On January 21, 2015 10:23:56 PM CET, Richard Henderson <r...@redhat.com> wrote: >On 12/29/2014 06:04 AM, Thomas Preud'homme wrote: >> Since 16bit byteswap can be done via an 8 bit rotation (and it is the >canonical form), >> the check for an optab only serves to prevent the bswap optimization >for >> targets that don't have a 16bit byteswap (but do have a rotation >instruction). See >> PR63259 (comments 6 and onwards) for more details. > >I question the choice to have rotate be the canonical form. > >Doesn't this make things more complicated for targets that >don't have rotate? Or, equivalently, no 16-bit rotate? >That would seem to cover 99% of all 32-bit risc machines.
I was asking for the generic expander to consider bswapHI. Rotates are certainly more likely to get combined with sth else. Richard. > >r~
