SET_EXPR_LOCATION usage for unused tree?

SET_EXPR_LOCATION usage for unused tree?

[Thomas Schwinge]

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Hi!

In gcc/c/c-parser.c:c_parser_omp_clause_num_threads (as well as other,
similar functions), what is the point of setting the boolean tree c's
location, given that this tree won't be used in the following?

          /* Attempt to statically determine when the number isn't positive.  */
          c = fold_build2_loc (expr_loc, LE_EXPR, boolean_type_node, t,
                           build_int_cst (TREE_TYPE (t), 0));
          if (CAN_HAVE_LOCATION_P (c))
            SET_EXPR_LOCATION (c, expr_loc);
          if (c == boolean_true_node)
            {
              warning_at (expr_loc, 0,
                          "%<num_threads%> value must be positive");
              t = integer_one_node;
            }
          [c not used anymore]

Both with and without the SET_EXPR_LOCATION, the error is the same:

    ../../loop.c: In function 'main':
    ../../loop.c:10:34: warning: 'num_threads' value must be positive
     #pragma omp parallel num_threads(-1)
                                  ^


Grüße,
 Thomas

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Re: SET_EXPR_LOCATION usage for unused tree?

[Richard Biener]

On Thu, Mar 13, 2014 at 10:44 PM, Thomas Schwinge
<thomas@codesourcery.com> wrote:
> Hi!
>
> In gcc/c/c-parser.c:c_parser_omp_clause_num_threads (as well as other,
> similar functions), what is the point of setting the boolean tree c's
> location, given that this tree won't be used in the following?
>
>           /* Attempt to statically determine when the number isn't positive.  */
>           c = fold_build2_loc (expr_loc, LE_EXPR, boolean_type_node, t,
>                            build_int_cst (TREE_TYPE (t), 0));
>           if (CAN_HAVE_LOCATION_P (c))
>             SET_EXPR_LOCATION (c, expr_loc);
>           if (c == boolean_true_node)
>             {
>               warning_at (expr_loc, 0,
>                           "%<num_threads%> value must be positive");
>               t = integer_one_node;
>             }
>           [c not used anymore]
>
> Both with and without the SET_EXPR_LOCATION, the error is the same:
>
>     ../../loop.c: In function 'main':
>     ../../loop.c:10:34: warning: 'num_threads' value must be positive
>      #pragma omp parallel num_threads(-1)
>                                   ^

That can be even simplified to avoid building the tree if it doesn't simplify
with

   c = fold_binary (LE_EXPR, boolean_type_node, t, build_int_cst
(TREE_TYPE (t), 0));
   if (c && c == boolean_true_node)
     {
        warning_at (....

Richard.

>
> Grüße,
>  Thomas