On Tue, Oct 9, 2012 at 4:39 PM, Peter Maydell <peter.mayd...@linaro.org>wrote:
> On 9 October 2012 11:21, Matthew Gretton-Dann
> <matthew.gretton-d...@linaro.org> wrote:
> > On 9 October 2012 10:37, Jubi Taneja <jubitan...@gmail.com> wrote:
> >> I wanted to see the difference in objdump of an application where I can
> make
> >> the difference between the VFPV3 and VFPV4 support. I tried enabling the
> >> flag -mfpu=vfpv3 and -mfpu=vfpv4 for ARM Cortex A15 toolchain in my test
> >> code but cannot see the difference in two objdumps.
> >
> > Try the following (tested against FSF GCC:
> >
> > /* arm-none-linux-gnueabi-gcc -mcpu=cortex-a15 -mfpu=vfpv4 -S -o-
> > /tmp/fma.c -mfloat-abi=hard -O2 */
> > float f(float a, float b, float c)
> > {
> > return a * b + c;
> > }
> > /* end of tmp.c */
>
> I would have expected that you would need a gcc option to tell it that
> non-IEEE floating point results are OK. Otherwise it's not valid to
> emit a fused multiply-add for a*b+c because IEEE specifies that you
> should get a rounding step between the multiply and the add. Or
> does gcc default to non-IEEE arithmetic?
>
I need to know more about it. I can comment after verifying it.
>
> -- PMM
>
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