/* Branch prediction routines for the GNU compiler.
- Copyright (C) 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
+ Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005
+ Free Software Foundation, Inc.
This file is part of GCC.
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, 59 Temple Place - Suite 330, Boston, MA
-02111-1307, USA. */
+Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA. */
/* References:
real_inv_br_prob_base, real_one_half, real_bb_freq_max;
/* Random guesstimation given names. */
-#define PROB_VERY_UNLIKELY (REG_BR_PROB_BASE / 10 - 1)
+#define PROB_VERY_UNLIKELY (REG_BR_PROB_BASE / 100 - 1)
#define PROB_EVEN (REG_BR_PROB_BASE / 2)
#define PROB_VERY_LIKELY (REG_BR_PROB_BASE - PROB_VERY_UNLIKELY)
#define PROB_ALWAYS (REG_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 estimate_loops_at_level (struct loop *loop);
-static void propagate_freq (struct loop *);
-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 compute_function_frequency (void);
static void choose_function_section (void);
static bool can_predict_insn_p (rtx);
&& (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;
&& (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;
{
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;
}
bool
tree_predicted_by_p (basic_block bb, enum br_predictor predictor)
{
- struct edge_prediction *i = bb_ann (bb)->predictions;
- for (i = bb_ann (bb)->predictions; i; i = i->next)
- if (i->predictor == predictor)
+ struct edge_prediction *i;
+ for (i = bb->predictions; i; i = i->ep_next)
+ if (i->ep_predictor == predictor)
return true;
return false;
}
-void
+/* 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 (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)
+{
+ 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 (!any_condjump_p (insn))
- abort ();
+ gcc_assert (any_condjump_p (insn));
if (!flag_guess_branch_prob)
return;
void
tree_predict_edge (edge e, enum br_predictor predictor, int probability)
{
- struct edge_prediction *i = ggc_alloc (sizeof (struct edge_prediction));
+ gcc_assert (profile_status != PROFILE_GUESSED);
+ 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 = bb_ann (e->src)->predictions;
- bb_ann (e->src)->predictions = i;
- i->probability = probability;
- i->predictor = predictor;
- i->edge = e;
+ i->ep_next = e->src->predictions;
+ e->src->predictions = i;
+ i->ep_probability = probability;
+ i->ep_predictor = predictor;
+ i->ep_edge = e;
+ }
+}
+
+/* Remove all predictions on given basic block that are attached
+ to edge E. */
+void
+remove_predictions_associated_with_edge (edge e)
+{
+ if (e->src->predictions)
+ {
+ struct edge_prediction **prediction = &e->src->predictions;
+ while (*prediction)
+ {
+ if ((*prediction)->ep_edge == e)
+ *prediction = (*prediction)->ep_next;
+ else
+ prediction = &((*prediction)->ep_next);
+ }
+ }
}
/* Return true when we can store prediction on insn INSN.
/* Save the prediction into CFG in case we are seeing non-degenerated
conditional jump. */
- if (EDGE_COUNT (bb->succs) > 1)
+ if (!single_succ_p (bb))
{
BRANCH_EDGE (bb)->probability = combined_probability;
FALLTHRU_EDGE (bb)->probability
= REG_BR_PROB_BASE - combined_probability;
}
}
- else if (EDGE_COUNT (bb->succs) > 1)
+ else if (!single_succ_p (bb))
{
int prob = INTVAL (XEXP (prob_note, 0));
FALLTHRU_EDGE (bb)->probability = REG_BR_PROB_BASE - prob;
}
else
- EDGE_SUCC (bb, 0)->probability = REG_BR_PROB_BASE;
+ single_succ_edge (bb)->probability = REG_BR_PROB_BASE;
}
/* Combine predictions into single probability and store them into CFG.
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;
{
if (!bb->count)
set_even_probabilities (bb);
- bb_ann (bb)->predictions = NULL;
- if (file)
- fprintf (file, "%i edges in bb %i predicted to even probabilities\n",
+ bb->predictions = NULL;
+ 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_ann (bb)->predictions; pred; pred = pred->next)
+ for (pred = bb->predictions; pred; pred = pred->ep_next)
{
- int predictor = pred->predictor;
- int probability = pred->probability;
+ int predictor = pred->ep_predictor;
+ int probability = pred->ep_probability;
- if (pred->edge != first)
+ if (pred->ep_edge != first)
probability = REG_BR_PROB_BASE - probability;
found = true;
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_ann (bb)->predictions; pred; pred = pred->next)
+ for (pred = bb->predictions; pred; pred = pred->ep_next)
{
- int predictor = pred->predictor;
- int probability = pred->probability;
+ int predictor = pred->ep_predictor;
+ int probability = pred->ep_probability;
- if (pred->edge != EDGE_SUCC (bb, 0))
+ if (pred->ep_edge != EDGE_SUCC (bb, 0))
probability = REG_BR_PROB_BASE - probability;
- dump_prediction (file, predictor, probability, bb,
+ dump_prediction (dump_file, predictor, probability, bb,
!first_match || best_predictor == predictor);
}
- bb_ann (bb)->predictions = NULL;
+ bb->predictions = NULL;
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;
- int exits;
- struct loop *loop = loops_info->parray[i];
- struct niter_desc desc;
- unsigned HOST_WIDE_INT niter;
+ unsigned j, n_exits;
+ VEC (edge, heap) *exits;
+ struct tree_niter_desc niter_desc;
+ edge ex;
- flow_loop_scan (loop, LOOP_EXIT_EDGES);
- exits = loop->num_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
- {
- edge *exits;
- unsigned j, n_exits;
- struct tree_niter_desc niter_desc;
-
- exits = get_loop_exit_edges (loop, &n_exits);
- 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;
- free (exits);
+ probability = ((REG_BR_PROB_BASE + nitercst / 2) / nitercst);
+ predict_edge (ex, predictor, probability);
}
+ 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's head as taken. */
- FOR_EACH_EDGE (e, ei, bb->succs)
- if (e->dest == loop->header
- && e->src == loop->latch)
- {
- header_found = 1;
- predict_edge_def (e, PRED_LOOP_BRANCH, TAKEN);
- }
+ if (bb == loop->latch)
+ {
+ e = find_edge (loop->latch, loop->header);
+ if (e)
+ {
+ header_found = 1;
+ predict_edge_def (e, PRED_LOOP_BRANCH, TAKEN);
+ }
+ }
/* 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)
- / 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_reset ();
+ 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
- || (EDGE_COUNT (e->dest->succs) == 1
- && EDGE_SUCC (e->dest, 0)->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)
/* If this PHI has itself as an argument, we cannot
determine the string length of this argument. However,
- if we can find a expected constant value for the other
+ if we can find an expected constant value for the other
PHI args then we can still be sure that this is
likely a constant. So be optimistic and just
continue with the next argument. */
}
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)
{
tree decl = get_callee_fndecl (expr);
if (!decl)
return NULL;
- if (DECL_BUILT_IN (decl) && DECL_FUNCTION_CODE (decl) == BUILT_IN_EXPECT)
+ 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)))
- && DECL_BUILT_IN (fndecl)
+ 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);
- modify_stmt (stmt);
+ GIMPLE_STMT_OPERAND (stmt, 1) = CALL_EXPR_ARG (call, 0);
+ update_stmt (stmt);
}
}
}
return;
op0 = TREE_OPERAND (cond, 0);
type = TREE_TYPE (op0);
- visited = BITMAP_XMALLOC ();
+ visited = BITMAP_ALLOC (NULL);
val = expr_expected_value (cond, visited);
- BITMAP_XFREE (visited);
+ BITMAP_FREE (visited);
if (val)
{
if (integer_zerop (val))
&& (!integer_zerop (val) && !integer_onep (val)))
{
*prediction = TAKEN;
- return PRED_NEGATIVE_RETURN;
+ return PRED_CONST_RETURN;
}
}
return PRED_NO_PREDICTION;
static void
apply_return_prediction (int *heads)
{
- tree return_stmt;
+ tree return_stmt = NULL;
tree return_val;
edge e;
tree phi;
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)
return;
- phi = SSA_NAME_DEF_STMT (return_val);
- while (phi)
- {
- tree next = PHI_CHAIN (phi);
- if (PHI_RESULT (phi) == return_val)
- break;
- phi = next;
- }
+ for (phi = SSA_NAME_DEF_STMT (return_val); phi; phi = PHI_CHAIN (phi))
+ if (PHI_RESULT (phi) == return_val)
+ break;
if (!phi)
return;
phi_num_args = PHI_NUM_ARGS (phi);
basic_block bb;
int *heads;
- heads = xmalloc (sizeof (int) * last_basic_block);
- memset (heads, -1, sizeof (int) * last_basic_block);
+ heads = XCNEWVEC (int, last_basic_block);
heads[ENTRY_BLOCK_PTR->next_bb->index] = last_basic_block;
apply_return_prediction (heads);
for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
{
tree stmt = bsi_stmt (bsi);
+ tree decl;
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;
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;
}
/* 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_TREE);
- if (dump_file && (dump_flags & TDF_DETAILS))
- flow_loops_dump (&loops_info, dump_file, NULL, 0);
+ loop_optimizer_init (0);
+ if (current_loops && 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);
tree_bb_level_predictions ();
- mark_irreducible_loops (&loops_info);
- predict_loops (&loops_info, false);
+ mark_irreducible_loops ();
+ record_loop_exits ();
+ if (current_loops)
+ 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
- && EDGE_COUNT (bb->preds) > 1)
+ 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);
- 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. */
-
-void
-expected_value_to_br_prob (void)
-{
- rtx insn, cond, ev = NULL_RTX, ev_reg = NULL_RTX;
-
- for (insn = get_insns (); insn ; insn = NEXT_INSN (insn))
- {
- 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. */
- if (cond != const_true_rtx && cond != const0_rtx)
- abort ();
- predict_insn_def (insn, PRED_BUILTIN_EXPECT,
- cond == const_true_rtx ? TAKEN : NOT_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
- && EDGE_COUNT (bb->succs) == 1
- && EDGE_SUCC (bb, 0)->dest->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
edge_iterator ei;
int y;
- if (heads[bb->index] < 0)
+ if (heads[bb->index] == ENTRY_BLOCK)
{
/* This is first time we need this field in heads array; so
find first dominator that we do not post-dominate (we are
basic_block next_ai = get_immediate_dominator (CDI_DOMINATORS, bb);
int head;
- while (heads[next_ai->index] < 0)
+ while (heads[next_ai->index] == ENTRY_BLOCK)
{
if (!dominated_by_p (CDI_POST_DOMINATORS, next_ai, bb))
break;
while (next_ai != bb)
{
next_ai = ai;
- if (heads[ai->index] == ENTRY_BLOCK)
- ai = ENTRY_BLOCK_PTR;
- else
- ai = BASIC_BLOCK (heads[ai->index]);
+ ai = BASIC_BLOCK (heads[ai->index]);
heads[next_ai->index] = head;
}
}
if (y == last_basic_block)
return;
FOR_EACH_EDGE (e, ei, BASIC_BLOCK (y)->succs)
- if (e->dest->index >= 0
+ if (e->dest->index >= NUM_FIXED_BLOCKS
&& dominated_by_p (CDI_POST_DOMINATORS, e->dest, bb))
predict_edge_def (e, pred, taken);
}
/* To keep queue of basic blocks to process. */
basic_block next;
- /* True if block needs to be visited in propagate_freq. */
- unsigned int tovisit:1;
-
/* Number of predecessors we need to visit first. */
int npredecessors;
} *block_info;
/* 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)
+propagate_freq (basic_block head, bitmap tovisit)
{
- basic_block head = loop->header;
basic_block bb;
basic_block last;
+ unsigned i;
edge e;
basic_block nextbb;
+ bitmap_iterator bi;
/* For each basic block we need to visit count number of his predecessors
we need to visit first. */
- FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
+ EXECUTE_IF_SET_IN_BITMAP (tovisit, 0, i, bi)
{
- if (BLOCK_INFO (bb)->tovisit)
- {
- edge_iterator ei;
- int count = 0;
+ edge_iterator ei;
+ int count = 0;
- FOR_EACH_EDGE (e, ei, bb->preds)
- if (BLOCK_INFO (e->src)->tovisit && !(e->flags & EDGE_DFS_BACK))
- count++;
- else if (BLOCK_INFO (e->src)->tovisit
- && dump_file && !EDGE_INFO (e)->back_edge)
- fprintf (dump_file,
- "Irreducible region hit, ignoring edge to %i->%i\n",
- e->src->index, bb->index);
- BLOCK_INFO (bb)->npredecessors = count;
+ /* 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. */
+ bb = BASIC_BLOCK (i);
+
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ {
+ bool visit = bitmap_bit_p (tovisit, e->src->index);
+
+ if (visit && !(e->flags & EDGE_DFS_BACK))
+ count++;
+ else if (visit && dump_file && !EDGE_INFO (e)->back_edge)
+ fprintf (dump_file,
+ "Irreducible region hit, ignoring edge to %i->%i\n",
+ e->src->index, bb->index);
}
+ BLOCK_INFO (bb)->npredecessors = count;
}
memcpy (&BLOCK_INFO (head)->frequency, &real_one, sizeof (real_one));
{
#ifdef ENABLE_CHECKING
FOR_EACH_EDGE (e, ei, bb->preds)
- if (BLOCK_INFO (e->src)->tovisit && !(e->flags & EDGE_DFS_BACK))
- abort ();
+ gcc_assert (!bitmap_bit_p (tovisit, e->src->index)
+ || (e->flags & EDGE_DFS_BACK));
#endif
FOR_EACH_EDGE (e, ei, bb->preds)
}
}
- BLOCK_INFO (bb)->tovisit = 0;
+ bitmap_clear_bit (tovisit, bb->index);
- /* Compute back edge frequencies. */
- FOR_EACH_EDGE (e, ei, bb->succs)
- if (e->dest == head)
- {
- sreal tmp;
+ e = find_edge (bb, head);
+ if (e)
+ {
+ sreal tmp;
- /* EDGE_INFO (e)->back_edge_prob
- = ((e->probability * BLOCK_INFO (bb)->frequency)
- / REG_BR_PROB_BASE); */
+ /* EDGE_INFO (e)->back_edge_prob
+ = ((e->probability * BLOCK_INFO (bb)->frequency)
+ / REG_BR_PROB_BASE); */
- sreal_init (&tmp, e->probability, 0);
- sreal_mul (&tmp, &tmp, &BLOCK_INFO (bb)->frequency);
- sreal_mul (&EDGE_INFO (e)->back_edge_prob,
- &tmp, &real_inv_br_prob_base);
- }
+ sreal_init (&tmp, e->probability, 0);
+ sreal_mul (&tmp, &tmp, &BLOCK_INFO (bb)->frequency);
+ sreal_mul (&EDGE_INFO (e)->back_edge_prob,
+ &tmp, &real_inv_br_prob_base);
+ }
/* Propagate to successor blocks. */
FOR_EACH_EDGE (e, ei, bb->succs)
edge e;
basic_block *bbs;
unsigned i;
+ bitmap tovisit = BITMAP_ALLOC (NULL);
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++)
- BLOCK_INFO (bbs[i])->tovisit = 1;
+ bitmap_set_bit (tovisit, bbs[i]->index);
free (bbs);
- propagate_freq (loop);
+ 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 (current_loops)
+ 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.
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;
}
/* We can not compute accurately for large thresholds due to scaled
frequencies. */
- if (threshold > BB_FREQ_MAX)
- abort ();
+ gcc_assert (threshold <= BB_FREQ_MAX);
/* Frequencies are out of range. This either means that function contains
internal loop executing more than BB_FREQ_MAX times or profile feedback
/* 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;
mark_dfs_back_edges ();
- EDGE_SUCC (ENTRY_BLOCK_PTR, 0)->probability = REG_BR_PROB_BASE;
+ single_succ_edge (ENTRY_BLOCK_PTR)->probability = REG_BR_PROB_BASE;
/* Set up block info for each basic block. */
alloc_aux_for_blocks (sizeof (struct block_info_def));
edge e;
edge_iterator ei;
- BLOCK_INFO (bb)->tovisit = 0;
FOR_EACH_EDGE (e, ei, bb->succs)
{
sreal_init (&EDGE_INFO (e)->back_edge_prob, e->probability, 0);
/* First compute probabilities locally for each loop from innermost
to outermost to examine probabilities for back edges. */
- estimate_loops_at_level (loops->tree_root);
+ estimate_loops ();
memcpy (&freq_max, &real_zero, sizeof (real_zero));
FOR_EACH_BB (bb)
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)
{
UNLIKELY_EXECUTED_TEXT_SECTION_NAME);
}
+static bool
+gate_estimate_probability (void)
+{
+ return flag_guess_branch_prob;
+}
struct tree_opt_pass pass_profile =
{
"profile", /* name */
- NULL, /* gate */
+ gate_estimate_probability, /* gate */
tree_estimate_probability, /* execute */
NULL, /* sub */
NULL, /* next */
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