#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Function.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/ADT/SmallPtrSet.h"
STATISTIC(NumAtomic, "Number of atomic phis lowered");
STATISTIC(NumSplits, "Number of critical edges split on demand");
+STATISTIC(NumReused, "Number of reused lowered phis");
char PHIElimination::ID = 0;
static RegisterPass<PHIElimination>
bool llvm::PHIElimination::runOnMachineFunction(MachineFunction &Fn) {
MRI = &Fn.getRegInfo();
- PHIDefs.clear();
- PHIKills.clear();
bool Changed = false;
// Split critical edges to help the coalescer
Changed |= EliminatePHINodes(Fn, *I);
// Remove dead IMPLICIT_DEF instructions.
- for (SmallPtrSet<MachineInstr*,4>::iterator I = ImpDefs.begin(),
+ for (SmallPtrSet<MachineInstr*, 4>::iterator I = ImpDefs.begin(),
E = ImpDefs.end(); I != E; ++I) {
MachineInstr *DefMI = *I;
unsigned DefReg = DefMI->getOperand(0).getReg();
- if (MRI->use_empty(DefReg))
+ if (MRI->use_nodbg_empty(DefReg))
DefMI->eraseFromParent();
}
+ // Clean up the lowered PHI instructions.
+ for (LoweredPHIMap::iterator I = LoweredPHIs.begin(), E = LoweredPHIs.end();
+ I != E; ++I)
+ Fn.DeleteMachineInstr(I->first);
+
+ LoweredPHIs.clear();
ImpDefs.clear();
VRegPHIUseCount.clear();
return Changed;
///
bool llvm::PHIElimination::EliminatePHINodes(MachineFunction &MF,
MachineBasicBlock &MBB) {
- if (MBB.empty() || MBB.front().getOpcode() != TargetInstrInfo::PHI)
+ if (MBB.empty() || !MBB.front().isPHI())
return false; // Quick exit for basic blocks without PHIs.
// Get an iterator to the first instruction after the last PHI node (this may
// also be the end of the basic block).
MachineBasicBlock::iterator AfterPHIsIt = SkipPHIsAndLabels(MBB, MBB.begin());
- while (MBB.front().getOpcode() == TargetInstrInfo::PHI)
+ while (MBB.front().isPHI())
LowerAtomicPHINode(MBB, AfterPHIsIt);
return true;
for (unsigned i = 1; i != MPhi->getNumOperands(); i += 2) {
unsigned SrcReg = MPhi->getOperand(i).getReg();
const MachineInstr *DefMI = MRI->getVRegDef(SrcReg);
- if (!DefMI || DefMI->getOpcode() != TargetInstrInfo::IMPLICIT_DEF)
+ if (!DefMI || !DefMI->isImplicitDef())
return false;
}
return true;
void llvm::PHIElimination::LowerAtomicPHINode(
MachineBasicBlock &MBB,
MachineBasicBlock::iterator AfterPHIsIt) {
+ ++NumAtomic;
// Unlink the PHI node from the basic block, but don't delete the PHI yet.
MachineInstr *MPhi = MBB.remove(MBB.begin());
MachineFunction &MF = *MBB.getParent();
const TargetRegisterClass *RC = MF.getRegInfo().getRegClass(DestReg);
unsigned IncomingReg = 0;
+ bool reusedIncoming = false; // Is IncomingReg reused from an earlier PHI?
// Insert a register to register copy at the top of the current block (but
// after any remaining phi nodes) which copies the new incoming register
// If all sources of a PHI node are implicit_def, just emit an
// implicit_def instead of a copy.
BuildMI(MBB, AfterPHIsIt, MPhi->getDebugLoc(),
- TII->get(TargetInstrInfo::IMPLICIT_DEF), DestReg);
+ TII->get(TargetOpcode::IMPLICIT_DEF), DestReg);
else {
- IncomingReg = MF.getRegInfo().createVirtualRegister(RC);
+ // Can we reuse an earlier PHI node? This only happens for critical edges,
+ // typically those created by tail duplication.
+ unsigned &entry = LoweredPHIs[MPhi];
+ if (entry) {
+ // An identical PHI node was already lowered. Reuse the incoming register.
+ IncomingReg = entry;
+ reusedIncoming = true;
+ ++NumReused;
+ DEBUG(dbgs() << "Reusing %reg" << IncomingReg << " for " << *MPhi);
+ } else {
+ entry = IncomingReg = MF.getRegInfo().createVirtualRegister(RC);
+ }
TII->copyRegToReg(MBB, AfterPHIsIt, DestReg, IncomingReg, RC, RC);
}
- // Record PHI def.
- assert(!hasPHIDef(DestReg) && "Vreg has multiple phi-defs?");
- PHIDefs[DestReg] = &MBB;
-
// Update live variable information if there is any.
LiveVariables *LV = getAnalysisIfAvailable<LiveVariables>();
if (LV) {
MachineInstr *PHICopy = prior(AfterPHIsIt);
if (IncomingReg) {
+ LiveVariables::VarInfo &VI = LV->getVarInfo(IncomingReg);
+
// Increment use count of the newly created virtual register.
- LV->getVarInfo(IncomingReg).NumUses++;
+ VI.NumUses++;
+ LV->setPHIJoin(IncomingReg);
+
+ // When we are reusing the incoming register, it may already have been
+ // killed in this block. The old kill will also have been inserted at
+ // AfterPHIsIt, so it appears before the current PHICopy.
+ if (reusedIncoming)
+ if (MachineInstr *OldKill = VI.findKill(&MBB)) {
+ DEBUG(dbgs() << "Remove old kill from " << *OldKill);
+ LV->removeVirtualRegisterKilled(IncomingReg, OldKill);
+ DEBUG(MBB.dump());
+ }
// Add information to LiveVariables to know that the incoming value is
// killed. Note that because the value is defined in several places (once
// 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(),
+ --VRegPHIUseCount[BBVRegPair(MPhi->getOperand(i+1).getMBB()->getNumber(),
MPhi->getOperand(i).getReg())];
// Now loop over all of the incoming arguments, changing them to copy into the
// path the PHI.
MachineBasicBlock &opBlock = *MPhi->getOperand(i*2+2).getMBB();
- // Record the kill.
- PHIKills[SrcReg].insert(&opBlock);
-
// If source is defined by an implicit def, there is no need to insert a
// copy.
MachineInstr *DefMI = MRI->getVRegDef(SrcReg);
- if (DefMI->getOpcode() == TargetInstrInfo::IMPLICIT_DEF) {
+ if (DefMI->isImplicitDef()) {
ImpDefs.insert(DefMI);
continue;
}
FindCopyInsertPoint(opBlock, MBB, SrcReg);
// Insert the copy.
- TII->copyRegToReg(opBlock, InsertPos, IncomingReg, SrcReg, RC, RC);
+ if (!reusedIncoming && IncomingReg)
+ TII->copyRegToReg(opBlock, InsertPos, IncomingReg, SrcReg, RC, RC);
// Now update live variable information if we have it. Otherwise we're done
if (!LV) continue;
// point later.
// Is it used by any PHI instructions in this block?
- bool ValueIsUsed = VRegPHIUseCount[BBVRegPair(&opBlock, SrcReg)] != 0;
+ bool ValueIsUsed = VRegPHIUseCount[BBVRegPair(opBlock.getNumber(), SrcReg)];
// 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 && !isLiveOut(SrcReg, opBlock, *LV)) {
+ 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, the first
// terminator instruction at the end of the block may also use the value.
// In this case, we should mark *it* as being the killing block, not the
// copy.
- MachineBasicBlock::iterator KillInst = prior(InsertPos);
+ MachineBasicBlock::iterator KillInst;
MachineBasicBlock::iterator Term = opBlock.getFirstTerminator();
- if (Term != opBlock.end()) {
- if (Term->readsRegister(SrcReg))
- KillInst = Term;
+ if (Term != opBlock.end() && Term->readsRegister(SrcReg)) {
+ KillInst = Term;
// Check that no other terminators use values.
#ifndef NDEBUG
- for (MachineBasicBlock::iterator TI = next(Term); TI != opBlock.end();
- ++TI) {
+ for (MachineBasicBlock::iterator TI = llvm::next(Term);
+ TI != opBlock.end(); ++TI) {
assert(!TI->readsRegister(SrcReg) &&
"Terminator instructions cannot use virtual registers unless"
"they are the first terminator in a block!");
}
#endif
+ } else if (reusedIncoming || !IncomingReg) {
+ // We may have to rewind a bit if we didn't insert a copy this time.
+ KillInst = Term;
+ while (KillInst != opBlock.begin())
+ if ((--KillInst)->readsRegister(SrcReg))
+ break;
+ } else {
+ // We just inserted this copy.
+ KillInst = prior(InsertPos);
}
+ assert(KillInst->readsRegister(SrcReg) && "Cannot find kill instruction");
// Finally, mark it killed.
LV->addVirtualRegisterKilled(SrcReg, KillInst);
}
}
- // Really delete the PHI instruction now!
- MF.DeleteMachineInstr(MPhi);
- ++NumAtomic;
+ // Really delete the PHI instruction now, if it is not in the LoweredPHIs map.
+ if (reusedIncoming || !IncomingReg)
+ MF.DeleteMachineInstr(MPhi);
}
/// analyzePHINodes - Gather information about the PHI nodes in here. In
for (MachineFunction::const_iterator I = Fn.begin(), E = Fn.end();
I != E; ++I)
for (MachineBasicBlock::const_iterator BBI = I->begin(), BBE = I->end();
- BBI != BBE && BBI->getOpcode() == TargetInstrInfo::PHI; ++BBI)
+ BBI != BBE && BBI->isPHI(); ++BBI)
for (unsigned i = 1, e = BBI->getNumOperands(); i != e; i += 2)
- ++VRegPHIUseCount[BBVRegPair(BBI->getOperand(i + 1).getMBB(),
+ ++VRegPHIUseCount[BBVRegPair(BBI->getOperand(i+1).getMBB()->getNumber(),
BBI->getOperand(i).getReg())];
}
bool llvm::PHIElimination::SplitPHIEdges(MachineFunction &MF,
MachineBasicBlock &MBB,
LiveVariables &LV) {
- if (MBB.empty() || MBB.front().getOpcode() != TargetInstrInfo::PHI)
+ if (MBB.empty() || !MBB.front().isPHI() || MBB.isLandingPad())
return false; // Quick exit for basic blocks without PHIs.
for (MachineBasicBlock::const_iterator BBI = MBB.begin(), BBE = MBB.end();
- BBI != BBE && BBI->getOpcode() == TargetInstrInfo::PHI; ++BBI) {
+ BBI != BBE && BBI->isPHI(); ++BBI) {
for (unsigned i = 1, e = BBI->getNumOperands(); i != e; i += 2) {
unsigned Reg = BBI->getOperand(i).getReg();
MachineBasicBlock *PreMBB = BBI->getOperand(i+1).getMBB();
// We break edges when registers are live out from the predecessor block
// (not considering PHI nodes). If the register is live in to this block
// anyway, we would gain nothing from splitting.
- if (!LV.isLiveIn(Reg, MBB) && isLiveOut(Reg, *PreMBB, LV))
+ if (!LV.isLiveIn(Reg, MBB) && LV.isLiveOut(Reg, *PreMBB))
SplitCriticalEdge(PreMBB, &MBB);
}
}
return true;
}
-bool llvm::PHIElimination::isLiveOut(unsigned Reg, const MachineBasicBlock &MBB,
- LiveVariables &LV) {
- LiveVariables::VarInfo &VI = LV.getVarInfo(Reg);
-
- // Loop over all of the successors of the basic block, checking to see if
- // the value is either live in the block, or if it is killed in the block.
- std::vector<MachineBasicBlock*> OpSuccBlocks;
- for (MachineBasicBlock::const_succ_iterator SI = MBB.succ_begin(),
- E = MBB.succ_end(); SI != E; ++SI) {
- MachineBasicBlock *SuccMBB = *SI;
-
- // Is it alive in this successor?
- unsigned SuccIdx = SuccMBB->getNumber();
- if (VI.AliveBlocks.test(SuccIdx))
- return true;
- OpSuccBlocks.push_back(SuccMBB);
- }
-
- // Check to see if this value is live because there is a use in a successor
- // that kills it.
- switch (OpSuccBlocks.size()) {
- case 1: {
- MachineBasicBlock *SuccMBB = OpSuccBlocks[0];
- for (unsigned i = 0, e = VI.Kills.size(); i != e; ++i)
- if (VI.Kills[i]->getParent() == SuccMBB)
- return true;
- break;
- }
- case 2: {
- MachineBasicBlock *SuccMBB1 = OpSuccBlocks[0], *SuccMBB2 = OpSuccBlocks[1];
- for (unsigned i = 0, e = VI.Kills.size(); i != e; ++i)
- if (VI.Kills[i]->getParent() == SuccMBB1 ||
- VI.Kills[i]->getParent() == SuccMBB2)
- return true;
- break;
- }
- default:
- std::sort(OpSuccBlocks.begin(), OpSuccBlocks.end());
- for (unsigned i = 0, e = VI.Kills.size(); i != e; ++i)
- if (std::binary_search(OpSuccBlocks.begin(), OpSuccBlocks.end(),
- VI.Kills[i]->getParent()))
- return true;
- }
- return false;
-}
-
MachineBasicBlock *PHIElimination::SplitCriticalEdge(MachineBasicBlock *A,
MachineBasicBlock *B) {
assert(A && B && "Missing MBB end point");
++NumSplits;
MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
- MF->insert(next(MachineFunction::iterator(A)), NMBB);
- DEBUG(errs() << "PHIElimination splitting critical edge:"
+ MF->insert(llvm::next(MachineFunction::iterator(A)), NMBB);
+ DEBUG(dbgs() << "PHIElimination splitting critical edge:"
" BB#" << A->getNumber()
<< " -- BB#" << NMBB->getNumber()
<< " -- BB#" << B->getNumber() << '\n');
// Fix PHI nodes in B so they refer to NMBB instead of A
for (MachineBasicBlock::iterator i = B->begin(), e = B->end();
- i != e && i->getOpcode() == TargetInstrInfo::PHI; ++i)
+ i != e && i->isPHI(); ++i)
for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
if (i->getOperand(ni+1).getMBB() == A)
i->getOperand(ni+1).setMBB(NMBB);
projects / oota-llvm.git / blobdiff