On 03/11/2011 07:28 AM, Alexandre Julliard wrote:
Adam Martinson<[email protected]> writes:
@@ -236,7 +241,40 @@ extern int getopt_long_only (int ___argc, char *const
*___argv,
#endif /* HAVE_GETOPT_LONG */
#ifndef HAVE_FFS
-int ffs( int x );
+ #if defined(__i386__) || defined(__x86_64__)
+ #define HAVE_FFS
+ static inline int ffs( int x )
+ {
+ if (!x)
+ {
+ return 0;
+ }
+ else
+ {
+ int ret;
+ __asm__("bsfl %1, %0; incl %0" : "=r" (ret) : "r" (x));
+ return ret;
+ }
+ }
+ #elif defined(__GNUC__)&& GCC_VERSION>= 29503
+ #define HAVE_FFS
+ #define ffs(x) __builtin_ffs(x)
+ #else
+ int ffs( int x );
+ #endif
+#endif
You'd have to show benchmarks to prove that this complexity is
necessary. Given that ffs() should already be inlined on all decent
platforms, I doubt you'd be able to demonstrate a difference (if
anything, your version would be slower because of the extra increment).
I did this because it was easy and I was doing ctz() anyhow; I don't
actually need these versions of ffs() for anything. On any system with
HAVE_FFS the system version takes precedence.
