I think this is what you want, from 'man gcc'. Its interesting to note that
the NEON mode, which provides SIMD, also does not do denormals:
-mfpu=name
-mfpe=number
-mfp=number
This specifies what floating point hardware (or hardware emulation) is
available on the target. Permissible names are: fpa, fpe2, fpe3, maverick,
vfp, vfpv3, vfpv3-fp16, vfpv3-d16, vfpv3-d16-fp16, vfpv3xd, vfpv3xd-fp16,
neon, neon-fp16, vfpv4, vfpv4-d16, fpv4-sp-d16 and neon-vfpv4. -mfp and
-mfpe are synonyms for -mfpu=fpenumber, for compatibility with older
versions of GCC.
If -msoft-float is specified this specifies the format of floating point
values.
If the selected floating-point hardware includes the NEON extension (e.g.
-mfpu=neon), note that floating-point operations will not be used by GCC's
auto-vectorization pass unless -funsafe-math-optimizations is also
specified. This is because NEON hardware does not fully implement the IEEE
754 standard for floating-point arithmetic (in particular denormal values
are treated as zero), so the use of NEON instructions may lead to a loss of
precision.
.hc
> _______________________________________________
On 01/20/2013 06:54 AM, katja wrote:
> I was assuming, or maybe just hoping? that Raspberry Pi (and ARM
> devices in general) would not suffer from Denormal's disease like
> Intel processors do. But guess what: Pi's float coprocessor is IEEE
> 754 compliant and does all denormals by default (can check with
> attached denorm-test.pd). Bummer! As if one would use an ARM device to
> calculate the size of a Majorana particle, rather than doing simple
> dsp. Do we really need to enable PD-BIGORSMALL() checks for this poor
> little processor? There seems to be something called 'RunFast mode'
> for Pi's float processor vfpv2, but I see no way how to enable this
> via gcc. Option -ffast-math is allowed but doesn't do the trick. Can't
> find an option to set vfpv2 specifically, in gcc docs.
>
> Katja
>
>
>
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