diff options
Diffstat (limited to 'gcc/predict.c')
| -rw-r--r-- | gcc/predict.c | 100 |
1 files changed, 80 insertions, 20 deletions
diff --git a/gcc/predict.c b/gcc/predict.c index ca6a901..5114552 100644 --- a/gcc/predict.c +++ b/gcc/predict.c @@ -827,11 +827,14 @@ unlikely_executed_bb_p (basic_block bb) /* We can not predict the probabilities of outgoing edges of bb. Set them evenly and hope for the best. If UNLIKELY_EDGES is not null, distribute even probability for all edges not mentioned in the set. These edges - are given PROB_VERY_UNLIKELY probability. */ + are given PROB_VERY_UNLIKELY probability. Similarly for LIKELY_EDGES, + if we have exactly one likely edge, make the other edges predicted + as not probable. */ static void set_even_probabilities (basic_block bb, - hash_set<edge> *unlikely_edges = NULL) + hash_set<edge> *unlikely_edges = NULL, + hash_set<edge_prediction *> *likely_edges = NULL) { unsigned nedges = 0, unlikely_count = 0; edge e = NULL; @@ -843,7 +846,7 @@ set_even_probabilities (basic_block bb, all -= e->probability; else if (!unlikely_executed_edge_p (e)) { - nedges ++; + nedges++; if (unlikely_edges != NULL && unlikely_edges->contains (e)) { all -= profile_probability::very_unlikely (); @@ -852,26 +855,54 @@ set_even_probabilities (basic_block bb, } /* Make the distribution even if all edges are unlikely. */ + unsigned likely_count = likely_edges ? likely_edges->elements () : 0; if (unlikely_count == nedges) { unlikely_edges = NULL; unlikely_count = 0; } - unsigned c = nedges - unlikely_count; - - FOR_EACH_EDGE (e, ei, bb->succs) - if (e->probability.initialized_p ()) - ; - else if (!unlikely_executed_edge_p (e)) - { - if (unlikely_edges != NULL && unlikely_edges->contains (e)) - e->probability = profile_probability::very_unlikely (); + /* If we have one likely edge, then use its probability and distribute + remaining probabilities as even. */ + if (likely_count == 1) + { + FOR_EACH_EDGE (e, ei, bb->succs) + if (e->probability.initialized_p ()) + ; + else if (!unlikely_executed_edge_p (e)) + { + edge_prediction *prediction = *likely_edges->begin (); + int p = prediction->ep_probability; + profile_probability prob + = profile_probability::from_reg_br_prob_base (p); + profile_probability remainder = prob.invert (); + + if (prediction->ep_edge == e) + e->probability = prob; + else + e->probability = remainder.apply_scale (1, nedges - 1); + } else - e->probability = all.apply_scale (1, c).guessed (); - } - else - e->probability = profile_probability::never (); + e->probability = profile_probability::never (); + } + else + { + /* Make all unlikely edges unlikely and the rest will have even + probability. */ + unsigned scale = nedges - unlikely_count; + FOR_EACH_EDGE (e, ei, bb->succs) + if (e->probability.initialized_p ()) + ; + else if (!unlikely_executed_edge_p (e)) + { + if (unlikely_edges != NULL && unlikely_edges->contains (e)) + e->probability = profile_probability::very_unlikely (); + else + e->probability = all.apply_scale (1, scale); + } + else + e->probability = profile_probability::never (); + } } /* Add REG_BR_PROB note to JUMP with PROB. */ @@ -1175,6 +1206,7 @@ combine_predictions_for_bb (basic_block bb, bool dry_run) if (nedges != 2) { hash_set<edge> unlikely_edges (4); + hash_set<edge_prediction *> likely_edges (4); /* Identify all edges that have a probability close to very unlikely. Doing the approach for very unlikely doesn't worth for doing as @@ -1182,11 +1214,16 @@ combine_predictions_for_bb (basic_block bb, bool dry_run) edge_prediction **preds = bb_predictions->get (bb); if (preds) for (pred = *preds; pred; pred = pred->ep_next) - if (pred->ep_probability <= PROB_VERY_UNLIKELY) - unlikely_edges.add (pred->ep_edge); + { + if (pred->ep_probability <= PROB_VERY_UNLIKELY) + unlikely_edges.add (pred->ep_edge); + if (pred->ep_probability >= PROB_VERY_LIKELY + || pred->ep_predictor == PRED_BUILTIN_EXPECT) + likely_edges.add (pred); + } if (!dry_run) - set_even_probabilities (bb, &unlikely_edges); + set_even_probabilities (bb, &unlikely_edges, &likely_edges); clear_bb_predictions (bb); if (dump_file) { @@ -2575,7 +2612,30 @@ tree_predict_by_opcode (basic_block bb) enum br_predictor predictor; HOST_WIDE_INT probability; - if (!stmt || gimple_code (stmt) != GIMPLE_COND) + if (!stmt) + return; + + if (gswitch *sw = dyn_cast <gswitch *> (stmt)) + { + tree index = gimple_switch_index (sw); + tree val = expr_expected_value (index, auto_bitmap (), + &predictor, &probability); + if (val && TREE_CODE (val) == INTEGER_CST) + { + edge e = find_taken_edge_switch_expr (sw, val); + if (predictor == PRED_BUILTIN_EXPECT) + { + int percent = PARAM_VALUE (BUILTIN_EXPECT_PROBABILITY); + gcc_assert (percent >= 0 && percent <= 100); + predict_edge (e, PRED_BUILTIN_EXPECT, + HITRATE (percent)); + } + else + predict_edge_def (e, predictor, TAKEN); + } + } + + if (gimple_code (stmt) != GIMPLE_COND) return; FOR_EACH_EDGE (then_edge, ei, bb->succs) if (then_edge->flags & EDGE_TRUE_VALUE) |