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Do a simple instcombine xforms to delete llvm.stackrestore cases.

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llvm-svn: 25294
This commit is contained in:
Chris Lattner 2006-01-13 21:28:09 +00:00
parent b839f31954
commit 61a2fca725
1 changed files with 33 additions and 0 deletions
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33
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -4671,6 +4671,39 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
SPI->replaceAllUsesWith(PrevSPI);
return EraseInstFromFunction(CI);
}
} else {
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::stackrestore: {
// If the save is right next to the restore, remove the restore. This can
// happen when variable allocas are DCE'd.
if (IntrinsicInst *SS = dyn_cast<IntrinsicInst>(II->getOperand(1))) {
if (SS->getIntrinsicID() == Intrinsic::stacksave) {
BasicBlock::iterator BI = SS;
if (&*++BI == II)
return EraseInstFromFunction(CI);
}
}
// If the stack restore is in a return/unwind block and if there are no
// allocas or calls between the restore and the return, nuke the restore.
TerminatorInst *TI = II->getParent()->getTerminator();
if (isa<ReturnInst>(TI) || isa<UnwindInst>(TI)) {
BasicBlock::iterator BI = II;
bool CannotRemove = false;
for (++BI; &*BI != TI; ++BI) {
if (isa<AllocaInst>(BI) ||
(isa<CallInst>(BI) && !isa<IntrinsicInst>(BI))) {
CannotRemove = true;
break;
}
}
if (!CannotRemove)
return EraseInstFromFunction(CI);
}
break;
}
}
}
return visitCallSite(II);