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optimize away stackrestore calls that have no intervening alloca or call.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47258 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2008-02-18 06:12:38 +00:00
parent 28cb2051c8
commit bf1d8a7099
2 changed files with 58 additions and 13 deletions
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28
lib/Transforms/Scalar/InstructionCombining.cpp
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@@ -8199,22 +8199,30 @@ Instruction *InstCombiner::visitCallInst(CallInst &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.
// Scan down this block to see if there is another stack restore in the
// same block without an intervening call/alloca.
BasicBlock::iterator BI = II;
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))) {
bool CannotRemove = false;
for (++BI; &*BI != TI; ++BI) {
if (isa<AllocaInst>(BI)) {
CannotRemove = true;
break;
}
if (isa<CallInst>(BI)) {
if (!isa<IntrinsicInst>(BI)) {
CannotRemove = true;
break;
}
}
if (!CannotRemove)
// If there is a stackrestore below this one, remove this one.
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.
if (!CannotRemove && (isa<ReturnInst>(TI) || isa<UnwindInst>(TI)))
return EraseInstFromFunction(CI);
break;
}
}