); ++I)
	RestMBB->addLiveIn(*I);

	// Create a new block MoveMBB to hold the move instruction.
	MachineBasicBlock *MoveMBB = MF.CreateMachineBasicBlock(BB);
	MF.insert(std::next(MachineFunction::iterator(MBB)), MoveMBB);
	MoveMBB->addLiveIn(SrcReg);
	for (auto I = LiveRegs.begin(); I != LiveRegs.end(); ++I)
	MoveMBB->addLiveIn(*I);

	// At the end of MBB, create a conditional branch to RestMBB if the
	// condition is false, otherwise fall through to MoveMBB.
	BuildMI(&MBB, DL, TII->get(SystemZ::BRC))
	.addImm(CCValid).addImm(CCMask ^ CCValid).addMBB(RestMBB);
	MBB.addSuccessor(RestMBB);
	MBB.addSuccessor(MoveMBB);

	// In MoveMBB, emit an instruction to move SrcReg into DestReg,
	// then fall through to RestMBB.
	BuildMI(*MoveMBB, MoveMBB->end(), DL, TII->get(SystemZ::COPY), DestReg)
	.addReg(MI.getOperand(2).getReg(), getRegState(MI.getOperand(2)));
	MoveMBB->addSuccessor(RestMBB);

	NextMBBI = MBB.end();
	MI.eraseFromParent();
	LOCRMuxJumps++;
	return true;
	}

	/// If MBBI references a pseudo instruction that should be selected here,
	/// do it and return true. Otherwise return false.
	bool SystemZPostRewrite::selectMI(MachineBasicBlock &MBB,
	MachineBasicBlock::iterator MBBI,
	MachineBasicBlock::iterator &NextMBBI) {
	MachineInstr &MI = *MBBI;
	unsigned Opcode = MI.getOpcode();

	// Note: If this could be done during regalloc in foldMemoryOperandImpl()
	// while also updating the LiveIntervals, there would be no need for the
	// MemFoldPseudo to begin with.
	int TargetMemOpcode = SystemZ::getTargetMemOpcode(Opcode);
	if (TargetMemOpcode != -1) {
	MI.setDesc(TII->get(TargetMemOpcode));
	MI.tieOperands(0, 1);
	Register DstReg = MI.getOperand(0).getReg();
	MachineOperand &SrcMO = MI.getOperand(1);
	if (DstReg != SrcMO.getReg()) {
	BuildMI(MBB, &MI, MI.getDebugLoc(), TII->get(SystemZ::COPY), DstReg)
	.addReg(SrcMO.getReg());
	SrcMO.setReg(DstReg);
	MemFoldCopies++;
	}
	return true;
	}

	switch (Opcode) {
	case SystemZ::LOCRMux:
	selectLOCRMux(MBB, MBBI, NextMBBI, SystemZ::LOCR, SystemZ::LOCFHR);
	return true;
	case SystemZ::SELRMux:
	selectSELRMux(MBB, MBBI, NextMBBI, SystemZ::SELR, SystemZ::SELFHR);
	return true;
	}

	return false;
	}

	/// Iterate over the instructions in basic block MBB and select any
	/// pseudo instructions. Return true if anything was modified.
	bool SystemZPostRewrite::selectMBB(MachineBasicBlock &MBB) {
	bool Modified = false;

	MachineBasicBlock::iterator MBBI = MBB.begin(), E = MBB.end();
	while (MBBI != E) {
	MachineBasicBlock::iterator NMBBI = std::next(MBBI);
	Modified \|= selectMI(MBB, MBBI, NMBBI);
	MBBI = NMBBI;
	}

	return Modified;
	}

	bool SystemZPostRewrite::runOnMachineFunction(MachineFunction &MF) {
	TII = static_cast<const SystemZInstrInfo *>(MF.getSubtarget().getInstrInfo());

	bool Modified = false;
	for (auto &MBB : MF)
	Modified \|= selectMBB(MBB);

	return Modified;
	}