[PATCH][PING][PR 81376] Remove unnecessary float casts in comparisons

[Richard Biener]

On Mon, Oct 9, 2017 at 11:12 AM, Yuri Gribov <tetra2005@gmail.com> wrote:
> Hi all,
>
> This patch gets rid of float casts in comparisons when all values of
> casted integral type are exactly representable by the float type
> (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81376).
>
> Bootstrapped and regtested on x64_64. Ok to commit?

+bool format_helper::can_represent_integral_type_p (tree type) const
+{
+  gcc_assert (! decimal_p () && INTEGRAL_TYPE_P (type) && "NYI");

"NYI"?

+        /* Determine the largest type.  */
+

excess vertical space

+        signop sign1 = TYPE_SIGN (type1),
+          sign2 = TYPE_SIGN (type2);
+        int prec1 = TYPE_PRECISION (type1),
+          prec2 = TYPE_PRECISION (type2);
+
+        bool type1_largest_p = (sign1 == sign2 && prec2 <= prec1)
+          || (sign1 == SIGNED && sign2 == UNSIGNED && prec2 < prec1);
+        bool type2_largest_p = (sign1 == sign2 && prec1 <= prec2)
+          || (sign1 == UNSIGNED && sign2 == SIGNED && prec1 < prec2);
+       }
+       (switch

I dislike too many temporaries, isn't

  (if (TYPE_PRECISION (type1) > TYPE_PRECISION (type2))
    (cmp @1 (convert @2)
    (if (TYPE_PRECISION (type2) > TYPE_PRECISION (type1))
     (cmp (convert @1) @2)
     (if (TYPE_SIGN (type1) == TYPE_SIGN (type2))
      (cmp @1 @2)))))

easier to follow?  Note the if-else cascade, note the (convert ..)s do not
need an explicit type.

I wonder if we anywhere "canonicalize" non-simple comparison operators
(unle, ltgt, etc.) for comparisons involving integer-to-float
converted operands.

Thanks,
Richard.

> -Y