On Sat, Sep 27, 2014 at 08:45:18PM +0200, Oleg Endo wrote: > On Sat, 2014-09-27 at 11:10 -0700, Andi Kleen wrote: > > From: Andi Kleen <a...@linux.intel.com> > > > > In my tests the optimized glibc out of line strcmp is always faster than > > using inline rep ; cmpsb, even for small strings. The Intel optimization > > manual > > also recommends to not use it. So remove the cmpstrnsi instruction. > > > > Tested on Sandy Bridge, Westmere Intel CPUs. > > > > gcc/: > > > > 2014-09-27 Andi Kleen <a...@linux.intel.com> > > > > * config/i386/i386.md (cmpstrnsi, cmpintqi): Remove expanders. > > This has been mentioned a while ago, e.g. > https://gcc.gnu.org/ml/gcc/2002-10/msg01616.html > https://gcc.gnu.org/ml/gcc/2003-04/msg00166.html > > Instead of just completely removing it, how about disabling it for newer > CPU types if not optimizing for size?
I believe it was slow even on old CPUs. But back then glibc may have been even slower. Not sure it is worth keeping it for -Os, especially given that parts of it have already bitrotted. -Andi
