[Bug tree-optimization/69467] [6 Regression] Pattern X * C1 CMP 0 to X CMP 0 causes performance drop on 32-bit x86.

[ysrumyan at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69467

--- Comment #3 from Yuri Rumyantsev <ysrumyan at gmail dot com> ---
Richard,

I checked that performance is back with your patch.

Thanks.

2016-01-25 17:50 GMT+03:00 rguenth at gcc dot gnu.org
<gcc-bugzilla@gcc.gnu.org>:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69467
>
> Richard Biener <rguenth at gcc dot gnu.org> changed:
>
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>              Status|UNCONFIRMED                 |ASSIGNED
>    Last reconfirmed|                            |2016-01-25
>            Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
>    Target Milestone|---                         |6.0
>      Ever confirmed|0                           |1
>
> --- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
> To restore the state before the move from fold to match.pd we'd need to mark
> any such pattern involving compares as the outermost expr (and thus match
> on GIMPLE_CONDs) with an explicit && single_use () check.  Fix for this one:
>
> Index: gcc/match.pd
> ===================================================================
> --- gcc/match.pd        (revision 232792)
> +++ gcc/match.pd        (working copy)
> @@ -1821,12 +1821,13 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>  (for cmp (simple_comparison)
>       scmp (swapped_simple_comparison)
>   (simplify
> -  (cmp (mult @0 INTEGER_CST@1) integer_zerop@2)
> +  (cmp (mult@3 @0 INTEGER_CST@1) integer_zerop@2)
>    /* Handle unfolded multiplication by zero.  */
>    (if (integer_zerop (@1))
>     (cmp @1 @2)
>     (if (ANY_INTEGRAL_TYPE_P (TREE_TYPE (@0))
> -       && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0)))
> +       && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0))
> +       && single_use (@3))
>      /* If @1 is negative we swap the sense of the comparison.  */
>      (if (tree_int_cst_sgn (@1) < 0)
>       (scmp @0 @2)
>
> --
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