On 2012.09.11 at 16:00 +0100, Andrew Haley wrote: > On 09/11/2012 03:56 PM, Pete Flugstad wrote: > > Hi, > > > > I'm trying to profile (using valgrind's callgrind) some code that > > uses sin/cos and I'm seeing some things I'm not expecting. > > > > My OS is Ubuntu 12.04/x86_64, hardware is an Intel Xeon X5690. GCC > > is the distro version, gcc (Ubuntu/Linaro 4.6.1-9ubuntu3) 4.6.1. I'm > > compiling with -O2. > > > > The strange thing is that I'm seeing sincos (from libm.so) is > > showing up in the callgrind output. From reading the manual, GCC > > should replace our calls to sin and cos with __builtin_ versions, > > right? > > Yes, it does, and one of the things that expanding the builtins does is > call sincos(). BTW, s_sincos.S was removed from glibc a while ago. So if you're running a recent glibc version you end up with the slow floating-point sin/cos implementation, that causes a 50% slowdown. See: http://sourceware.org/bugzilla/show_bug.cgi?id=14412 However Intel has recently posted fast SSE sin/cos/sincos versions for libm (sinf, cosf and sincosf). I think gcc should be updated to call those instead. -- Markus
