Hi!
This patch attempts to optimize VEC_BASE if we know
that offsetof of base is 0 (unless the compiler is doing something
strange, it is true).
It doesn't have a clear code size effect, some .text sections
grew, supposedly because of more inlining, some .text sections shrunk.
Bootstrapped/regtested on x86_64-linux and i686-linux.
2011-11-07 Jakub Jelinek <ja...@redhat.com>
* vec.h (VEC_BASE): If base is at offset 0 in the structure,
use &(P)->base even if P is NULL.
--- gcc/vec.h.jj 2011-09-08 11:21:10.000000000 +0200
+++ gcc/vec.h 2011-11-07 18:45:33.000000000 +0100
@@ -549,7 +549,12 @@ typedef struct VEC(T,A)
\
} VEC(T,A)
/* Convert to base type. */
+#if GCC_VERSION >= 4000
+#define VEC_BASE(P) \
+ ((offsetof (__typeof (*P), base) == 0 || (P)) ? &(P)->base : 0)
+#else
#define VEC_BASE(P) ((P) ? &(P)->base : 0)
+#endif
/* Vector of integer-like object. */
#define DEF_VEC_I(T) \
Jakub
