[llvm] [InstSimplify] Correctly handle comparison with zero-size allocs (PR #115728)

[Nikita Popov via llvm-commits]

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@@ -282,8 +285,9 @@ define i1 @zst_alloca_end() {
 define i1 @zst_global_start() {
 ; CHECK-LABEL: @zst_global_start(
 ; CHECK-NEXT:    [[A:%.*]] = alloca i64, align 8
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq ptr [[A]], @gz
 ; CHECK-NEXT:    call void @escape(ptr [[A]], ptr @gz)
-; CHECK-NEXT:    ret i1 false
+; CHECK-NEXT:    ret i1 [[CMP]]
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nikic wrote:

Currently LLVM doesn't make assumptions about how different allocations types are positioned relative to each other. We'd have to add LangRef wording for this, to require that allocas and globals allocations cannot be adjacent.

https://github.com/llvm/llvm-project/pull/115728