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
