Re: FW: [PING] Re: [Patch][GCC][middle-end] - Generate FRINTZ for (double)(int) under -ffast-math on aarch64

[Joseph Myers <joseph@codesourcery.com>]

On Fri, 15 Oct 2021, Richard Biener via Gcc-patches wrote:

> On Fri, Sep 24, 2021 at 2:59 PM Jirui Wu via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > Hi,
> >
> > Ping: https://gcc.gnu.org/pipermail/gcc-patches/2021-August/577846.html
> >
> > The patch is attached as text for ease of use. Is there anything that needs to change?
> >
> > Ok for master? If OK, can it be committed for me, I have no commit rights.
> 
> I'm still not sure about the correctness.  I suppose the
> flag_fp_int_builtin_inexact && !flag_trapping_math is supposed to guard
> against spurious inexact exceptions, shouldn't that be
> !flag_fp_int_builtin_inexact || !flag_trapping_math instead?

The following remarks may be relevant here, but are not intended as an 
assertion of what is correct in this case.

1. flag_fp_int_builtin_inexact is the more permissive case ("inexact" may 
or may not be raised).  All existing uses in back ends are 
"flag_fp_int_builtin_inexact || !flag_trapping_math" or equivalent.

2. flag_fp_int_builtin_inexact only applies to certain built-in functions 
(as listed in invoke.texi).  It's always unspecified, even in C2X, whether 
casts of non-integer values from floating-point to integer types raise 
"inexact".  So flag_fp_int_builtin_inexact should not be checked in insn 
patterns corresponding to simple casts from floating-point to integer, 
only in insn patterns corresponding to the built-in functions listed for 
-fno-fp-int-builtin-inexact in invoke.texi (or for operations that combine 
such a built-in function with a cast of the *result* to integer type).

-- 
Joseph S. Myers
joseph@codesourcery.com