[llvm] [SROA] adjust struct layout requirements for struct to vector canonicalization (PR #201967)

[Yaxun Liu via llvm-commits]

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@@ -17,28 +17,19 @@ declare void @llvm.memcpy.p0.p0.i64(ptr noalias writeonly captures(none), ptr no
 ; uninitialized memory becomes a placeholder value. If you instead delay struct to vector canonicalization and allow memcpyopt
 ; to run, you'll get a 4-byte store of 0.
 define ptr @store_only_fp_tail() {
-; NO-CANON-LABEL: define ptr @store_only_fp_tail() {
-; NO-CANON-NEXT:    [[DOTSROA_3:%.*]] = alloca { float, float, float }, align 8
-; NO-CANON-NEXT:    [[DOTSROA_4:%.*]] = alloca { float, float, float, float, float, float, float, float, float, float, float }, align 8
-; NO-CANON-NEXT:    [[DOTSROA_0_SROA_1:%.*]] = alloca { float, float, float }, align 8
-; NO-CANON-NEXT:    [[DOTSROA_2:%.*]] = alloca { float, float, float, float, float, float, float, float, float, float, float }, align 8
-; NO-CANON-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 8 [[DOTSROA_3]], ptr align 8 [[DOTSROA_0_SROA_1]], i64 12, i1 false)
-; NO-CANON-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 8 [[DOTSROA_4]], ptr align 8 [[DOTSROA_2]], i64 44, i1 false)
-; NO-CANON-NEXT:    store float 0.000000e+00, ptr null, align 1
-; NO-CANON-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 1 getelementptr inbounds (i8, ptr null, i64 4), ptr align 8 [[DOTSROA_3]], i64 12, i1 false)
-; NO-CANON-NEXT:    store float 0.000000e+00, ptr getelementptr inbounds (i8, ptr null, i64 16), align 1
-; NO-CANON-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr align 1 getelementptr inbounds (i8, ptr null, i64 20), ptr align 8 [[DOTSROA_4]], i64 44, i1 false)
-; NO-CANON-NEXT:    ret ptr null
+; GOOD-LABEL: define ptr @store_only_fp_tail() {
+; GOOD-NEXT:    store float 0.000000e+00, ptr null, align 1
+; GOOD-NEXT:    store <3 x float> undef, ptr getelementptr inbounds (i8, ptr null, i64 4), align 1
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yxsamliu wrote:

This new `undef` keeps the formatter check red. Can we avoid spelling it in the CHECK lines, e.g. by matching the value with `{{.*}}`, or otherwise keep the old test shape so this PR only covers the layout-size change?

https://github.com/llvm/llvm-project/pull/201967