[PATCH] Improve ifcvt (PR tree-optimization/79389)

[Bernd Schmidt]

On 02/23/2017 02:36 PM, Jakub Jelinek wrote:
> and both UNLT and GE can be reversed.  But if the arguments of the condition
> are canonicalized, we run into:
>   /* Test for an integer condition, or a floating-point comparison
>      in which NaNs can be ignored.  */
>   if (CONST_INT_P (arg0)
>       || (GET_MODE (arg0) != VOIDmode
>           && GET_MODE_CLASS (mode) != MODE_CC
>           && !HONOR_NANS (mode)))
>     return reverse_condition (code);
> and thus always return UNKNOWN.

So... do you think we could add (in gcc-8, probably, although if it 
fixes this regression...)

    else if (GET_MODE (arg0) != VOIDmode
             && GET_MODE_CLASS (mode) != MODE_CC
             && HONOR_NANS (mode))
      return reverse_condition_maybe_unordered (code);

to make this work?


Bernd