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Fix liveness calculation when splitting critical edges during PHI elimination.

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- Edges are split before any phis are eliminated, so the code is SSA.

- Create a proper IR BasicBlock for the split edges.

- LiveVariables::addNewBlock now has same syntax as
  MachineDominatorTree::addNewBlock. Algorithm calculates predecessor live-out
  set rather than successor live-in set.

This feature still causes some miscompilations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86867 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen
2009-11-11 19:31:31 +00:00
parent eba4ed9cbb
commit 3e20475fee
4 changed files with 83 additions and 55 deletions
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41
lib/CodeGen/LiveVariables.cpp
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@ -650,34 +650,35 @@ void LiveVariables::analyzePHINodes(const MachineFunction& Fn) {
.push_back(BBI->getOperand(i).getReg());
}
void LiveVariables::addNewBlock(MachineBasicBlock *A, MachineBasicBlock *B) {
unsigned NumA = A->getNumber();
unsigned NumB = B->getNumber();
/// addNewBlock - Add a new basic block BB as an empty succcessor to DomBB. All
/// variables that are live out of DomBB will be marked as passing live through
/// BB.
void LiveVariables::addNewBlock(MachineBasicBlock *BB,
MachineBasicBlock *DomBB) {
const unsigned NumNew = BB->getNumber();
const unsigned NumDom = DomBB->getNumber();
// Update info for all live variables
for (unsigned i = 0, e = VirtRegInfo.size(); i != e; ++i) {
VarInfo &VI = VirtRegInfo[i];
for (unsigned Reg = TargetRegisterInfo::FirstVirtualRegister,
E = MRI->getLastVirtReg()+1; Reg != E; ++Reg) {
VarInfo &VI = getVarInfo(Reg);
// Anything live through B is also live through A.
if (VI.AliveBlocks.test(NumB)) {
VI.AliveBlocks.set(NumA);
// Anything live through DomBB is also live through BB.
if (VI.AliveBlocks.test(NumDom)) {
VI.AliveBlocks.set(NumNew);
continue;
}
// If we're not killed in B, we are not live in
if (!VI.findKill(B))
// Variables not defined in DomBB cannot be live out.
const MachineInstr *Def = MRI->getVRegDef(Reg);
if (!Def || Def->getParent() != DomBB)
continue;
unsigned Reg = i+TargetRegisterInfo::FirstVirtualRegister;
// Killed by DomBB?
if (VI.findKill(DomBB))
continue;
// 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;
}
}
// This register is defined in DomBB and live out
VI.AliveBlocks.set(NumNew);
}
}