[llvm] [BasicAA] Use nuw attribute of GEPs (PR #98608)

[Hari Limaye via llvm-commits]

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@@ -1239,6 +1240,20 @@ AliasResult BasicAAResult::aliasGEP(
     }
   }
 
+  // If the difference between pointers is Offset +<nuw> Indices then we know
+  // that the addition does not wrap the pointer index type (add nuw) and the
+  // constant Offset is a lower bound on the distance between the pointers. We
+  // can then prove NoAlias via Offset u>= VLeftSize.
+  //    +                +                     +
+  //    | BaseOffset     |   +<nuw> Indices    |
+  //    ---------------->|-------------------->|
+  //    |-->VLeftSize    |                     |-------> VRightSize
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hazzlim wrote:

Done.

https://github.com/llvm/llvm-project/pull/98608