#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
bool sink3AddrInstruction(MachineInstr *MI, unsigned Reg,
MachineBasicBlock::iterator OldPos);
+ bool isRevCopyChain(unsigned FromReg, unsigned ToReg, int Maxlen);
+
bool noUseAfterLastDef(unsigned Reg, unsigned Dist, unsigned &LastDef);
bool isProfitableToCommute(unsigned regA, unsigned regB, unsigned regC,
MachineInstr *MI, unsigned Dist);
- bool commuteInstruction(MachineBasicBlock::iterator &mi,
- unsigned RegB, unsigned RegC, unsigned Dist);
+ bool commuteInstruction(MachineInstr *MI,
+ unsigned RegBIdx, unsigned RegCIdx, unsigned Dist);
bool isProfitableToConv3Addr(unsigned RegA, unsigned RegB);
unsigned SrcIdx, unsigned DstIdx,
unsigned Dist, bool shouldOnlyCommute);
+ bool tryInstructionCommute(MachineInstr *MI,
+ unsigned DstOpIdx,
+ unsigned BaseOpIdx,
+ bool BaseOpKilled,
+ unsigned Dist);
void scanUses(unsigned DstReg);
void processCopy(MachineInstr *MI);
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
- AU.addRequired<AliasAnalysis>();
+ AU.addRequired<AAResultsWrapperPass>();
AU.addPreserved<LiveVariables>();
AU.addPreserved<SlotIndexes>();
AU.addPreserved<LiveIntervals>();
char TwoAddressInstructionPass::ID = 0;
INITIALIZE_PASS_BEGIN(TwoAddressInstructionPass, "twoaddressinstruction",
"Two-Address instruction pass", false, false)
-INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
+INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
INITIALIZE_PASS_END(TwoAddressInstructionPass, "twoaddressinstruction",
"Two-Address instruction pass", false, false)
// Check if it's safe to move this instruction.
bool SeenStore = true; // Be conservative.
- if (!MI->isSafeToMove(TII, AA, SeenStore))
+ if (!MI->isSafeToMove(AA, SeenStore))
return false;
unsigned DefReg = 0;
return true;
}
+/// getSingleDef -- return the MachineInstr* if it is the single def of the Reg
+/// in current BB.
+static MachineInstr *getSingleDef(unsigned Reg, MachineBasicBlock *BB,
+ const MachineRegisterInfo *MRI) {
+ MachineInstr *Ret = nullptr;
+ for (MachineInstr &DefMI : MRI->def_instructions(Reg)) {
+ if (DefMI.getParent() != BB || DefMI.isDebugValue())
+ continue;
+ if (!Ret)
+ Ret = &DefMI;
+ else if (Ret != &DefMI)
+ return nullptr;
+ }
+ return Ret;
+}
+
+/// Check if there is a reversed copy chain from FromReg to ToReg:
+/// %Tmp1 = copy %Tmp2;
+/// %FromReg = copy %Tmp1;
+/// %ToReg = add %FromReg ...
+/// %Tmp2 = copy %ToReg;
+/// MaxLen specifies the maximum length of the copy chain the func
+/// can walk through.
+bool TwoAddressInstructionPass::isRevCopyChain(unsigned FromReg, unsigned ToReg,
+ int Maxlen) {
+ unsigned TmpReg = FromReg;
+ for (int i = 0; i < Maxlen; i++) {
+ MachineInstr *Def = getSingleDef(TmpReg, MBB, MRI);
+ if (!Def || !Def->isCopy())
+ return false;
+
+ TmpReg = Def->getOperand(1).getReg();
+
+ if (TmpReg == ToReg)
+ return true;
+ }
+ return false;
+}
+
/// noUseAfterLastDef - Return true if there are no intervening uses between the
/// last instruction in the MBB that defines the specified register and the
/// two-address instruction which is being processed. It also returns the last
if (!noUseAfterLastDef(regB, Dist, LastDefB))
return true;
+ // Look for situation like this:
+ // %reg101 = MOV %reg100
+ // %reg102 = ...
+ // %reg103 = ADD %reg102, %reg101
+ // ... = %reg103 ...
+ // %reg100 = MOV %reg103
+ // If there is a reversed copy chain from reg101 to reg103, commute the ADD
+ // to eliminate an otherwise unavoidable copy.
+ // FIXME:
+ // We can extend the logic further: If an pair of operands in an insn has
+ // been merged, the insn could be regarded as a virtual copy, and the virtual
+ // copy could also be used to construct a copy chain.
+ // To more generally minimize register copies, ideally the logic of two addr
+ // instruction pass should be integrated with register allocation pass where
+ // interference graph is available.
+ if (isRevCopyChain(regC, regA, 3))
+ return true;
+
+ if (isRevCopyChain(regB, regA, 3))
+ return false;
+
// Since there are no intervening uses for both registers, then commute
// if the def of regC is closer. Its live interval is shorter.
return LastDefB && LastDefC && LastDefC > LastDefB;
/// commuteInstruction - Commute a two-address instruction and update the basic
/// block, distance map, and live variables if needed. Return true if it is
/// successful.
-bool TwoAddressInstructionPass::
-commuteInstruction(MachineBasicBlock::iterator &mi,
- unsigned RegB, unsigned RegC, unsigned Dist) {
- MachineInstr *MI = mi;
+bool TwoAddressInstructionPass::commuteInstruction(MachineInstr *MI,
+ unsigned RegBIdx,
+ unsigned RegCIdx,
+ unsigned Dist) {
+ unsigned RegC = MI->getOperand(RegCIdx).getReg();
DEBUG(dbgs() << "2addr: COMMUTING : " << *MI);
- MachineInstr *NewMI = TII->commuteInstruction(MI);
+ MachineInstr *NewMI = TII->commuteInstruction(MI, false, RegBIdx, RegCIdx);
if (NewMI == nullptr) {
DEBUG(dbgs() << "2addr: COMMUTING FAILED!\n");
unsigned Reg = DstReg;
while (MachineInstr *UseMI = findOnlyInterestingUse(Reg, MBB, MRI, TII,IsCopy,
NewReg, IsDstPhys)) {
- if (IsCopy && !Processed.insert(UseMI))
+ if (IsCopy && !Processed.insert(UseMI).second)
break;
DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(UseMI);
return false;
bool SeenStore = true;
- if (!MI->isSafeToMove(TII, AA, SeenStore))
+ if (!MI->isSafeToMove(AA, SeenStore))
return false;
if (TII->getInstrLatency(InstrItins, MI) > 1)
return false;
bool SeenStore = true;
- if (!KillMI->isSafeToMove(TII, AA, SeenStore))
+ if (!KillMI->isSafeToMove(AA, SeenStore))
return false;
SmallSet<unsigned, 2> Uses;
return true;
}
+/// Tries to commute the operand 'BaseOpIdx' and some other operand in the
+/// given machine instruction to improve opportunities for coalescing and
+/// elimination of a register to register copy.
+///
+/// 'DstOpIdx' specifies the index of MI def operand.
+/// 'BaseOpKilled' specifies if the register associated with 'BaseOpIdx'
+/// operand is killed by the given instruction.
+/// The 'Dist' arguments provides the distance of MI from the start of the
+/// current basic block and it is used to determine if it is profitable
+/// to commute operands in the instruction.
+///
+/// Returns true if the transformation happened. Otherwise, returns false.
+bool TwoAddressInstructionPass::tryInstructionCommute(MachineInstr *MI,
+ unsigned DstOpIdx,
+ unsigned BaseOpIdx,
+ bool BaseOpKilled,
+ unsigned Dist) {
+ unsigned DstOpReg = MI->getOperand(DstOpIdx).getReg();
+ unsigned BaseOpReg = MI->getOperand(BaseOpIdx).getReg();
+ unsigned OpsNum = MI->getDesc().getNumOperands();
+ unsigned OtherOpIdx = MI->getDesc().getNumDefs();
+ for (; OtherOpIdx < OpsNum; OtherOpIdx++) {
+ // The call of findCommutedOpIndices below only checks if BaseOpIdx
+ // and OtherOpIdx are commutable, it does not really searches for
+ // other commutable operands and does not change the values of passed
+ // variables.
+ if (OtherOpIdx == BaseOpIdx ||
+ !TII->findCommutedOpIndices(MI, BaseOpIdx, OtherOpIdx))
+ continue;
+
+ unsigned OtherOpReg = MI->getOperand(OtherOpIdx).getReg();
+ bool AggressiveCommute = false;
+
+ // If OtherOp dies but BaseOp does not, swap the OtherOp and BaseOp
+ // operands. This makes the live ranges of DstOp and OtherOp joinable.
+ bool DoCommute =
+ !BaseOpKilled && isKilled(*MI, OtherOpReg, MRI, TII, LIS, false);
+
+ if (!DoCommute &&
+ isProfitableToCommute(DstOpReg, BaseOpReg, OtherOpReg, MI, Dist)) {
+ DoCommute = true;
+ AggressiveCommute = true;
+ }
+
+ // If it's profitable to commute, try to do so.
+ if (DoCommute && commuteInstruction(MI, BaseOpIdx, OtherOpIdx, Dist)) {
+ ++NumCommuted;
+ if (AggressiveCommute)
+ ++NumAggrCommuted;
+ return true;
+ }
+ }
+ return false;
+}
+
/// tryInstructionTransform - For the case where an instruction has a single
/// pair of tied register operands, attempt some transformations that may
/// either eliminate the tied operands or improve the opportunities for
if (TargetRegisterInfo::isVirtualRegister(regA))
scanUses(regA);
- // Check if it is profitable to commute the operands.
- unsigned SrcOp1, SrcOp2;
- unsigned regC = 0;
- unsigned regCIdx = ~0U;
- bool TryCommute = false;
- bool AggressiveCommute = false;
- if (MI.isCommutable() && MI.getNumOperands() >= 3 &&
- TII->findCommutedOpIndices(&MI, SrcOp1, SrcOp2)) {
- if (SrcIdx == SrcOp1)
- regCIdx = SrcOp2;
- else if (SrcIdx == SrcOp2)
- regCIdx = SrcOp1;
-
- if (regCIdx != ~0U) {
- regC = MI.getOperand(regCIdx).getReg();
- if (!regBKilled && isKilled(MI, regC, MRI, TII, LIS, false))
- // If C dies but B does not, swap the B and C operands.
- // This makes the live ranges of A and C joinable.
- TryCommute = true;
- else if (isProfitableToCommute(regA, regB, regC, &MI, Dist)) {
- TryCommute = true;
- AggressiveCommute = true;
- }
- }
- }
-
- // If it's profitable to commute, try to do so.
- if (TryCommute && commuteInstruction(mi, regB, regC, Dist)) {
- ++NumCommuted;
- if (AggressiveCommute)
- ++NumAggrCommuted;
+ bool Commuted = tryInstructionCommute(&MI, DstIdx, SrcIdx, regBKilled, Dist);
+
+ // If the instruction is convertible to 3 Addr, instead
+ // of returning try 3 Addr transformation aggresively and
+ // use this variable to check later. Because it might be better.
+ // For example, we can just use `leal (%rsi,%rdi), %eax` and `ret`
+ // instead of the following code.
+ // addl %esi, %edi
+ // movl %edi, %eax
+ // ret
+ if (Commuted && !MI.isConvertibleTo3Addr())
return false;
- }
if (shouldOnlyCommute)
return false;
// If there is one more use of regB later in the same MBB, consider
// re-schedule this MI below it.
- if (EnableRescheduling && rescheduleMIBelowKill(mi, nmi, regB)) {
+ if (!Commuted && EnableRescheduling && rescheduleMIBelowKill(mi, nmi, regB)) {
++NumReSchedDowns;
return true;
}
+ // If we commuted, regB may have changed so we should re-sample it to avoid
+ // confusing the three address conversion below.
+ if (Commuted) {
+ regB = MI.getOperand(SrcIdx).getReg();
+ regBKilled = isKilled(MI, regB, MRI, TII, LIS, true);
+ }
+
if (MI.isConvertibleTo3Addr()) {
// This instruction is potentially convertible to a true
// three-address instruction. Check if it is profitable.
}
}
+ // Return if it is commuted but 3 addr conversion is failed.
+ if (Commuted)
+ return false;
+
// If there is one more use of regB later in the same MBB, consider
// re-schedule it before this MI if it's legal.
if (EnableRescheduling && rescheduleKillAboveMI(mi, nmi, regB)) {
SrcRegMap[RegA] = RegB;
}
-
if (AllUsesCopied) {
if (!IsEarlyClobber) {
// Replace other (un-tied) uses of regB with LastCopiedReg.
MF = &Func;
const TargetMachine &TM = MF->getTarget();
MRI = &MF->getRegInfo();
- TII = TM.getSubtargetImpl()->getInstrInfo();
- TRI = TM.getSubtargetImpl()->getRegisterInfo();
- InstrItins = TM.getSubtargetImpl()->getInstrItineraryData();
+ TII = MF->getSubtarget().getInstrInfo();
+ TRI = MF->getSubtarget().getRegisterInfo();
+ InstrItins = MF->getSubtarget().getInstrItineraryData();
LV = getAnalysisIfAvailable<LiveVariables>();
LIS = getAnalysisIfAvailable<LiveIntervals>();
- AA = &getAnalysis<AliasAnalysis>();
+ AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
OptLevel = TM.getOptLevel();
bool MadeChange = false;
unsigned DstReg = mi->getOperand(DstIdx).getReg();
if (SrcReg != DstReg &&
tryInstructionTransform(mi, nmi, SrcIdx, DstIdx, Dist, false)) {
- // The tied operands have been eliminated or shifted further down the
- // block to ease elimination. Continue processing with 'nmi'.
+ // The tied operands have been eliminated or shifted further down
+ // the block to ease elimination. Continue processing with 'nmi'.
TiedOperands.clear();
mi = nmi;
continue;
projects / oota-llvm.git / blobdiff