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gcc/gcc/tree-ssa-ifcombine.c
David Li 22c5fa5fbf dumping cleanup phase 1 -- Removing TODO_dump_func 
From-SVN: r175051
2011-06-14 19:39:36 +00:00

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/* Combining of if-expressions on trees.
Copyright (C) 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
Contributed by Richard Guenther <rguenther@suse.de>
This file is part of GCC.
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 3, or (at your option)
any later version.
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 GCC; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
#include "basic-block.h"
#include "timevar.h"
#include "tree-pretty-print.h"
#include "tree-flow.h"
#include "tree-pass.h"
#include "tree-dump.h"
/* This pass combines COND_EXPRs to simplify control flow. It
currently recognizes bit tests and comparisons in chains that
represent logical and or logical or of two COND_EXPRs.
It does so by walking basic blocks in a approximate reverse
post-dominator order and trying to match CFG patterns that
represent logical and or logical or of two COND_EXPRs.
Transformations are done if the COND_EXPR conditions match
either
1. two single bit tests X & (1 << Yn) (for logical and)
2. two bit tests X & Yn (for logical or)
3. two comparisons X OPn Y (for logical or)
To simplify this pass, removing basic blocks and dead code
is left to CFG cleanup and DCE. */
/* Recognize a if-then-else CFG pattern starting to match with the
COND_BB basic-block containing the COND_EXPR. The recognized
then end else blocks are stored to *THEN_BB and *ELSE_BB. If
*THEN_BB and/or *ELSE_BB are already set, they are required to
match the then and else basic-blocks to make the pattern match.
Returns true if the pattern matched, false otherwise. */
static bool
recognize_if_then_else (basic_block cond_bb,
basic_block *then_bb, basic_block *else_bb)
{
edge t, e;
if (EDGE_COUNT (cond_bb->succs) != 2)
return false;
/* Find the then/else edges. */
t = EDGE_SUCC (cond_bb, 0);
e = EDGE_SUCC (cond_bb, 1);
if (!(t->flags & EDGE_TRUE_VALUE))
{
edge tmp = t;
t = e;
e = tmp;
}
if (!(t->flags & EDGE_TRUE_VALUE)
|| !(e->flags & EDGE_FALSE_VALUE))
return false;
/* Check if the edge destinations point to the required block. */
if (*then_bb
&& t->dest != *then_bb)
return false;
if (*else_bb
&& e->dest != *else_bb)
return false;
if (!*then_bb)
*then_bb = t->dest;
if (!*else_bb)
*else_bb = e->dest;
return true;
}
/* Verify if the basic block BB does not have side-effects. Return
true in this case, else false. */
static bool
bb_no_side_effects_p (basic_block bb)
{
gimple_stmt_iterator gsi;
for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
{
gimple stmt = gsi_stmt (gsi);
if (gimple_has_side_effects (stmt)
|| gimple_vuse (stmt))
return false;
}
return true;
}
/* Verify if all PHI node arguments in DEST for edges from BB1 or
BB2 to DEST are the same. This makes the CFG merge point
free from side-effects. Return true in this case, else false. */
static bool
same_phi_args_p (basic_block bb1, basic_block bb2, basic_block dest)
{
edge e1 = find_edge (bb1, dest);
edge e2 = find_edge (bb2, dest);
gimple_stmt_iterator gsi;
gimple phi;
for (gsi = gsi_start_phis (dest); !gsi_end_p (gsi); gsi_next (&gsi))
{
phi = gsi_stmt (gsi);
if (!operand_equal_p (PHI_ARG_DEF_FROM_EDGE (phi, e1),
PHI_ARG_DEF_FROM_EDGE (phi, e2), 0))
return false;
}
return true;
}
/* Return the best representative SSA name for CANDIDATE which is used
in a bit test. */
static tree
get_name_for_bit_test (tree candidate)
{
/* Skip single-use names in favor of using the name from a
non-widening conversion definition. */
if (TREE_CODE (candidate) == SSA_NAME
&& has_single_use (candidate))
{
gimple def_stmt = SSA_NAME_DEF_STMT (candidate);
if (is_gimple_assign (def_stmt)
&& CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt)))
{
if (TYPE_PRECISION (TREE_TYPE (candidate))
<= TYPE_PRECISION (TREE_TYPE (gimple_assign_rhs1 (def_stmt))))
return gimple_assign_rhs1 (def_stmt);
}
}
return candidate;
}
/* Recognize a single bit test pattern in GIMPLE_COND and its defining
statements. Store the name being tested in *NAME and the bit
in *BIT. The GIMPLE_COND computes *NAME & (1 << *BIT).
Returns true if the pattern matched, false otherwise. */
static bool
recognize_single_bit_test (gimple cond, tree *name, tree *bit)
{
gimple stmt;
/* Get at the definition of the result of the bit test. */
if (gimple_cond_code (cond) != NE_EXPR
|| TREE_CODE (gimple_cond_lhs (cond)) != SSA_NAME
|| !integer_zerop (gimple_cond_rhs (cond)))
return false;
stmt = SSA_NAME_DEF_STMT (gimple_cond_lhs (cond));
if (!is_gimple_assign (stmt))
return false;
/* Look at which bit is tested. One form to recognize is
D.1985_5 = state_3(D) >> control1_4(D);
D.1986_6 = (int) D.1985_5;
D.1987_7 = op0 & 1;
if (D.1987_7 != 0) */
if (gimple_assign_rhs_code (stmt) == BIT_AND_EXPR
&& integer_onep (gimple_assign_rhs2 (stmt))
&& TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME)
{
tree orig_name = gimple_assign_rhs1 (stmt);
/* Look through copies and conversions to eventually
find the stmt that computes the shift. */
stmt = SSA_NAME_DEF_STMT (orig_name);
while (is_gimple_assign (stmt)
&& ((CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (stmt))
&& (TYPE_PRECISION (TREE_TYPE (gimple_assign_lhs (stmt)))
<= TYPE_PRECISION (TREE_TYPE (gimple_assign_rhs1 (stmt)))))
|| gimple_assign_ssa_name_copy_p (stmt)))
stmt = SSA_NAME_DEF_STMT (gimple_assign_rhs1 (stmt));
/* If we found such, decompose it. */
if (is_gimple_assign (stmt)
&& gimple_assign_rhs_code (stmt) == RSHIFT_EXPR)
{
/* op0 & (1 << op1) */
*bit = gimple_assign_rhs2 (stmt);
*name = gimple_assign_rhs1 (stmt);
}
else
{
/* t & 1 */
*bit = integer_zero_node;
*name = get_name_for_bit_test (orig_name);
}
return true;
}
/* Another form is
D.1987_7 = op0 & (1 << CST)
if (D.1987_7 != 0) */
if (gimple_assign_rhs_code (stmt) == BIT_AND_EXPR
&& TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME
&& integer_pow2p (gimple_assign_rhs2 (stmt)))
{
*name = gimple_assign_rhs1 (stmt);
*bit = build_int_cst (integer_type_node,
tree_log2 (gimple_assign_rhs2 (stmt)));
return true;
}
/* Another form is
D.1986_6 = 1 << control1_4(D)
D.1987_7 = op0 & D.1986_6
if (D.1987_7 != 0) */
if (gimple_assign_rhs_code (stmt) == BIT_AND_EXPR
&& TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME
&& TREE_CODE (gimple_assign_rhs2 (stmt)) == SSA_NAME)
{
gimple tmp;
/* Both arguments of the BIT_AND_EXPR can be the single-bit
specifying expression. */
tmp = SSA_NAME_DEF_STMT (gimple_assign_rhs1 (stmt));
if (is_gimple_assign (tmp)
&& gimple_assign_rhs_code (tmp) == LSHIFT_EXPR
&& integer_onep (gimple_assign_rhs1 (tmp)))
{
*name = gimple_assign_rhs2 (stmt);
*bit = gimple_assign_rhs2 (tmp);
return true;
}
tmp = SSA_NAME_DEF_STMT (gimple_assign_rhs2 (stmt));
if (is_gimple_assign (tmp)
&& gimple_assign_rhs_code (tmp) == LSHIFT_EXPR
&& integer_onep (gimple_assign_rhs1 (tmp)))
{
*name = gimple_assign_rhs1 (stmt);
*bit = gimple_assign_rhs2 (tmp);
return true;
}
}
return false;
}
/* Recognize a bit test pattern in a GIMPLE_COND and its defining
statements. Store the name being tested in *NAME and the bits
in *BITS. The COND_EXPR computes *NAME & *BITS.
Returns true if the pattern matched, false otherwise. */
static bool
recognize_bits_test (gimple cond, tree *name, tree *bits)
{
gimple stmt;
/* Get at the definition of the result of the bit test. */
if (gimple_cond_code (cond) != NE_EXPR
|| TREE_CODE (gimple_cond_lhs (cond)) != SSA_NAME
|| !integer_zerop (gimple_cond_rhs (cond)))
return false;
stmt = SSA_NAME_DEF_STMT (gimple_cond_lhs (cond));
if (!is_gimple_assign (stmt)
|| gimple_assign_rhs_code (stmt) != BIT_AND_EXPR)
return false;
*name = get_name_for_bit_test (gimple_assign_rhs1 (stmt));
*bits = gimple_assign_rhs2 (stmt);
return true;
}
/* If-convert on a and pattern with a common else block. The inner
if is specified by its INNER_COND_BB, the outer by OUTER_COND_BB.
Returns true if the edges to the common else basic-block were merged. */
static bool
ifcombine_ifandif (basic_block inner_cond_bb, basic_block outer_cond_bb)
{
gimple_stmt_iterator gsi;
gimple inner_cond, outer_cond;
tree name1, name2, bit1, bit2;
inner_cond = last_stmt (inner_cond_bb);
if (!inner_cond
|| gimple_code (inner_cond) != GIMPLE_COND)
return false;
outer_cond = last_stmt (outer_cond_bb);
if (!outer_cond
|| gimple_code (outer_cond) != GIMPLE_COND)
return false;
/* See if we test a single bit of the same name in both tests. In
that case remove the outer test, merging both else edges,
and change the inner one to test for
name & (bit1 | bit2) == (bit1 | bit2). */
if (recognize_single_bit_test (inner_cond, &name1, &bit1)
&& recognize_single_bit_test (outer_cond, &name2, &bit2)
&& name1 == name2)
{
tree t, t2;
/* Do it. */
gsi = gsi_for_stmt (inner_cond);
t = fold_build2 (LSHIFT_EXPR, TREE_TYPE (name1),
build_int_cst (TREE_TYPE (name1), 1), bit1);
t2 = fold_build2 (LSHIFT_EXPR, TREE_TYPE (name1),
build_int_cst (TREE_TYPE (name1), 1), bit2);
t = fold_build2 (BIT_IOR_EXPR, TREE_TYPE (name1), t, t2);
t = force_gimple_operand_gsi (&gsi, t, true, NULL_TREE,
true, GSI_SAME_STMT);
t2 = fold_build2 (BIT_AND_EXPR, TREE_TYPE (name1), name1, t);
t2 = force_gimple_operand_gsi (&gsi, t2, true, NULL_TREE,
true, GSI_SAME_STMT);
t = fold_build2 (EQ_EXPR, boolean_type_node, t2, t);
t = canonicalize_cond_expr_cond (t);
if (!t)
return false;
gimple_cond_set_condition_from_tree (inner_cond, t);
update_stmt (inner_cond);
/* Leave CFG optimization to cfg_cleanup. */
gimple_cond_set_condition_from_tree (outer_cond, boolean_true_node);
update_stmt (outer_cond);
if (dump_file)
{
fprintf (dump_file, "optimizing double bit test to ");
print_generic_expr (dump_file, name1, 0);
fprintf (dump_file, " & T == T\nwith temporary T = (1 << ");
print_generic_expr (dump_file, bit1, 0);
fprintf (dump_file, ") | (1 << ");
print_generic_expr (dump_file, bit2, 0);
fprintf (dump_file, ")\n");
}
return true;
}
/* See if we have two comparisons that we can merge into one. */
else if (TREE_CODE_CLASS (gimple_cond_code (inner_cond)) == tcc_comparison
&& TREE_CODE_CLASS (gimple_cond_code (outer_cond)) == tcc_comparison)
{
tree t;
if (!(t = maybe_fold_and_comparisons (gimple_cond_code (inner_cond),
gimple_cond_lhs (inner_cond),
gimple_cond_rhs (inner_cond),
gimple_cond_code (outer_cond),
gimple_cond_lhs (outer_cond),
gimple_cond_rhs (outer_cond))))
return false;
t = canonicalize_cond_expr_cond (t);
if (!t)
return false;
gimple_cond_set_condition_from_tree (inner_cond, t);
update_stmt (inner_cond);
/* Leave CFG optimization to cfg_cleanup. */
gimple_cond_set_condition_from_tree (outer_cond, boolean_true_node);
update_stmt (outer_cond);
if (dump_file)
{
fprintf (dump_file, "optimizing two comparisons to ");
print_generic_expr (dump_file, t, 0);
fprintf (dump_file, "\n");
}
return true;
}
return false;
}
/* If-convert on a or pattern with a common then block. The inner
if is specified by its INNER_COND_BB, the outer by OUTER_COND_BB.
Returns true, if the edges leading to the common then basic-block
were merged. */
static bool
ifcombine_iforif (basic_block inner_cond_bb, basic_block outer_cond_bb)
{
gimple inner_cond, outer_cond;
tree name1, name2, bits1, bits2;
inner_cond = last_stmt (inner_cond_bb);
if (!inner_cond
|| gimple_code (inner_cond) != GIMPLE_COND)
return false;
outer_cond = last_stmt (outer_cond_bb);
if (!outer_cond
|| gimple_code (outer_cond) != GIMPLE_COND)
return false;
/* See if we have two bit tests of the same name in both tests.
In that case remove the outer test and change the inner one to
test for name & (bits1 | bits2) != 0. */
if (recognize_bits_test (inner_cond, &name1, &bits1)
&& recognize_bits_test (outer_cond, &name2, &bits2))
{
gimple_stmt_iterator gsi;
tree t;
/* Find the common name which is bit-tested. */
if (name1 == name2)
;
else if (bits1 == bits2)
{
t = name2;
name2 = bits2;
bits2 = t;
t = name1;
name1 = bits1;
bits1 = t;
}
else if (name1 == bits2)
{
t = name2;
name2 = bits2;
bits2 = t;
}
else if (bits1 == name2)
{
t = name1;
name1 = bits1;
bits1 = t;
}
else
return false;
/* As we strip non-widening conversions in finding a common
name that is tested make sure to end up with an integral
type for building the bit operations. */
if (TYPE_PRECISION (TREE_TYPE (bits1))
>= TYPE_PRECISION (TREE_TYPE (bits2)))
{
bits1 = fold_convert (unsigned_type_for (TREE_TYPE (bits1)), bits1);
name1 = fold_convert (TREE_TYPE (bits1), name1);
bits2 = fold_convert (unsigned_type_for (TREE_TYPE (bits2)), bits2);
bits2 = fold_convert (TREE_TYPE (bits1), bits2);
}
else
{
bits2 = fold_convert (unsigned_type_for (TREE_TYPE (bits2)), bits2);
name1 = fold_convert (TREE_TYPE (bits2), name1);
bits1 = fold_convert (unsigned_type_for (TREE_TYPE (bits1)), bits1);
bits1 = fold_convert (TREE_TYPE (bits2), bits1);
}
/* Do it. */
gsi = gsi_for_stmt (inner_cond);
t = fold_build2 (BIT_IOR_EXPR, TREE_TYPE (name1), bits1, bits2);
t = force_gimple_operand_gsi (&gsi, t, true, NULL_TREE,
true, GSI_SAME_STMT);
t = fold_build2 (BIT_AND_EXPR, TREE_TYPE (name1), name1, t);
t = force_gimple_operand_gsi (&gsi, t, true, NULL_TREE,
true, GSI_SAME_STMT);
t = fold_build2 (NE_EXPR, boolean_type_node, t,
build_int_cst (TREE_TYPE (t), 0));
t = canonicalize_cond_expr_cond (t);
if (!t)
return false;
gimple_cond_set_condition_from_tree (inner_cond, t);
update_stmt (inner_cond);
/* Leave CFG optimization to cfg_cleanup. */
gimple_cond_set_condition_from_tree (outer_cond, boolean_false_node);
update_stmt (outer_cond);
if (dump_file)
{
fprintf (dump_file, "optimizing bits or bits test to ");
print_generic_expr (dump_file, name1, 0);
fprintf (dump_file, " & T != 0\nwith temporary T = ");
print_generic_expr (dump_file, bits1, 0);
fprintf (dump_file, " | ");
print_generic_expr (dump_file, bits2, 0);
fprintf (dump_file, "\n");
}
return true;
}
/* See if we have two comparisons that we can merge into one.
This happens for C++ operator overloading where for example
GE_EXPR is implemented as GT_EXPR || EQ_EXPR. */
else if (TREE_CODE_CLASS (gimple_cond_code (inner_cond)) == tcc_comparison
&& TREE_CODE_CLASS (gimple_cond_code (outer_cond)) == tcc_comparison)
{
tree t;
if (!(t = maybe_fold_or_comparisons (gimple_cond_code (inner_cond),
gimple_cond_lhs (inner_cond),
gimple_cond_rhs (inner_cond),
gimple_cond_code (outer_cond),
gimple_cond_lhs (outer_cond),
gimple_cond_rhs (outer_cond))))
return false;
t = canonicalize_cond_expr_cond (t);
if (!t)
return false;
gimple_cond_set_condition_from_tree (inner_cond, t);
update_stmt (inner_cond);
/* Leave CFG optimization to cfg_cleanup. */
gimple_cond_set_condition_from_tree (outer_cond, boolean_false_node);
update_stmt (outer_cond);
if (dump_file)
{
fprintf (dump_file, "optimizing two comparisons to ");
print_generic_expr (dump_file, t, 0);
fprintf (dump_file, "\n");
}
return true;
}
return false;
}
/* Recognize a CFG pattern and dispatch to the appropriate
if-conversion helper. We start with BB as the innermost
worker basic-block. Returns true if a transformation was done. */
static bool
tree_ssa_ifcombine_bb (basic_block inner_cond_bb)
{
basic_block then_bb = NULL, else_bb = NULL;
if (!recognize_if_then_else (inner_cond_bb, &then_bb, &else_bb))
return false;
/* Recognize && and || of two conditions with a common
then/else block which entry edges we can merge. That is:
if (a || b)
;
and
if (a && b)
;
This requires a single predecessor of the inner cond_bb. */
if (single_pred_p (inner_cond_bb))
{
basic_block outer_cond_bb = single_pred (inner_cond_bb);
/* The && form is characterized by a common else_bb with
the two edges leading to it mergable. The latter is
guaranteed by matching PHI arguments in the else_bb and
the inner cond_bb having no side-effects. */
if (recognize_if_then_else (outer_cond_bb, &inner_cond_bb, &else_bb)
&& same_phi_args_p (outer_cond_bb, inner_cond_bb, else_bb)
&& bb_no_side_effects_p (inner_cond_bb))
{
/* We have
<outer_cond_bb>
if (q) goto inner_cond_bb; else goto else_bb;
<inner_cond_bb>
if (p) goto ...; else goto else_bb;
...
<else_bb>
...
*/
return ifcombine_ifandif (inner_cond_bb, outer_cond_bb);
}
/* The || form is characterized by a common then_bb with the
two edges leading to it mergable. The latter is guaranteed
by matching PHI arguments in the then_bb and the inner cond_bb
having no side-effects. */
if (recognize_if_then_else (outer_cond_bb, &then_bb, &inner_cond_bb)
&& same_phi_args_p (outer_cond_bb, inner_cond_bb, then_bb)
&& bb_no_side_effects_p (inner_cond_bb))
{
/* We have
<outer_cond_bb>
if (q) goto then_bb; else goto inner_cond_bb;
<inner_cond_bb>
if (q) goto then_bb; else goto ...;
<then_bb>
...
*/
return ifcombine_iforif (inner_cond_bb, outer_cond_bb);
}
}
return false;
}
/* Main entry for the tree if-conversion pass. */
static unsigned int
tree_ssa_ifcombine (void)
{
basic_block *bbs;
bool cfg_changed = false;
int i;
bbs = blocks_in_phiopt_order ();
calculate_dominance_info (CDI_DOMINATORS);
for (i = 0; i < n_basic_blocks - NUM_FIXED_BLOCKS; ++i)
{
basic_block bb = bbs[i];
gimple stmt = last_stmt (bb);
if (stmt
&& gimple_code (stmt) == GIMPLE_COND)
cfg_changed |= tree_ssa_ifcombine_bb (bb);
}
free (bbs);
return cfg_changed ? TODO_cleanup_cfg : 0;
}
static bool
gate_ifcombine (void)
{
return 1;
}
struct gimple_opt_pass pass_tree_ifcombine =
{
{
GIMPLE_PASS,
"ifcombine", /* name */
gate_ifcombine, /* gate */
tree_ssa_ifcombine, /* execute */
NULL, /* sub */
NULL, /* next */
0, /* static_pass_number */
TV_TREE_IFCOMBINE, /* tv_id */
PROP_cfg | PROP_ssa, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
TODO_ggc_collect
| TODO_update_ssa
| TODO_verify_ssa /* todo_flags_finish */
}
};
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