Messages in this thread | | | Subject | Re: [RFC][PATCH] Faster generic_fls | From | Andi Kleen <> | Date | 01 May 2003 03:46:18 +0200 |
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Linus Torvalds <torvalds@transmeta.com> writes:
> Yeah, except if you want best code generation you should probably use > > static inline int fls(int x) > { > int bit; > /* Only well-defined for non-zero */ > asm("bsrl %1,%0":"=r" (bit):"rm" (x));
"g" should work for the second operand too and it'll give gcc slightly more choices with possibly better code.
But the __builtin is probably preferable if gcc supports it because a builtin can be scheduled, inline assembly can't.
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