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Allow multiple terminators to read virtual registers.

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Find the kill as the last terminator to read SrcReg.

Patch by Philipp Brüschweiler!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159722 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2012-07-04 19:52:05 +00:00
parent b872078701
commit 9e51b14faa
1 changed files with 28 additions and 32 deletions
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60
lib/CodeGen/PHIElimination.cpp
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@ -194,7 +194,7 @@ static bool isSourceDefinedByImplicitDef(const MachineInstr *MPhi,
/// LowerAtomicPHINode - Lower the PHI node at the top of the specified block,
/// under the assuption that it needs to be lowered in a way that supports
/// under the assumption that it needs to be lowered in a way that supports
/// atomic execution of PHIs. This lowering method is always correct all of the
/// time.
///
@ -355,39 +355,35 @@ void PHIElimination::LowerAtomicPHINode(
// 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, 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;
MachineBasicBlock::iterator Term = opBlock.getFirstTerminator();
if (Term != opBlock.end() && Term->readsRegister(SrcReg)) {
KillInst = Term;
// register. In most cases this is the copy, however, terminator
// instructions at the end of the block may also use the value. In this
// case, we should mark the last such terminator as being the killing
// block, not the copy.
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;
}
// Check that no other terminators use values.
#ifndef NDEBUG
for (MachineBasicBlock::iterator TI = llvm::next(Term);
TI != opBlock.end(); ++TI) {
if (TI->isDebugValue())
continue;
assert(!TI->readsRegister(SrcReg) &&
"Terminator instructions cannot use virtual registers unless"
"they are the first terminator in a block!");
if (KillInst == opBlock.end()) {
// No terminator uses the register.
if (reusedIncoming || !IncomingReg) {
// We may have to rewind a bit if we didn't insert a copy this time.
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);
}
#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()) {
--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");