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[InstCombine] don't assume 'inbounds' for bitcast deref or null pointer in non-default address space

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Follow-up to D68244 to account for a corner case discussed in:
https://bugs.llvm.org/show_bug.cgi?id=43501

Add one more restriction: if the pointer is deref-or-null and in a non-default
(non-zero) address space, we can't assume inbounds.

Differential Revision: https://reviews.llvm.org/D68706

llvm-svn: 374728
This commit is contained in:
Sanjay Patel 2019-10-13 17:19:08 +00:00
parent 5dbe65e8a0
commit 048e400ca3
2 changed files with 12 additions and 4 deletions
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12
lib/Transforms/InstCombine/InstCombineCasts.cpp
View File

@ -2344,8 +2344,16 @@ Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
// If the source pointer is dereferenceable, then assume it points to an
// allocated object and apply "inbounds" to the GEP.
bool CanBeNull;
if (Src->getPointerDereferenceableBytes(DL, CanBeNull))
GEP->setIsInBounds();
if (Src->getPointerDereferenceableBytes(DL, CanBeNull)) {
// In a non-default address space (not 0), a null pointer can not be
// assumed inbounds, so ignore that case (dereferenceable_or_null).
// The reason is that 'null' is not treated differently in these address
// spaces, and we consequently ignore the 'gep inbounds' special case
// for 'null' which allows 'inbounds' on 'null' if the indices are
// zeros.
if (SrcPTy->getAddressSpace() == 0 || !CanBeNull)
GEP->setIsInBounds();
}
return GEP;
}
}

4
test/Transforms/InstCombine/load-bitcast-vec.ll
View File

@ -100,11 +100,11 @@ define float @matching_scalar_smallest_deref_addrspace(<4 x float> addrspace(4)*
ret float %r
}
; TODO: Is a null pointer inbounds in any address space?
; A null pointer can't be assumed inbounds in a non-default address space.
define float @matching_scalar_smallest_deref_or_null_addrspace(<4 x float> addrspace(4)* dereferenceable_or_null(1) %p) {
; CHECK-LABEL: @matching_scalar_smallest_deref_or_null_addrspace(
; CHECK-NEXT: [[BC:%.*]] = getelementptr inbounds <4 x float>, <4 x float> addrspace(4)* [[P:%.*]], i64 0, i64 0
; CHECK-NEXT: [[BC:%.*]] = getelementptr <4 x float>, <4 x float> addrspace(4)* [[P:%.*]], i64 0, i64 0
; CHECK-NEXT: [[R:%.*]] = load float, float addrspace(4)* [[BC]], align 16
; CHECK-NEXT: ret float [[R]]
;