/* 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
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
+<http://www.gnu.org/licenses/>. */
/* References:
#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. */
static void combine_predictions_for_insn (rtx, basic_block);
static void dump_prediction (FILE *, enum br_predictor, int, basic_block, int);
-static void estimate_loops_at_level (struct loop *, bitmap);
-static void propagate_freq (struct loop *, bitmap);
-static void estimate_bb_frequencies (struct loops *);
-static void predict_paths_leading_to (basic_block, int *, enum br_predictor, enum prediction);
-static bool last_basic_block_p (basic_block);
+static void predict_paths_leading_to (basic_block, enum br_predictor, enum prediction);
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. */
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;
/* 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;
/* 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;
}
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)))
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->next)
- if (i->predictor == predictor)
+ 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;
}
+/* Return true when the probability of edge is reliable.
+
+ The profile guessing code is good at predicting branch outcome (ie.
+ taken/not taken), that is predicted right slightly over 75% of time.
+ It is however notoriously poor on predicting the probability itself.
+ In general the profile appear a lot flatter (with probabilities closer
+ to 50%) than the reality so it is bad idea to use it to drive optimization
+ such as those disabling dynamic branch prediction for well predictable
+ branches.
+
+ There are two exceptions - edges leading to noreturn edges and edges
+ predicted by number of iterations heuristics are predicted well. This macro
+ should be able to distinguish those, but at the moment it simply check for
+ noreturn heuristic that is only one giving probability over 99% or bellow
+ 1%. In future we might want to propagate reliability information across the
+ CFG if we find this information useful on multiple places. */
+static bool
+probability_reliable_p (int prob)
+{
+ return (profile_status == PROFILE_READ
+ || (profile_status == PROFILE_GUESSED
+ && (prob <= HITRATE (1) || prob >= HITRATE (99))));
+}
+
+/* Same predicate as above, working on edges. */
+bool
+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 (const_rtx note)
+{
+ gcc_assert (REG_NOTE_KIND (note) == REG_BR_PROB);
+ return probability_reliable_p (INTVAL (XEXP (note, 0)));
+}
+
static void
predict_insn (rtx insn, 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));
-
- i->next = e->src->predictions;
- e->src->predictions = i;
- i->probability = probability;
- i->predictor = predictor;
- i->edge = e;
+ struct edge_prediction *i = XNEW (struct edge_prediction);
+ void **preds = pointer_map_insert (bb_predictions, e->src);
+
+ i->ep_next = *preds;
+ *preds = i;
+ i->ep_probability = probability;
+ i->ep_predictor = predictor;
+ i->ep_edge = e;
}
}
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)->edge == e)
- *prediction = (*prediction)->next;
+ if ((*prediction)->ep_edge == e)
+ {
+ next = (*prediction)->ep_next;
+ free (*prediction);
+ *prediction = next;
+ }
else
- prediction = &((*prediction)->next);
+ 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)
Remove now useless prediction entries. */
static void
-combine_predictions_for_bb (FILE *file, basic_block bb)
+combine_predictions_for_bb (basic_block bb)
{
int best_probability = PROB_EVEN;
int best_predictor = END_PREDICTORS;
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)))
{
if (!bb->count)
set_even_probabilities (bb);
- bb->predictions = NULL;
- if (file)
- fprintf (file, "%i edges in bb %i predicted to even probabilities\n",
+ clear_bb_predictions (bb);
+ if (dump_file)
+ fprintf (dump_file, "%i edges in bb %i predicted to even probabilities\n",
nedges, bb->index);
return;
}
- if (file)
- fprintf (file, "Predictions for bb %i\n", bb->index);
+ 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->next)
+ preds = pointer_map_contains (bb_predictions, bb);
+ if (preds)
{
- int predictor = pred->predictor;
- int probability = pred->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->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,
first_match = true;
if (!found)
- dump_prediction (file, PRED_NO_PREDICTION, combined_probability, bb, true);
+ dump_prediction (dump_file, PRED_NO_PREDICTION, combined_probability, bb, true);
else
{
- dump_prediction (file, PRED_DS_THEORY, combined_probability, bb,
+ dump_prediction (dump_file, PRED_DS_THEORY, combined_probability, bb,
!first_match);
- dump_prediction (file, PRED_FIRST_MATCH, best_probability, bb,
+ dump_prediction (dump_file, PRED_FIRST_MATCH, best_probability, bb,
first_match);
}
if (first_match)
combined_probability = best_probability;
- dump_prediction (file, PRED_COMBINED, combined_probability, bb, true);
+ dump_prediction (dump_file, PRED_COMBINED, combined_probability, bb, true);
- for (pred = bb->predictions; pred; pred = pred->next)
+ if (preds)
{
- int predictor = pred->predictor;
- int probability = pred->probability;
+ for (pred = *preds; pred; pred = pred->ep_next)
+ {
+ int predictor = pred->ep_predictor;
+ int probability = pred->ep_probability;
- if (pred->edge != EDGE_SUCC (bb, 0))
- probability = REG_BR_PROB_BASE - probability;
- dump_prediction (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)
{
}
}
-/* Predict edge probabilities by exploiting loop structure.
- When RTLSIMPLELOOPS is set, attempt to count number of iterations by analyzing
- RTL otherwise use tree based approach. */
+/* Predict edge probabilities by exploiting loop structure. */
+
static void
-predict_loops (struct loops *loops_info, bool rtlsimpleloops)
+predict_loops (void)
{
- unsigned i;
+ loop_iterator li;
+ struct loop *loop;
- if (!rtlsimpleloops)
- scev_initialize (loops_info);
+ scev_initialize ();
/* Try to predict out blocks in a loop that are not part of a
natural loop. */
- for (i = 1; i < loops_info->num; i++)
+ FOR_EACH_LOOP (li, loop, 0)
{
basic_block bb, *bbs;
- unsigned j;
- unsigned n_exits;
- struct loop *loop = loops_info->parray[i];
- struct niter_desc desc;
- unsigned HOST_WIDE_INT niter;
- edge *exits;
+ unsigned j, n_exits;
+ VEC (edge, heap) *exits;
+ struct tree_niter_desc niter_desc;
+ edge ex;
- exits = get_loop_exit_edges (loop, &n_exits);
+ exits = get_loop_exit_edges (loop);
+ n_exits = VEC_length (edge, exits);
- if (rtlsimpleloops)
+ for (j = 0; VEC_iterate (edge, exits, j, ex); j++)
{
- iv_analysis_loop_init (loop);
- find_simple_exit (loop, &desc);
-
- if (desc.simple_p && desc.const_iter)
+ 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;
+ if (!niter || TREE_CODE (niter_desc.niter) != INTEGER_CST)
+ niter = loop_niter_by_eval (loop, ex);
+
+ if (TREE_CODE (niter) == INTEGER_CST)
{
- int prob;
- niter = desc.niter + 1;
- if (niter == 0) /* We might overflow here. */
- niter = desc.niter;
-
- prob = (REG_BR_PROB_BASE
- - (REG_BR_PROB_BASE + niter /2) / niter);
- /* Branch prediction algorithm gives 0 frequency for everything
- after the end of loop for loop having 0 probability to finish. */
- if (prob == REG_BR_PROB_BASE)
- prob = REG_BR_PROB_BASE - 1;
- predict_edge (desc.in_edge, PRED_LOOP_ITERATIONS,
- prob);
+ if (host_integerp (niter, 1)
+ && compare_tree_int (niter, max-1) == -1)
+ nitercst = tree_low_cst (niter, 1) + 1;
+ else
+ nitercst = max;
+ predictor = PRED_LOOP_ITERATIONS;
}
- }
- else
- {
- struct tree_niter_desc niter_desc;
-
- for (j = 0; j < n_exits; j++)
+ /* 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)
{
- tree niter = NULL;
-
- if (number_of_iterations_exit (loop, exits[j], &niter_desc))
- niter = niter_desc.niter;
- if (!niter || TREE_CODE (niter_desc.niter) != INTEGER_CST)
- niter = loop_niter_by_eval (loop, exits[j]);
-
- if (TREE_CODE (niter) == INTEGER_CST)
- {
- int probability;
- if (host_integerp (niter, 1)
- && tree_int_cst_lt (niter,
- build_int_cstu (NULL_TREE,
- REG_BR_PROB_BASE - 1)))
- {
- HOST_WIDE_INT nitercst = tree_low_cst (niter, 1) + 1;
- probability = (REG_BR_PROB_BASE + nitercst / 2) / nitercst;
- }
- else
- probability = 1;
+ nitercst = estimated_loop_iterations_int (loop, false);
+ if (nitercst < 0)
+ continue;
+ if (nitercst > max)
+ nitercst = max;
- predict_edge (exits[j], PRED_LOOP_ITERATIONS, probability);
- }
+ predictor = PRED_LOOP_ITERATIONS_GUESSED;
}
+ else
+ continue;
+ probability = ((REG_BR_PROB_BASE + nitercst / 2) / nitercst);
+ predict_edge (ex, predictor, probability);
}
- free (exits);
+ VEC_free (edge, heap, exits);
bbs = get_loop_body (loop);
statements construct loops via "non-loop" constructs
in the source language and are better to be handled
separately. */
- if ((rtlsimpleloops && !can_predict_insn_p (BB_END (bb)))
- || predicted_by_p (bb, PRED_CONTINUE))
+ if (predicted_by_p (bb, PRED_CONTINUE))
continue;
/* Loop branch heuristics - predict an edge back to a
/* Loop exit heuristics - predict an edge exiting the loop if the
conditional has no loop header successors as not taken. */
- if (!header_found)
- FOR_EACH_EDGE (e, ei, bb->succs)
- if (e->dest->index < 0
- || !flow_bb_inside_loop_p (loop, e->dest))
- predict_edge
- (e, PRED_LOOP_EXIT,
- (REG_BR_PROB_BASE
- - predictor_info [(int) PRED_LOOP_EXIT].hitrate)
- / n_exits);
+ 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
+ considered in row, the loop would be predicted to iterate
+ almost never. The code to divide probability by number of
+ exits is very rough. It should compute the number of exits
+ taken in each patch through function (not the overall number
+ of exits that might be a lot higher for loops with wide switch
+ statements in them) and compute n-th square root.
+
+ We limit the minimal probability by 2% to avoid
+ EDGE_PROBABILITY_RELIABLE from trusting the branch prediction
+ as this was causing regression in perl benchmark containing such
+ a wide loop. */
+
+ int probability = ((REG_BR_PROB_BASE
+ - predictor_info [(int) PRED_LOOP_EXIT].hitrate)
+ / n_exits);
+ if (probability < HITRATE (2))
+ probability = HITRATE (2);
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ if (e->dest->index < NUM_FIXED_BLOCKS
+ || !flow_bb_inside_loop_p (loop, e->dest))
+ predict_edge (e, PRED_LOOP_EXIT, probability);
+ }
}
/* Free basic blocks from get_loop_body. */
free (bbs);
}
- if (!rtlsimpleloops)
- {
- scev_finalize ();
- current_loops = NULL;
- }
+ scev_finalize ();
}
/* Attempt to predict probabilities of BB outgoing edges using local
}
}
-/* Statically estimate the probability that a branch will be taken and produce
- estimated profile. When profile feedback is present never executed portions
- of function gets estimated. */
-
-void
-estimate_probability (struct loops *loops_info)
-{
- basic_block bb;
-
- connect_infinite_loops_to_exit ();
- calculate_dominance_info (CDI_DOMINATORS);
- calculate_dominance_info (CDI_POST_DOMINATORS);
-
- predict_loops (loops_info, true);
-
- iv_analysis_done ();
-
- /* Attempt to predict conditional jumps using a number of heuristics. */
- FOR_EACH_BB (bb)
- {
- rtx last_insn = BB_END (bb);
- edge e;
- edge_iterator ei;
-
- if (! can_predict_insn_p (last_insn))
- continue;
-
- FOR_EACH_EDGE (e, ei, bb->succs)
- {
- /* Predict early returns to be probable, as we've already taken
- care for error returns and other are often used for fast paths
- trought function. */
- if ((e->dest == EXIT_BLOCK_PTR
- || (single_succ_p (e->dest)
- && single_succ (e->dest) == EXIT_BLOCK_PTR))
- && !predicted_by_p (bb, PRED_NULL_RETURN)
- && !predicted_by_p (bb, PRED_CONST_RETURN)
- && !predicted_by_p (bb, PRED_NEGATIVE_RETURN)
- && !last_basic_block_p (e->dest))
- predict_edge_def (e, PRED_EARLY_RETURN, TAKEN);
-
- /* Look for block we are guarding (i.e. we dominate it,
- but it doesn't postdominate us). */
- if (e->dest != EXIT_BLOCK_PTR && e->dest != bb
- && dominated_by_p (CDI_DOMINATORS, e->dest, e->src)
- && !dominated_by_p (CDI_POST_DOMINATORS, e->src, e->dest))
- {
- rtx insn;
-
- /* The call heuristic claims that a guarded function call
- is improbable. This is because such calls are often used
- to signal exceptional situations such as printing error
- messages. */
- for (insn = BB_HEAD (e->dest); insn != NEXT_INSN (BB_END (e->dest));
- insn = NEXT_INSN (insn))
- if (CALL_P (insn)
- /* Constant and pure calls are hardly used to signalize
- something exceptional. */
- && ! CONST_OR_PURE_CALL_P (insn))
- {
- predict_edge_def (e, PRED_CALL, NOT_TAKEN);
- break;
- }
- }
- }
- bb_estimate_probability_locally (bb);
- }
-
- /* Attach the combined probability to each conditional jump. */
- FOR_EACH_BB (bb)
- combine_predictions_for_insn (BB_END (bb), bb);
-
- remove_fake_edges ();
- estimate_bb_frequencies (loops_info);
- free_dominance_info (CDI_POST_DOMINATORS);
- if (profile_status == PROFILE_ABSENT)
- profile_status = PROFILE_GUESSED;
-}
-
/* Set edge->probability for each successor edge of BB. */
void
guess_outgoing_edge_probabilities (basic_block bb)
}
return val;
}
- if (TREE_CODE (def) != MODIFY_EXPR || TREE_OPERAND (def, 0) != expr)
+ if (TREE_CODE (def) != GIMPLE_MODIFY_STMT
+ || GIMPLE_STMT_OPERAND (def, 0) != expr)
return NULL;
- return expr_expected_value (TREE_OPERAND (def, 1), visited);
+ return expr_expected_value (GIMPLE_STMT_OPERAND (def, 1), visited);
}
else if (TREE_CODE (expr) == CALL_EXPR)
{
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))
op1 = expr_expected_value (TREE_OPERAND (expr, 1), visited);
if (!op1)
return NULL;
- res = fold (build (TREE_CODE (expr), TREE_TYPE (expr), op0, op1));
+ res = fold_build2 (TREE_CODE (expr), TREE_TYPE (expr), op0, op1);
if (TREE_CONSTANT (res))
return res;
return NULL;
op0 = expr_expected_value (TREE_OPERAND (expr, 0), visited);
if (!op0)
return NULL;
- res = fold (build1 (TREE_CODE (expr), TREE_TYPE (expr), op0));
+ res = fold_build1 (TREE_CODE (expr), TREE_TYPE (expr), op0);
if (TREE_CONSTANT (res))
return res;
return NULL;
{
tree stmt = bsi_stmt (bi);
tree fndecl;
- tree arglist;
+ tree call;
- if (TREE_CODE (stmt) == MODIFY_EXPR
- && TREE_CODE (TREE_OPERAND (stmt, 1)) == CALL_EXPR
- && (fndecl = get_callee_fndecl (TREE_OPERAND (stmt, 1)))
+ if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
+ && (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 (TREE_OPERAND (stmt, 1), 1))
- && TREE_CHAIN (arglist))
+ && call_expr_nargs (call) == 2)
{
- TREE_OPERAND (stmt, 1) = TREE_VALUE (arglist);
+ GIMPLE_STMT_OPERAND (stmt, 1) = CALL_EXPR_ARG (call, 0);
update_stmt (stmt);
}
}
&& (!integer_zerop (val) && !integer_onep (val)))
{
*prediction = TAKEN;
- return PRED_NEGATIVE_RETURN;
+ return PRED_CONST_RETURN;
}
}
return PRED_NO_PREDICTION;
/* Find the basic block with return expression and look up for possible
return value trying to apply RETURN_PREDICTION heuristics. */
static void
-apply_return_prediction (int *heads)
+apply_return_prediction (void)
{
- tree return_stmt;
+ tree return_stmt = NULL;
tree return_val;
edge e;
tree phi;
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)
return_val = TREE_OPERAND (return_stmt, 0);
if (!return_val)
return;
- if (TREE_CODE (return_val) == MODIFY_EXPR)
- return_val = TREE_OPERAND (return_val, 1);
+ if (TREE_CODE (return_val) == GIMPLE_MODIFY_STMT)
+ return_val = GIMPLE_STMT_OPERAND (return_val, 1);
if (TREE_CODE (return_val) != SSA_NAME
|| !SSA_NAME_DEF_STMT (return_val)
|| TREE_CODE (SSA_NAME_DEF_STMT (return_val)) != PHI_NODE)
{
pred = return_prediction (PHI_ARG_DEF (phi, i), &direction);
if (pred != PRED_NO_PREDICTION)
- predict_paths_leading_to (PHI_ARG_EDGE (phi, i)->src, heads, pred,
+ predict_paths_leading_to (PHI_ARG_EDGE (phi, i)->src, pred,
direction);
}
}
tree_bb_level_predictions (void)
{
basic_block bb;
- int *heads;
-
- heads = xmalloc (sizeof (int) * last_basic_block);
- memset (heads, -1, sizeof (int) * last_basic_block);
- heads[ENTRY_BLOCK_PTR->next_bb->index] = last_basic_block;
- apply_return_prediction (heads);
+ apply_return_prediction ();
FOR_EACH_BB (bb)
{
block_stmt_iterator bsi = bsi_last (bb);
- for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
+ for (bsi = bsi_start (bb); !bsi_end_p (bsi);)
{
tree stmt = bsi_stmt (bsi);
+ tree decl;
+ bool next = false;
+
switch (TREE_CODE (stmt))
{
- case MODIFY_EXPR:
- if (TREE_CODE (TREE_OPERAND (stmt, 1)) == CALL_EXPR)
+ case GIMPLE_MODIFY_STMT:
+ if (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == CALL_EXPR)
{
- stmt = TREE_OPERAND (stmt, 1);
+ stmt = GIMPLE_STMT_OPERAND (stmt, 1);
goto call_expr;
}
break;
case CALL_EXPR:
call_expr:;
if (call_expr_flags (stmt) & ECF_NORETURN)
- predict_paths_leading_to (bb, heads, PRED_NORETURN,
+ predict_paths_leading_to (bb, PRED_NORETURN,
NOT_TAKEN);
+ decl = get_callee_fndecl (stmt);
+ if (decl
+ && lookup_attribute ("cold",
+ DECL_ATTRIBUTES (decl)))
+ predict_paths_leading_to (bb, PRED_COLD_FUNCTION,
+ NOT_TAKEN);
+ break;
+ case PREDICT_EXPR:
+ predict_paths_leading_to (bb, PREDICT_EXPR_PREDICTOR (stmt),
+ PREDICT_EXPR_OUTCOME (stmt));
+ bsi_remove (&bsi, true);
+ next = true;
break;
default:
break;
}
+ if (!next)
+ bsi_next (&bsi);
}
}
+}
- 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 void
+static unsigned int
tree_estimate_probability (void)
{
basic_block bb;
- struct loops loops_info;
- flow_loops_find (&loops_info);
+ loop_optimizer_init (0);
if (dump_file && (dump_flags & TDF_DETAILS))
- flow_loops_dump (&loops_info, dump_file, NULL, 0);
+ 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 (&loops_info);
- predict_loops (&loops_info, false);
+ mark_irreducible_loops ();
+ record_loop_exits ();
+ if (number_of_loops () > 1)
+ predict_loops ();
FOR_EACH_BB (bb)
{
{
/* Predict early returns to be probable, as we've already taken
care for error returns and other cases are often used for
- fast paths trought 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,
{
tree stmt = bsi_stmt (bi);
if ((TREE_CODE (stmt) == CALL_EXPR
- || (TREE_CODE (stmt) == MODIFY_EXPR
- && TREE_CODE (TREE_OPERAND (stmt, 1)) == CALL_EXPR))
+ || (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
+ && TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1))
+ == CALL_EXPR))
/* Constant and pure calls are hardly used to signalize
something exceptional. */
&& TREE_SIDE_EFFECTS (stmt))
tree_predict_by_opcode (bb);
}
FOR_EACH_BB (bb)
- combine_predictions_for_bb (dump_file, 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;
- if (0) /* FIXME: Enable once we are pass down the profile to RTL level. */
- strip_builtin_expect ();
- estimate_bb_frequencies (&loops_info);
+ strip_builtin_expect ();
+ estimate_bb_frequencies ();
free_dominance_info (CDI_POST_DOMINATORS);
remove_fake_exit_edges ();
- flow_loops_free (&loops_info);
+ loop_optimizer_finalize ();
if (dump_file && (dump_flags & TDF_DETAILS))
dump_tree_cfg (dump_file, dump_flags);
if (profile_status == PROFILE_ABSENT)
profile_status = PROFILE_GUESSED;
+ return 0;
}
\f
-/* __builtin_expect dropped tokens into the insn stream describing expected
- values of registers. Generate branch probabilities based off these
- values. */
+/* Predict edges to succestors of CUR whose sources are not postdominated by
+ BB by PRED and recurse to all postdominators. */
-void
-expected_value_to_br_prob (void)
+static void
+predict_paths_for_bb (basic_block cur, basic_block bb,
+ enum br_predictor pred,
+ enum prediction taken)
{
- rtx insn, cond, ev = NULL_RTX, ev_reg = NULL_RTX;
+ edge e;
+ edge_iterator ei;
+ basic_block son;
- for (insn = get_insns (); insn ; insn = NEXT_INSN (insn))
+ /* We are looking for all edges forming edge cut induced by
+ set of all blocks postdominated by BB. */
+ FOR_EACH_EDGE (e, ei, cur->preds)
+ if (e->src->index >= NUM_FIXED_BLOCKS
+ && !dominated_by_p (CDI_POST_DOMINATORS, e->src, bb))
{
- switch (GET_CODE (insn))
- {
- case NOTE:
- /* Look for expected value notes. */
- if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EXPECTED_VALUE)
- {
- ev = NOTE_EXPECTED_VALUE (insn);
- ev_reg = XEXP (ev, 0);
- delete_insn (insn);
- }
- continue;
-
- case CODE_LABEL:
- /* Never propagate across labels. */
- ev = NULL_RTX;
- continue;
-
- case JUMP_INSN:
- /* Look for simple conditional branches. If we haven't got an
- expected value yet, no point going further. */
- if (!JUMP_P (insn) || ev == NULL_RTX
- || ! any_condjump_p (insn))
- continue;
- break;
-
- default:
- /* Look for insns that clobber the EV register. */
- if (ev && reg_set_p (ev_reg, insn))
- ev = NULL_RTX;
- continue;
- }
-
- /* Collect the branch condition, hopefully relative to EV_REG. */
- /* ??? At present we'll miss things like
- (expected_value (eq r70 0))
- (set r71 -1)
- (set r80 (lt r70 r71))
- (set pc (if_then_else (ne r80 0) ...))
- as canonicalize_condition will render this to us as
- (lt r70, r71)
- Could use cselib to try and reduce this further. */
- cond = XEXP (SET_SRC (pc_set (insn)), 0);
- cond = canonicalize_condition (insn, cond, 0, NULL, ev_reg,
- false, false);
- if (! cond || XEXP (cond, 0) != ev_reg
- || GET_CODE (XEXP (cond, 1)) != CONST_INT)
- continue;
-
- /* Substitute and simplify. Given that the expression we're
- building involves two constants, we should wind up with either
- true or false. */
- cond = gen_rtx_fmt_ee (GET_CODE (cond), VOIDmode,
- XEXP (ev, 1), XEXP (cond, 1));
- cond = simplify_rtx (cond);
-
- /* Turn the condition into a scaled branch probability. */
- gcc_assert (cond == const_true_rtx || cond == const0_rtx);
- predict_insn_def (insn, PRED_BUILTIN_EXPECT,
- cond == const_true_rtx ? TAKEN : NOT_TAKEN);
+ gcc_assert (bb == cur || dominated_by_p (CDI_POST_DOMINATORS, cur, bb));
+ predict_edge_def (e, pred, taken);
}
-}
-\f
-/* 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));
+ for (son = first_dom_son (CDI_POST_DOMINATORS, cur);
+ son;
+ son = next_dom_son (CDI_POST_DOMINATORS, son))
+ predict_paths_for_bb (son, bb, pred, taken);
}
/* 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
- such that we do not post-dominate it) (but we fill this information
- on demand, so -1 may be there in case this was not needed yet). */
+ FLAGS. */
static void
-predict_paths_leading_to (basic_block bb, int *heads, enum br_predictor pred,
+predict_paths_leading_to (basic_block bb, enum br_predictor pred,
enum prediction taken)
{
- edge e;
- edge_iterator ei;
- int y;
-
- if (heads[bb->index] < 0)
- {
- /* This is first time we need this field in heads array; so
- find first dominator that we do not post-dominate (we are
- using already known members of heads array). */
- basic_block ai = bb;
- basic_block next_ai = get_immediate_dominator (CDI_DOMINATORS, bb);
- int head;
-
- while (heads[next_ai->index] < 0)
- {
- if (!dominated_by_p (CDI_POST_DOMINATORS, next_ai, bb))
- break;
- heads[next_ai->index] = ai->index;
- ai = next_ai;
- next_ai = get_immediate_dominator (CDI_DOMINATORS, next_ai);
- }
- if (!dominated_by_p (CDI_POST_DOMINATORS, next_ai, bb))
- head = next_ai->index;
- else
- head = heads[next_ai->index];
- while (next_ai != bb)
- {
- next_ai = ai;
- if (heads[ai->index] == ENTRY_BLOCK)
- ai = ENTRY_BLOCK_PTR;
- else
- ai = BASIC_BLOCK (heads[ai->index]);
- heads[next_ai->index] = head;
- }
- }
- y = heads[bb->index];
-
- /* Now find the edge that leads to our branch and aply the prediction. */
-
- if (y == last_basic_block)
- return;
- FOR_EACH_EDGE (e, ei, BASIC_BLOCK (y)->succs)
- if (e->dest->index >= 0
- && dominated_by_p (CDI_POST_DOMINATORS, e->dest, bb))
- predict_edge_def (e, pred, taken);
+ predict_paths_for_bb (bb, bb, pred, taken);
}
\f
/* This is used to carry information about basic blocks. It is
/* Similar information for edges. */
typedef struct edge_info_def
{
- /* In case edge is an loopback edge, the probability edge will be reached
+ /* In case edge is a loopback edge, the probability edge will be reached
in case header is. Estimated number of iterations of the loop can be
then computed as 1 / (1 - back_edge_prob). */
sreal back_edge_prob;
- /* True if the edge is an loopback edge in the natural loop. */
+ /* True if the edge is a loopback edge in the natural loop. */
unsigned int back_edge:1;
} *edge_info;
#define EDGE_INFO(E) ((edge_info) (E)->aux)
/* Helper function for estimate_bb_frequencies.
- Propagate the frequencies for LOOP. */
+ Propagate the frequencies in blocks marked in
+ TOVISIT, starting in HEAD. */
static void
-propagate_freq (struct loop *loop, bitmap tovisit)
+propagate_freq (basic_block head, bitmap tovisit)
{
- basic_block head = loop->header;
basic_block bb;
basic_block last;
unsigned i;
/* The outermost "loop" includes the exit block, which we can not
look up via BASIC_BLOCK. Detect this and use EXIT_BLOCK_PTR
directly. Do the same for the entry block. */
- if (i == (unsigned)ENTRY_BLOCK)
- bb = ENTRY_BLOCK_PTR;
- else if (i == (unsigned)EXIT_BLOCK)
- bb = EXIT_BLOCK_PTR;
- else
- bb = BASIC_BLOCK (i);
+ bb = BASIC_BLOCK (i);
FOR_EACH_EDGE (e, ei, bb->preds)
{
/* Estimate probabilities of loopback edges in loops at same nest level. */
static void
-estimate_loops_at_level (struct loop *first_loop, bitmap tovisit)
+estimate_loops_at_level (struct loop *first_loop)
{
struct loop *loop;
edge e;
basic_block *bbs;
unsigned i;
+ bitmap tovisit = BITMAP_ALLOC (NULL);
- estimate_loops_at_level (loop->inner, tovisit);
+ estimate_loops_at_level (loop->inner);
- /* Do not do this for dummy function loop. */
- if (EDGE_COUNT (loop->latch->succs) > 0)
- {
- /* Find current loop back edge and mark it. */
- e = loop_latch_edge (loop);
- EDGE_INFO (e)->back_edge = 1;
- }
+ /* Find current loop back edge and mark it. */
+ e = loop_latch_edge (loop);
+ EDGE_INFO (e)->back_edge = 1;
bbs = get_loop_body (loop);
for (i = 0; i < loop->num_nodes; i++)
bitmap_set_bit (tovisit, bbs[i]->index);
free (bbs);
- propagate_freq (loop, tovisit);
+ propagate_freq (loop->header, tovisit);
+ BITMAP_FREE (tovisit);
}
}
+/* Propagates frequencies through structure of loops. */
+
+static void
+estimate_loops (void)
+{
+ bitmap tovisit = BITMAP_ALLOC (NULL);
+ basic_block bb;
+
+ /* Start by estimating the frequencies in the loops. */
+ if (number_of_loops () > 1)
+ estimate_loops_at_level (current_loops->tree_root->inner);
+
+ /* Now propagate the frequencies through all the blocks. */
+ FOR_ALL_BB (bb)
+ {
+ bitmap_set_bit (tovisit, bb->index);
+ }
+ propagate_freq (ENTRY_BLOCK_PTR, tovisit);
+ BITMAP_FREE (tovisit);
+}
+
/* Convert counts measured by profile driven feedback to frequencies.
Return nonzero iff there was any nonzero execution count. */
count_max = MAX (true_count_max, 1);
FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
bb->frequency = (bb->count * BB_FREQ_MAX + count_max / 2) / count_max;
+
return true_count_max;
}
/* Estimate basic blocks frequency by given branch probabilities. */
-static void
-estimate_bb_frequencies (struct loops *loops)
+void
+estimate_bb_frequencies (void)
{
basic_block bb;
sreal freq_max;
if (!flag_branch_probabilities || !counts_to_freqs ())
{
static int real_values_initialized = 0;
- bitmap tovisit;
if (!real_values_initialized)
{
single_succ_edge (ENTRY_BLOCK_PTR)->probability = REG_BR_PROB_BASE;
/* Set up block info for each basic block. */
- tovisit = BITMAP_ALLOC (NULL);
alloc_aux_for_blocks (sizeof (struct block_info_def));
alloc_aux_for_edges (sizeof (struct edge_info_def));
FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
/* First compute probabilities locally for each loop from innermost
to outermost to examine probabilities for back edges. */
- estimate_loops_at_level (loops->tree_root, tovisit);
+ estimate_loops ();
memcpy (&freq_max, &real_zero, sizeof (real_zero));
FOR_EACH_BB (bb)
free_aux_for_blocks ();
free_aux_for_edges ();
- BITMAP_FREE (tovisit);
}
compute_function_frequency ();
if (flag_reorder_functions)
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)
{
return flag_guess_branch_prob;
}
-struct tree_opt_pass pass_profile =
+/* Build PREDICT_EXPR. */
+tree
+build_predict_expr (enum br_predictor predictor, enum prediction taken)
+{
+ tree t = build1 (PREDICT_EXPR, NULL_TREE, build_int_cst (NULL, predictor));
+ PREDICT_EXPR_OUTCOME (t) = taken;
+ return t;
+}
+
+const char *
+predictor_name (enum br_predictor predictor)
+{
+ return predictor_info[predictor].name;
+}
+
+struct gimple_opt_pass pass_profile =
{
+ {
+ GIMPLE_PASS,
"profile", /* name */
gate_estimate_probability, /* gate */
tree_estimate_probability, /* execute */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_ggc_collect | TODO_verify_ssa, /* todo_flags_finish */
- 0 /* letter */
+ TODO_ggc_collect | TODO_verify_ssa /* todo_flags_finish */
+ }
};