[clang] [clang] Avoid memcopy for small structure with padding under -ftrivial-auto-var-init (PR #71677)

[via cfe-commits]

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@@ -1506,8 +1497,16 @@ TEST_CUSTOM(unmatchedreverse, unmatchedreverse, { .c = 42  });
 // CHECK-O0:    call void @llvm.memcpy
 // CHECK-NOT:   !annotation
 // CHECK-O0:    call void @{{.*}}used{{.*}}%custom)
-// PATTERN-O1:  store i32 -1431655894, ptr {{.*}}, align 4
-// ZERO-O1:     store i32 42, ptr {{.*}}, align 4
+// PATTERN-O1:  store i8 42, ptr {{.*}}, align 4
+// PATTERN-O1-NEXT:  %[[I:[^ ]*]] = getelementptr inbounds i8, ptr %custom, i64 1
+// PATTERN-O1-NEXT:  store i8 -86, ptr %[[I]], align {{.*}}
+// PATTERN-O1-NEXT:  %[[I:[^ ]*]] = getelementptr inbounds i8, ptr %custom, i64 2
+// PATTERN-O1-NEXT:  store i8 -86, ptr %[[I]], align {{.*}}
+// PATTERN-O1-NEXT:  %[[I:[^ ]*]] = getelementptr inbounds i8, ptr %custom, i64 3
+// PATTERN-O1-NEXT:  store i8 -86, ptr %[[I]], align {{.*}}
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serge-sans-paille wrote:

That's my feeling too.

https://github.com/llvm/llvm-project/pull/71677