Messages in this thread | | | Subject | Re: [PATCH] add slice by 8 algorithm to crc32.c | From | Joakim Tjernlund <> | Date | Mon, 8 Aug 2011 13:24:38 +0200 |
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Joakim Tjernlund/Transmode wrote on 2011/08/08 13:11:14: > > "George Spelvin" <linux@horizon.com> wrote on 2011/08/08 12:52:01: > > > > > I prefer to keep the current code which (at the time) generated good code > > > for at least ppc: > > > /* Align it */ > > > if (unlikely((long)buf & 3 && len)) { > > > do { > > > DO_CRC(*buf++); > > > } while ((--len) && ((long)buf)&3); > > > } > > > > Ah, I was looking at fzago's initial patch; I hadn't realized you'd > > tweaked it. That's pretty much what I was talking about. > > > > Would > > if (unlikely((long)buf & 3) && len) { > > > > give the compiler better hints? len != 0 is awfully > > likely, actually. > > Doesn't matter on ppc(gcc 4.4.4). The whole while loop is moved out of line > in both cases and the generated asm is identical.
Actually, it does make a difference(must remember to save file before gcc :) Hard to tell if its any better though. Strangle this impacted the inner loop as well, it gained an extra addi.
Jocke
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