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Make BasicAliasAnalysis and Value::getUnderlyingObject use

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GEPOperator's hasNoPointer0verflow(), and make a few places in instcombine
that create GEPs that may overflow clear the NoOverflow value. Among
other things, this partially addresses PR2831.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76252 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2009-07-17 22:25:10 +00:00
parent 8f080f0233
commit 3a7a68c108
3 changed files with 28 additions and 16 deletions
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20
lib/Transforms/Scalar/InstructionCombining.cpp
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@@ -2310,7 +2310,10 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
cast<PointerType>(CI->getOperand(0)->getType())->getAddressSpace();
Value *I2 = InsertBitCastBefore(CI->getOperand(0),
Context->getPointerType(Type::Int8Ty, AS), I);
I2 = InsertNewInstBefore(GetElementPtrInst::Create(I2, Other, "ctg2"), I);
GetElementPtrInst *GEP = GetElementPtrInst::Create(I2, Other, "ctg2");
// A GEP formed from an arbitrary add may overflow.
cast<GEPOperator>(GEP)->setHasNoPointerOverflow(false);
I2 = InsertNewInstBefore(GEP, I);
return new PtrToIntInst(I2, CI->getType());
}
}
@@ -8942,7 +8945,12 @@ Instruction *InstCombiner::visitIntToPtr(IntToPtrInst &CI) {
// If Offset is evenly divisible by Size, we can do this xform.
if (Size && !APIntOps::srem(Offset, APInt(Offset.getBitWidth(), Size))){
Offset = APIntOps::sdiv(Offset, APInt(Offset.getBitWidth(), Size));
return GetElementPtrInst::Create(X, Context->getConstantInt(Offset));
GetElementPtrInst *GEP =
GetElementPtrInst::Create(X, Context->getConstantInt(Offset));
// A gep synthesized from inttoptr+add+ptrtoint must be assumed to
// potentially overflow, in the absense of further analysis.
cast<GEPOperator>(GEP)->setHasNoPointerOverflow(false);
return GEP;
}
}
// TODO: Could handle other cases, e.g. where add is indexing into field of
@@ -8966,8 +8974,12 @@ Instruction *InstCombiner::visitIntToPtr(IntToPtrInst &CI) {
Instruction *P = InsertNewInstBefore(new IntToPtrInst(X, CI.getType(),
"tmp"), CI);
return GetElementPtrInst::Create(P,
Context->getConstantInt(Offset), "tmp");
GetElementPtrInst *GEP =
GetElementPtrInst::Create(P, Context->getConstantInt(Offset), "tmp");
// A gep synthesized from inttoptr+add+ptrtoint must be assumed to
// potentially overflow, in the absense of further analysis.
cast<GEPOperator>(GEP)->setHasNoPointerOverflow(false);
return GEP;
}
}
return 0;