x86_64 ABI tests, which currently cause failures

With the x86_64 Linux ELF ABI, we're currently failing two of these
three tests, which have been disabled for now.  The problem is mixed
structures such as struct { double x; char c; }, which the x86_64 ABI
specifies are to be passed/returned in one integer register and one SSE
register; our current approach, marking the structure as VT_QLONG or
VT_QFLOAT, fails in this case.

(It's possible to fix this by getting rid of VT_QLONG and VT_QFLOAT
entirely as at https://github.com/pipcet/tinycc, but the changes aren't
properly isolated at present. Anyway, there might be a less disruptive
fix.)

tests/abitest.c

@@ -130,6 +130,89 @@ static int ret_2double_test(void) {
   return run_callback(src, ret_2double_test_callback);
 }
 
+/*
+ * ret_mixed_test:
+ *
+ * On x86-64, a struct with a double and a 64-bit integer should be
+ * passed in one SSE register and one integer register.
+ */
+typedef struct ret_mixed_test_type_s {double x; long long y;} ret_mixed_test_type;
+typedef ret_mixed_test_type (*ret_mixed_test_function_type) (ret_mixed_test_type);
+
+static int ret_mixed_test_callback(void *ptr) {
+  ret_mixed_test_function_type f = (ret_mixed_test_function_type)ptr;
+  ret_mixed_test_type a = {10, 35};
+  ret_mixed_test_type r;
+  r = f(a);
+  return ((r.x == a.x*5) && (r.y == a.y*3)) ? 0 : -1;
+}
+
+static int ret_mixed_test(void) {
+  const char *src =
+  "typedef struct ret_mixed_test_type_s {double x; long long y;} ret_mixed_test_type;"
+  "ret_mixed_test_type f(ret_mixed_test_type a) {\n"
+  "  ret_mixed_test_type r = {a.x*5, a.y*3};\n"
+  "  return r;\n"
+  "}\n";
+
+  return run_callback(src, ret_mixed_test_callback);
+}
+
+/*
+ * ret_mixed2_test:
+ *
+ * On x86-64, a struct with two floats and two 32-bit integers should
+ * be passed in one SSE register and one integer register.
+ */
+typedef struct ret_mixed2_test_type_s {float x,x2; int y,y2;} ret_mixed2_test_type;
+typedef ret_mixed2_test_type (*ret_mixed2_test_function_type) (ret_mixed2_test_type);
+
+static int ret_mixed2_test_callback(void *ptr) {
+  ret_mixed2_test_function_type f = (ret_mixed2_test_function_type)ptr;
+  ret_mixed2_test_type a = {10, 5, 35, 7 };
+  ret_mixed2_test_type r;
+  r = f(a);
+  return ((r.x == a.x*5) && (r.y == a.y*3)) ? 0 : -1;
+}
+
+static int ret_mixed2_test(void) {
+  const char *src =
+  "typedef struct ret_mixed2_test_type_s {float x, x2; int y,y2;} ret_mixed2_test_type;"
+  "ret_mixed2_test_type f(ret_mixed2_test_type a) {\n"
+  "  ret_mixed2_test_type r = {a.x*5, 0, a.y*3, 0};\n"
+  "  return r;\n"
+  "}\n";
+
+  return run_callback(src, ret_mixed2_test_callback);
+}
+
+/*
+ * ret_mixed3_test:
+ *
+ * On x86-64, this struct should be passed in two integer registers.
+ */
+typedef struct ret_mixed3_test_type_s {float x; int y; float x2; int y2;} ret_mixed3_test_type;
+typedef ret_mixed3_test_type (*ret_mixed3_test_function_type) (ret_mixed3_test_type);
+
+static int ret_mixed3_test_callback(void *ptr) {
+  ret_mixed3_test_function_type f = (ret_mixed3_test_function_type)ptr;
+  ret_mixed3_test_type a = {10, 5, 35, 7 };
+  ret_mixed3_test_type r;
+  r = f(a);
+  return ((r.x == a.x*5) && (r.y2 == a.y*3)) ? 0 : -1;
+}
+
+static int ret_mixed3_test(void) {
+  const char *src =
+  "typedef struct ret_mixed3_test_type_s {float x; int y; float x2; int y2;} ret_mixed3_test_type;"
+  "ret_mixed3_test_type f(ret_mixed3_test_type a) {\n"
+  "  ret_mixed3_test_type r = {a.x*5, 0, 0, a.y*3};\n"
+  "  return r;\n"
+  "}\n";
+
+  return run_callback(src, ret_mixed3_test_callback);
+}
+
 /*
  * reg_pack_test: return a small struct which should be packed into
  * registers (Win32) during return.
@@ -477,6 +560,9 @@ int main(int argc, char **argv) {
   RUN_TEST(ret_longdouble_test);
   RUN_TEST(ret_2float_test);
   RUN_TEST(ret_2double_test);
+  /* RUN_TEST(ret_mixed_test); currently broken on x86_64 */
+  /* RUN_TEST(ret_mixed2_test); currently broken on x86_64 */
+  RUN_TEST(ret_mixed3_test);
   RUN_TEST(reg_pack_test);
   RUN_TEST(reg_pack_longlong_test);
   RUN_TEST(sret_test);