Messages in this thread | | | From | Denis Vlasenko <> | Subject | Re: [PATCH 1/12] random pt4: Create new rol32/ror32 bitops | Date | Tue, 25 Jan 2005 23:02:55 +0200 |
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On Friday 21 January 2005 23:41, Matt Mackall wrote: > --- rnd2.orig/include/linux/bitops.h 2005-01-19 22:57:54.000000000 -0800 > +++ rnd2/include/linux/bitops.h 2005-01-20 09:20:24.641660815 -0800 > @@ -134,4 +134,26 @@ > return sizeof(w) == 4 ? generic_hweight32(w) : generic_hweight64(w); > } > > +/* > + * rol32 - rotate a 32-bit value left > + * > + * @word: value to rotate > + * @shift: bits to roll > + */ > +static inline __u32 rol32(__u32 word, int shift) > +{ > + return (word << shift) | (word >> (32 - shift)); > +} > + > +/* > + * ror32 - rotate a 32-bit value right > + * > + * @word: value to rotate > + * @shift: bits to roll > + */ > +static inline __u32 ror32(__u32 word, int shift) > +{ > + return (word >> shift) | (word << (32 - shift)); > +} > + > #endif
gcc generates surprisingly good assembly for this, I coudn't beat it for 32bit rotations. Cool!
So you are absolutely right here with not trying to asm optimize it.
OTOH 64bit gcc rol is worse. -- vda
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