[PATCH 5/14] i386 / Use early clobber to eliminate rotate in desc

[alan at lxorguk.ukuu.org.uk (Alan Cox)]

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