macro: make sure ALIGN() can be calculated constant by the compiler

If we pass a constant value to ALIGN() gcc should have the chance to
calculate the value during compilation rather than runtime, so let's
avoid a static inline call if we can.

src/shared/macro.h

@@ -53,7 +53,18 @@
 #define STRINGIFY(x) XSTRINGIFY(x)
 
 /* Rounds up */
-#define ALIGN(l) ALIGN_TO((l), sizeof(void*))
+
+#define ALIGN4(l) (((l) + 3) & ~3)
+#define ALIGN8(l) (((l) + 7) & ~7)
+
+#if __SIZEOF_POINTER__ == 8
+#define ALIGN(l) ALIGN8(l)
+#elif __SIZEOF_POINTER__ == 4
+#define ALIGN(l) ALIGN4(l)
+#else
+#error "Wut? Pointers are neither 4 nor 8 bytes long?"
+#endif
+
 static inline size_t ALIGN_TO(size_t l, size_t ali) {
         return ((l + ali - 1) & ~(ali - 1));
 }