/* Basic block reordering routines for the GNU compiler.
Copyright (C) 2000 Free Software Foundation, Inc.
- This file is part of GNU CC.
+ This file is part of GCC.
- GNU CC is free software; you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
+ 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 version.
- GNU CC is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
+ GCC is distributed in the hope that it will be useful, but WITHOUT
+ ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
+ License for more details.
You should have received a copy of the GNU General Public License
- along with GNU CC; see the file COPYING. If not, write to
- the Free Software Foundation, 59 Temple Place - Suite 330,
- Boston, MA 02111-1307, USA. */
+ 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. */
/* References:
"Profile Guided Code Positioning"
Pettis and Hanson; PLDI '90.
+
+ TODO:
+
+ (1) Consider:
+
+ if (p) goto A; // predict taken
+ foo ();
+ A:
+ if (q) goto B; // predict taken
+ bar ();
+ B:
+ baz ();
+ return;
+
+ We'll currently reorder this as
+
+ if (!p) goto C;
+ A:
+ if (!q) goto D;
+ B:
+ baz ();
+ return;
+ D:
+ bar ();
+ goto B;
+ C:
+ foo ();
+ goto A;
+
+ A better ordering is
+
+ if (!p) goto C;
+ if (!q) goto D;
+ B:
+ baz ();
+ return;
+ C:
+ foo ();
+ if (q) goto B;
+ D:
+ bar ();
+ goto B;
+
+ This requires that we be able to duplicate the jump at A, and
+ adjust the graph traversal such that greedy placement doesn't
+ fix D before C is considered.
+
+ (2) Coordinate with shorten_branches to minimize the number of
+ long branches.
+
+ (3) Invent a method by which sufficiently non-predicted code can
+ be moved to either the end of the section or another section
+ entirely. Some sort of NOTE_INSN note would work fine.
+
+ This completely scroggs all debugging formats, so the user
+ would have to explicitly ask for it.
*/
#include "config.h"
#include "system.h"
#include "tree.h"
#include "rtl.h"
-#include "tm_p.h"
-#include "basic-block.h"
-#include "insn-config.h"
-#include "regs.h"
#include "hard-reg-set.h"
+#include "basic-block.h"
#include "flags.h"
#include "output.h"
-#include "function.h"
-#include "except.h"
-#include "toplev.h"
-#include "recog.h"
-#include "insn-flags.h"
-#include "expr.h"
-#include "obstack.h"
-
-
-/* The contents of the current function definition are allocated
- in this obstack, and all are freed at the end of the function.
- For top-level functions, this is temporary_obstack.
- Separate obstacks are made for nested functions. */
-
-extern struct obstack *function_obstack;
-
-
-typedef struct reorder_block_def {
- int flags;
- int index;
- basic_block add_jump;
- edge succ;
- rtx end;
- int block_begin;
- int block_end;
- rtx eff_head;
- rtx eff_end;
-} *reorder_block_def;
-
-static struct reorder_block_def rbd_init
-= {
- 0, /* flags */
- 0, /* index */
- NULL, /* add_jump */
- NULL, /* succ */
- NULL_RTX, /* end */
- 0, /* block_begin */
- 0, /* block_end */
- NULL_RTX, /* eff_head */
- NULL_RTX /* eff_end */
-};
-
-
-#define REORDER_BLOCK_HEAD 0x1
-#define REORDER_BLOCK_VISITED 0x2
-
-#define REORDER_BLOCK_FLAGS(bb) \
- ((reorder_block_def) (bb)->aux)->flags
-
-#define REORDER_BLOCK_INDEX(bb) \
- ((reorder_block_def) (bb)->aux)->index
-
-#define REORDER_BLOCK_ADD_JUMP(bb) \
- ((reorder_block_def) (bb)->aux)->add_jump
+#include "cfglayout.h"
-#define REORDER_BLOCK_SUCC(bb) \
- ((reorder_block_def) (bb)->aux)->succ
-
-#define REORDER_BLOCK_OLD_END(bb) \
- ((reorder_block_def) (bb)->aux)->end
-
-#define REORDER_BLOCK_BEGIN(bb) \
- ((reorder_block_def) (bb)->aux)->block_begin
-
-#define REORDER_BLOCK_END(bb) \
- ((reorder_block_def) (bb)->aux)->block_end
-
-#define REORDER_BLOCK_EFF_HEAD(bb) \
- ((reorder_block_def) (bb)->aux)->eff_head
-
-#define REORDER_BLOCK_EFF_END(bb) \
- ((reorder_block_def) (bb)->aux)->eff_end
-
-
-static int reorder_index;
-static basic_block reorder_last_visited;
-
-enum reorder_skip_type {REORDER_SKIP_BEFORE, REORDER_SKIP_AFTER,
- REORDER_SKIP_BLOCK_END};
-
-
-/* Local function prototypes. */
-static rtx skip_insns_between_block PARAMS ((basic_block,
- enum reorder_skip_type));
-static basic_block get_common_dest PARAMS ((basic_block, basic_block));
-static basic_block chain_reorder_blocks PARAMS ((edge, basic_block));
-static void make_reorder_chain PARAMS ((basic_block));
-static void fixup_reorder_chain PARAMS ((void));
-#ifdef ENABLE_CHECKING
-static void verify_insn_chain PARAMS ((void));
+#ifndef HAVE_epilogue
+#define HAVE_epilogue 0
#endif
-/* Skip over insns BEFORE or AFTER BB which are typically associated with
- basic block BB. */
+/* Local function prototypes. */
+static void make_reorder_chain PARAMS ((void));
+static basic_block make_reorder_chain_1 PARAMS ((basic_block, basic_block));
+\f
+/* Compute an ordering for a subgraph beginning with block BB. Record the
+ ordering in RBI()->index and chained through RBI()->next. */
-static rtx
-skip_insns_between_block (bb, skip_type)
- basic_block bb;
- enum reorder_skip_type skip_type;
+static void
+make_reorder_chain ()
{
- rtx insn, last_insn;
+ basic_block last_block = NULL;
+ basic_block prev = NULL;
+ int nbb_m1 = n_basic_blocks - 1;
+ basic_block next;
- if (skip_type == REORDER_SKIP_BEFORE)
+ /* If we've not got epilogue in RTL, we must fallthru to the exit.
+ Force the last block to be at the end. */
+ /* ??? Some ABIs (e.g. MIPS) require the return insn to be at the
+ end of the function for stack unwinding purposes. */
+ if (! HAVE_epilogue)
{
- if (bb == ENTRY_BLOCK_PTR)
- return 0;
-
- last_insn = bb->head;
- for (insn = PREV_INSN (bb->head);
- insn && insn != BASIC_BLOCK (bb->index - 1)->end;
- last_insn = insn, insn = PREV_INSN (insn))
- {
- if (NEXT_INSN (insn) != last_insn)
- break;
-
- if (GET_CODE (insn) == NOTE
- && NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_END
- && NOTE_LINE_NUMBER (insn) != NOTE_INSN_BASIC_BLOCK
- && NOTE_LINE_NUMBER (insn) != NOTE_INSN_BLOCK_END)
- continue;
-
- break;
- }
+ last_block = BASIC_BLOCK (nbb_m1);
+ RBI (last_block)->visited = 1;
+ nbb_m1 -= 1;
}
- else
+
+ /* Loop until we've placed every block. */
+ do
{
- last_insn = bb->end;
+ int i;
- if (bb == EXIT_BLOCK_PTR)
- return 0;
+ next = NULL;
- for (insn = NEXT_INSN (bb->end);
- insn;
- last_insn = insn, insn = NEXT_INSN (insn))
- {
- if (bb->index + 1 != n_basic_blocks
- && insn == BASIC_BLOCK (bb->index + 1)->head)
- break;
+ /* Find the next unplaced block. */
+ /* ??? Get rid of this loop, and track which blocks are not yet
+ placed more directly, so as to avoid the O(N^2) worst case.
+ Perhaps keep a doubly-linked list of all to-be-placed blocks;
+ remove from the list as we place. The head of that list is
+ what we're looking for here. */
- if (GET_CODE (insn) == BARRIER
- || GET_CODE (insn) == JUMP_INSN
- || (GET_CODE (insn) == NOTE
- && (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END
- || NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END)))
- continue;
-
- if (GET_CODE (insn) == CODE_LABEL
- && GET_CODE (NEXT_INSN (insn)) == JUMP_INSN
- && (GET_CODE (PATTERN (NEXT_INSN (insn))) == ADDR_VEC
- || GET_CODE (PATTERN
- (NEXT_INSN (insn))) == ADDR_DIFF_VEC))
- {
- insn = NEXT_INSN (insn);
- continue;
- }
-
- /* Skip to next non-deleted insn. */
- if (GET_CODE (insn) == NOTE
- && (NOTE_LINE_NUMBER (insn) == NOTE_INSN_DELETED
- || NOTE_LINE_NUMBER (insn) == NOTE_INSN_DELETED_LABEL))
- continue;
-
- break;
- }
-
- if (skip_type == REORDER_SKIP_BLOCK_END)
+ for (i = 0; i <= nbb_m1 && !next; ++i)
{
- int found_block_end = 0;
-
- for (; insn; last_insn = insn, insn = NEXT_INSN (insn))
- {
- if (bb->index + 1 != n_basic_blocks
- && insn == BASIC_BLOCK (bb->index + 1)->head)
- break;
-
- if (GET_CODE (insn) == NOTE
- && NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END)
- {
- found_block_end = 1;
- continue;
- }
-
- if (GET_CODE (insn) == NOTE
- && NOTE_LINE_NUMBER (insn) == NOTE_INSN_DELETED)
- continue;
-
- if (GET_CODE (insn) == NOTE
- && NOTE_LINE_NUMBER (insn) >= 0
- && NEXT_INSN (insn)
- && GET_CODE (NEXT_INSN (insn)) == NOTE
- && (NOTE_LINE_NUMBER (NEXT_INSN (insn))
- == NOTE_INSN_BLOCK_END))
- continue;
- break;
- }
-
- if (! found_block_end)
- last_insn = 0;
+ basic_block bb = BASIC_BLOCK (i);
+ if (! RBI (bb)->visited)
+ next = bb;
}
+ if (next)
+ prev = make_reorder_chain_1 (next, prev);
}
+ while (next);
- return last_insn;
-}
-
-
-/* Return common destination for blocks BB0 and BB1. */
-
-static basic_block
-get_common_dest (bb0, bb1)
- basic_block bb0, bb1;
-{
- edge e0, e1;
-
- for (e0 = bb0->succ; e0; e0 = e0->succ_next)
+ /* Terminate the chain. */
+ if (! HAVE_epilogue)
{
- for (e1 = bb1->succ; e1; e1 = e1->succ_next)
- {
- if (e0->dest == e1->dest)
- {
- return e0->dest;
- }
- }
+ RBI (prev)->next = last_block;
+ prev = last_block;
}
- return 0;
+ RBI (prev)->next = NULL;
}
+/* A helper function for make_reorder_chain.
+
+ We do not follow EH edges, or non-fallthru edges to noreturn blocks.
+ These are assumed to be the error condition and we wish to cluster
+ all of them at the very end of the function for the benefit of cache
+ locality for the rest of the function.
-/* Move the destination block for edge E after chain end block CEB
- Adding jumps and labels is deferred until fixup_reorder_chain. */
+ ??? We could do slightly better by noticing earlier that some subgraph
+ has all paths leading to noreturn functions, but for there to be more
+ than one block in such a subgraph is rare. */
static basic_block
-chain_reorder_blocks (e, ceb)
- edge e;
- basic_block ceb;
+make_reorder_chain_1 (bb, prev)
+ basic_block bb;
+ basic_block prev;
{
- basic_block sb = e->src;
- basic_block db = e->dest;
- rtx cebe_insn, cebbe_insn, dbh_insn, dbe_insn;
- edge ee, last_edge;
-
- enum cond_types {NO_COND, PREDICT_THEN_WITH_ELSE, PREDICT_ELSE,
- PREDICT_THEN_NO_ELSE, PREDICT_NOT_THEN_NO_ELSE};
- enum cond_types cond_type;
- enum cond_block_types {NO_COND_BLOCK, THEN_BLOCK, ELSE_BLOCK,
- NO_ELSE_BLOCK};
- enum cond_block_types cond_block_type;
-
- if (rtl_dump_file)
- fprintf (rtl_dump_file,
- "Edge from basic block %d to basic block %d last visited %d\n",
- sb->index, db->index, ceb->index);
-
- dbh_insn = REORDER_BLOCK_EFF_HEAD (db);
- cebe_insn = REORDER_BLOCK_EFF_END (ceb);
- cebbe_insn = skip_insns_between_block (ceb, REORDER_SKIP_BLOCK_END);
-
- {
- int block_begins = 0;
- rtx insn;
-
- for (insn = dbh_insn; insn && insn != db->end; insn = NEXT_INSN (insn))
- {
- if (GET_CODE (insn) == NOTE
- && NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_BEG)
- {
- block_begins += 1;
- break;
- }
- }
- REORDER_BLOCK_BEGIN (sb) = block_begins;
- }
+ edge e;
+ basic_block next;
+ rtx note;
- if (cebbe_insn)
+ /* Mark this block visited. */
+ if (prev)
{
- int block_ends = 0;
- rtx insn;
+ restart:
+ RBI (prev)->next = bb;
- for (insn = cebe_insn; insn; insn = NEXT_INSN (insn))
- {
- if (PREV_INSN (insn) == cebbe_insn)
- break;
- if (GET_CODE (insn) == NOTE
- && NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END)
- {
- block_ends += 1;
- continue;
- }
- }
- REORDER_BLOCK_END (ceb) = block_ends;
+ if (rtl_dump_file && prev->index + 1 != bb->index)
+ fprintf (rtl_dump_file, "Reordering block %d after %d\n",
+ bb->index, prev->index);
}
-
- /* Blocks are in original order. */
- if (sb->index == ceb->index
- && ceb->index + 1 == db->index && NEXT_INSN (cebe_insn))
- return db;
-
- /* Get the type of block and type of condition. */
- cond_type = NO_COND;
- cond_block_type = NO_COND_BLOCK;
- if (GET_CODE (sb->end) == JUMP_INSN && ! simplejump_p (sb->end)
- && condjump_p (sb->end))
- {
- if (e->flags & EDGE_FALLTHRU)
- cond_block_type = THEN_BLOCK;
- else if (get_common_dest (sb->succ->dest, sb))
- cond_block_type = NO_ELSE_BLOCK;
- else
- cond_block_type = ELSE_BLOCK;
-
- if (sb->succ->succ_next
- && get_common_dest (sb->succ->dest, sb))
- {
- if (cond_block_type == THEN_BLOCK)
- {
- if (! (REORDER_BLOCK_FLAGS (sb->succ->succ_next->dest)
- & REORDER_BLOCK_VISITED))
- cond_type = PREDICT_THEN_NO_ELSE;
- else
- cond_type = PREDICT_NOT_THEN_NO_ELSE;
- }
- else if (cond_block_type == NO_ELSE_BLOCK)
- {
- if (! (REORDER_BLOCK_FLAGS (sb->succ->dest)
- & REORDER_BLOCK_VISITED))
- cond_type = PREDICT_NOT_THEN_NO_ELSE;
- else
- cond_type = PREDICT_THEN_NO_ELSE;
- }
- }
- else
- {
- if (cond_block_type == THEN_BLOCK)
- {
- if (! (REORDER_BLOCK_FLAGS (sb->succ->succ_next->dest)
- & REORDER_BLOCK_VISITED))
- cond_type = PREDICT_THEN_WITH_ELSE;
- else
- cond_type = PREDICT_ELSE;
- }
- else if (cond_block_type == ELSE_BLOCK
- && sb->succ->dest != EXIT_BLOCK_PTR)
- {
- if (! (REORDER_BLOCK_FLAGS (sb->succ->dest)
- & REORDER_BLOCK_VISITED))
- cond_type = PREDICT_ELSE;
- else
- cond_type = PREDICT_THEN_WITH_ELSE;
- }
- }
- }
-
- if (rtl_dump_file)
+ else
{
- static const char * cond_type_str [] = {"not cond jump", "predict then",
- "predict else",
- "predict then w/o else",
- "predict not then w/o else"};
- static const char * cond_block_type_str [] = {"not then or else block",
- "then block",
- "else block",
- "then w/o else block"};
-
- fprintf (rtl_dump_file, " %s (looking at %s)\n",
- cond_type_str[(int)cond_type],
- cond_block_type_str[(int)cond_block_type]);
+ if (bb->index != 0)
+ abort ();
}
+ RBI (bb)->visited = 1;
+ prev = bb;
- /* Reflect that then block will move and we'll jump to it. */
- if (cond_block_type != THEN_BLOCK
- && (cond_type == PREDICT_ELSE
- || cond_type == PREDICT_NOT_THEN_NO_ELSE))
- {
- if (rtl_dump_file)
- fprintf (rtl_dump_file,
- " then jump from block %d to block %d\n",
- sb->index, sb->succ->dest->index);
-
- /* Jump to reordered then block. */
- REORDER_BLOCK_ADD_JUMP (sb) = sb->succ->dest;
- }
-
- /* Reflect that then block will jump back when we have no else. */
- if (cond_block_type != THEN_BLOCK
- && cond_type == PREDICT_NOT_THEN_NO_ELSE)
- {
- for (ee = sb->succ->dest->succ;
- ee && ! (ee->flags & EDGE_FALLTHRU);
- ee = ee->succ_next)
- continue;
+ if (bb->succ == NULL)
+ return prev;
- if (ee && ! (GET_CODE (sb->succ->dest->end) == JUMP_INSN
- && ! simplejump_p (sb->succ->dest->end)))
- {
- REORDER_BLOCK_ADD_JUMP (sb->succ->dest) = ee->dest;
- }
- }
+ /* Find the most probable block. */
- /* Reflect that else block will jump back. */
- if (cond_block_type == ELSE_BLOCK
- && (cond_type == PREDICT_THEN_WITH_ELSE || cond_type == PREDICT_ELSE))
+ next = NULL;
+ if (any_condjump_p (bb->end)
+ && (note = find_reg_note (bb->end, REG_BR_PROB, 0)) != NULL)
{
- last_edge=db->succ;
+ int taken, probability;
+ edge e_taken, e_fall;
- if (last_edge
- && last_edge->dest != EXIT_BLOCK_PTR
- && GET_CODE (last_edge->dest->head) == CODE_LABEL
- && ! (GET_CODE (db->end) == JUMP_INSN))
- {
- if (rtl_dump_file)
- fprintf (rtl_dump_file,
- " else jump from block %d to block %d\n",
- db->index, last_edge->dest->index);
+ probability = INTVAL (XEXP (note, 0));
+ taken = probability > REG_BR_PROB_BASE / 2;
- REORDER_BLOCK_ADD_JUMP (db) = last_edge->dest;
- }
- }
-
- /* This block's successor has already been reordered. This can happen
- when we reorder a chain starting at a then or else. */
- for (last_edge = db->succ;
- last_edge && ! (last_edge->flags & EDGE_FALLTHRU);
- last_edge = last_edge->succ_next)
- continue;
-
- if (last_edge
- && last_edge->dest != EXIT_BLOCK_PTR
- && (REORDER_BLOCK_FLAGS (last_edge->dest)
- & REORDER_BLOCK_VISITED))
- {
- if (rtl_dump_file)
- fprintf (rtl_dump_file,
- " end of chain jump from block %d to block %d\n",
- db->index, last_edge->dest->index);
+ /* Find the normal taken edge and the normal fallthru edge.
- REORDER_BLOCK_ADD_JUMP (db) = last_edge->dest;
- }
+ Note, conditional jumps with other side effects may not
+ be fully optimized. In this case it is possible for
+ the conditional jump to branch to the same location as
+ the fallthru path.
- dbh_insn = REORDER_BLOCK_EFF_HEAD (db);
- cebe_insn = REORDER_BLOCK_EFF_END (ceb);
- dbe_insn = REORDER_BLOCK_EFF_END (db);
+ We should probably work to improve optimization of that
+ case; however, it seems silly not to also deal with such
+ problems here if they happen to occur. */
- /* Leave behind any lexical block markers. */
- if (debug_info_level > DINFO_LEVEL_TERSE
- && ceb->index + 1 < db->index)
- {
- rtx insn, last_insn = get_last_insn ();
- insn = NEXT_INSN (ceb->end);
- if (! insn)
- insn = REORDER_BLOCK_OLD_END (ceb);
-
- if (NEXT_INSN (cebe_insn) == 0)
- set_last_insn (cebe_insn);
- for (; insn && insn != db->head/*dbh_insn*/;
- insn = NEXT_INSN (insn))
+ e_taken = e_fall = NULL;
+ for (e = bb->succ; e ; e = e->succ_next)
{
- if (GET_CODE (insn) == NOTE
- && (NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_BEG))
- {
- cebe_insn = emit_note_after (NOTE_INSN_BLOCK_BEG, cebe_insn);
- delete_insn (insn);
- }
- if (GET_CODE (insn) == NOTE
- && (NOTE_LINE_NUMBER (insn) == NOTE_INSN_BLOCK_END))
- {
- cebe_insn = emit_note_after (NOTE_INSN_BLOCK_END, cebe_insn);
- delete_insn (insn);
- }
+ if (e->flags & EDGE_FALLTHRU)
+ e_fall = e;
+ else if (! (e->flags & EDGE_EH))
+ e_taken = e;
}
- set_last_insn (last_insn);
- }
-
- /* Rechain predicted block. */
- NEXT_INSN (cebe_insn) = dbh_insn;
- PREV_INSN (dbh_insn) = cebe_insn;
-
- REORDER_BLOCK_OLD_END (db) = NEXT_INSN (dbe_insn);
- if (db->index != n_basic_blocks - 1)
- NEXT_INSN (dbe_insn) = 0;
-
- return db;
-}
-
-
-/* Reorder blocks starting at block BB. */
-static void
-make_reorder_chain (bb)
- basic_block bb;
-{
- edge e;
- basic_block visited_edge = NULL;
- rtx block_end;
- int probability;
-
- if (bb == EXIT_BLOCK_PTR)
- return;
-
- /* Find the most probable block. */
- e = bb->succ;
- block_end = bb->end;
- if (GET_CODE (block_end) == JUMP_INSN && condjump_p (block_end))
- {
- rtx note = find_reg_note (block_end, REG_BR_PROB, 0);
-
- if (note)
- probability = INTVAL (XEXP (note, 0));
- else
- probability = 0;
-
- if (probability >= REG_BR_PROB_BASE / 2)
- e = bb->succ->succ_next;
- }
-
- /* Add chosen successor to chain and recurse on it. */
- if (e && e->dest != EXIT_BLOCK_PTR
- && e->dest != e->src
- && (! (REORDER_BLOCK_FLAGS (e->dest) & REORDER_BLOCK_VISITED)
- || (REORDER_BLOCK_FLAGS (e->dest) == REORDER_BLOCK_HEAD)))
- {
- if (! (REORDER_BLOCK_FLAGS (bb) & REORDER_BLOCK_VISITED))
- {
- REORDER_BLOCK_FLAGS (bb) |= REORDER_BLOCK_HEAD;
- REORDER_BLOCK_INDEX (bb) = reorder_index++;
- REORDER_BLOCK_FLAGS (bb) |= REORDER_BLOCK_VISITED;
- }
-
- if (REORDER_BLOCK_FLAGS (e->dest) & REORDER_BLOCK_VISITED)
- REORDER_BLOCK_FLAGS (e->dest) &= ~REORDER_BLOCK_HEAD;
-
- REORDER_BLOCK_SUCC (bb) = e;
-
- visited_edge = e->dest;
-
- reorder_last_visited = chain_reorder_blocks (e, bb);
-
- if (e->dest
- && ! (REORDER_BLOCK_FLAGS (e->dest)
- & REORDER_BLOCK_VISITED))
- make_reorder_chain (e->dest);
- }
- else
- {
- if (! (REORDER_BLOCK_FLAGS (bb) & REORDER_BLOCK_VISITED))
- {
- REORDER_BLOCK_INDEX (bb) = reorder_index++;
- REORDER_BLOCK_FLAGS (bb) |= REORDER_BLOCK_VISITED;
- }
+ next = (taken ? e_taken : e_fall)->dest;
}
- /* Recurse on the successors. */
- for (e = bb->succ; e; e = e->succ_next)
+ /* In the absence of a prediction, disturb things as little as possible
+ by selecting the old "next" block from the list of successors. If
+ there had been a fallthru edge, that will be the one. */
+ if (! next)
{
- if (e->dest && e->dest == EXIT_BLOCK_PTR)
- continue;
-
- if (e->dest
- && e->dest != e->src
- && e->dest != visited_edge
- && ! (REORDER_BLOCK_FLAGS (e->dest)
- & REORDER_BLOCK_VISITED))
- {
- reorder_last_visited
- = chain_reorder_blocks (e, reorder_last_visited);
- make_reorder_chain (e->dest);
- }
+ for (e = bb->succ; e ; e = e->succ_next)
+ if (e->dest->index == bb->index + 1)
+ {
+ if ((e->flags & EDGE_FALLTHRU)
+ || (e->dest->succ
+ && ! (e->flags & (EDGE_ABNORMAL_CALL | EDGE_EH))))
+ next = e->dest;
+ break;
+ }
}
-}
-
-/* Fixup jumps and labels after reordering basic blocks. */
+ /* Make sure we didn't select a silly next block. */
+ if (! next || next == EXIT_BLOCK_PTR || RBI (next)->visited)
+ next = NULL;
-static void
-fixup_reorder_chain ()
-{
- int i, j;
- rtx insn;
- int orig_num_blocks = n_basic_blocks;
-
- /* Set the new last insn. */
- {
- int max_val = 0;
- int max_index = 0;
- for (j = 0; j < n_basic_blocks; j++)
+ /* Recurse on the successors. Unroll the last call, as the normal
+ case is exactly one or two edges, and we can tail recurse. */
+ for (e = bb->succ; e; e = e->succ_next)
+ if (e->dest != EXIT_BLOCK_PTR
+ && ! RBI (e->dest)->visited
+ && e->dest->succ
+ && ! (e->flags & (EDGE_ABNORMAL_CALL | EDGE_EH)))
{
- int val = REORDER_BLOCK_INDEX (BASIC_BLOCK (j));
- if (val > max_val)
+ if (next)
{
- max_val = val;
- max_index = j;
+ prev = make_reorder_chain_1 (next, prev);
+ next = RBI (e->dest)->visited ? NULL : e->dest;
}
+ else
+ next = e->dest;
}
- insn = REORDER_BLOCK_EFF_END (BASIC_BLOCK (max_index));
- NEXT_INSN (insn) = NULL_RTX;
- set_last_insn (insn);
- }
-
- /* Add jumps and labels to fixup blocks. */
- for (i = 0; i < orig_num_blocks; i++)
- {
- int need_block = 0;
- basic_block bbi = BASIC_BLOCK (i);
- if (REORDER_BLOCK_ADD_JUMP (bbi))
- {
- rtx label_insn, jump_insn, barrier_insn;
-
- if (GET_CODE (REORDER_BLOCK_ADD_JUMP (bbi)->head) == CODE_LABEL)
- label_insn = REORDER_BLOCK_ADD_JUMP (bbi)->head;
- else
- {
- rtx new_label = gen_label_rtx ();
- label_insn = emit_label_before (new_label,
- REORDER_BLOCK_ADD_JUMP (bbi)->head);
- REORDER_BLOCK_ADD_JUMP (bbi)->head = label_insn;
- }
-
- if (GET_CODE (bbi->end) != JUMP_INSN)
- {
- jump_insn = emit_jump_insn_after (gen_jump (label_insn),
- bbi->end);
- bbi->end = jump_insn;
- need_block = 0;
- }
- else
- {
- jump_insn = emit_jump_insn_after (gen_jump (label_insn),
- REORDER_BLOCK_EFF_END (bbi));
- need_block = 1;
- }
-
- JUMP_LABEL (jump_insn) = label_insn;
- ++LABEL_NUSES (label_insn);
- barrier_insn = emit_barrier_after (jump_insn);
-
- /* Add block for jump. Typically this is when a then is not
- predicted and we are jumping to the moved then block. */
- if (need_block)
- {
- basic_block nb;
-
- VARRAY_GROW (basic_block_info, ++n_basic_blocks);
- create_basic_block (n_basic_blocks - 1, jump_insn,
- jump_insn, NULL);
- nb = BASIC_BLOCK (n_basic_blocks - 1);
- nb->global_live_at_start
- = OBSTACK_ALLOC_REG_SET (function_obstack);
- nb->global_live_at_end
- = OBSTACK_ALLOC_REG_SET (function_obstack);
-
- COPY_REG_SET (nb->global_live_at_start,
- bbi->global_live_at_start);
- COPY_REG_SET (nb->global_live_at_end,
- bbi->global_live_at_start);
- BASIC_BLOCK (nb->index)->local_set = 0;
-
- nb->aux = xcalloc (1, sizeof (struct reorder_block_def));
- REORDER_BLOCK_INDEX (nb) = REORDER_BLOCK_INDEX (bbi) + 1;
- /* Relink to new block. */
- nb->succ = bbi->succ;
- nb->succ->src = nb;
-
- make_edge (NULL, bbi, nb, 0);
- bbi->succ->succ_next
- = bbi->succ->succ_next->succ_next;
- nb->succ->succ_next = 0;
- /* Fix reorder block index to reflect new block. */
- for (j = 0; j < n_basic_blocks - 1; j++)
- {
- basic_block bbj = BASIC_BLOCK (j);
- if (REORDER_BLOCK_INDEX (bbj)
- >= REORDER_BLOCK_INDEX (bbi) + 1)
- REORDER_BLOCK_INDEX (bbj)++;
- }
- }
- }
- }
-}
-
-
-/* Perform sanity checks on the insn chain.
- 1. Check that next/prev pointers are consistent in both the forward and
- reverse direction.
- 2. Count insns in chain, going both directions, and check if equal.
- 3. Check that get_last_insn () returns the actual end of chain. */
-#ifdef ENABLE_CHECKING
-static void
-verify_insn_chain ()
-{
- rtx x,
- prevx,
- nextx;
- int insn_cnt1,
- insn_cnt2;
-
- prevx = NULL;
- insn_cnt1 = 1;
- for (x = get_insns (); x; x = NEXT_INSN (x))
- {
- if (PREV_INSN (x) != prevx)
- {
- fprintf (stderr, "Forward traversal: insn chain corrupt.\n");
- fprintf (stderr, "previous insn:\n");
- debug_rtx (prevx);
- fprintf (stderr, "current insn:\n");
- debug_rtx (x);
- abort ();
- }
- ++insn_cnt1;
- prevx = x;
- }
-
- if (prevx != get_last_insn ())
+ if (next)
{
- fprintf (stderr, "last_insn corrupt.\n");
- abort ();
+ bb = next;
+ goto restart;
}
- nextx = NULL;
- insn_cnt2 = 1;
- for (x = get_last_insn (); x; x = PREV_INSN (x))
- {
- if (NEXT_INSN (x) != nextx)
- {
- fprintf (stderr, "Reverse traversal: insn chain corrupt.\n");
- fprintf (stderr, "current insn:\n");
- debug_rtx (x);
- fprintf (stderr, "next insn:\n");
- debug_rtx (nextx);
- abort ();
- }
- ++insn_cnt2;
- nextx = x;
- }
-
- if (insn_cnt1 != insn_cnt2)
- {
- fprintf (stderr, "insn_cnt1 (%d) not equal to insn_cnt2 (%d).\n",
- insn_cnt1, insn_cnt2);
- abort ();
- }
+ return prev;
}
-#endif
-/* Reorder basic blocks. */
+/* Reorder basic blocks. The main entry point to this file. */
void
reorder_basic_blocks ()
{
- int i, j;
- struct loops loops_info;
- int num_loops;
-
- if (profile_arc_flag)
- return;
-
if (n_basic_blocks <= 1)
return;
- /* Exception edges are not currently handled. */
- for (i = 0; i < n_basic_blocks; i++)
- {
- edge e;
-
- for (e = BASIC_BLOCK (i)->succ; e && ! (e->flags & EDGE_EH);
- e = e->succ_next)
- continue;
+ cfg_layout_initialize ();
- if (e && (e->flags & EDGE_EH))
- return;
- }
-
- reorder_index = 0;
-
- /* Find natural loops using the CFG. */
- num_loops = flow_loops_find (&loops_info);
-
- /* Dump loop information. */
- flow_loops_dump (&loops_info, rtl_dump_file, 0);
+ make_reorder_chain ();
- /* Estimate using heuristics if no profiling info is available. */
- if (! flag_branch_probabilities)
- estimate_probability (&loops_info);
-
- reorder_last_visited = BASIC_BLOCK (0);
-
- for (i = 0; i < n_basic_blocks; i++)
- {
- basic_block bbi = BASIC_BLOCK (i);
- bbi->aux = xcalloc (1, sizeof (struct reorder_block_def));
- *((struct reorder_block_def *)bbi->aux) = rbd_init;
- REORDER_BLOCK_EFF_END (bbi)
- = skip_insns_between_block (bbi, REORDER_SKIP_AFTER);
- if (i == 0)
- REORDER_BLOCK_EFF_HEAD (bbi) = get_insns ();
- else
- {
- rtx prev_eff_end = REORDER_BLOCK_EFF_END (BASIC_BLOCK (i - 1));
- REORDER_BLOCK_EFF_HEAD (bbi) = NEXT_INSN (prev_eff_end);
- }
- }
-
- /* If we've not got epilogue in RTL, we must fallthru to the exit.
- Force the last block to be at the end. */
- /* ??? Some ABIs (e.g. MIPS) require the return insn to be at the
- end of the function for stack unwinding purposes. */
-
-#ifndef HAVE_epilogue
-#define HAVE_epilogue 0
-#endif
-
- if (! HAVE_epilogue)
- {
- basic_block last = BASIC_BLOCK (n_basic_blocks - 1);
- REORDER_BLOCK_INDEX (last) = n_basic_blocks - 1;
- REORDER_BLOCK_FLAGS (last) |= REORDER_BLOCK_VISITED;
- }
-
- make_reorder_chain (BASIC_BLOCK (0));
-
- fixup_reorder_chain ();
-
-#ifdef ENABLE_CHECKING
- verify_insn_chain ();
-#endif
-
- /* Put basic_block_info in new order. */
- for (i = 0; i < n_basic_blocks - 1; i++)
- {
- for (j = i; i != REORDER_BLOCK_INDEX (BASIC_BLOCK (j)); j++)
- continue;
-
- if (REORDER_BLOCK_INDEX (BASIC_BLOCK (j)) == i
- && i != j)
- {
- basic_block tempbb;
- int temprbi;
- int rbi = REORDER_BLOCK_INDEX (BASIC_BLOCK (j));
-
- temprbi = BASIC_BLOCK (rbi)->index;
- BASIC_BLOCK (rbi)->index = BASIC_BLOCK (j)->index;
- BASIC_BLOCK (j)->index = temprbi;
- tempbb = BASIC_BLOCK (rbi);
- BASIC_BLOCK (rbi) = BASIC_BLOCK (j);
- BASIC_BLOCK (j) = tempbb;
- }
- }
-
-#ifdef ENABLE_CHECKING
- verify_flow_info ();
-#endif
-
- for (i = 0; i < n_basic_blocks; i++)
- free (BASIC_BLOCK (i)->aux);
-
- /* Free loop information. */
- flow_loops_free (&loops_info);
+ if (rtl_dump_file)
+ dump_flow_info (rtl_dump_file);
+ cfg_layout_finalize ();
}
-
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