[llvm] [InstCombine] Strip trailing zero GEP indices (PR #151338)

[Nikita Popov via llvm-commits]

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@@ -215,10 +215,7 @@ define i1 @test10_struct(i32 %x) {
 
 define i1 @test10_struct_noinbounds(i32 %x) {
 ; CHECK-LABEL: @test10_struct_noinbounds(
-; CHECK-NEXT:    [[P:%.*]] = getelementptr [[FOO:%.*]], ptr @GS, i32 [[X:%.*]], i32 0
-; CHECK-NEXT:    [[Q:%.*]] = load i32, ptr [[P]], align 4
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i32 [[Q]], 9
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
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nikic wrote:

This looks suspicious, but is correct: We know that zero is the only valid value of `%x`. The replaceGEPIdxWithZero() fold doesn't handle a trailing zero index in this case.

https://github.com/llvm/llvm-project/pull/151338