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Re: Match-and-simplify and COND_EXPR


On Thu, Nov 6, 2014 at 2:40 AM, Richard Biener <rguenther@suse.de> wrote:
> On Thu, 6 Nov 2014, Richard Biener wrote:
>
>> On Wed, 5 Nov 2014, Andrew Pinski wrote:
>>
>> > Hi,
>> >   I was trying to hook up tree-ssa-phiopt to match-and-simplify using
>> > either gimple_build (or rather using gimple_simplify depending on if
>> > we want to produce cond_expr for conditional move).  I ran into a
>> > problem.
>> > With the pattern below:
>> > /* a ? 0 : 1 -> a if 0 and 1 are integral types. */
>> > (simplify
>> >   (cond_expr @0 integer_zerop integer_onep)
>> >   (if (INTEGRAL_TYPE_P (type))
>> >     (convert @0)))
>>
>> Ok, so you are capturing a GENERIC expr here but nothing knows that.
>> It would work if you'd do (ugh)
>>
>> (for op (lt le eq ne ge gt)
>>  (simplify
>>   (cond_expr (op @0 @1) integer_zerop integer_onep)
>>   (if (INTEGRAL_TYPE_P (type))
>>    (convert (op @0 @1)))))
>> (simplify
>>  (cond_expr SSA_NAME@0 integer_zerop integer_onep)
>>   (if (INTEGRAL_TYPE_P (type))
>>    (convert @0))))
>>
>> as a workaround.  To make your version work will require (quite)
>> some special-casing in the code generator or maybe the resimplify
>> helper.  Let me see if I can cook up a "simple" fix.
>
> Sth like below (for the real fix this has to be replicated in
> all gimple_resimplifyN functions).  I'm missing a testcase
> where the pattern would apply (and not be already folded by fold),
> so I didn't check if it actually works.

You do need to check if seq is NULL though as gimple_build depends on
seq not being NULL.  But otherwise yes this works for me.

>
> Bah, of course we should fix COND_EXPRs to not embed a GENERIC
> expr...

Yes totally agree.  For my changes to tree-ssa-phiopt, I no longer
embed it.  Though we need to change loop ifconvert still.

Thanks,
Andrew

>
> Richard.
>
> Index: gcc/gimple-match-head.c
> ===================================================================
> --- gcc/gimple-match-head.c     (revision 217035)
> +++ gcc/gimple-match-head.c     (working copy)
> @@ -90,6 +90,13 @@ gimple_resimplify1 (gimple_seq *seq,
>                     code_helper *res_code, tree type, tree *res_ops,
>                     tree (*valueize)(tree))
>  {
> +  /* ???  Stupid tcc_comparison GENERIC trees in COND_EXPRs.  */
> +  if (COMPARISON_CLASS_P (res_ops[0]))
> +    res_ops[0] = gimple_build (seq,
> +                              TREE_CODE (res_ops[0]), TREE_TYPE (res_ops[0]),
> +                              TREE_OPERAND (res_ops[0], 0),
> +                              TREE_OPERAND (res_ops[0], 1));
> +
>    if (constant_for_folding (res_ops[0]))
>      {
>        tree tem = NULL_TREE;
>


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