Re: [PATCH] Fix ICE in expand_cse_reciprocals (PR tree-optimization/42078)

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

On Wed, Nov 18, 2009 at 6:30 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> The recent changes to execute_cse_reciprocals cause ICE on the attached
> testcase.  The problem is that the first loop over the imm uses ignores
> debug stmts (which is correct, whether any debug stmts reference arg1 or not
> shouldn't influence the decision on whether to do the transformation or
> not), but the second loop assumes all imm uses are assignments with
> RDIV_EXPR.  The following patch fixes it by creating a debug temp 1 / arg1
> and using it instead of arg1 in the debug stmts.  Alternatively we could
> drop the debug stmts, dwarf3/4 isn't able to express floating point
> operations anyway (well, in theory it is, but we'd need to implement
> floating point arithmetics using integer operations, which would be really
> huge).
>
> Ok for trunk if bootstrap/regtest passes?

Ugh.  Instead of adding so much code I'd prefer to drop the debug stmt.

Ok with that change.

Thanks,
Richard.

> 2009-11-18  Jakub Jelinek  <jakub@redhat.com>
>
>        PR tree-optimization/42078
>        * tree-ssa-math-opts.c (execute_cse_reciprocals): Handle
>        updating of debug stmt immediate uses.
>
>        * gcc.dg/pr42078.c: New test.
>
> --- gcc/tree-ssa-math-opts.c.jj 2009-11-18 14:56:33.000000000 +0100
> +++ gcc/tree-ssa-math-opts.c    2009-11-18 14:27:37.000000000 +0100
> @@ -534,6 +534,7 @@ execute_cse_reciprocals (void)
>                  bool md_code, fail;
>                  imm_use_iterator ui;
>                  use_operand_p use_p;
> +                 tree debug_expr_decl = NULL_TREE;
>
>                  code = DECL_FUNCTION_CODE (fndecl);
>                  md_code = DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_MD;
> @@ -568,6 +569,38 @@ execute_cse_reciprocals (void)
>
>                  FOR_EACH_IMM_USE_STMT (stmt, ui, arg1)
>                    {
> +                     if (is_gimple_debug (stmt))
> +                       {
> +                         use_operand_p use_p;
> +
> +                         if (!debug_expr_decl)
> +                           {
> +                             gimple def_temp;
> +                             tree val;
> +                             gimple_stmt_iterator ngsi;
> +
> +                             debug_expr_decl = make_node (DEBUG_EXPR_DECL);
> +                             val = fold_convert (TREE_TYPE (arg1),
> +                                                 integer_one_node);
> +                             val = build2 (RDIV_EXPR, TREE_TYPE (arg1),
> +                                           val, arg1);
> +                             def_temp
> +                               = gimple_build_debug_bind (debug_expr_decl,
> +                                                          val, stmt1);
> +                             DECL_ARTIFICIAL (debug_expr_decl) = 1;
> +                             TREE_TYPE (debug_expr_decl) = TREE_TYPE (arg1);
> +                             DECL_MODE (debug_expr_decl)
> +                               = TYPE_MODE (TREE_TYPE (arg1));
> +
> +                             ngsi = gsi_for_stmt (stmt1);
> +                             gsi_insert_after (&ngsi, def_temp,
> +                                               GSI_NEW_STMT);
> +                           }
> +                         FOR_EACH_IMM_USE_ON_STMT (use_p, ui)
> +                           SET_USE (use_p, debug_expr_decl);
> +                         update_stmt (stmt);
> +                         continue;
> +                       }
>                      gimple_assign_set_rhs_code (stmt, MULT_EXPR);
>                      fold_stmt_inplace (stmt);
>                      update_stmt (stmt);
> --- gcc/testsuite/gcc.dg/pr42078.c.jj   2009-11-18 14:58:17.000000000 +0100
> +++ gcc/testsuite/gcc.dg/pr42078.c      2009-11-18 14:55:54.000000000 +0100
> @@ -0,0 +1,22 @@
> +/* PR tree-optimization/42078 */
> +/* { dg-do compile } */
> +/* { dg-options "-g -O -ffast-math" } */
> +
> +double sqrt (double x);
> +
> +float
> +foo (float x)
> +{
> +  float y = sqrt (x);
> +  return x / y;
> +}
> +
> +float
> +bar (float x)
> +{
> +  float y = sqrt (x);
> +  float a = y;
> +  float b = y;
> +  float c = y;
> +  return x / y;
> +}
>
>        Jakub
>