[Bug tree-optimization/103088] [12 regression] 500.perlbench from spec 2017 fails since r12-4698

["aldyh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103088

Aldy Hernandez <aldyh at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|NEW                         |RESOLVED

--- Comment #15 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
(In reply to Martin Liška from comment #14)
> > > Richi the configury bits you shared once upon a time had
> > > -fno-unsafe-math-optimizations for 500.perlbench.  Are there known issues with
> > > this test for -ffast-math that we had -fno-unsafe-math-optimizations?
> > 
> > Indeed - interesting.  I don't remember anything and I have originally
> > copied this config from our testers which means iff then maybe
> > Martin knows ... ;)
> 
> Yes, I can confirm we have 
> 
>    EXTRA_OPTIMIZE      = -fno-strict-aliasing -fno-unsafe-math-optimizations
> 
> for perlbench benchmark. It's also mentioned in portability Issues:
> https://www.spec.org/cpu2017/Docs/benchmarks/500.perlbench_r.html
> 
> ```
> 3. GCC -Ofast and unsafe math: Users of GCC's -Ofast option may encounter
> problems with the test workload failing to validate. If you go to the run
> directory and look at file test.out.mis, you may see output such as:
> ...
> ```
> 
> So I would close this as invalid as it's a known limitation.

Well, the output mentioned in the PR is not exactly the validation error in the
above link, but I'm not going to argue.

For the record, the underlying problem is the inlining of Perl_do_ncmp() into
Perl_pp_ge().  Interestingly it has some NaN checking code.

Now can someone give me back the 5 hours I've spent on this ;-).