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Re: i386 rounding modes and workaround solution
Oops, I think I barely missed the flamewar button...
I wasn't aware that my gcc version (included in a major GNU/Linux
distribution, v 2.96) lags a lot behind the development work. Next
time I will do my homework better ;-)
The reason I brought up the issue here was that I couldn't find
much useful information on the web.
On Mon, 10 Sep 2001, Tim Prince wrote:
> If you are familiar with current P4 models, you will be aware
> that using more than 2 values of the fldcw mask will degrade
> performance seriously. Which processors do you consider as
> belonging to the x86 family?
The factor 4 was on a Pentium 3. I also tested it on an Athlon,
without exact timings, but it did have quite an impact as well.
I checked the manuals; you are correct that alternating between two
values of the FLDCW (as with f-i conversion) is no problem on a P4,
but (int) floor() might be. Thank you for the remark.
Han-Kwang Nienhuys
FOM Institute voor Atomic and Molecular Physics,
Amsterdam, The Netherlands