Re: [PATCH][tree-complex.c] PR tree-optimization/70291: Inline floating-point complex multiplication more aggressively

[Kyrill Tkachov <kyrylo dot tkachov at foss dot arm dot com>]

On 02/05/18 17:45, Wilco Dijkstra wrote:
> Richard Biener wrote:
>
> > why use BUILT_IN_ISUNORDERED but not a GIMPLE_COND with
> > UNORDERED_EXPR?  Note again that might trap/throw with -fsignalling-nans
> > so better avoid this transform for flag_signalling_nans as well...
> Both currently trap on signalling NaNs due to the implementation of the C99
> builtins being buggy (PR66462).
>
> However since the inputs are results of FP operations, they are guaranteed
> to be quiet NaNs in this case, so no extra test for signalling NaNs is required.

I'm happy to remove the check on flag_signaling_nans from the patch.

Kyrill

> > Which also means that we can dispatch to this simple variant not only for
> > flag_complex_method != 2 but for !HONOR_NANS && !HONOR_INFINITIES?
> > Maybe that should be done as followup.
> With -ffinite-math-only the isunordered will be optimized anyway. So it's just
> to avoid generating unnecessary dead code.
>
> Wilco