/* Loop unswitching.
|
/* Loop unswitching.
|
Copyright (C) 2004, 2005, 2007 Free Software Foundation, Inc.
|
Copyright (C) 2004, 2005, 2007 Free Software Foundation, Inc.
|
|
|
This file is part of GCC.
|
This file is part of GCC.
|
|
|
GCC is free software; you can redistribute it and/or modify it
|
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
|
under the terms of the GNU General Public License as published by the
|
Free Software Foundation; either version 3, or (at your option) any
|
Free Software Foundation; either version 3, or (at your option) any
|
later version.
|
later version.
|
|
|
GCC is distributed in the hope that it will be useful, but WITHOUT
|
GCC is distributed in the hope that it will be useful, but WITHOUT
|
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
|
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
|
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
|
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
|
for more details.
|
for more details.
|
|
|
You should have received a copy of the GNU General Public License
|
You should have received a copy of the GNU General Public License
|
along with GCC; see the file COPYING3. If not see
|
along with GCC; see the file COPYING3. If not see
|
<http://www.gnu.org/licenses/>. */
|
<http://www.gnu.org/licenses/>. */
|
|
|
#include "config.h"
|
#include "config.h"
|
#include "system.h"
|
#include "system.h"
|
#include "coretypes.h"
|
#include "coretypes.h"
|
#include "tm.h"
|
#include "tm.h"
|
#include "tree.h"
|
#include "tree.h"
|
#include "rtl.h"
|
#include "rtl.h"
|
#include "tm_p.h"
|
#include "tm_p.h"
|
#include "hard-reg-set.h"
|
#include "hard-reg-set.h"
|
#include "basic-block.h"
|
#include "basic-block.h"
|
#include "output.h"
|
#include "output.h"
|
#include "diagnostic.h"
|
#include "diagnostic.h"
|
#include "tree-flow.h"
|
#include "tree-flow.h"
|
#include "tree-dump.h"
|
#include "tree-dump.h"
|
#include "timevar.h"
|
#include "timevar.h"
|
#include "cfgloop.h"
|
#include "cfgloop.h"
|
#include "domwalk.h"
|
#include "domwalk.h"
|
#include "params.h"
|
#include "params.h"
|
#include "tree-pass.h"
|
#include "tree-pass.h"
|
|
|
/* This file implements the loop unswitching, i.e. transformation of loops like
|
/* This file implements the loop unswitching, i.e. transformation of loops like
|
|
|
while (A)
|
while (A)
|
{
|
{
|
if (inv)
|
if (inv)
|
B;
|
B;
|
|
|
X;
|
X;
|
|
|
if (!inv)
|
if (!inv)
|
C;
|
C;
|
}
|
}
|
|
|
where inv is the loop invariant, into
|
where inv is the loop invariant, into
|
|
|
if (inv)
|
if (inv)
|
{
|
{
|
while (A)
|
while (A)
|
{
|
{
|
B;
|
B;
|
X;
|
X;
|
}
|
}
|
}
|
}
|
else
|
else
|
{
|
{
|
while (A)
|
while (A)
|
{
|
{
|
X;
|
X;
|
C;
|
C;
|
}
|
}
|
}
|
}
|
|
|
Inv is considered invariant iff the values it compares are both invariant;
|
Inv is considered invariant iff the values it compares are both invariant;
|
tree-ssa-loop-im.c ensures that all the suitable conditions are in this
|
tree-ssa-loop-im.c ensures that all the suitable conditions are in this
|
shape. */
|
shape. */
|
|
|
static struct loop *tree_unswitch_loop (struct loops *, struct loop *, basic_block,
|
static struct loop *tree_unswitch_loop (struct loops *, struct loop *, basic_block,
|
tree);
|
tree);
|
static bool tree_unswitch_single_loop (struct loops *, struct loop *, int);
|
static bool tree_unswitch_single_loop (struct loops *, struct loop *, int);
|
static tree tree_may_unswitch_on (basic_block, struct loop *);
|
static tree tree_may_unswitch_on (basic_block, struct loop *);
|
|
|
/* Main entry point. Perform loop unswitching on all suitable LOOPS. */
|
/* Main entry point. Perform loop unswitching on all suitable LOOPS. */
|
|
|
unsigned int
|
unsigned int
|
tree_ssa_unswitch_loops (struct loops *loops)
|
tree_ssa_unswitch_loops (struct loops *loops)
|
{
|
{
|
int i, num;
|
int i, num;
|
struct loop *loop;
|
struct loop *loop;
|
bool changed = false;
|
bool changed = false;
|
|
|
/* Go through inner loops (only original ones). */
|
/* Go through inner loops (only original ones). */
|
num = loops->num;
|
num = loops->num;
|
|
|
for (i = 1; i < num; i++)
|
for (i = 1; i < num; i++)
|
{
|
{
|
/* Removed loop? */
|
/* Removed loop? */
|
loop = loops->parray[i];
|
loop = loops->parray[i];
|
if (!loop)
|
if (!loop)
|
continue;
|
continue;
|
|
|
if (loop->inner)
|
if (loop->inner)
|
continue;
|
continue;
|
|
|
changed |= tree_unswitch_single_loop (loops, loop, 0);
|
changed |= tree_unswitch_single_loop (loops, loop, 0);
|
}
|
}
|
|
|
if (changed)
|
if (changed)
|
return TODO_cleanup_cfg;
|
return TODO_cleanup_cfg;
|
return 0;
|
return 0;
|
}
|
}
|
|
|
/* Checks whether we can unswitch LOOP on condition at end of BB -- one of its
|
/* Checks whether we can unswitch LOOP on condition at end of BB -- one of its
|
basic blocks (for what it means see comments below). */
|
basic blocks (for what it means see comments below). */
|
|
|
static tree
|
static tree
|
tree_may_unswitch_on (basic_block bb, struct loop *loop)
|
tree_may_unswitch_on (basic_block bb, struct loop *loop)
|
{
|
{
|
tree stmt, def, cond, use;
|
tree stmt, def, cond, use;
|
basic_block def_bb;
|
basic_block def_bb;
|
ssa_op_iter iter;
|
ssa_op_iter iter;
|
|
|
/* BB must end in a simple conditional jump. */
|
/* BB must end in a simple conditional jump. */
|
stmt = last_stmt (bb);
|
stmt = last_stmt (bb);
|
if (!stmt || TREE_CODE (stmt) != COND_EXPR)
|
if (!stmt || TREE_CODE (stmt) != COND_EXPR)
|
return NULL_TREE;
|
return NULL_TREE;
|
|
|
/* Condition must be invariant. */
|
/* Condition must be invariant. */
|
FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
|
FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
|
{
|
{
|
def = SSA_NAME_DEF_STMT (use);
|
def = SSA_NAME_DEF_STMT (use);
|
def_bb = bb_for_stmt (def);
|
def_bb = bb_for_stmt (def);
|
if (def_bb
|
if (def_bb
|
&& flow_bb_inside_loop_p (loop, def_bb))
|
&& flow_bb_inside_loop_p (loop, def_bb))
|
return NULL_TREE;
|
return NULL_TREE;
|
}
|
}
|
|
|
cond = COND_EXPR_COND (stmt);
|
cond = COND_EXPR_COND (stmt);
|
/* To keep the things simple, we do not directly remove the conditions,
|
/* To keep the things simple, we do not directly remove the conditions,
|
but just replace tests with 0/1. Prevent the infinite loop where we
|
but just replace tests with 0/1. Prevent the infinite loop where we
|
would unswitch again on such a condition. */
|
would unswitch again on such a condition. */
|
if (integer_zerop (cond) || integer_nonzerop (cond))
|
if (integer_zerop (cond) || integer_nonzerop (cond))
|
return NULL_TREE;
|
return NULL_TREE;
|
|
|
return cond;
|
return cond;
|
}
|
}
|
|
|
/* Simplifies COND using checks in front of the entry of the LOOP. Just very
|
/* Simplifies COND using checks in front of the entry of the LOOP. Just very
|
simplish (sufficient to prevent us from duplicating loop in unswitching
|
simplish (sufficient to prevent us from duplicating loop in unswitching
|
unnecessarily). */
|
unnecessarily). */
|
|
|
static tree
|
static tree
|
simplify_using_entry_checks (struct loop *loop, tree cond)
|
simplify_using_entry_checks (struct loop *loop, tree cond)
|
{
|
{
|
edge e = loop_preheader_edge (loop);
|
edge e = loop_preheader_edge (loop);
|
tree stmt;
|
tree stmt;
|
|
|
while (1)
|
while (1)
|
{
|
{
|
stmt = last_stmt (e->src);
|
stmt = last_stmt (e->src);
|
if (stmt
|
if (stmt
|
&& TREE_CODE (stmt) == COND_EXPR
|
&& TREE_CODE (stmt) == COND_EXPR
|
&& operand_equal_p (COND_EXPR_COND (stmt), cond, 0))
|
&& operand_equal_p (COND_EXPR_COND (stmt), cond, 0))
|
return (e->flags & EDGE_TRUE_VALUE
|
return (e->flags & EDGE_TRUE_VALUE
|
? boolean_true_node
|
? boolean_true_node
|
: boolean_false_node);
|
: boolean_false_node);
|
|
|
if (!single_pred_p (e->src))
|
if (!single_pred_p (e->src))
|
return cond;
|
return cond;
|
|
|
e = single_pred_edge (e->src);
|
e = single_pred_edge (e->src);
|
if (e->src == ENTRY_BLOCK_PTR)
|
if (e->src == ENTRY_BLOCK_PTR)
|
return cond;
|
return cond;
|
}
|
}
|
}
|
}
|
|
|
/* Unswitch single LOOP. NUM is number of unswitchings done; we do not allow
|
/* Unswitch single LOOP. NUM is number of unswitchings done; we do not allow
|
it to grow too much, it is too easy to create example on that the code would
|
it to grow too much, it is too easy to create example on that the code would
|
grow exponentially. */
|
grow exponentially. */
|
|
|
static bool
|
static bool
|
tree_unswitch_single_loop (struct loops *loops, struct loop *loop, int num)
|
tree_unswitch_single_loop (struct loops *loops, struct loop *loop, int num)
|
{
|
{
|
basic_block *bbs;
|
basic_block *bbs;
|
struct loop *nloop;
|
struct loop *nloop;
|
unsigned i;
|
unsigned i;
|
tree cond = NULL_TREE, stmt;
|
tree cond = NULL_TREE, stmt;
|
bool changed = false;
|
bool changed = false;
|
|
|
/* Do not unswitch too much. */
|
/* Do not unswitch too much. */
|
if (num > PARAM_VALUE (PARAM_MAX_UNSWITCH_LEVEL))
|
if (num > PARAM_VALUE (PARAM_MAX_UNSWITCH_LEVEL))
|
{
|
{
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
fprintf (dump_file, ";; Not unswitching anymore, hit max level\n");
|
fprintf (dump_file, ";; Not unswitching anymore, hit max level\n");
|
return false;
|
return false;
|
}
|
}
|
|
|
/* Only unswitch innermost loops. */
|
/* Only unswitch innermost loops. */
|
if (loop->inner)
|
if (loop->inner)
|
{
|
{
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
fprintf (dump_file, ";; Not unswitching, not innermost loop\n");
|
fprintf (dump_file, ";; Not unswitching, not innermost loop\n");
|
return false;
|
return false;
|
}
|
}
|
|
|
/* The loop should not be too large, to limit code growth. */
|
/* The loop should not be too large, to limit code growth. */
|
if (tree_num_loop_insns (loop)
|
if (tree_num_loop_insns (loop)
|
> (unsigned) PARAM_VALUE (PARAM_MAX_UNSWITCH_INSNS))
|
> (unsigned) PARAM_VALUE (PARAM_MAX_UNSWITCH_INSNS))
|
{
|
{
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
fprintf (dump_file, ";; Not unswitching, loop too big\n");
|
fprintf (dump_file, ";; Not unswitching, loop too big\n");
|
return false;
|
return false;
|
}
|
}
|
|
|
i = 0;
|
i = 0;
|
bbs = get_loop_body (loop);
|
bbs = get_loop_body (loop);
|
|
|
while (1)
|
while (1)
|
{
|
{
|
/* Find a bb to unswitch on. */
|
/* Find a bb to unswitch on. */
|
for (; i < loop->num_nodes; i++)
|
for (; i < loop->num_nodes; i++)
|
if ((cond = tree_may_unswitch_on (bbs[i], loop)))
|
if ((cond = tree_may_unswitch_on (bbs[i], loop)))
|
break;
|
break;
|
|
|
if (i == loop->num_nodes)
|
if (i == loop->num_nodes)
|
{
|
{
|
free (bbs);
|
free (bbs);
|
return changed;
|
return changed;
|
}
|
}
|
|
|
cond = simplify_using_entry_checks (loop, cond);
|
cond = simplify_using_entry_checks (loop, cond);
|
stmt = last_stmt (bbs[i]);
|
stmt = last_stmt (bbs[i]);
|
if (integer_nonzerop (cond))
|
if (integer_nonzerop (cond))
|
{
|
{
|
/* Remove false path. */
|
/* Remove false path. */
|
COND_EXPR_COND (stmt) = boolean_true_node;
|
COND_EXPR_COND (stmt) = boolean_true_node;
|
changed = true;
|
changed = true;
|
}
|
}
|
else if (integer_zerop (cond))
|
else if (integer_zerop (cond))
|
{
|
{
|
/* Remove true path. */
|
/* Remove true path. */
|
COND_EXPR_COND (stmt) = boolean_false_node;
|
COND_EXPR_COND (stmt) = boolean_false_node;
|
changed = true;
|
changed = true;
|
}
|
}
|
else
|
else
|
break;
|
break;
|
|
|
update_stmt (stmt);
|
update_stmt (stmt);
|
i++;
|
i++;
|
}
|
}
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
fprintf (dump_file, ";; Unswitching loop\n");
|
fprintf (dump_file, ";; Unswitching loop\n");
|
|
|
initialize_original_copy_tables ();
|
initialize_original_copy_tables ();
|
/* Unswitch the loop on this condition. */
|
/* Unswitch the loop on this condition. */
|
nloop = tree_unswitch_loop (loops, loop, bbs[i], cond);
|
nloop = tree_unswitch_loop (loops, loop, bbs[i], cond);
|
if (!nloop)
|
if (!nloop)
|
{
|
{
|
free_original_copy_tables ();
|
free_original_copy_tables ();
|
free (bbs);
|
free (bbs);
|
return changed;
|
return changed;
|
}
|
}
|
|
|
/* Update the SSA form after unswitching. */
|
/* Update the SSA form after unswitching. */
|
update_ssa (TODO_update_ssa);
|
update_ssa (TODO_update_ssa);
|
free_original_copy_tables ();
|
free_original_copy_tables ();
|
|
|
/* Invoke itself on modified loops. */
|
/* Invoke itself on modified loops. */
|
tree_unswitch_single_loop (loops, nloop, num + 1);
|
tree_unswitch_single_loop (loops, nloop, num + 1);
|
tree_unswitch_single_loop (loops, loop, num + 1);
|
tree_unswitch_single_loop (loops, loop, num + 1);
|
free (bbs);
|
free (bbs);
|
return true;
|
return true;
|
}
|
}
|
|
|
/* Unswitch a LOOP w.r. to given basic block UNSWITCH_ON. We only support
|
/* Unswitch a LOOP w.r. to given basic block UNSWITCH_ON. We only support
|
unswitching of innermost loops. COND is the condition determining which
|
unswitching of innermost loops. COND is the condition determining which
|
loop is entered -- the new loop is entered if COND is true. Returns NULL
|
loop is entered -- the new loop is entered if COND is true. Returns NULL
|
if impossible, new loop otherwise. */
|
if impossible, new loop otherwise. */
|
|
|
static struct loop *
|
static struct loop *
|
tree_unswitch_loop (struct loops *loops, struct loop *loop,
|
tree_unswitch_loop (struct loops *loops, struct loop *loop,
|
basic_block unswitch_on, tree cond)
|
basic_block unswitch_on, tree cond)
|
{
|
{
|
basic_block condition_bb;
|
basic_block condition_bb;
|
|
|
/* Some sanity checking. */
|
/* Some sanity checking. */
|
gcc_assert (flow_bb_inside_loop_p (loop, unswitch_on));
|
gcc_assert (flow_bb_inside_loop_p (loop, unswitch_on));
|
gcc_assert (EDGE_COUNT (unswitch_on->succs) == 2);
|
gcc_assert (EDGE_COUNT (unswitch_on->succs) == 2);
|
gcc_assert (loop->inner == NULL);
|
gcc_assert (loop->inner == NULL);
|
|
|
return loop_version (loops, loop, unshare_expr (cond),
|
return loop_version (loops, loop, unshare_expr (cond),
|
&condition_bb, false);
|
&condition_bb, false);
|
}
|
}
|
|
|
