On Mon, May 12, 2025 at 06:35:15PM -0400, Michael Meissner wrote:
> On Mon, May 12, 2025 at 01:24:04PM +0530, Surya Kumari Jangala wrote:
> > Hi Mike,
> > Irrespective of whether -Ofast is used or not, should’nt we generate
> > XSCMPUDP instruction for ‘isgreater()’ operation? This is because XSCMPGTDP
> > insn will generate a trap if either operand is an SNaN or a QNaN. Whereas,
> > XSCMPUDP insn will generate a trap only if either operand is an SNaN. The
> > issue with the failing glibc tests is that an “Invalid operation” exception
> > is being thrown due to qNaNs.
>
> But -Ofast says not to worry about Nans (signalling or otherwise). But if
> Segher desires, I remove the test for Ofast.
That is not what -Ofast means at all. It means "-O3, but also
-ffast-math, and some other not recommendable things". Its name is a
total misnomer: it often is not faster than even -O2 (the baseline
here), but it also is very non-standard-compliant and similar things.
"-Ofast-and-loose" might be a name that does make sense. As the
dictionary says:
"If you say that someone is playing fast and loose, you are
expressing disapproval of them for behaving in a deceitful, immoral,
or irresponsible way."
And yeah, xscmpgtdp is plain wrong no matter what flags are used, unless
we adopt a -fuck-up flag :-(
Segher
