[llvm] [SROA] Unfold gep of index select (PR #80983)

[Artem Belevich via llvm-commits]

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@@ -202,8 +206,10 @@ define i32 @test_select_idx_escaped(i1 %c, ptr %p) {
 ; CHECK-NEXT:    [[GEP1:%.*]] = getelementptr inbounds i8, ptr [[ALLOCA]], i64 24
 ; CHECK-NEXT:    store i32 2, ptr [[GEP1]], align 4
 ; CHECK-NEXT:    [[IDX:%.*]] = select i1 [[C:%.*]], i64 24, i64 0
-; CHECK-NEXT:    [[GEP2:%.*]] = getelementptr inbounds i8, ptr [[ALLOCA]], i64 [[IDX]]
-; CHECK-NEXT:    [[RES:%.*]] = load i32, ptr [[GEP2]], align 4
+; CHECK-NEXT:    [[DOTSROA_GEP:%.*]] = getelementptr inbounds i8, ptr [[ALLOCA]], i64 24
+; CHECK-NEXT:    [[DOTSROA_GEP1:%.*]] = getelementptr inbounds i8, ptr [[ALLOCA]], i64 0
+; CHECK-NEXT:    [[IDX_SROA_SEL:%.*]] = select i1 [[C]], ptr [[DOTSROA_GEP]], ptr [[DOTSROA_GEP1]]
+; CHECK-NEXT:    [[RES:%.*]] = load i32, ptr [[IDX_SROA_SEL]], align 4
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Artem-B wrote:

Yup. In practice, we have instcombine+SROA in multiple places in the pipeline, so next instcombine will probably merge these GEPs again. 

https://github.com/llvm/llvm-project/pull/80983