Alan Cox wrote:
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.
True, although I thought gcc considered the above an idiom and would
generate a rotate instruction. Perhaps it should be | rather than +.
-hpa
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