[Bug middle-end/11823] Optimizing large jump tables for switch statements

[steven at gcc dot gnu dot org]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11823



------- Additional Comments From steven at gcc dot gnu dot org  2003-08-07 13:01 -------
You should look at stmt.c:expand_end_case_type(), under the comment:

      /* If range of values is much bigger than number of values,
         make a sequence of conditional branches instead of a dispatch.
         If the switch-index is a constant, do it this way
         because we can optimize it.  */

The heuristic following this comment now does:

               || compare_tree_int (range, 10 * count) > 0

where "count" is the number of case labels, and range is the range of the case
labels.  In your example, count==11, and range==110, so you just hit the case
where it still gets expanded with a jump table.  (I suppose you knew this,
judging from your example ;-)

So why not replace this heuristic with something like:

               || compare_tree_int (range, (optimize_size ? 3 : 10) * count) > 0

and see if it helps...