The auto-vectorizer is overly aggressive when not constrained by the
vectorizer cost model. Although the cost model is by no means perfect,
it does a reasonable job of avoiding many poor vectorization decisions.
Since the auto-vectorizer is enabled by default at -O3 and above, we
should also enable the vectorizer cost model by default at -O3 and
above.
Bootstrapped and tested on powerpc64-unknown-linux-gnu with no new
regressions. Ok for trunk?
Thanks,
Bill
2012-07-15 Bill Schmidt <wschm...@linux.ibm.com>
* opts.c (default_option): Add -fvect-cost-model to default options
at -O3 and above.
Index: gcc/opts.c
===================================================================
--- gcc/opts.c (revision 189481)
+++ gcc/opts.c (working copy)
@@ -501,6 +501,7 @@ static const struct default_options default_option
{ OPT_LEVELS_3_PLUS, OPT_funswitch_loops, NULL, 1 },
{ OPT_LEVELS_3_PLUS, OPT_fgcse_after_reload, NULL, 1 },
{ OPT_LEVELS_3_PLUS, OPT_ftree_vectorize, NULL, 1 },
+ { OPT_LEVELS_3_PLUS, OPT_fvect_cost_model, NULL, 1 },
{ OPT_LEVELS_3_PLUS, OPT_fipa_cp_clone, NULL, 1 },
{ OPT_LEVELS_3_PLUS, OPT_ftree_partial_pre, NULL, 1 },
