Make BasicAliasAnalysis and Value::getUnderlyingObject use
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
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 9ddd0e0..dbdf449 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -2310,7 +2310,10 @@
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 @@
// 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 *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;