X-Git-Url: http://git.sourceforge.jp/view?a=blobdiff_plain;f=gcc%2Fpredict.c;h=0cf6b9606bc3b5355f10218db4495f6f328f36ee;hb=fa82692649ee531fb15b1a2f9828eae1173c946e;hp=39de19b21aa685554844e9364f15f4791f1b1e0d;hpb=4ae20857c0da0cab2fbed33d10d6b4d504aa9862;p=pf3gnuchains%2Fgcc-fork.git diff --git a/gcc/predict.c b/gcc/predict.c index 39de19b21aa..0cf6b9606bc 100644 --- a/gcc/predict.c +++ b/gcc/predict.c @@ -1,12 +1,12 @@ /* Branch prediction routines for the GNU compiler. - Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005 + Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2007 Free Software Foundation, Inc. This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free -Software Foundation; either version 2, or (at your option) any later +Software Foundation; either version 3, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY @@ -15,9 +15,8 @@ FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License -along with GCC; see the file COPYING. If not, write to the Free -Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA -02110-1301, USA. */ +along with GCC; see the file COPYING3. If not see +. */ /* References: @@ -60,6 +59,7 @@ Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA #include "timevar.h" #include "tree-scalar-evolution.h" #include "cfgloop.h" +#include "pointer-set.h" /* real constants: 0, 1, 1-1/REG_BR_PROB_BASE, REG_BR_PROB_BASE, 1/REG_BR_PROB_BASE, 0.5, BB_FREQ_MAX. */ @@ -75,10 +75,9 @@ static sreal real_zero, real_one, real_almost_one, real_br_prob_base, static void combine_predictions_for_insn (rtx, basic_block); static void dump_prediction (FILE *, enum br_predictor, int, basic_block, int); static void predict_paths_leading_to (basic_block, int *, enum br_predictor, enum prediction); -static bool last_basic_block_p (basic_block); static void compute_function_frequency (void); static void choose_function_section (void); -static bool can_predict_insn_p (rtx); +static bool can_predict_insn_p (const_rtx); /* Information we hold about each branch predictor. Filled using information from predict.def. */ @@ -112,12 +111,19 @@ static const struct predictor_info predictor_info[]= { for maximal performance. */ bool -maybe_hot_bb_p (basic_block bb) +maybe_hot_bb_p (const_basic_block bb) { if (profile_info && flag_branch_probabilities && (bb->count < profile_info->sum_max / PARAM_VALUE (HOT_BB_COUNT_FRACTION))) return false; + if (!profile_info || !flag_branch_probabilities) + { + if (cfun->function_frequency == FUNCTION_FREQUENCY_UNLIKELY_EXECUTED) + return false; + if (cfun->function_frequency == FUNCTION_FREQUENCY_HOT) + return true; + } if (bb->frequency < BB_FREQ_MAX / PARAM_VALUE (HOT_BB_FREQUENCY_FRACTION)) return false; return true; @@ -126,12 +132,15 @@ maybe_hot_bb_p (basic_block bb) /* Return true in case BB is cold and should be optimized for size. */ bool -probably_cold_bb_p (basic_block bb) +probably_cold_bb_p (const_basic_block bb) { if (profile_info && flag_branch_probabilities && (bb->count < profile_info->sum_max / PARAM_VALUE (HOT_BB_COUNT_FRACTION))) return true; + if ((!profile_info || !flag_branch_probabilities) + && cfun->function_frequency == FUNCTION_FREQUENCY_UNLIKELY_EXECUTED) + return true; if (bb->frequency < BB_FREQ_MAX / PARAM_VALUE (HOT_BB_FREQUENCY_FRACTION)) return true; return false; @@ -139,10 +148,13 @@ probably_cold_bb_p (basic_block bb) /* Return true in case BB is probably never executed. */ bool -probably_never_executed_bb_p (basic_block bb) +probably_never_executed_bb_p (const_basic_block bb) { if (profile_info && flag_branch_probabilities) return ((bb->count + profile_info->runs / 2) / profile_info->runs) == 0; + if ((!profile_info || !flag_branch_probabilities) + && cfun->function_frequency == FUNCTION_FREQUENCY_UNLIKELY_EXECUTED) + return true; return false; } @@ -150,7 +162,7 @@ probably_never_executed_bb_p (basic_block bb) PREDICTOR. */ bool -rtl_predicted_by_p (basic_block bb, enum br_predictor predictor) +rtl_predicted_by_p (const_basic_block bb, enum br_predictor predictor) { rtx note; if (!INSN_P (BB_END (bb))) @@ -162,14 +174,24 @@ rtl_predicted_by_p (basic_block bb, enum br_predictor predictor) return false; } +/* This map contains for a basic block the list of predictions for the + outgoing edges. */ + +static struct pointer_map_t *bb_predictions; + /* Return true if the one of outgoing edges is already predicted by PREDICTOR. */ bool -tree_predicted_by_p (basic_block bb, enum br_predictor predictor) +tree_predicted_by_p (const_basic_block bb, enum br_predictor predictor) { struct edge_prediction *i; - for (i = bb->predictions; i; i = i->ep_next) + void **preds = pointer_map_contains (bb_predictions, bb); + + if (!preds) + return false; + + for (i = *preds; i; i = i->ep_next) if (i->ep_predictor == predictor) return true; return false; @@ -201,14 +223,14 @@ probability_reliable_p (int prob) /* Same predicate as above, working on edges. */ bool -edge_probability_reliable_p (edge e) +edge_probability_reliable_p (const_edge e) { return probability_reliable_p (e->probability); } /* Same predicate as edge_probability_reliable_p, working on notes. */ bool -br_prob_note_reliable_p (rtx note) +br_prob_note_reliable_p (const_rtx note) { gcc_assert (REG_NOTE_KIND (note) == REG_BR_PROB); return probability_reliable_p (INTVAL (XEXP (note, 0))); @@ -271,10 +293,11 @@ tree_predict_edge (edge e, enum br_predictor predictor, int probability) if ((e->src != ENTRY_BLOCK_PTR && EDGE_COUNT (e->src->succs) > 1) && flag_guess_branch_prob && optimize) { - struct edge_prediction *i = ggc_alloc (sizeof (struct edge_prediction)); + struct edge_prediction *i = XNEW (struct edge_prediction); + void **preds = pointer_map_insert (bb_predictions, e->src); - i->ep_next = e->src->predictions; - e->src->predictions = i; + i->ep_next = *preds; + *preds = i; i->ep_probability = probability; i->ep_predictor = predictor; i->ep_edge = e; @@ -286,24 +309,56 @@ tree_predict_edge (edge e, enum br_predictor predictor, int probability) void remove_predictions_associated_with_edge (edge e) { - if (e->src->predictions) + void **preds; + + if (!bb_predictions) + return; + + preds = pointer_map_contains (bb_predictions, e->src); + + if (preds) { - struct edge_prediction **prediction = &e->src->predictions; + struct edge_prediction **prediction = (struct edge_prediction **) preds; + struct edge_prediction *next; + while (*prediction) { if ((*prediction)->ep_edge == e) - *prediction = (*prediction)->ep_next; + { + next = (*prediction)->ep_next; + free (*prediction); + *prediction = next; + } else prediction = &((*prediction)->ep_next); } } } +/* Clears the list of predictions stored for BB. */ + +static void +clear_bb_predictions (basic_block bb) +{ + void **preds = pointer_map_contains (bb_predictions, bb); + struct edge_prediction *pred, *next; + + if (!preds) + return; + + for (pred = *preds; pred; pred = next) + { + next = pred->ep_next; + free (pred); + } + *preds = NULL; +} + /* Return true when we can store prediction on insn INSN. At the moment we represent predictions only on conditional jumps, not at computed jump or other complicated cases. */ static bool -can_predict_insn_p (rtx insn) +can_predict_insn_p (const_rtx insn) { return (JUMP_P (insn) && any_condjump_p (insn) @@ -526,6 +581,7 @@ combine_predictions_for_bb (basic_block bb) int nedges = 0; edge e, first = NULL, second = NULL; edge_iterator ei; + void **preds; FOR_EACH_EDGE (e, ei, bb->succs) if (!(e->flags & (EDGE_EH | EDGE_FAKE))) @@ -547,7 +603,7 @@ combine_predictions_for_bb (basic_block bb) { if (!bb->count) set_even_probabilities (bb); - bb->predictions = NULL; + clear_bb_predictions (bb); if (dump_file) fprintf (dump_file, "%i edges in bb %i predicted to even probabilities\n", nedges, bb->index); @@ -557,31 +613,36 @@ combine_predictions_for_bb (basic_block bb) if (dump_file) fprintf (dump_file, "Predictions for bb %i\n", bb->index); - /* We implement "first match" heuristics and use probability guessed - by predictor with smallest index. */ - for (pred = bb->predictions; pred; pred = pred->ep_next) + preds = pointer_map_contains (bb_predictions, bb); + if (preds) { - int predictor = pred->ep_predictor; - int probability = pred->ep_probability; + /* We implement "first match" heuristics and use probability guessed + by predictor with smallest index. */ + for (pred = *preds; pred; pred = pred->ep_next) + { + int predictor = pred->ep_predictor; + int probability = pred->ep_probability; - if (pred->ep_edge != first) - probability = REG_BR_PROB_BASE - probability; + if (pred->ep_edge != first) + probability = REG_BR_PROB_BASE - probability; - found = true; - if (best_predictor > predictor) - best_probability = probability, best_predictor = predictor; + found = true; + if (best_predictor > predictor) + best_probability = probability, best_predictor = predictor; - d = (combined_probability * probability - + (REG_BR_PROB_BASE - combined_probability) - * (REG_BR_PROB_BASE - probability)); + d = (combined_probability * probability + + (REG_BR_PROB_BASE - combined_probability) + * (REG_BR_PROB_BASE - probability)); - /* Use FP math to avoid overflows of 32bit integers. */ - if (d == 0) - /* If one probability is 0% and one 100%, avoid division by zero. */ - combined_probability = REG_BR_PROB_BASE / 2; - else - combined_probability = (((double) combined_probability) * probability - * REG_BR_PROB_BASE / d + 0.5); + /* Use FP math to avoid overflows of 32bit integers. */ + if (d == 0) + /* If one probability is 0% and one 100%, avoid division by zero. */ + combined_probability = REG_BR_PROB_BASE / 2; + else + combined_probability = (((double) combined_probability) + * probability + * REG_BR_PROB_BASE / d + 0.5); + } } /* Decide which heuristic to use. In case we didn't match anything, @@ -605,17 +666,20 @@ combine_predictions_for_bb (basic_block bb) combined_probability = best_probability; dump_prediction (dump_file, PRED_COMBINED, combined_probability, bb, true); - for (pred = bb->predictions; pred; pred = pred->ep_next) + if (preds) { - int predictor = pred->ep_predictor; - int probability = pred->ep_probability; + for (pred = *preds; pred; pred = pred->ep_next) + { + int predictor = pred->ep_predictor; + int probability = pred->ep_probability; - if (pred->ep_edge != EDGE_SUCC (bb, 0)) - probability = REG_BR_PROB_BASE - probability; - dump_prediction (dump_file, predictor, probability, bb, - !first_match || best_predictor == predictor); + if (pred->ep_edge != EDGE_SUCC (bb, 0)) + probability = REG_BR_PROB_BASE - probability; + dump_prediction (dump_file, predictor, probability, bb, + !first_match || best_predictor == predictor); + } } - bb->predictions = NULL; + clear_bb_predictions (bb); if (!bb->count) { @@ -650,6 +714,10 @@ predict_loops (void) for (j = 0; VEC_iterate (edge, exits, j, ex); j++) { tree niter = NULL; + HOST_WIDE_INT nitercst; + int max = PARAM_VALUE (PARAM_MAX_PREDICTED_ITERATIONS); + int probability; + enum br_predictor predictor; if (number_of_iterations_exit (loop, ex, &niter_desc, false)) niter = niter_desc.niter; @@ -658,20 +726,31 @@ predict_loops (void) if (TREE_CODE (niter) == INTEGER_CST) { - int probability; - int max = PARAM_VALUE (PARAM_MAX_PREDICTED_ITERATIONS); if (host_integerp (niter, 1) && compare_tree_int (niter, max-1) == -1) - { - HOST_WIDE_INT nitercst = tree_low_cst (niter, 1) + 1; - probability = ((REG_BR_PROB_BASE + nitercst / 2) - / nitercst); - } + nitercst = tree_low_cst (niter, 1) + 1; else - probability = ((REG_BR_PROB_BASE + max / 2) / max); + nitercst = max; + predictor = PRED_LOOP_ITERATIONS; + } + /* If we have just one exit and we can derive some information about + the number of iterations of the loop from the statements inside + the loop, use it to predict this exit. */ + else if (n_exits == 1) + { + nitercst = estimated_loop_iterations_int (loop, false); + if (nitercst < 0) + continue; + if (nitercst > max) + nitercst = max; - predict_edge (ex, PRED_LOOP_ITERATIONS, probability); + predictor = PRED_LOOP_ITERATIONS_GUESSED; } + else + continue; + + probability = ((REG_BR_PROB_BASE + nitercst / 2) / nitercst); + predict_edge (ex, predictor, probability); } VEC_free (edge, heap, exits); @@ -706,7 +785,11 @@ predict_loops (void) /* Loop exit heuristics - predict an edge exiting the loop if the conditional has no loop header successors as not taken. */ - if (!header_found) + if (!header_found + /* If we already used more reliable loop exit predictors, do not + bother with PRED_LOOP_EXIT. */ + && !predicted_by_p (bb, PRED_LOOP_ITERATIONS_GUESSED) + && !predicted_by_p (bb, PRED_LOOP_ITERATIONS)) { /* For loop with many exits we don't want to predict all exits with the pretty large probability, because if all exits are @@ -913,16 +996,14 @@ expr_expected_value (tree expr, bitmap visited) if (DECL_BUILT_IN_CLASS (decl) == BUILT_IN_NORMAL && DECL_FUNCTION_CODE (decl) == BUILT_IN_EXPECT) { - tree arglist = TREE_OPERAND (expr, 1); tree val; - if (arglist == NULL_TREE - || TREE_CHAIN (arglist) == NULL_TREE) - return NULL; - val = TREE_VALUE (TREE_CHAIN (TREE_OPERAND (expr, 1))); + if (call_expr_nargs (expr) != 2) + return NULL; + val = CALL_EXPR_ARG (expr, 0); if (TREE_CONSTANT (val)) return val; - return TREE_VALUE (TREE_CHAIN (TREE_OPERAND (expr, 1))); + return CALL_EXPR_ARG (expr, 1); } } if (BINARY_CLASS_P (expr) || COMPARISON_CLASS_P (expr)) @@ -965,17 +1046,17 @@ strip_builtin_expect (void) { tree stmt = bsi_stmt (bi); tree fndecl; - tree arglist; + tree call; if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT - && TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == CALL_EXPR - && (fndecl = get_callee_fndecl (GIMPLE_STMT_OPERAND (stmt, 1))) + && (call = GIMPLE_STMT_OPERAND (stmt, 1)) + && TREE_CODE (call) == CALL_EXPR + && (fndecl = get_callee_fndecl (call)) && DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL && DECL_FUNCTION_CODE (fndecl) == BUILT_IN_EXPECT - && (arglist = TREE_OPERAND (GIMPLE_STMT_OPERAND (stmt, 1), 1)) - && TREE_CHAIN (arglist)) + && call_expr_nargs (call) == 2) { - GIMPLE_STMT_OPERAND (stmt, 1) = TREE_VALUE (arglist); + GIMPLE_STMT_OPERAND (stmt, 1) = CALL_EXPR_ARG (call, 0); update_stmt (stmt); } } @@ -1135,7 +1216,7 @@ return_prediction (tree val, enum prediction *prediction) && (!integer_zerop (val) && !integer_onep (val))) { *prediction = TAKEN; - return PRED_NEGATIVE_RETURN; + return PRED_CONST_RETURN; } } return PRED_NO_PREDICTION; @@ -1158,7 +1239,8 @@ apply_return_prediction (int *heads) FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds) { return_stmt = last_stmt (e->src); - if (TREE_CODE (return_stmt) == RETURN_EXPR) + if (return_stmt + && TREE_CODE (return_stmt) == RETURN_EXPR) break; } if (!e) @@ -1218,6 +1300,7 @@ tree_bb_level_predictions (void) for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) { tree stmt = bsi_stmt (bsi); + tree decl; switch (TREE_CODE (stmt)) { case GIMPLE_MODIFY_STMT: @@ -1232,6 +1315,12 @@ call_expr:; if (call_expr_flags (stmt) & ECF_NORETURN) predict_paths_leading_to (bb, heads, PRED_NORETURN, NOT_TAKEN); + decl = get_callee_fndecl (stmt); + if (decl + && lookup_attribute ("cold", + DECL_ATTRIBUTES (decl))) + predict_paths_leading_to (bb, heads, PRED_COLD_FUNCTION, + NOT_TAKEN); break; default: break; @@ -1242,6 +1331,20 @@ call_expr:; free (heads); } +#ifdef ENABLE_CHECKING + +/* Callback for pointer_map_traverse, asserts that the pointer map is + empty. */ + +static bool +assert_is_empty (const void *key ATTRIBUTE_UNUSED, void **value, + void *data ATTRIBUTE_UNUSED) +{ + gcc_assert (!*value); + return false; +} +#endif + /* Predict branch probabilities and estimate profile of the tree CFG. */ static unsigned int tree_estimate_probability (void) @@ -1249,18 +1352,22 @@ tree_estimate_probability (void) basic_block bb; loop_optimizer_init (0); - if (current_loops && dump_file && (dump_flags & TDF_DETAILS)) + if (dump_file && (dump_flags & TDF_DETAILS)) flow_loops_dump (dump_file, NULL, 0); add_noreturn_fake_exit_edges (); connect_infinite_loops_to_exit (); - calculate_dominance_info (CDI_DOMINATORS); + /* We use loop_niter_by_eval, which requires that the loops have + preheaders. */ + create_preheaders (CP_SIMPLE_PREHEADERS); calculate_dominance_info (CDI_POST_DOMINATORS); + bb_predictions = pointer_map_create (); tree_bb_level_predictions (); mark_irreducible_loops (); - if (current_loops) + record_loop_exits (); + if (number_of_loops () > 1) predict_loops (); FOR_EACH_BB (bb) @@ -1272,20 +1379,41 @@ tree_estimate_probability (void) { /* Predict early returns to be probable, as we've already taken care for error returns and other cases are often used for - fast paths through function. */ - if (e->dest == EXIT_BLOCK_PTR - && TREE_CODE (last_stmt (bb)) == RETURN_EXPR - && !single_pred_p (bb)) + fast paths through function. + + Since we've already removed the return statements, we are + looking for CFG like: + + if (conditional) + { + .. + goto return_block + } + some other blocks + return_block: + return_stmt. */ + if (e->dest != bb->next_bb + && e->dest != EXIT_BLOCK_PTR + && single_succ_p (e->dest) + && single_succ_edge (e->dest)->dest == EXIT_BLOCK_PTR + && TREE_CODE (last_stmt (e->dest)) == RETURN_EXPR) { edge e1; edge_iterator ei1; - FOR_EACH_EDGE (e1, ei1, bb->preds) - if (!predicted_by_p (e1->src, PRED_NULL_RETURN) - && !predicted_by_p (e1->src, PRED_CONST_RETURN) - && !predicted_by_p (e1->src, PRED_NEGATIVE_RETURN) - && !last_basic_block_p (e1->src)) - predict_edge_def (e1, PRED_TREE_EARLY_RETURN, NOT_TAKEN); + if (single_succ_p (bb)) + { + FOR_EACH_EDGE (e1, ei1, bb->preds) + if (!predicted_by_p (e1->src, PRED_NULL_RETURN) + && !predicted_by_p (e1->src, PRED_CONST_RETURN) + && !predicted_by_p (e1->src, PRED_NEGATIVE_RETURN)) + predict_edge_def (e1, PRED_TREE_EARLY_RETURN, NOT_TAKEN); + } + else + if (!predicted_by_p (e->src, PRED_NULL_RETURN) + && !predicted_by_p (e->src, PRED_CONST_RETURN) + && !predicted_by_p (e->src, PRED_NEGATIVE_RETURN)) + predict_edge_def (e, PRED_TREE_EARLY_RETURN, NOT_TAKEN); } /* Look for block we are guarding (ie we dominate it, @@ -1323,6 +1451,12 @@ tree_estimate_probability (void) FOR_EACH_BB (bb) combine_predictions_for_bb (bb); +#ifdef ENABLE_CHECKING + pointer_map_traverse (bb_predictions, assert_is_empty, NULL); +#endif + pointer_map_destroy (bb_predictions); + bb_predictions = NULL; + strip_builtin_expect (); estimate_bb_frequencies (); free_dominance_info (CDI_POST_DOMINATORS); @@ -1335,20 +1469,6 @@ tree_estimate_probability (void) return 0; } -/* Check whether this is the last basic block of function. Commonly - there is one extra common cleanup block. */ -static bool -last_basic_block_p (basic_block bb) -{ - if (bb == EXIT_BLOCK_PTR) - return false; - - return (bb->next_bb == EXIT_BLOCK_PTR - || (bb->next_bb->next_bb == EXIT_BLOCK_PTR - && single_succ_p (bb) - && single_succ (bb)->next_bb == EXIT_BLOCK_PTR)); -} - /* Sets branch probabilities according to PREDiction and FLAGS. HEADS[bb->index] should be index of basic block in that we need to alter branch predictions (i.e. the first of our dominators @@ -1610,7 +1730,7 @@ estimate_loops (void) basic_block bb; /* Start by estimating the frequencies in the loops. */ - if (current_loops) + if (number_of_loops () > 1) estimate_loops_at_level (current_loops->tree_root->inner); /* Now propagate the frequencies through all the blocks. */ @@ -1761,7 +1881,15 @@ compute_function_frequency (void) basic_block bb; if (!profile_info || !flag_branch_probabilities) - return; + { + if (lookup_attribute ("cold", DECL_ATTRIBUTES (current_function_decl)) + != NULL) + cfun->function_frequency = FUNCTION_FREQUENCY_UNLIKELY_EXECUTED; + else if (lookup_attribute ("hot", DECL_ATTRIBUTES (current_function_decl)) + != NULL) + cfun->function_frequency = FUNCTION_FREQUENCY_HOT; + return; + } cfun->function_frequency = FUNCTION_FREQUENCY_UNLIKELY_EXECUTED; FOR_EACH_BB (bb) {