On Wed, Nov 07, 2007 at 03:05:17PM +0100, Serge Torres wrote: > Hi, > > I'm using gcc 4.1.2 on an openPower 720 (Power5 processors) box running > Linux OpenSUSE 10.2. > > I would like to compile a C program with the fused multiply-add and > multiply-sub instructions enabled. I can't figure out the right set of > options. > > I've been trying many combinations of -mcpu=power5, -mhard-float, > -mfused-madd, -m64 but none has worked yet. > > An idea any one? Or even better: a personnal successful experience. > > Cheers, > > Serge Torres > > PS : IBM XL V 9 works (as matter of fact, with no particular option) Just to be sure, have you compiled the program with optimization (such as -O, -O2, or -O3)? The GCC combiner that builds up complex insns like multiply and add is only run when optimizing. I happen to have a PowerPC cross compiler built from a few weeks ago, and it generates fmadd and fmadds instructions if I use -mcpu=power5 and -mfused-madd. -- Michael Meissner, AMD 90 Central Street, MS 83-29, Boxborough, MA, 01719, USA michael.meissner@xxxxxxx
