18 Feb
2004
18 Feb
'04
7:53 a.m.
On Wed, Feb 18, 2004 at 01:20:30 +0100, Tim Blechmann wrote:
I'm not
up-to-date on benchmarks so I cant comment, but just to
clarify the denormal thing in P4's is not a bug, its how you handle
denormals, the only difference is that the P4 takes longer to handle
them so you get away with it less often.
Ideally DSP software would be written so that it never generates them,
but, erm, well, developers are lazy, y'know :)
sure, denormals are not a bug,
but the behaviour on dsp systems that
aren't denormal-save is similar to a bug ;-)
> On the P4 its possible that you can set some flags to use SSE
> instructions instead of 387 and tell the SSE unit to never produce
> denormals, but last time I tried it, gcc 3.something generated bad
> code (illegal instructions). wait ... you imply that the sse unit doesn't
produce denormals, so that
a -march=sse _should_ solve all dsp user problems?
i heard that gcc 3.2 produces illegal instructions, but that it's solved
in gcc 3.3 ... can anyone confirm / deny this?
SSE /can/ be prevented from producing denormals, it probably doesnt by
default because it would violate the IEEE float spec.
- Steve