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Implement PR1201 and test/Transforms/InstCombine/malloc-free-delete.ll

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llvm-svn: 35981
This commit is contained in:
Chris Lattner 2007-04-14 00:20:02 +00:00
parent 1d90754cf7
commit 6f64f54168
1 changed files with 23 additions and 8 deletions
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31
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -8367,13 +8367,6 @@ Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
Value *Op = FI.getOperand(0);
// Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
if (CastInst *CI = dyn_cast<CastInst>(Op))
if (isa<PointerType>(CI->getOperand(0)->getType())) {
FI.setOperand(0, CI->getOperand(0));
return &FI;
}
// free undef -> unreachable.
if (isa<UndefValue>(Op)) {
// Insert a new store to null because we cannot modify the CFG here.
@ -8381,11 +8374,33 @@ Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
UndefValue::get(PointerType::get(Type::Int1Ty)), &FI);
return EraseInstFromFunction(FI);
}
// If we have 'free null' delete the instruction. This can happen in stl code
// when lots of inlining happens.
if (isa<ConstantPointerNull>(Op))
return EraseInstFromFunction(FI);
// Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
if (BitCastInst *CI = dyn_cast<BitCastInst>(Op)) {
FI.setOperand(0, CI->getOperand(0));
return &FI;
}
// Change free (gep X, 0,0,0,0) into free(X)
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) {
if (GEPI->hasAllZeroIndices()) {
AddToWorkList(GEPI);
FI.setOperand(0, GEPI->getOperand(0));
return &FI;
}
}
// Change free(malloc) into nothing, if the malloc has a single use.
if (MallocInst *MI = dyn_cast<MallocInst>(Op))
if (MI->hasOneUse()) {
EraseInstFromFunction(FI);
return EraseInstFromFunction(*MI);
}
return 0;
}