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A dead malloc, a free(NULL) and a free(undef) are all trivially dead

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instructions.

This doesn't introduce any optimizations we weren't doing before (except
potentially due to pass ordering issues), now passes will eliminate them sooner
as part of their own cleanups.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142787 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky
2011-10-24 04:35:36 +00:00
parent 38af3d5a8d
commit 4a3935c27e
2 changed files with 9 additions and 2 deletions
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8
lib/Transforms/Utils/Local.cpp
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@ -28,6 +28,7 @@
#include "llvm/Analysis/DIBuilder.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/ProfileInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Target/TargetData.h"
@ -257,6 +258,13 @@ bool llvm::isInstructionTriviallyDead(Instruction *I) {
II->getIntrinsicID() == Intrinsic::lifetime_end)
return isa<UndefValue>(II->getArgOperand(1));
}
if (extractMallocCall(I)) return true;
if (CallInst *CI = isFreeCall(I))
if (Constant *C = dyn_cast<Constant>(CI->getArgOperand(0)))
return C->isNullValue() || isa<UndefValue>(C);
return false;
}