Messages in this thread | | | Subject | Re: [PATCH 5/14] i386 / Use early clobber to eliminate rotate in desc | From | Alan Cox <> | Date | Wed, 17 Aug 2005 15:22:22 +0100 |
| |
On Maw, 2005-08-16 at 17:06 -0700, H. Peter Anvin wrote: > At least i386 and x86-64 gcc should recognize > > ((foo << x) + (foo >> (32-x))) > > ... as a 32-bit rotate
Only for 1 <= x <= 31. For the x = 0 case the code posted is undefined and at least in some cases gcc will do "interesting" things as a result such as treating >> 32 as >> 0.
Alan
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |