ia32: small structs are returned in int regs on darwin

ir/be/ia32/bearch_ia32.c

@@ -1691,8 +1691,12 @@ static void ia32_lower_for_target(void)
 	 *  on the callframe and we can't just use an arbitrary position on the
 	 *  stackframe)
 	 */
-	lower_calls_with_compounds(LF_RETURN_HIDDEN | LF_DONT_LOWER_ARGUMENTS
-	                           | LF_RETURN_SMALL_ARRAY_IN_INTS);
+	bool darwin_abi = be_gas_object_file_format == OBJECT_FILE_FORMAT_MACH_O;
+	compound_call_lowering_flags lower_call_flags
+		= LF_RETURN_HIDDEN | LF_DONT_LOWER_ARGUMENTS
+		| LF_RETURN_SMALL_ARRAY_IN_INTS
+		| (darwin_abi ? LF_RETURN_SMALL_STRUCT_IN_INTS : LF_NONE);
+	lower_calls_with_compounds(lower_call_flags);
 	be_after_irp_transform("lower-calls");
 
 	/* replace floating point operations by function calls */

ir/lower/lower_calls.c

@@ -86,10 +86,13 @@ static void remove_compound_param_entities(ir_graph *irg)
 
 static unsigned return_in_ints(compound_call_lowering_flags flags, ir_type *tp)
 {
-	if (!(flags & LF_RETURN_SMALL_ARRAY_IN_INTS))
-		return 0;
-	if (!is_Array_type(tp))
+	if (is_Array_type(tp)) {
+		if (!(flags&LF_RETURN_SMALL_ARRAY_IN_INTS))
+			return 0;
+	} else if (!(flags & LF_RETURN_SMALL_STRUCT_IN_INTS)) {
+		assert(is_aggregate_type(tp));
 		return 0;
+	}
 	unsigned size   = get_type_size_bytes(tp);
 	unsigned n_regs = size / get_mode_size_bytes(int_return_mode);
 	if (n_regs > 2)

ir/lower/lower_calls.h

@@ -24,6 +24,8 @@ typedef enum compound_call_lowering_flags {
 	/** Return small arays as integer values instead of storing them into
 	 * memory. */
 	LF_RETURN_SMALL_ARRAY_IN_INTS = 1 << 2,
+	/** Return small structs as integer values */
+	LF_RETURN_SMALL_STRUCT_IN_INTS = 1 << 3,
 } compound_call_lowering_flags;
 ENUM_BITSET(compound_call_lowering_flags)