Re: [PATCH] unswitch: Fold case label lo/hi values to index type [PR105770]

[Richard Biener <richard.guenther@gmail.com>]

> Am 31.05.2022 um 11:33 schrieb Jakub Jelinek via Gcc-patches <gcc-patches@gcc.gnu.org>:
> 
> Hi!
> 
> The following testcase ICEs because we use different types in comparison,
> idx has int type, while CASE_LOW has char type.
> 
> While I believe all CASE_{LOW,HIGH} in the same switch have to use the same
> or compatible type, the index expression can have a promoted type as happens
> in this testcase.  Other spots that handle switches do such foldings too.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

Ok.

Richard 

> 2022-05-31  Jakub Jelinek  <jakub@redhat.com>
> 
>    PR tree-optimization/105770
>    * tree-ssa-loop-unswitch.cc (find_unswitching_predicates_for_bb): Cast
>    CASE_LOW and CASE_HIGH to TREE_TYPE (idx) before comparisons with idx.
> 
>    * gcc.dg/pr105770.c: New test.
> 
> --- gcc/tree-ssa-loop-unswitch.cc.jj    2022-05-25 11:07:29.754185772 +0200
> +++ gcc/tree-ssa-loop-unswitch.cc    2022-05-30 10:57:23.165131441 +0200
> @@ -494,6 +494,7 @@ find_unswitching_predicates_for_bb (basi
>     {
>       unsigned nlabels = gimple_switch_num_labels (stmt);
>       tree idx = gimple_switch_index (stmt);
> +      tree idx_type = TREE_TYPE (idx);
>       if (TREE_CODE (idx) != SSA_NAME
>      || nlabels < 1)
>    return;
> @@ -526,16 +527,18 @@ find_unswitching_predicates_for_bb (basi
>      if (CASE_HIGH (lab) != NULL_TREE)
>        {
>          tree cmp1 = fold_build2 (GE_EXPR, boolean_type_node, idx,
> -                       CASE_LOW (lab));
> +                       fold_convert (idx_type,
> +                             CASE_LOW (lab)));
>          tree cmp2 = fold_build2 (LE_EXPR, boolean_type_node, idx,
> -                       CASE_HIGH (lab));
> +                       fold_convert (idx_type,
> +                             CASE_HIGH (lab)));
>          cmp = fold_build2 (BIT_AND_EXPR, boolean_type_node, cmp1, cmp2);
>          lab_range.set (CASE_LOW (lab), CASE_HIGH (lab));
>        }
>      else
>        {
>          cmp = fold_build2 (EQ_EXPR, boolean_type_node, idx,
> -                 CASE_LOW (lab));
> +                 fold_convert (idx_type, CASE_LOW (lab)));
>          lab_range.set (CASE_LOW (lab));
>        }
> 
> --- gcc/testsuite/gcc.dg/pr105770.c.jj    2022-05-30 11:08:30.603530499 +0200
> +++ gcc/testsuite/gcc.dg/pr105770.c    2022-05-30 11:07:12.066406193 +0200
> @@ -0,0 +1,19 @@
> +/* PR tree-optimization/105770 */
> +/* { dg-do compile } */
> +/* { dg-options "-O1 -funswitch-loops -fno-tree-forwprop" } */
> +
> +char a;
> +
> +void
> +foo (void)
> +{
> +  while (a)
> +    switch (a)
> +      {
> +      case ' ':
> +      case '\t':
> +    return;
> +      }
> +
> +  __builtin_unreachable ();
> +}
> 
>    Jakub
>