Add option for whether ceil etc. can raise "inexact", adjust x86 conditions

[Jan Hubicka]

> 
> Well, it's of course the poor-mans solution compared to providing our own
> ifunc-enabled libm ...

One benefit here would be that we could have our own calling convention for
this.  So for floor/ceil we may just declare registers to be preserved (as
they are on all modern AVX enabled cpus) which would make the code size/speed
tradeoffs more interesting.

Honza
> 
> I would expect that for SSE 4.1 the PLT and call overhead is measurable
> and an inline run-time check be quite a bit more efficient.  As you have a
> testcase would it be possible to measure that by hand-editing the assembly
> (or the benchmark source in case it is not fortran...)?
> 
> The whole point of having the inline expansions was to have inline expansions,
> avoding the need to spill the whole set of SSE regs around such calls.
> 
> > I was just surprised by the glibc check, what would you consider a
> > recent-enough glibc?  Or is the check mainly necessary to ensure we
> > are indeed using glibc and not some other libc (and thus something
> > like we do for TARGET_LIBC_PROVIDES_SSP would do)?
> >
> > I will try to come up with a patch.
> 
> I don't think this is the appropriate solution.  Try disabling the inline
> expansion and run SPEC (without -march=sse4.1 of course).
> 
> I realize that doing the inline-expansion with a runtime check
> is going to be quite tricky and the GCC local IFUNC trick doesn't
> solve the inlining (but we might be able to avoid spilling with some
> IPA RA help and/or attributes?).
> 
> Richard.
> 
> > Thanks,
> >
> > Martin