Re: genmatch: guess the type of a?b:c as b instead of a

[Jeff Law <law at redhat dot com>]

On 06/06/2015 05:34 AM, Marc Glisse wrote:
> Hello,
>
> as discussed around
> https://gcc.gnu.org/ml/gcc-patches/2015-06/msg00041.html
> we are currently guessing the type of a?b:c incorrectly. This does not
> affect current simplifications, because the only 'cond' in output
> patterns are at the outermost level, so their type is forced to 'type'
> and never guessed. Indeed, the patch does not change the generated
> *-match.c. It would allow removing an explicit cond:itype in a patch
> posted by Jeff.
>
> I tested it on a dummy .pd file containing:
> (simplify
>   (plus @0 (plus @1 @2))
>   (negate (cond @0 @1 @2)))
>
> and the generated files differ by:
>
> -  res = fold_build3_loc (loc, COND_EXPR, TREE_TYPE (ops1[0]), ops1[0],
> ops1[1], ops1[2]);
> +  res = fold_build3_loc (loc, COND_EXPR, TREE_TYPE (ops1[1]), ops1[0],
> ops1[1], ops1[2]);
>
> (and something similar for gimple)
>
> I wondered about using something like
> VOID_TYPE_P (TREE_TYPE (ops1[1])) ? TREE_TYPE (ops1[2]) : TREE_TYPE
> (ops1[1])
> but I don't think that will be necessary.
>
> Bootstrap is currently broken on many platforms with comparison
> failures, but since it went that far and generated the same *-match.c
> files, that seems sufficient testing.
>
> 2015-06-08  Marc Glisse  <marc.glisse@inria.fr>
>
>      * genmatch.c (expr::gen_transform): For conditions, guess the type
>      from the second operand.
Thanks for taking care of this.  I'd gone back and verified the type was 
needed, but didn't have to time reduce a testcase for it prior to going 
on PTO.

Jeff