diff options
Diffstat (limited to 'gcc/tree-ssa-loop-ivopts.c')
| -rw-r--r-- | gcc/tree-ssa-loop-ivopts.c | 53 |
1 files changed, 47 insertions, 6 deletions
diff --git a/gcc/tree-ssa-loop-ivopts.c b/gcc/tree-ssa-loop-ivopts.c index a620aca..c0c800a7 100644 --- a/gcc/tree-ssa-loop-ivopts.c +++ b/gcc/tree-ssa-loop-ivopts.c @@ -3603,20 +3603,32 @@ try_add_cand_for (struct ivopts_data *data, bitmap ivs, bitmap inv, bitmap act_inv = BITMAP_XMALLOC (); unsigned i; struct cost_pair *cp; + bitmap_iterator bi; + struct iv_cand *cand; + bitmap depends_on; bitmap_copy (best_ivs, ivs); bitmap_copy (best_inv, inv); - for (i = 0; i < use->n_map_members; i++) + /* First try important candidates. Only if it fails, try the specific ones. + Rationale -- in loops with many variables the best choice often is to use + just one generic biv. If we added here many ivs specific to the uses, + the optimization algorithm later would be likely to get stuck in a local + minimum, thus causing us to create too many ivs. The approach from + few ivs to more seems more likely to be succesful -- starting from few + ivs, replacing an expensive use by a specific iv should always be a + win. */ + EXECUTE_IF_SET_IN_BITMAP (data->important_candidates, 0, i, bi) { - cp = use->cost_map + i; - if (cp->cost == INFTY) + cand = iv_cand (data, i); + + if (get_use_iv_cost (data, use, cand, &depends_on) == INFTY) continue; bitmap_copy (act_ivs, ivs); - bitmap_set_bit (act_ivs, cp->cand->id); - if (cp->depends_on) - bitmap_a_or_b (act_inv, inv, cp->depends_on); + bitmap_set_bit (act_ivs, cand->id); + if (depends_on) + bitmap_a_or_b (act_inv, inv, depends_on); else bitmap_copy (act_inv, inv); act_cost = set_cost_up_to (data, act_ivs, act_inv, use->id + 1); @@ -3629,6 +3641,35 @@ try_add_cand_for (struct ivopts_data *data, bitmap ivs, bitmap inv, } } + if (best_cost == INFTY) + { + for (i = 0; i < use->n_map_members; i++) + { + cp = use->cost_map + i; + if (cp->cost == INFTY) + continue; + + /* Already tried this. */ + if (cp->cand->important) + continue; + + bitmap_copy (act_ivs, ivs); + bitmap_set_bit (act_ivs, cp->cand->id); + if (cp->depends_on) + bitmap_a_or_b (act_inv, inv, cp->depends_on); + else + bitmap_copy (act_inv, inv); + act_cost = set_cost_up_to (data, act_ivs, act_inv, use->id + 1); + + if (act_cost < best_cost) + { + best_cost = act_cost; + bitmap_copy (best_ivs, act_ivs); + bitmap_copy (best_inv, act_inv); + } + } + } + bitmap_copy (ivs, best_ivs); bitmap_copy (inv, best_inv); |