fix broken C interop

Author: MESYETI

source/backends/x86_64.d

@@ -652,15 +652,8 @@ class BackendX86_64 : CompilerBackend {
 					output ~= "mov rbp, rsp\n";
 					output ~= "and rsp, 0xFFFFFFFFFFFFFFF0\n";
 
-					size_t alignSize = word.params.length * 8;
-
-					while (alignSize % 16 != 0) {
-						alignSize += 8;
-					}
-					alignSize -= word.params.length * 8;
-
-					if (alignSize > 0) {
-						output ~= format("sub rsp, %d\n", alignSize);
+					if ((word.params.length > 6) && (word.params.length % 2 != 0)) {
+						output ~= format("sub rsp, 8\n");
 					}
 
 					if (word.params.length > 6) {