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/>. */
/* This file contains optimizer of the control flow. The main entry point is
cleanup_cfg. Following optimizations are performed:
#include "tree-pass.h"
#include "cfgloop.h"
#include "expr.h"
+#include "df.h"
+#include "dce.h"
+#include "dbgcnt.h"
#define FORWARDER_BLOCK_P(BB) ((BB)->flags & BB_FORWARDER_BLOCK)
/* Set to true when we are running first pass of try_optimize_cfg loop. */
static bool first_pass;
+
+/* Set to true if crossjumps occured in the latest run of try_optimize_cfg. */
+static bool crossjumps_occured;
+
static bool try_crossjump_to_edge (int, edge, edge);
static bool try_crossjump_bb (int, basic_block);
static bool outgoing_edges_match (int, basic_block, basic_block);
static bool try_optimize_cfg (int);
static bool try_simplify_condjump (basic_block);
static bool try_forward_edges (int, basic_block);
-static edge thread_jump (int, edge, basic_block);
+static edge thread_jump (edge, basic_block);
static bool mark_effect (rtx, bitmap);
static void notice_new_block (basic_block);
static void update_forwarder_flag (basic_block);
if exist, NULL otherwise. */
static edge
-thread_jump (int mode, edge e, basic_block b)
+thread_jump (edge e, basic_block b)
{
rtx set1, set2, cond1, cond2, insn;
enum rtx_code code1, code2, reversed_code2;
if (for_each_rtx (&cond2, mentions_nonequal_regs, nonequal))
goto failed_exit;
- /* In case liveness information is available, we need to prove equivalence
- only of the live values. */
- if (mode & CLEANUP_UPDATE_LIFE)
- AND_REG_SET (nonequal, b->il.rtl->global_live_at_end);
-
EXECUTE_IF_SET_IN_REG_SET (nonequal, 0, i, rsi)
goto failed_exit;
int counter;
bool threaded = false;
int nthreaded_edges = 0;
- bool may_thread = first_pass | (b->flags & BB_DIRTY);
+ bool may_thread = first_pass | df_get_bb_dirty (b);
/* Skip complex edges because we don't know how to update them.
{
basic_block new_target = NULL;
bool new_target_threaded = false;
- may_thread |= target->flags & BB_DIRTY;
+ may_thread |= df_get_bb_dirty (target);
if (FORWARDER_BLOCK_P (target)
&& !(single_succ_edge (target)->flags & EDGE_CROSSING)
of probabilities. */
else if ((mode & CLEANUP_THREADING) && may_thread)
{
- edge t = thread_jump (mode, e, target);
+ edge t = thread_jump (e, target);
if (t)
{
if (!threaded_edges)
merge_blocks_move_predecessor_nojumps (basic_block a, basic_block b)
{
rtx barrier;
- bool only_notes;
/* If we are partitioning hot/cold basic blocks, we don't want to
mess up unconditional or indirect jumps that cross between hot
gcc_assert (BARRIER_P (barrier));
delete_insn (barrier);
- /* Move block and loop notes out of the chain so that we do not
- disturb their order.
-
- ??? A better solution would be to squeeze out all the non-nested notes
- and adjust the block trees appropriately. Even better would be to have
- a tighter connection between block trees and rtl so that this is not
- necessary. */
- only_notes = squeeze_notes (&BB_HEAD (a), &BB_END (a));
- gcc_assert (!only_notes);
-
/* Scramble the insn chain. */
if (BB_END (a) != PREV_INSN (BB_HEAD (b)))
reorder_insns_nobb (BB_HEAD (a), BB_END (a), PREV_INSN (BB_HEAD (b)));
- a->flags |= BB_DIRTY;
+ df_set_bb_dirty (a);
if (dump_file)
fprintf (dump_file, "Moved block %d before %d and merged.\n",
{
rtx barrier, real_b_end;
rtx label, table;
- bool only_notes;
/* If we are partitioning hot/cold basic blocks, we don't want to
mess up unconditional or indirect jumps that cross between hot
if (barrier && BARRIER_P (barrier))
delete_insn (barrier);
- /* Move block and loop notes out of the chain so that we do not
- disturb their order.
-
- ??? A better solution would be to squeeze out all the non-nested notes
- and adjust the block trees appropriately. Even better would be to have
- a tighter connection between block trees and rtl so that this is not
- necessary. */
- only_notes = squeeze_notes (&BB_HEAD (b), &BB_END (b));
- gcc_assert (!only_notes);
-
/* Scramble the insn chain. */
reorder_insns_nobb (BB_HEAD (b), BB_END (b), BB_END (a));
if (REG_NOTE_KIND (note) == REG_DEAD && STACK_REG_P (XEXP (note, 0)))
SET_HARD_REG_BIT (i2_regset, REGNO (XEXP (note, 0)));
- GO_IF_HARD_REG_EQUAL (i1_regset, i2_regset, done);
-
- return false;
-
- done:
- ;
+ if (!hard_reg_set_equal_p (i1_regset, i2_regset))
+ return false;
}
#endif
return ninsns;
}
-/* Return true iff the condbranches at the end of BB1 and BB2 match. */
-bool
-condjump_equiv_p (struct equiv_info *info, bool call_init)
-{
- basic_block bb1 = info->x_block;
- basic_block bb2 = info->y_block;
- edge b1 = BRANCH_EDGE (bb1);
- edge b2 = BRANCH_EDGE (bb2);
- edge f1 = FALLTHRU_EDGE (bb1);
- edge f2 = FALLTHRU_EDGE (bb2);
- bool reverse, match;
- rtx set1, set2, cond1, cond2;
- rtx src1, src2;
- enum rtx_code code1, code2;
-
- /* Get around possible forwarders on fallthru edges. Other cases
- should be optimized out already. */
- if (FORWARDER_BLOCK_P (f1->dest))
- f1 = single_succ_edge (f1->dest);
-
- if (FORWARDER_BLOCK_P (f2->dest))
- f2 = single_succ_edge (f2->dest);
-
- /* To simplify use of this function, return false if there are
- unneeded forwarder blocks. These will get eliminated later
- during cleanup_cfg. */
- if (FORWARDER_BLOCK_P (f1->dest)
- || FORWARDER_BLOCK_P (f2->dest)
- || FORWARDER_BLOCK_P (b1->dest)
- || FORWARDER_BLOCK_P (b2->dest))
- return false;
-
- if (f1->dest == f2->dest && b1->dest == b2->dest)
- reverse = false;
- else if (f1->dest == b2->dest && b1->dest == f2->dest)
- reverse = true;
- else
- return false;
-
- set1 = pc_set (BB_END (bb1));
- set2 = pc_set (BB_END (bb2));
- if ((XEXP (SET_SRC (set1), 1) == pc_rtx)
- != (XEXP (SET_SRC (set2), 1) == pc_rtx))
- reverse = !reverse;
-
- src1 = SET_SRC (set1);
- src2 = SET_SRC (set2);
- cond1 = XEXP (src1, 0);
- cond2 = XEXP (src2, 0);
- code1 = GET_CODE (cond1);
- if (reverse)
- code2 = reversed_comparison_code (cond2, BB_END (bb2));
- else
- code2 = GET_CODE (cond2);
-
- if (code2 == UNKNOWN)
- return false;
-
- if (call_init && !struct_equiv_init (STRUCT_EQUIV_START | info->mode, info))
- gcc_unreachable ();
- /* Make the sources of the pc sets unreadable so that when we call
- insns_match_p it won't process them.
- The death_notes_match_p from insns_match_p won't see the local registers
- used for the pc set, but that could only cause missed optimizations when
- there are actually condjumps that use stack registers. */
- SET_SRC (set1) = pc_rtx;
- SET_SRC (set2) = pc_rtx;
- /* Verify codes and operands match. */
- if (code1 == code2)
- {
- match = (insns_match_p (BB_END (bb1), BB_END (bb2), info)
- && rtx_equiv_p (&XEXP (cond1, 0), XEXP (cond2, 0), 1, info)
- && rtx_equiv_p (&XEXP (cond1, 1), XEXP (cond2, 1), 1, info));
-
- }
- else if (code1 == swap_condition (code2))
- {
- match = (insns_match_p (BB_END (bb1), BB_END (bb2), info)
- && rtx_equiv_p (&XEXP (cond1, 1), XEXP (cond2, 0), 1, info)
- && rtx_equiv_p (&XEXP (cond1, 0), XEXP (cond2, 1), 1, info));
-
- }
- else
- match = false;
- SET_SRC (set1) = src1;
- SET_SRC (set2) = src2;
- match &= verify_changes (0);
-
- /* If we return true, we will join the blocks. Which means that
- we will only have one branch prediction bit to work with. Thus
- we require the existing branches to have probabilities that are
- roughly similar. */
- if (match
- && !optimize_size
- && maybe_hot_bb_p (bb1)
- && maybe_hot_bb_p (bb2))
- {
- int prob2;
-
- if (b1->dest == b2->dest)
- prob2 = b2->probability;
- else
- /* Do not use f2 probability as f2 may be forwarded. */
- prob2 = REG_BR_PROB_BASE - b2->probability;
-
- /* Fail if the difference in probabilities is greater than 50%.
- This rules out two well-predicted branches with opposite
- outcomes. */
- if (abs (b1->probability - prob2) > REG_BR_PROB_BASE / 2)
- {
- if (dump_file)
- fprintf (dump_file,
- "Outcomes of branch in bb %i and %i differ too much (%i %i)\n",
- bb1->index, bb2->index, b1->probability, prob2);
-
- match = false;
- }
- }
-
- if (dump_file && match)
- fprintf (dump_file, "Conditionals in bb %i and %i match.\n",
- bb1->index, bb2->index);
-
- if (!match)
- cancel_changes (0);
- return match;
-}
-
/* Return true iff outgoing edges of BB1 and BB2 match, together with
the branch instruction. This means that if we commonize the control
flow before end of the basic block, the semantic remains unchanged.
partition boundaries). See the comments at the top of
bb-reorder.c:partition_hot_cold_basic_blocks for complete details. */
- if (flag_reorder_blocks_and_partition && no_new_pseudos)
+ if (flag_reorder_blocks_and_partition && reload_completed)
return false;
/* Search backward through forwarder blocks. We don't need to worry
"Cross jumping from bb %i to bb %i; %i common insns\n",
src1->index, src2->index, nmatch);
- redirect_to->count += src1->count;
- redirect_to->frequency += src1->frequency;
/* We may have some registers visible through the block. */
- redirect_to->flags |= BB_DIRTY;
+ df_set_bb_dirty (redirect_to);
/* Recompute the frequencies and counts of outgoing edges. */
FOR_EACH_EDGE (s, ei, redirect_to->succs)
/ (redirect_to->frequency + src1->frequency));
}
+ /* Adjust count and frequency for the block. An earlier jump
+ threading pass may have left the profile in an inconsistent
+ state (see update_bb_profile_for_threading) so we must be
+ prepared for overflows. */
+ redirect_to->count += src1->count;
+ redirect_to->frequency += src1->frequency;
+ if (redirect_to->frequency > BB_FREQ_MAX)
+ redirect_to->frequency = BB_FREQ_MAX;
update_br_prob_note (redirect_to);
/* Edit SRC1 to go to REDIRECT_TO at NEWPOS1. */
FOR_EACH_EDGE (e, ei, bb->preds)
{
if (e->flags & EDGE_FALLTHRU)
- fallthru = e;
+ {
+ fallthru = e;
+ break;
+ }
}
changed = false;
e = EDGE_PRED (ev, ix);
ix++;
- /* As noted above, first try with the fallthru predecessor. */
+ /* As noted above, first try with the fallthru predecessor (or, a
+ fallthru predecessor if we are in cfglayout mode). */
if (fallthru)
{
/* Don't combine the fallthru edge into anything else.
/* If nothing changed since the last attempt, there is nothing
we can do. */
if (!first_pass
- && (!(e->src->flags & BB_DIRTY)
- && !(fallthru->src->flags & BB_DIRTY)))
+ && (!(df_get_bb_dirty (e->src))
+ && !(df_get_bb_dirty (fallthru->src))))
continue;
if (try_crossjump_to_edge (mode, e, fallthru))
/* If nothing changed since the last attempt, there is nothing
we can do. */
if (!first_pass
- && (!(e->src->flags & BB_DIRTY)
- && !(e2->src->flags & BB_DIRTY)))
+ && (!(df_get_bb_dirty (e->src))
+ && !(df_get_bb_dirty (e2->src))))
continue;
if (try_crossjump_to_edge (mode, e, e2))
}
}
+ if (changed)
+ crossjumps_occured = true;
+
return changed;
}
int iterations = 0;
basic_block bb, b, next;
- if (mode & CLEANUP_CROSSJUMP)
- add_noreturn_fake_exit_edges ();
-
- if (mode & (CLEANUP_UPDATE_LIFE | CLEANUP_CROSSJUMP | CLEANUP_THREADING))
+ if (mode & (CLEANUP_CROSSJUMP | CLEANUP_THREADING))
clear_bb_flags ();
+ crossjumps_occured = false;
+
FOR_EACH_BB (bb)
update_forwarder_flag (bb);
{
rtx label = BB_HEAD (b);
- delete_insn_chain (label, label);
- /* In the case label is undeletable, move it after the
+ delete_insn_chain (label, label, false);
+ /* If the case label is undeletable, move it after the
BASIC_BLOCK note. */
- if (NOTE_LINE_NUMBER (BB_HEAD (b)) == NOTE_INSN_DELETED_LABEL)
+ if (NOTE_KIND (BB_HEAD (b)) == NOTE_INSN_DELETED_LABEL)
{
rtx bb_note = NEXT_INSN (BB_HEAD (b));
reorder_insns_nobb (label, label, bb_note);
BB_HEAD (b) = bb_note;
+ if (BB_END (b) == bb_note)
+ BB_END (b) = label;
}
if (dump_file)
fprintf (dump_file, "Deleted label in block %i.\n",
while (changed);
}
- if (mode & CLEANUP_CROSSJUMP)
- remove_fake_exit_edges ();
-
FOR_ALL_BB (b)
b->flags &= ~(BB_FORWARDER_BLOCK | BB_NONTHREADABLE_BLOCK);
return changed;
}
-/* Merges sequential blocks if possible. */
-
-bool
-merge_seq_blocks (void)
+/* Delete any jump tables never referenced. We can't delete them at the
+ time of removing tablejump insn as they are referenced by the preceding
+ insns computing the destination, so we delay deleting and garbagecollect
+ them once life information is computed. */
+void
+delete_dead_jumptables (void)
{
basic_block bb;
- bool changed = false;
- for (bb = ENTRY_BLOCK_PTR->next_bb; bb != EXIT_BLOCK_PTR; )
+ /* A dead jump table does not belong to any basic block. Scan insns
+ between two adjacent basic blocks. */
+ FOR_EACH_BB (bb)
{
- if (single_succ_p (bb)
- && can_merge_blocks_p (bb, single_succ (bb)))
+ rtx insn, next;
+
+ for (insn = NEXT_INSN (BB_END (bb));
+ insn && !NOTE_INSN_BASIC_BLOCK_P (insn);
+ insn = next)
{
- /* Merge the blocks and retry. */
- merge_blocks (bb, single_succ (bb));
- changed = true;
- continue;
- }
+ next = NEXT_INSN (insn);
+ if (LABEL_P (insn)
+ && LABEL_NUSES (insn) == LABEL_PRESERVE_P (insn)
+ && JUMP_P (next)
+ && (GET_CODE (PATTERN (next)) == ADDR_VEC
+ || GET_CODE (PATTERN (next)) == ADDR_DIFF_VEC))
+ {
+ rtx label = insn, jump = next;
- bb = bb->next_bb;
- }
+ if (dump_file)
+ fprintf (dump_file, "Dead jumptable %i removed\n",
+ INSN_UID (insn));
- return changed;
+ next = NEXT_INSN (next);
+ delete_insn (jump);
+ delete_insn (label);
+ }
+ }
+ }
}
+
\f
/* Tidy the CFG by deleting unreachable code and whatnot. */
changed = true;
/* We've possibly created trivially dead code. Cleanup it right
now to introduce more opportunities for try_optimize_cfg. */
- if (!(mode & (CLEANUP_NO_INSN_DEL | CLEANUP_UPDATE_LIFE))
+ if (!(mode & (CLEANUP_NO_INSN_DEL))
&& !reload_completed)
delete_trivially_dead_insns (get_insns (), max_reg_num ());
}
compact_blocks ();
+ /* To tail-merge blocks ending in the same noreturn function (e.g.
+ a call to abort) we have to insert fake edges to exit. Do this
+ here once. The fake edges do not interfere with any other CFG
+ cleanups. */
+ if (mode & CLEANUP_CROSSJUMP)
+ add_noreturn_fake_exit_edges ();
+
+ if (!dbg_cnt (cfg_cleanup))
+ return changed;
+
while (try_optimize_cfg (mode))
{
delete_unreachable_blocks (), changed = true;
- if (mode & CLEANUP_UPDATE_LIFE)
- {
- /* Cleaning up CFG introduces more opportunities for dead code
- removal that in turn may introduce more opportunities for
- cleaning up the CFG. */
- if (!update_life_info_in_dirty_blocks (UPDATE_LIFE_GLOBAL_RM_NOTES,
- PROP_DEATH_NOTES
- | PROP_SCAN_DEAD_CODE
- | PROP_KILL_DEAD_CODE
- | ((mode & CLEANUP_LOG_LINKS)
- ? PROP_LOG_LINKS : 0)))
- break;
- }
- else if (!(mode & CLEANUP_NO_INSN_DEL)
- && (mode & CLEANUP_EXPENSIVE)
- && !reload_completed)
+ if (!(mode & CLEANUP_NO_INSN_DEL))
{
- if (!delete_trivially_dead_insns (get_insns (), max_reg_num ()))
+ /* Try to remove some trivially dead insns when doing an expensive
+ cleanup. But delete_trivially_dead_insns doesn't work after
+ reload (it only handles pseudos) and run_fast_dce is too costly
+ to run in every iteration.
+
+ For effective cross jumping, we really want to run a fast DCE to
+ clean up any dead conditions, or they get in the way of performing
+ useful tail merges.
+
+ Other transformations in cleanup_cfg are not so sensitive to dead
+ code, so delete_trivially_dead_insns or even doing nothing at all
+ is good enough. */
+ if ((mode & CLEANUP_EXPENSIVE) && !reload_completed
+ && !delete_trivially_dead_insns (get_insns (), max_reg_num ()))
break;
+ else if ((mode & CLEANUP_CROSSJUMP)
+ && crossjumps_occured)
+ run_fast_dce ();
}
else
break;
-
- /* Don't call delete_dead_jumptables in cfglayout mode, because
- that function assumes that jump tables are in the insns stream.
- But we also don't _have_ to delete dead jumptables in cfglayout
- mode because we shouldn't even be looking at things that are
- not in a basic block. Dead jumptables are cleaned up when
- going out of cfglayout mode. */
- if (!(mode & CLEANUP_CFGLAYOUT))
- delete_dead_jumptables ();
}
+ if (mode & CLEANUP_CROSSJUMP)
+ remove_fake_exit_edges ();
+
+ /* Don't call delete_dead_jumptables in cfglayout mode, because
+ that function assumes that jump tables are in the insns stream.
+ But we also don't _have_ to delete dead jumptables in cfglayout
+ mode because we shouldn't even be looking at things that are
+ not in a basic block. Dead jumptables are cleaned up when
+ going out of cfglayout mode. */
+ if (!(mode & CLEANUP_CFGLAYOUT))
+ delete_dead_jumptables ();
+
timevar_pop (TV_CLEANUP_CFG);
return changed;
{
delete_unreachable_blocks ();
- if (cfun->tail_call_emit)
+ if (crtl->tail_call_emit)
fixup_tail_calls ();
return 0;
}
-struct tree_opt_pass pass_jump =
+struct rtl_opt_pass pass_jump =
{
+ {
+ RTL_PASS,
"sibling", /* name */
NULL, /* gate */
rest_of_handle_jump, /* execute */
0, /* properties_provided */
0, /* properties_destroyed */
TODO_ggc_collect, /* todo_flags_start */
- TODO_dump_func |
TODO_verify_flow, /* todo_flags_finish */
- 'i' /* letter */
+ }
};
rest_of_handle_jump2 (void)
{
delete_trivially_dead_insns (get_insns (), max_reg_num ());
- reg_scan (get_insns (), max_reg_num ());
if (dump_file)
dump_flow_info (dump_file, dump_flags);
cleanup_cfg ((optimize ? CLEANUP_EXPENSIVE : 0)
}
-struct tree_opt_pass pass_jump2 =
+struct rtl_opt_pass pass_jump2 =
{
+ {
+ RTL_PASS,
"jump", /* name */
NULL, /* gate */
rest_of_handle_jump2, /* execute */
0, /* properties_provided */
0, /* properties_destroyed */
TODO_ggc_collect, /* todo_flags_start */
- TODO_dump_func, /* todo_flags_finish */
- 'j' /* letter */
+ TODO_dump_func | TODO_verify_rtl_sharing,/* todo_flags_finish */
+ }
};
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