[PATCH] D68706: [InstCombine] don't assume 'inbounds' for bitcast deref or null pointer in non-default address space

[Sanjay Patel via Phabricator via llvm-commits]

spatel updated this revision to Diff 224108.
spatel added a comment.

Patch updated:
No diffs in this patch itself, but rebased after adding test at rL374190 <https://reviews.llvm.org/rL374190>.
I don't have much experience with addrspaces or inbounds, so let me know if I should change anything else.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D68706/new/

https://reviews.llvm.org/D68706

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
  llvm/test/Transforms/InstCombine/load-bitcast-vec.ll


Index: llvm/test/Transforms/InstCombine/load-bitcast-vec.ll
===================================================================
--- llvm/test/Transforms/InstCombine/load-bitcast-vec.ll
+++ llvm/test/Transforms/InstCombine/load-bitcast-vec.ll
@@ -100,11 +100,11 @@
   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]]
 ;
Index: llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -2344,8 +2344,12 @@
       // 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).
+        if (SrcPTy->getAddressSpace() == 0 || !CanBeNull)
+          GEP->setIsInBounds();
+      }
       return GEP;
     }
   }


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