Migrate x86-64-abi-sret-vs-2word-struct-param.cpp from

llvm/test/FrontendC++ and FileCheckize.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@137762 91177308-0d34-0410-b5e6-96231b3b80d8

test/CodeGenCXX/x86-64-abi-sret-vs-2word-struct-param.cpp

+// RUN: %clang_cc1 -emit-llvm %s -o - | FileCheck %s
+// XTARGET: x86
+// PR4242
+// (PR 4242 bug is on 64-bit only, test passes on x86-32 as well)
+
+struct S {
+    void* data[3];
+};
+
+struct T {
+    void* data[2];
+};
+
+// CHECK: %struct.T* byval
+extern "C" S fail(int, int, int, int, T t, void* p) {
+    S s;
+    s.data[0] = t.data[0];
+    s.data[1] = t.data[1];
+    s.data[2] = p;
+    return s;
+}
+
+// CHECK: %struct.T* byval
+extern "C" S* succeed(S* sret, int, int, int, int, T t, void* p) {
+    sret->data[0] = t.data[0];
+    sret->data[1] = t.data[1];
+    sret->data[2] = p;
+    return sret;
+}