Hi Segher, On Mon, May 28, 2018 at 05:35:12AM -0500, Segher Boessenkool wrote: > On Fri, May 25, 2018 at 12:07:33PM +0800, wei.guo.si...@gmail.com wrote: > > _GLOBAL(memcmp) > > cmpdi cr1,r5,0 > > > > - /* Use the short loop if both strings are not 8B aligned */ > > - or r6,r3,r4 > > + /* Use the short loop if the src/dst addresses are not > > + * with the same offset of 8 bytes align boundary. > > + */ > > + xor r6,r3,r4 > > andi. r6,r6,7 > > > > - /* Use the short loop if length is less than 32B */ > > - cmpdi cr6,r5,31 > > + /* Fall back to short loop if compare at aligned addrs > > + * with less than 8 bytes. > > + */ > > + cmpdi cr6,r5,7 > > > > beq cr1,.Lzero > > - bne .Lshort > > - bgt cr6,.Llong > > + bgt cr6,.Lno_short > > If this doesn't use cr0 anymore, you can do rlwinm r6,r6,0,7 instead of > andi r6,r6,7 . > CR0 is used at .Lno_short handling.
> > +.Lsameoffset_8bytes_make_align_start: > > + /* attempt to compare bytes not aligned with 8 bytes so that > > + * rest comparison can run based on 8 bytes alignment. > > + */ > > + andi. r6,r3,7 > > + > > + /* Try to compare the first double word which is not 8 bytes aligned: > > + * load the first double word at (src & ~7UL) and shift left appropriate > > + * bits before comparision. > > + */ > > + clrlwi r6,r3,29 > > + rlwinm r6,r6,3,0,28 > > Those last two lines are together just > rlwinm r6,r3,3,0x1c > Yes. I will combine them. > > + subfc. r5,r6,r5 > > Why subfc? You don't use the carry. OK. I will use subfc instead. > > > + rlwinm r6,r6,3,0,28 > > That's > slwi r6,r6,3 Yes. > > > + bgt cr0,8f > > + li r3,-1 > > +8: > > + blr > > blelr > li r3,-1 > blr Sure. That looks more impact. > > (and more of the same things elsewhere). > > > Segher Thanks for your good comments. BR, - Simon
