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Don't count PHI instructions toward the limit for tail duplicating a block. 

llvm-svn: 90326
This commit is contained in:
Bob Wilson 2009-12-02 17:15:24 +00:00
parent d831ef4945
commit fffbc0c5d9
1 changed files with 6 additions and 4 deletions
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10
llvm/lib/CodeGen/TailDuplication.cpp
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@ -129,20 +129,22 @@ bool TailDuplicatePass::TailDuplicate(MachineBasicBlock *TailBB,
// Check the instructions in the block to determine whether tail-duplication
// is invalid or unlikely to be profitable.
unsigned i = 0;
unsigned InstrCount = 0;
bool HasCall = false;
for (MachineBasicBlock::iterator I = TailBB->begin();
I != TailBB->end(); ++I, ++i) {
I != TailBB->end(); ++I) {
// Non-duplicable things shouldn't be tail-duplicated.
if (I->getDesc().isNotDuplicable()) return false;
// Don't duplicate more than the threshold.
if (i == MaxDuplicateCount) return false;
if (InstrCount == MaxDuplicateCount) return false;
// Remember if we saw a call.
if (I->getDesc().isCall()) HasCall = true;
if (I->getOpcode() != TargetInstrInfo::PHI)
InstrCount += 1;
}
// Heuristically, don't tail-duplicate calls if it would expand code size,
// as it's less likely to be worth the extra cost.
if (i > 1 && HasCall)
if (InstrCount > 1 && HasCall)
return false;
// Iterate through all the unique predecessors and tail-duplicate this