#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineInstr.h"
class PHIElimination : public MachineFunctionPass {
MachineRegisterInfo *MRI; // Machine register information
LiveVariables *LV;
+ LiveIntervals *LIS;
public:
static char ID; // Pass identification, replacement for typeid
void PHIElimination::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addPreserved<LiveVariables>();
+ AU.addPreserved<LiveIntervals>();
AU.addPreserved<MachineDominatorTree>();
AU.addPreserved<MachineLoopInfo>();
MachineFunctionPass::getAnalysisUsage(AU);
bool PHIElimination::runOnMachineFunction(MachineFunction &MF) {
MRI = &MF.getRegInfo();
LV = getAnalysisIfAvailable<LiveVariables>();
+ LIS = getAnalysisIfAvailable<LiveIntervals>();
bool Changed = false;
// This pass takes the function out of SSA form.
MRI->leaveSSA();
- // Split critical edges to help the coalescer
- if (!DisableEdgeSplitting && LV) {
+ // Split critical edges to help the coalescer. This does not yet support
+ // updating LiveIntervals, so we disable it.
+ if (!DisableEdgeSplitting && LV && !LIS) {
MachineLoopInfo *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
Changed |= SplitPHIEdges(MF, *I, MLI);
E = ImpDefs.end(); I != E; ++I) {
MachineInstr *DefMI = *I;
unsigned DefReg = DefMI->getOperand(0).getReg();
- if (MRI->use_nodbg_empty(DefReg))
+ if (MRI->use_nodbg_empty(DefReg)) {
+ if (LIS)
+ LIS->RemoveMachineInstrFromMaps(DefMI);
DefMI->eraseFromParent();
+ }
}
// Clean up the lowered PHI instructions.
for (LoweredPHIMap::iterator I = LoweredPHIs.begin(), E = LoweredPHIs.end();
- I != E; ++I)
+ I != E; ++I) {
+ if (LIS)
+ LIS->RemoveMachineInstrFromMaps(I->first);
MF.DeleteMachineInstr(I->first);
+ }
LoweredPHIs.clear();
ImpDefs.clear();
VRegPHIUseCount.clear();
+ if (LIS)
+ MF.verify(this, "After PHI elimination");
+
return Changed;
}
}
}
+ // Update LiveIntervals for the new copy or implicit def.
+ if (LIS) {
+ MachineInstr *NewInstr = prior(AfterPHIsIt);
+ LIS->InsertMachineInstrInMaps(NewInstr);
+
+ SlotIndex MBBStartIndex = LIS->getMBBStartIdx(&MBB);
+ SlotIndex DestCopyIndex = LIS->getInstructionIndex(NewInstr);
+ if (IncomingReg) {
+ // Add the region from the beginning of MBB to the copy instruction to
+ // IncomingReg's live interval.
+ LiveInterval &IncomingLI = LIS->getOrCreateInterval(IncomingReg);
+ VNInfo *IncomingVNI = IncomingLI.getVNInfoAt(MBBStartIndex);
+ if (!IncomingVNI)
+ IncomingVNI = IncomingLI.getNextValue(MBBStartIndex,
+ LIS->getVNInfoAllocator());
+ IncomingLI.addRange(LiveRange(MBBStartIndex,
+ DestCopyIndex.getRegSlot(),
+ IncomingVNI));
+ }
+
+ LiveInterval &DestLI = LIS->getOrCreateInterval(DestReg);
+ if (NewInstr->getOperand(0).isDead()) {
+ // A dead PHI's live range begins and ends at the start of the MBB, but
+ // the lowered copy, which will still be dead, needs to begin and end at
+ // the copy instruction.
+ VNInfo *OrigDestVNI = DestLI.getVNInfoAt(MBBStartIndex);
+ assert(OrigDestVNI && "PHI destination should be live at block entry.");
+ DestLI.removeRange(MBBStartIndex, MBBStartIndex.getDeadSlot());
+ DestLI.createDeadDef(DestCopyIndex.getRegSlot(),
+ LIS->getVNInfoAllocator());
+ DestLI.removeValNo(OrigDestVNI);
+ } else {
+ // Otherwise, remove the region from the beginning of MBB to the copy
+ // instruction from DestReg's live interval.
+ DestLI.removeRange(MBBStartIndex, DestCopyIndex.getRegSlot());
+ VNInfo *DestVNI = DestLI.getVNInfoAt(DestCopyIndex.getRegSlot());
+ assert(DestVNI && "PHI destination should be live at its definition.");
+ DestVNI->def = DestCopyIndex.getRegSlot();
+ }
+ }
+
// Adjust the VRegPHIUseCount map to account for the removal of this PHI node.
for (unsigned i = 1; i != MPhi->getNumOperands(); i += 2)
--VRegPHIUseCount[BBVRegPair(MPhi->getOperand(i+1).getMBB()->getNumber(),
findPHICopyInsertPoint(&opBlock, &MBB, SrcReg);
// Insert the copy.
+ MachineInstr *NewSrcInstr = 0;
if (!reusedIncoming && IncomingReg) {
if (SrcUndef) {
// The source register is undefined, so there is no need for a real
// COPY, but we still need to ensure joint dominance by defs.
// Insert an IMPLICIT_DEF instruction.
- BuildMI(opBlock, InsertPos, MPhi->getDebugLoc(),
- TII->get(TargetOpcode::IMPLICIT_DEF), IncomingReg);
+ NewSrcInstr = BuildMI(opBlock, InsertPos, MPhi->getDebugLoc(),
+ TII->get(TargetOpcode::IMPLICIT_DEF),
+ IncomingReg);
// Clean up the old implicit-def, if there even was one.
if (MachineInstr *DefMI = MRI->getVRegDef(SrcReg))
if (DefMI->isImplicitDef())
ImpDefs.insert(DefMI);
} else {
- BuildMI(opBlock, InsertPos, MPhi->getDebugLoc(),
- TII->get(TargetOpcode::COPY), IncomingReg)
- .addReg(SrcReg, 0, SrcSubReg);
+ NewSrcInstr = BuildMI(opBlock, InsertPos, MPhi->getDebugLoc(),
+ TII->get(TargetOpcode::COPY), IncomingReg)
+ .addReg(SrcReg, 0, SrcSubReg);
}
}
- // Now update live variable information if we have it. Otherwise we're done
- if (SrcUndef || !LV) continue;
-
- // We want to be able to insert a kill of the register if this PHI (aka, the
- // copy we just inserted) is the last use of the source value. Live
- // variable analysis conservatively handles this by saying that the value is
- // live until the end of the block the PHI entry lives in. If the value
- // really is dead at the PHI copy, there will be no successor blocks which
- // have the value live-in.
-
- // Also check to see if this register is in use by another PHI node which
- // has not yet been eliminated. If so, it will be killed at an appropriate
- // point later.
-
- // Is it used by any PHI instructions in this block?
- bool ValueIsUsed = VRegPHIUseCount[BBVRegPair(opBlock.getNumber(), SrcReg)];
+ // We only need to update the LiveVariables kill of SrcReg if this was the
+ // last PHI use of SrcReg to be lowered on this CFG edge and it is not live
+ // out of the predecessor. We can also ignore undef sources.
+ if (LV && !SrcUndef &&
+ !VRegPHIUseCount[BBVRegPair(opBlock.getNumber(), SrcReg)] &&
+ !LV->isLiveOut(SrcReg, opBlock)) {
+ // We want to be able to insert a kill of the register if this PHI (aka,
+ // the copy we just inserted) is the last use of the source value. Live
+ // variable analysis conservatively handles this by saying that the value
+ // is live until the end of the block the PHI entry lives in. If the value
+ // really is dead at the PHI copy, there will be no successor blocks which
+ // have the value live-in.
+
+ // Okay, if we now know that the value is not live out of the block, we
+ // can add a kill marker in this block saying that it kills the incoming
+ // value!
- // Okay, if we now know that the value is not live out of the block, we can
- // add a kill marker in this block saying that it kills the incoming value!
- if (!ValueIsUsed && !LV->isLiveOut(SrcReg, opBlock)) {
// In our final twist, we have to decide which instruction kills the
// register. In most cases this is the copy, however, terminator
// instructions at the end of the block may also use the value. In this
unsigned opBlockNum = opBlock.getNumber();
LV->getVarInfo(SrcReg).AliveBlocks.reset(opBlockNum);
}
+
+ if (LIS) {
+ if (NewSrcInstr) {
+ LIS->InsertMachineInstrInMaps(NewSrcInstr);
+ LIS->addLiveRangeToEndOfBlock(IncomingReg, NewSrcInstr);
+ }
+
+ if (!SrcUndef &&
+ !VRegPHIUseCount[BBVRegPair(opBlock.getNumber(), SrcReg)]) {
+ LiveInterval &SrcLI = LIS->getInterval(SrcReg);
+
+ bool isLiveOut = false;
+ for (MachineBasicBlock::succ_iterator SI = opBlock.succ_begin(),
+ SE = opBlock.succ_end(); SI != SE; ++SI) {
+ if (SrcLI.liveAt(LIS->getMBBStartIdx(*SI))) {
+ isLiveOut = true;
+ break;
+ }
+ }
+
+ if (!isLiveOut) {
+ MachineBasicBlock::iterator KillInst = opBlock.end();
+ MachineBasicBlock::iterator FirstTerm = opBlock.getFirstTerminator();
+ for (MachineBasicBlock::iterator Term = FirstTerm;
+ Term != opBlock.end(); ++Term) {
+ if (Term->readsRegister(SrcReg))
+ KillInst = Term;
+ }
+
+ if (KillInst == opBlock.end()) {
+ // No terminator uses the register.
+
+ if (reusedIncoming || !IncomingReg) {
+ // We may have to rewind a bit if we didn't just insert a copy.
+ KillInst = FirstTerm;
+ while (KillInst != opBlock.begin()) {
+ --KillInst;
+ if (KillInst->isDebugValue())
+ continue;
+ if (KillInst->readsRegister(SrcReg))
+ break;
+ }
+ } else {
+ // We just inserted this copy.
+ KillInst = prior(InsertPos);
+ }
+ }
+ assert(KillInst->readsRegister(SrcReg) &&
+ "Cannot find kill instruction");
+
+ SlotIndex LastUseIndex = LIS->getInstructionIndex(KillInst);
+ SrcLI.removeRange(LastUseIndex.getRegSlot(),
+ LIS->getMBBEndIdx(&opBlock));
+ }
+ }
+ }
}
// Really delete the PHI instruction now, if it is not in the LoweredPHIs map.
- if (reusedIncoming || !IncomingReg)
+ if (reusedIncoming || !IncomingReg) {
+ if (LIS)
+ LIS->RemoveMachineInstrFromMaps(MPhi);
MF.DeleteMachineInstr(MPhi);
+ }
}
/// analyzePHINodes - Gather information about the PHI nodes in here. In
projects / oota-llvm.git / commitdiff