Re: -Ofast/-ffast-math and SPEC 511.pov miscompilation with gcc 13.0

[Richard Biener <richard.guenther@gmail.com>]

On Fri, Feb 3, 2023 at 12:39 AM Vineet Gupta <vineetg@rivosinc.com> wrote:
>
> Hi,
>
> I've noticed SPEC 2017, 511.pov failing for RV64 on bleeding edge gcc.
> This is with -Ofast -march=rv64gcv_zba_zbb_zbc_zbs.
> Problem also happens with -O3 -ffast-math (and goes away with fast-math
> removed)
>
> I've bisected it to b7fd7fb50111 ("frange: drop endpoints to min/max
> representable numbers for -ffinite-math-only")
> With that commit evrp is eliding a bunch of if conditions as they
> pertain to inf (in code snippet below, it elides code corresponding to
> lines 1401-1418 with line 1417 being elided causing the failure).
>
> I think I know the answer, but  just wanted to confirm if that is the
> intended behavior given -Ofast / -ffast-math

It's the intended behavior of -ffinite-math-only which is part of
-Ofast / -ffast-math.  There's a CLOSED INVALID bug in bugzilla
about the povray failure as well.

Richard.

> Thx,
> -Vineet
>
>
> |New->Angle = __builtin_huge_val(); ||||switch(New->Type) ||{ ||...
> ||1246: if(Parse_Camera_Mods(New) == false) ||EXIT ||... ||} ||||1401:
> if (New->Up[X] == ||||__builtin_huge_val|()|) { ... } 1417: if
> (New->Angle != |||__builtin_huge_val|()) ||{ ||1419: if ((New->Type ==
> PERSPECTIVE_CAMERA) |||