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 compute_function_frequency (void);
static void choose_function_section (void);
static bool can_predict_insn_p (rtx);
+static void estimate_bb_frequencies (void);
/* Information we hold about each branch predictor.
Filled using information from predict.def. */
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 (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)
{
}
}
-/* 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;
- 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 (i = 1; i < current_loops->num; i++)
{
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;
+ struct loop *loop = current_loops->parray[i];
+ 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);
+ tree niter = NULL;
- if (desc.simple_p && desc.const_iter)
- {
- int prob;
- niter = desc.niter + 1;
- if (niter == 0) /* We might overflow here. */
- niter = desc.niter;
- if (niter
- > (unsigned int) PARAM_VALUE (PARAM_MAX_PREDICTED_ITERATIONS))
- niter = PARAM_VALUE (PARAM_MAX_PREDICTED_ITERATIONS);
-
- 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);
- }
- }
- else
- {
- struct tree_niter_desc niter_desc;
+ 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);
- for (j = 0; j < n_exits; j++)
+ if (TREE_CODE (niter) == INTEGER_CST)
{
- tree niter = NULL;
-
- if (number_of_iterations_exit (loop, exits[j], &niter_desc, false))
- 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;
+ int max = PARAM_VALUE (PARAM_MAX_PREDICTED_ITERATIONS);
+ if (host_integerp (niter, 1)
+ && tree_int_cst_lt (niter,
+ build_int_cstu (NULL_TREE, max - 1)))
{
- int probability;
- int max = PARAM_VALUE (PARAM_MAX_PREDICTED_ITERATIONS);
- if (host_integerp (niter, 1)
- && tree_int_cst_lt (niter,
- build_int_cstu (NULL_TREE, max - 1)))
- {
- HOST_WIDE_INT nitercst = tree_low_cst (niter, 1) + 1;
- probability = ((REG_BR_PROB_BASE + nitercst / 2)
- / nitercst);
- }
- else
- probability = ((REG_BR_PROB_BASE + max / 2) / max);
-
- predict_edge (exits[j], PRED_LOOP_ITERATIONS, probability);
+ HOST_WIDE_INT nitercst = tree_low_cst (niter, 1) + 1;
+ probability = ((REG_BR_PROB_BASE + nitercst / 2)
+ / nitercst);
}
- }
+ else
+ probability = ((REG_BR_PROB_BASE + max / 2) / max);
+ predict_edge (ex, PRED_LOOP_ITERATIONS, 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 < NUM_FIXED_BLOCKS
- || !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);
+ {
+ /* 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)
{
tree fndecl;
tree arglist;
- 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
+ && TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == CALL_EXPR
+ && (fndecl = get_callee_fndecl (GIMPLE_STMT_OPERAND (stmt, 1)))
&& DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL
&& DECL_FUNCTION_CODE (fndecl) == BUILT_IN_EXPECT
- && (arglist = TREE_OPERAND (TREE_OPERAND (stmt, 1), 1))
+ && (arglist = TREE_OPERAND (GIMPLE_STMT_OPERAND (stmt, 1), 1))
&& TREE_CHAIN (arglist))
{
- TREE_OPERAND (stmt, 1) = TREE_VALUE (arglist);
+ GIMPLE_STMT_OPERAND (stmt, 1) = TREE_VALUE (arglist);
update_stmt (stmt);
}
}
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)
basic_block bb;
int *heads;
- heads = XNEWVEC (int, last_basic_block);
- memset (heads, ENTRY_BLOCK, 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);
tree stmt = bsi_stmt (bsi);
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;
}
/* 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);
- 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 ();
tree_bb_level_predictions ();
- mark_irreducible_loops (&loops_info);
- predict_loops (&loops_info, false);
+ mark_irreducible_loops ();
+ 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. */
+ fast paths through function. */
if (e->dest == EXIT_BLOCK_PTR
&& TREE_CODE (last_stmt (bb)) == RETURN_EXPR
&& !single_pred_p (bb))
{
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))
combine_predictions_for_bb (bb);
strip_builtin_expect ();
- estimate_bb_frequencies (&loops_info);
+ 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;
-}
-\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. */
- gcc_assert (cond == const_true_rtx || cond == const0_rtx);
- predict_insn_def (insn, PRED_BUILTIN_EXPECT,
- cond == const_true_rtx ? TAKEN : NOT_TAKEN);
- }
+ return 0;
}
\f
/* Check whether this is the last basic block of function. Commonly
#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;
/* 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 (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.
/* Estimate basic blocks frequency by given branch probabilities. */
static void
-estimate_bb_frequencies (struct loops *loops)
+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)
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