[clang] [clang] Handle trivial_abi attribute for Microsoft ABI. (PR #88857)

[Reid Kleckner via cfe-commits]

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@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -triple x86_64-pc-windows-msvc -std=c++11 -fcxx-exceptions -fexceptions -emit-llvm -o - %s | FileCheck %s
+
+// CHECK: %[[STRUCT_TRIVIAL:.*]] = type { ptr }
+struct __attribute__((trivial_abi)) Trivial {
+  int *p;
+  Trivial() : p(0) {}
+  Trivial(const Trivial &) noexcept = default;
+};
+
+// CHECK-LABEL: define{{.*}} i64 @"?retTrivial@@YA?AUTrivial@@XZ"(
+// CHECK: %retval = alloca %[[STRUCT_TRIVIAL]], align 8
+// CHECK: %call = call noundef ptr @"??0Trivial@@QEAA at XZ"(ptr noundef nonnull align 8 dereferenceable(8) %retval)
+// CHECK: %coerce.dive = getelementptr inbounds %[[STRUCT_TRIVIAL]], ptr %retval, i32 0, i32 0
+// CHECK: %0 = load ptr, ptr %coerce.dive, align 8
+// CHECK: %coerce.val.pi = ptrtoint ptr %0 to i64
+// CHECK: ret i64 %coerce.val.pi
+Trivial retTrivial() {
+  Trivial s;
+  return s;
+}
+
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rnk wrote:

I stand corrected, but I think it makes the point that this logic can be confusing, and it's worth testing. :)

https://github.com/llvm/llvm-project/pull/88857