On 2011-12-20 10:34:35 +0000, Jonathan Wakely wrote: > On 20 December 2011 10:20, Ico wrote: > > > > Still, I'm not sure if sse is part of the problem and/or solution. > > It's the solution. > > > I have been reducing the program to see what the smallest code is > > that still shows this behaviour. Latest version is below. > > > > > > $ gcc -msse -mfpmath=sse -O3 -march=native test.c > > What is "native" for your system, i686? (also, what does gcc > -dumpmachine show?) i686 doesn't support SSE, you need at least > pentium3. I can reproduce the "problem" on an x86_64 machine, so it is not due to the traditional FPU. I just think that the multiplication by 0 is faster (because much easier than the generic case), as I've said in my other message. But to have such an optimization, I wouldn't complain. :) -- Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/> 100% accessible validated (X)HTML - Blog: <http://www.vinc17.net/blog/> Work: CR INRIA - computer arithmetic / Arénaire project (LIP, ENS-Lyon)
