//
// The LLVM Compiler Infrastructure
//
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
-#include "llvm/CodeGen/SSARegMap.h"
-#include "llvm/Target/MRegisterInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
+#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
using namespace llvm;
+STATISTIC(NumTwoAddressInstrs, "Number of two-address instructions");
+STATISTIC(NumCommuted , "Number of instructions commuted to coalesce");
+STATISTIC(NumConvertedTo3Addr, "Number of instructions promoted to 3-address");
+STATISTIC(Num3AddrSunk, "Number of 3-address instructions sunk");
+
+static cl::opt<bool>
+EnableReMat("2-addr-remat", cl::init(false), cl::Hidden,
+ cl::desc("Two-addr conversion should remat when possible."));
+
namespace {
- Statistic<> NumTwoAddressInstrs("twoaddressinstruction",
- "Number of two-address instructions");
- Statistic<> NumCommuted("twoaddressinstruction",
- "Number of instructions commuted to coallesce");
- Statistic<> NumConvertedTo3Addr("twoaddressinstruction",
- "Number of instructions promoted to 3-address");
+ class VISIBILITY_HIDDEN TwoAddressInstructionPass
+ : public MachineFunctionPass {
+ const TargetInstrInfo *TII;
+ const TargetRegisterInfo *TRI;
+ MachineRegisterInfo *MRI;
+ LiveVariables *LV;
- struct TwoAddressInstructionPass : public MachineFunctionPass {
- virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+ bool Sink3AddrInstruction(MachineBasicBlock *MBB, MachineInstr *MI,
+ unsigned Reg,
+ MachineBasicBlock::iterator OldPos);
+ public:
+ static char ID; // Pass identification, replacement for typeid
+ TwoAddressInstructionPass() : MachineFunctionPass((intptr_t)&ID) {}
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<LiveVariables>();
+ AU.addPreserved<LiveVariables>();
+ AU.addPreservedID(MachineLoopInfoID);
+ AU.addPreservedID(MachineDominatorsID);
+ AU.addPreservedID(PHIEliminationID);
+ MachineFunctionPass::getAnalysisUsage(AU);
+ }
- /// runOnMachineFunction - pass entry point
+ /// runOnMachineFunction - Pass entry point.
bool runOnMachineFunction(MachineFunction&);
};
+}
+
+char TwoAddressInstructionPass::ID = 0;
+static RegisterPass<TwoAddressInstructionPass>
+X("twoaddressinstruction", "Two-Address instruction pass");
+
+const PassInfo *const llvm::TwoAddressInstructionPassID = &X;
+
+/// Sink3AddrInstruction - A two-address instruction has been converted to a
+/// three-address instruction to avoid clobbering a register. Try to sink it
+/// past the instruction that would kill the above mentioned register to reduce
+/// register pressure.
+///
+bool TwoAddressInstructionPass::Sink3AddrInstruction(MachineBasicBlock *MBB,
+ MachineInstr *MI, unsigned SavedReg,
+ MachineBasicBlock::iterator OldPos) {
+ // Check if it's safe to move this instruction.
+ bool SeenStore = true; // Be conservative.
+ if (!MI->isSafeToMove(TII, SeenStore))
+ return false;
+
+ unsigned DefReg = 0;
+ SmallSet<unsigned, 4> UseRegs;
+
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isRegister())
+ continue;
+ unsigned MOReg = MO.getReg();
+ if (!MOReg)
+ continue;
+ if (MO.isUse() && MOReg != SavedReg)
+ UseRegs.insert(MO.getReg());
+ if (!MO.isDef())
+ continue;
+ if (MO.isImplicit())
+ // Don't try to move it if it implicitly defines a register.
+ return false;
+ if (DefReg)
+ // For now, don't move any instructions that define multiple registers.
+ return false;
+ DefReg = MO.getReg();
+ }
+
+ // Find the instruction that kills SavedReg.
+ MachineInstr *KillMI = NULL;
+
+ for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(SavedReg),
+ UE = MRI->use_end(); UI != UE; ++UI) {
+ MachineOperand &UseMO = UI.getOperand();
+ if (!UseMO.isKill())
+ continue;
+ KillMI = UseMO.getParent();
+ break;
+ }
+
+ if (!KillMI || KillMI->getParent() != MBB)
+ return false;
- RegisterPass<TwoAddressInstructionPass>
- X("twoaddressinstruction", "Two-Address instruction pass");
-};
+ // If any of the definitions are used by another instruction between the
+ // position and the kill use, then it's not safe to sink it.
+ //
+ // FIXME: This can be sped up if there is an easy way to query whether an
+ // instruction if before or after another instruction. Then we can use
+ // MachineRegisterInfo def / use instead.
+ MachineOperand *KillMO = NULL;
+ MachineBasicBlock::iterator KillPos = KillMI;
+ ++KillPos;
-const PassInfo *llvm::TwoAddressInstructionPassID = X.getPassInfo();
+ for (MachineBasicBlock::iterator I = next(OldPos); I != KillPos; ++I) {
+ MachineInstr *OtherMI = I;
-void TwoAddressInstructionPass::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<LiveVariables>();
- AU.addPreserved<LiveVariables>();
- AU.addPreservedID(PHIEliminationID);
- MachineFunctionPass::getAnalysisUsage(AU);
+ for (unsigned i = 0, e = OtherMI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = OtherMI->getOperand(i);
+ if (!MO.isRegister())
+ continue;
+ unsigned MOReg = MO.getReg();
+ if (!MOReg)
+ continue;
+ if (DefReg == MOReg)
+ return false;
+
+ if (MO.isKill()) {
+ if (OtherMI == KillMI && MOReg == SavedReg)
+ // Save the operand that kills the register. We want unset the kill
+ // marker is we can sink MI past it.
+ KillMO = &MO;
+ else if (UseRegs.count(MOReg))
+ // One of the uses is killed before the destination.
+ return false;
+ }
+ }
+ }
+
+ // Update kill and LV information.
+ KillMO->setIsKill(false);
+ KillMO = MI->findRegisterUseOperand(SavedReg, false, TRI);
+ KillMO->setIsKill(true);
+ LiveVariables::VarInfo& VarInfo = LV->getVarInfo(SavedReg);
+ VarInfo.removeKill(KillMI);
+ VarInfo.Kills.push_back(MI);
+
+ // Move instruction to its destination.
+ MBB->remove(MI);
+ MBB->insert(KillPos, MI);
+
+ ++Num3AddrSunk;
+ return true;
}
-/// runOnMachineFunction - Reduce two-address instructions to two
-/// operands.
+/// runOnMachineFunction - Reduce two-address instructions to two operands.
///
bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) {
- DEBUG(std::cerr << "Machine Function\n");
+ DOUT << "Machine Function\n";
const TargetMachine &TM = MF.getTarget();
- const MRegisterInfo &MRI = *TM.getRegisterInfo();
- const TargetInstrInfo &TII = *TM.getInstrInfo();
- LiveVariables &LV = getAnalysis<LiveVariables>();
+ MRI = &MF.getRegInfo();
+ TII = TM.getInstrInfo();
+ TRI = TM.getRegisterInfo();
+ LV = &getAnalysis<LiveVariables>();
bool MadeChange = false;
- DEBUG(std::cerr << "********** REWRITING TWO-ADDR INSTRS **********\n");
- DEBUG(std::cerr << "********** Function: "
- << MF.getFunction()->getName() << '\n');
+ DOUT << "********** REWRITING TWO-ADDR INSTRS **********\n";
+ DOUT << "********** Function: " << MF.getFunction()->getName() << '\n';
+
+ SmallPtrSet<MachineInstr*, 8> ReMattedInstrs;
for (MachineFunction::iterator mbbi = MF.begin(), mbbe = MF.end();
mbbi != mbbe; ++mbbi) {
for (MachineBasicBlock::iterator mi = mbbi->begin(), me = mbbi->end();
- mi != me; ++mi) {
- unsigned opcode = mi->getOpcode();
+ mi != me; ) {
+ MachineBasicBlock::iterator nmi = next(mi);
+ const TargetInstrDesc &TID = mi->getDesc();
+ bool FirstTied = true;
- // ignore if it is not a two-address instruction
- if (!TII.isTwoAddrInstr(opcode))
- continue;
+ for (unsigned si = 1, e = TID.getNumOperands(); si < e; ++si) {
+ int ti = TID.getOperandConstraint(si, TOI::TIED_TO);
+ if (ti == -1)
+ continue;
+
+ if (FirstTied) {
+ ++NumTwoAddressInstrs;
+ DOUT << '\t'; DEBUG(mi->print(*cerr.stream(), &TM));
+ }
+
+ FirstTied = false;
+
+ assert(mi->getOperand(si).isRegister() && mi->getOperand(si).getReg() &&
+ mi->getOperand(si).isUse() && "two address instruction invalid");
- ++NumTwoAddressInstrs;
- DEBUG(std::cerr << '\t'; mi->print(std::cerr, &TM));
- assert(mi->getOperand(1).isRegister() && mi->getOperand(1).getReg() &&
- mi->getOperand(1).isUse() && "two address instruction invalid");
-
- // if the two operands are the same we just remove the use
- // and mark the def as def&use, otherwise we have to insert a copy.
- if (mi->getOperand(0).getReg() != mi->getOperand(1).getReg()) {
- // rewrite:
- // a = b op c
- // to:
- // a = b
- // a = a op c
- unsigned regA = mi->getOperand(0).getReg();
- unsigned regB = mi->getOperand(1).getReg();
-
- assert(MRegisterInfo::isVirtualRegister(regA) &&
- MRegisterInfo::isVirtualRegister(regB) &&
- "cannot update physical register live information");
+ // If the two operands are the same we just remove the use
+ // and mark the def as def&use, otherwise we have to insert a copy.
+ if (mi->getOperand(ti).getReg() != mi->getOperand(si).getReg()) {
+ // Rewrite:
+ // a = b op c
+ // to:
+ // a = b
+ // a = a op c
+ unsigned regA = mi->getOperand(ti).getReg();
+ unsigned regB = mi->getOperand(si).getReg();
+
+ assert(TargetRegisterInfo::isVirtualRegister(regA) &&
+ TargetRegisterInfo::isVirtualRegister(regB) &&
+ "cannot update physical register live information");
#ifndef NDEBUG
- // First, verify that we do not have a use of a in the instruction (a =
- // b + a for example) because our transformation will not work. This
- // should never occur because we are in SSA form.
- for (unsigned i = 1; i != mi->getNumOperands(); ++i)
- assert(!mi->getOperand(i).isRegister() ||
- mi->getOperand(i).getReg() != regA);
+ // First, verify that we don't have a use of a in the instruction (a =
+ // b + a for example) because our transformation will not work. This
+ // should never occur because we are in SSA form.
+ for (unsigned i = 0; i != mi->getNumOperands(); ++i)
+ assert((int)i == ti ||
+ !mi->getOperand(i).isRegister() ||
+ mi->getOperand(i).getReg() != regA);
#endif
- // If this instruction is not the killing user of B, see if we can
- // rearrange the code to make it so. Making it the killing user will
- // allow us to coallesce A and B together, eliminating the copy we are
- // about to insert.
- if (!LV.KillsRegister(mi, regB)) {
- const TargetInstrDescriptor &TID = TII.get(opcode);
-
- // If this instruction is commutative, check to see if C dies. If so,
- // swap the B and C operands. This makes the live ranges of A and C
- // joinable.
- if (TID.Flags & M_COMMUTABLE) {
- assert(mi->getOperand(2).isRegister() &&
- "Not a proper commutative instruction!");
- unsigned regC = mi->getOperand(2).getReg();
- if (LV.KillsRegister(mi, regC)) {
- DEBUG(std::cerr << "2addr: COMMUTING : " << *mi);
- mi->SetMachineOperandReg(2, regB);
- mi->SetMachineOperandReg(1, regC);
- DEBUG(std::cerr << "2addr: COMMUTED TO: " << *mi);
- ++NumCommuted;
- regB = regC;
- goto InstructionRearranged;
+ // If this instruction is not the killing user of B, see if we can
+ // rearrange the code to make it so. Making it the killing user will
+ // allow us to coalesce A and B together, eliminating the copy we are
+ // about to insert.
+ if (!mi->killsRegister(regB)) {
+ // If this instruction is commutative, check to see if C dies. If
+ // so, swap the B and C operands. This makes the live ranges of A
+ // and C joinable.
+ // FIXME: This code also works for A := B op C instructions.
+ if (TID.isCommutable() && mi->getNumOperands() >= 3) {
+ assert(mi->getOperand(3-si).isRegister() &&
+ "Not a proper commutative instruction!");
+ unsigned regC = mi->getOperand(3-si).getReg();
+
+ if (mi->killsRegister(regC)) {
+ DOUT << "2addr: COMMUTING : " << *mi;
+ MachineInstr *NewMI = TII->commuteInstruction(mi);
+
+ if (NewMI == 0) {
+ DOUT << "2addr: COMMUTING FAILED!\n";
+ } else {
+ DOUT << "2addr: COMMUTED TO: " << *NewMI;
+ // If the instruction changed to commute it, update livevar.
+ if (NewMI != mi) {
+ LV->instructionChanged(mi, NewMI); // Update live variables
+ mbbi->insert(mi, NewMI); // Insert the new inst
+ mbbi->erase(mi); // Nuke the old inst.
+ mi = NewMI;
+ }
+
+ ++NumCommuted;
+ regB = regC;
+ goto InstructionRearranged;
+ }
+ }
}
- }
- // If this instruction is potentially convertible to a true
- // three-address instruction,
- if (TID.Flags & M_CONVERTIBLE_TO_3_ADDR)
- if (MachineInstr *New = TII.convertToThreeAddress(mi)) {
- DEBUG(std::cerr << "2addr: CONVERTING 2-ADDR: " << *mi);
- DEBUG(std::cerr << "2addr: TO 3-ADDR: " << *New);
- LV.instructionChanged(mi, New); // Update live variables
- mbbi->insert(mi, New); // Insert the new inst
- mbbi->erase(mi); // Nuke the old inst.
- mi = New;
- ++NumConvertedTo3Addr;
- assert(!TII.isTwoAddrInstr(New->getOpcode()) &&
- "convertToThreeAddress returned a 2-addr instruction??");
- // Done with this instruction.
- continue;
+
+ // If this instruction is potentially convertible to a true
+ // three-address instruction,
+ if (TID.isConvertibleTo3Addr()) {
+ // FIXME: This assumes there are no more operands which are tied
+ // to another register.
+#ifndef NDEBUG
+ for (unsigned i = si + 1, e = TID.getNumOperands(); i < e; ++i)
+ assert(TID.getOperandConstraint(i, TOI::TIED_TO) == -1);
+#endif
+
+ if (MachineInstr *New=TII->convertToThreeAddress(mbbi, mi, *LV)) {
+ DOUT << "2addr: CONVERTING 2-ADDR: " << *mi;
+ DOUT << "2addr: TO 3-ADDR: " << *New;
+ bool Sunk = false;
+
+ if (New->findRegisterUseOperand(regB, false, TRI))
+ // FIXME: Temporary workaround. If the new instruction doesn't
+ // uses regB, convertToThreeAddress must have created more
+ // then one instruction.
+ Sunk = Sink3AddrInstruction(mbbi, New, regB, mi);
+
+ mbbi->erase(mi); // Nuke the old inst.
+
+ if (!Sunk) {
+ mi = New;
+ nmi = next(mi);
+ }
+
+ ++NumConvertedTo3Addr;
+ break; // Done with this instruction.
+ }
}
- }
- InstructionRearranged:
- const TargetRegisterClass* rc = MF.getSSARegMap()->getRegClass(regA);
- MRI.copyRegToReg(*mbbi, mi, regA, regB, rc);
+ }
- MachineBasicBlock::iterator prevMi = prior(mi);
- DEBUG(std::cerr << "\t\tprepend:\t"; prevMi->print(std::cerr, &TM));
+ InstructionRearranged:
+ const TargetRegisterClass* rc = MF.getRegInfo().getRegClass(regA);
+ MachineInstr *Orig = MRI->getVRegDef(regB);
+ const TargetInstrDesc &OrigTID = Orig->getDesc();
+ bool SawStore = false;
- // Update live variables for regA
- LiveVariables::VarInfo& varInfo = LV.getVarInfo(regA);
- varInfo.DefInst = prevMi;
+ if (EnableReMat && Orig && Orig->isSafeToMove(TII, SawStore) &&
+ OrigTID.isAsCheapAsAMove() && !OrigTID.mayLoad() &&
+ !OrigTID.isSimpleLoad()) {
+ DEBUG(cerr << "2addr: REMATTING : " << *Orig << "\n");
+ TII->reMaterialize(*mbbi, mi, regA, Orig);
+ ReMattedInstrs.insert(Orig);
+ } else {
+ TII->copyRegToReg(*mbbi, mi, regA, regB, rc, rc);
+ }
+
+ MachineBasicBlock::iterator prevMi = prior(mi);
+ DOUT << "\t\tprepend:\t"; DEBUG(prevMi->print(*cerr.stream(), &TM));
+
+ // Update live variables for regB.
+ LiveVariables::VarInfo& varInfoB = LV->getVarInfo(regB);
+
+ // regB is used in this BB.
+ varInfoB.UsedBlocks[mbbi->getNumber()] = true;
- // update live variables for regB
- if (LV.removeVirtualRegisterKilled(regB, mbbi, mi))
- LV.addVirtualRegisterKilled(regB, prevMi);
+ if (LV->removeVirtualRegisterKilled(regB, mbbi, mi))
+ LV->addVirtualRegisterKilled(regB, prevMi);
- if (LV.removeVirtualRegisterDead(regB, mbbi, mi))
- LV.addVirtualRegisterDead(regB, prevMi);
+ if (LV->removeVirtualRegisterDead(regB, mbbi, mi))
+ LV->addVirtualRegisterDead(regB, prevMi);
- // replace all occurences of regB with regA
- for (unsigned i = 1, e = mi->getNumOperands(); i != e; ++i) {
- if (mi->getOperand(i).isRegister() &&
- mi->getOperand(i).getReg() == regB)
- mi->SetMachineOperandReg(i, regA);
+ // Replace all occurences of regB with regA.
+ for (unsigned i = 0, e = mi->getNumOperands(); i != e; ++i) {
+ if (mi->getOperand(i).isRegister() &&
+ mi->getOperand(i).getReg() == regB)
+ mi->getOperand(i).setReg(regA);
+ }
}
+
+ assert(mi->getOperand(ti).isDef() && mi->getOperand(si).isUse());
+ mi->getOperand(ti).setReg(mi->getOperand(si).getReg());
+ MadeChange = true;
+
+ DOUT << "\t\trewrite to:\t"; DEBUG(mi->print(*cerr.stream(), &TM));
}
- assert(mi->getOperand(0).isDef());
- mi->getOperand(0).setUse();
- mi->RemoveOperand(1);
- MadeChange = true;
+ mi = nmi;
+ }
+ }
+
+ if (EnableReMat) {
+ // Check to see if the instructions that we rematerialized are now dead. If
+ // they are, expunge them here.
+ SmallPtrSet<MachineInstr*, 8>::iterator I = ReMattedInstrs.begin();
+ SmallPtrSet<MachineInstr*, 8>::iterator E = ReMattedInstrs.end();
+
+ for (; I != E; ++I) {
+ MachineInstr *MI = *I;
+ bool InstrDead = true;
+
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isRegister())
+ continue;
+ unsigned MOReg = MO.getReg();
+
+ if (!MOReg || !MO.isDef() || (MO.isImplicit() && MO.isDead()))
+ continue;
+
+ if (MRI->use_begin(MOReg) != MRI->use_end()) {
+ InstrDead = false;
+ break;
+ }
+ }
- DEBUG(std::cerr << "\t\trewrite to:\t"; mi->print(std::cerr, &TM));
+ if (InstrDead)
+ MI->eraseFromParent();
}
}