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Teach PHIElimination to split critical edges when -split-phi-edges is enabled.

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Critical edges leading to a PHI node are split when the PHI source variable is
live out from the predecessor block. This help the coalescer eliminate more
PHI joins.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86725 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen
2009-11-10 22:01:05 +00:00
parent e35e3c33dc
commit f235f13931
4 changed files with 133 additions and 5 deletions
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40
lib/CodeGen/LiveVariables.cpp
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@ -50,6 +50,14 @@ void LiveVariables::getAnalysisUsage(AnalysisUsage &AU) const {
MachineFunctionPass::getAnalysisUsage(AU);
}
MachineInstr *
LiveVariables::VarInfo::findKill(const MachineBasicBlock *MBB) const {
for (unsigned i = 0, e = Kills.size(); i != e; ++i)
if (Kills[i]->getParent() == MBB)
return Kills[i];
return NULL;
}
void LiveVariables::VarInfo::dump() const {
errs() << " Alive in blocks: ";
for (SparseBitVector<>::iterator I = AliveBlocks.begin(),
@ -641,3 +649,35 @@ void LiveVariables::analyzePHINodes(const MachineFunction& Fn) {
PHIVarInfo[BBI->getOperand(i + 1).getMBB()->getNumber()]
.push_back(BBI->getOperand(i).getReg());
}
void LiveVariables::addNewBlock(MachineBasicBlock *A, MachineBasicBlock *B) {
unsigned NumA = A->getNumber();
unsigned NumB = B->getNumber();
// Update info for all live variables
for (unsigned i = 0, e = VirtRegInfo.size(); i != e; ++i) {
VarInfo &VI = VirtRegInfo[i];
// Anything live through B is also live through A.
if (VI.AliveBlocks.test(NumB)) {
VI.AliveBlocks.set(NumA);
continue;
}
// If we're not killed in B, we are not live in
if (!VI.findKill(B))
continue;
unsigned Reg = i+TargetRegisterInfo::FirstVirtualRegister;
// Find a def outside B
for (MachineRegisterInfo::def_iterator di = MRI->def_begin(Reg),
de=MRI->def_end(); di != de; ++di) {
if (di->getParent() != B) {
// Reg was defined outside B and killed in B - it must be live in.
VI.AliveBlocks.set(NumA);
break;
}
}
}
}