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tree-if-conv.c
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tree-if-conv.c
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/* If-conversion for vectorizer.
Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
Free Software Foundation, Inc.
Contributed by Devang Patel <dpatel@apple.com>
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/>. */
/* This pass implements a tree level if-conversion of loops. Its
initial goal is to help the vectorizer to vectorize loops with
conditions.
A short description of if-conversion:
o Decide if a loop is if-convertible or not.
o Walk all loop basic blocks in breadth first order (BFS order).
o Remove conditional statements (at the end of basic block)
and propagate condition into destination basic blocks'
predicate list.
o Replace modify expression with conditional modify expression
using current basic block's condition.
o Merge all basic blocks
o Replace phi nodes with conditional modify expr
o Merge all basic blocks into header
Sample transformation:
INPUT
-----
# i_23 = PHI <0(0), i_18(10)>;
<L0>:;
j_15 = A[i_23];
if (j_15 > 41) goto <L1>; else goto <L17>;
<L17>:;
goto <bb 3> (<L3>);
<L1>:;
# iftmp.2_4 = PHI <0(8), 42(2)>;
<L3>:;
A[i_23] = iftmp.2_4;
i_18 = i_23 + 1;
if (i_18 <= 15) goto <L19>; else goto <L18>;
<L19>:;
goto <bb 1> (<L0>);
<L18>:;
OUTPUT
------
# i_23 = PHI <0(0), i_18(10)>;
<L0>:;
j_15 = A[i_23];
<L3>:;
iftmp.2_4 = j_15 > 41 ? 42 : 0;
A[i_23] = iftmp.2_4;
i_18 = i_23 + 1;
if (i_18 <= 15) goto <L19>; else goto <L18>;
<L19>:;
goto <bb 1> (<L0>);
<L18>:;
*/
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
#include "flags.h"
#include "timevar.h"
#include "basic-block.h"
#include "tree-pretty-print.h"
#include "gimple-pretty-print.h"
#include "tree-flow.h"
#include "tree-dump.h"
#include "cfgloop.h"
#include "tree-chrec.h"
#include "tree-data-ref.h"
#include "tree-scalar-evolution.h"
#include "tree-pass.h"
#include "dbgcnt.h"
/* List of basic blocks in if-conversion-suitable order. */
static basic_block *ifc_bbs;
/* Structure used to predicate basic blocks. This is attached to the
->aux field of the BBs in the loop to be if-converted. */
typedef struct bb_predicate_s {
/* The condition under which this basic block is executed. */
tree predicate;
/* PREDICATE is gimplified, and the sequence of statements is
recorded here, in order to avoid the duplication of computations
that occur in previous conditions. See PR44483. */
gimple_seq predicate_gimplified_stmts;
} *bb_predicate_p;
/* Returns true when the basic block BB has a predicate. */
static inline bool
bb_has_predicate (basic_block bb)
{
return bb->aux != NULL;
}
/* Returns the gimplified predicate for basic block BB. */
static inline tree
bb_predicate (basic_block bb)
{
return ((bb_predicate_p) bb->aux)->predicate;
}
/* Sets the gimplified predicate COND for basic block BB. */
static inline void
set_bb_predicate (basic_block bb, tree cond)
{
gcc_assert ((TREE_CODE (cond) == TRUTH_NOT_EXPR
&& is_gimple_condexpr (TREE_OPERAND (cond, 0)))
|| is_gimple_condexpr (cond));
((bb_predicate_p) bb->aux)->predicate = cond;
}
/* Returns the sequence of statements of the gimplification of the
predicate for basic block BB. */
static inline gimple_seq
bb_predicate_gimplified_stmts (basic_block bb)
{
return ((bb_predicate_p) bb->aux)->predicate_gimplified_stmts;
}
/* Sets the sequence of statements STMTS of the gimplification of the
predicate for basic block BB. */
static inline void
set_bb_predicate_gimplified_stmts (basic_block bb, gimple_seq stmts)
{
((bb_predicate_p) bb->aux)->predicate_gimplified_stmts = stmts;
}
/* Adds the sequence of statements STMTS to the sequence of statements
of the predicate for basic block BB. */
static inline void
add_bb_predicate_gimplified_stmts (basic_block bb, gimple_seq stmts)
{
gimple_seq_add_seq
(&(((bb_predicate_p) bb->aux)->predicate_gimplified_stmts), stmts);
}
/* Initializes to TRUE the predicate of basic block BB. */
static inline void
init_bb_predicate (basic_block bb)
{
bb->aux = XNEW (struct bb_predicate_s);
set_bb_predicate_gimplified_stmts (bb, NULL);
set_bb_predicate (bb, boolean_true_node);
}
/* Free the predicate of basic block BB. */
static inline void
free_bb_predicate (basic_block bb)
{
gimple_seq stmts;
if (!bb_has_predicate (bb))
return;
/* Release the SSA_NAMEs created for the gimplification of the
predicate. */
stmts = bb_predicate_gimplified_stmts (bb);
if (stmts)
{
gimple_stmt_iterator i;
for (i = gsi_start (stmts); !gsi_end_p (i); gsi_next (&i))
free_stmt_operands (gsi_stmt (i));
}
free (bb->aux);
bb->aux = NULL;
}
/* Free the predicate of BB and reinitialize it with the true
predicate. */
static inline void
reset_bb_predicate (basic_block bb)
{
free_bb_predicate (bb);
init_bb_predicate (bb);
}
/* Returns a new SSA_NAME of type TYPE that is assigned the value of
the expression EXPR. Inserts the statement created for this
computation before GSI and leaves the iterator GSI at the same
statement. */
static tree
ifc_temp_var (tree type, tree expr, gimple_stmt_iterator *gsi)
{
const char *name = "_ifc_";
tree var, new_name;
gimple stmt;
/* Create new temporary variable. */
var = create_tmp_var (type, name);
add_referenced_var (var);
/* Build new statement to assign EXPR to new variable. */
stmt = gimple_build_assign (var, expr);
/* Get SSA name for the new variable and set make new statement
its definition statement. */
new_name = make_ssa_name (var, stmt);
gimple_assign_set_lhs (stmt, new_name);
SSA_NAME_DEF_STMT (new_name) = stmt;
update_stmt (stmt);
gsi_insert_before (gsi, stmt, GSI_SAME_STMT);
return gimple_assign_lhs (stmt);
}
/* Return true when COND is a true predicate. */
static inline bool
is_true_predicate (tree cond)
{
return (cond == NULL_TREE
|| cond == boolean_true_node
|| integer_onep (cond));
}
/* Returns true when BB has a predicate that is not trivial: true or
NULL_TREE. */
static inline bool
is_predicated (basic_block bb)
{
return !is_true_predicate (bb_predicate (bb));
}
/* Parses the predicate COND and returns its comparison code and
operands OP0 and OP1. */
static enum tree_code
parse_predicate (tree cond, tree *op0, tree *op1)
{
gimple s;
if (TREE_CODE (cond) == SSA_NAME
&& is_gimple_assign (s = SSA_NAME_DEF_STMT (cond)))
{
if (TREE_CODE_CLASS (gimple_assign_rhs_code (s)) == tcc_comparison)
{
*op0 = gimple_assign_rhs1 (s);
*op1 = gimple_assign_rhs2 (s);
return gimple_assign_rhs_code (s);
}
else if (gimple_assign_rhs_code (s) == TRUTH_NOT_EXPR)
{
tree op = gimple_assign_rhs1 (s);
tree type = TREE_TYPE (op);
enum tree_code code = parse_predicate (op, op0, op1);
return code == ERROR_MARK ? ERROR_MARK
: invert_tree_comparison (code, HONOR_NANS (TYPE_MODE (type)));
}
return ERROR_MARK;
}
if (TREE_CODE_CLASS (TREE_CODE (cond)) == tcc_comparison)
{
*op0 = TREE_OPERAND (cond, 0);
*op1 = TREE_OPERAND (cond, 1);
return TREE_CODE (cond);
}
return ERROR_MARK;
}
/* Returns the fold of predicate C1 OR C2 at location LOC. */
static tree
fold_or_predicates (location_t loc, tree c1, tree c2)
{
tree op1a, op1b, op2a, op2b;
enum tree_code code1 = parse_predicate (c1, &op1a, &op1b);
enum tree_code code2 = parse_predicate (c2, &op2a, &op2b);
if (code1 != ERROR_MARK && code2 != ERROR_MARK)
{
tree t = maybe_fold_or_comparisons (code1, op1a, op1b,
code2, op2a, op2b);
if (t)
return t;
}
return fold_build2_loc (loc, TRUTH_OR_EXPR, boolean_type_node, c1, c2);
}
/* Add condition NC to the predicate list of basic block BB. */
static inline void
add_to_predicate_list (basic_block bb, tree nc)
{
tree bc, *tp;
if (is_true_predicate (nc))
return;
if (!is_predicated (bb))
bc = nc;
else
{
bc = bb_predicate (bb);
bc = fold_or_predicates (EXPR_LOCATION (bc), nc, bc);
if (is_true_predicate (bc))
{
reset_bb_predicate (bb);
return;
}
}
/* Allow a TRUTH_NOT_EXPR around the main predicate. */
if (TREE_CODE (bc) == TRUTH_NOT_EXPR)
tp = &TREE_OPERAND (bc, 0);
else
tp = &bc;
if (!is_gimple_condexpr (*tp))
{
gimple_seq stmts;
*tp = force_gimple_operand_1 (*tp, &stmts, is_gimple_condexpr, NULL_TREE);
add_bb_predicate_gimplified_stmts (bb, stmts);
}
set_bb_predicate (bb, bc);
}
/* Add the condition COND to the previous condition PREV_COND, and add
this to the predicate list of the destination of edge E. LOOP is
the loop to be if-converted. */
static void
add_to_dst_predicate_list (struct loop *loop, edge e,
tree prev_cond, tree cond)
{
if (!flow_bb_inside_loop_p (loop, e->dest))
return;
if (!is_true_predicate (prev_cond))
cond = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
prev_cond, cond);
add_to_predicate_list (e->dest, cond);
}
/* Return true if one of the successor edges of BB exits LOOP. */
static bool
bb_with_exit_edge_p (struct loop *loop, basic_block bb)
{
edge e;
edge_iterator ei;
FOR_EACH_EDGE (e, ei, bb->succs)
if (loop_exit_edge_p (loop, e))
return true;
return false;
}
/* Return true when PHI is if-convertible. PHI is part of loop LOOP
and it belongs to basic block BB.
PHI is not if-convertible if:
- it has more than 2 arguments.
When the flag_tree_loop_if_convert_stores is not set, PHI is not
if-convertible if:
- a virtual PHI is immediately used in another PHI node,
- there is a virtual PHI in a BB other than the loop->header. */
static bool
if_convertible_phi_p (struct loop *loop, basic_block bb, gimple phi)
{
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "-------------------------\n");
print_gimple_stmt (dump_file, phi, 0, TDF_SLIM);
}
if (bb != loop->header && gimple_phi_num_args (phi) != 2)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "More than two phi node args.\n");
return false;
}
if (flag_tree_loop_if_convert_stores)
return true;
/* When the flag_tree_loop_if_convert_stores is not set, check
that there are no memory writes in the branches of the loop to be
if-converted. */
if (!is_gimple_reg (SSA_NAME_VAR (gimple_phi_result (phi))))
{
imm_use_iterator imm_iter;
use_operand_p use_p;
if (bb != loop->header)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Virtual phi not on loop->header.\n");
return false;
}
FOR_EACH_IMM_USE_FAST (use_p, imm_iter, gimple_phi_result (phi))
{
if (gimple_code (USE_STMT (use_p)) == GIMPLE_PHI)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Difficult to handle this virtual phi.\n");
return false;
}
}
}
return true;
}
/* Records the status of a data reference. This struct is attached to
each DR->aux field. */
struct ifc_dr {
/* -1 when not initialized, 0 when false, 1 when true. */
int written_at_least_once;
/* -1 when not initialized, 0 when false, 1 when true. */
int rw_unconditionally;
};
#define IFC_DR(DR) ((struct ifc_dr *) (DR)->aux)
#define DR_WRITTEN_AT_LEAST_ONCE(DR) (IFC_DR (DR)->written_at_least_once)
#define DR_RW_UNCONDITIONALLY(DR) (IFC_DR (DR)->rw_unconditionally)
/* Returns true when the memory references of STMT are read or written
unconditionally. In other words, this function returns true when
for every data reference A in STMT there exist other accesses to
a data reference with the same base with predicates that add up (OR-up) to
the true predicate: this ensures that the data reference A is touched
(read or written) on every iteration of the if-converted loop. */
static bool
memrefs_read_or_written_unconditionally (gimple stmt,
VEC (data_reference_p, heap) *drs)
{
int i, j;
data_reference_p a, b;
tree ca = bb_predicate (gimple_bb (stmt));
for (i = 0; VEC_iterate (data_reference_p, drs, i, a); i++)
if (DR_STMT (a) == stmt)
{
bool found = false;
int x = DR_RW_UNCONDITIONALLY (a);
if (x == 0)
return false;
if (x == 1)
continue;
for (j = 0; VEC_iterate (data_reference_p, drs, j, b); j++)
{
tree ref_base_a = DR_REF (a);
tree ref_base_b = DR_REF (b);
if (DR_STMT (b) == stmt)
continue;
while (TREE_CODE (ref_base_a) == COMPONENT_REF
|| TREE_CODE (ref_base_a) == IMAGPART_EXPR
|| TREE_CODE (ref_base_a) == REALPART_EXPR)
ref_base_a = TREE_OPERAND (ref_base_a, 0);
while (TREE_CODE (ref_base_b) == COMPONENT_REF
|| TREE_CODE (ref_base_b) == IMAGPART_EXPR
|| TREE_CODE (ref_base_b) == REALPART_EXPR)
ref_base_b = TREE_OPERAND (ref_base_b, 0);
if (!operand_equal_p (ref_base_a, ref_base_b, 0))
{
tree cb = bb_predicate (gimple_bb (DR_STMT (b)));
if (DR_RW_UNCONDITIONALLY (b) == 1
|| is_true_predicate (cb)
|| is_true_predicate (ca
= fold_or_predicates (EXPR_LOCATION (cb), ca, cb)))
{
DR_RW_UNCONDITIONALLY (a) = 1;
DR_RW_UNCONDITIONALLY (b) = 1;
found = true;
break;
}
}
}
if (!found)
{
DR_RW_UNCONDITIONALLY (a) = 0;
return false;
}
}
return true;
}
/* Returns true when the memory references of STMT are unconditionally
written. In other words, this function returns true when for every
data reference A written in STMT, there exist other writes to the
same data reference with predicates that add up (OR-up) to the true
predicate: this ensures that the data reference A is written on
every iteration of the if-converted loop. */
static bool
write_memrefs_written_at_least_once (gimple stmt,
VEC (data_reference_p, heap) *drs)
{
int i, j;
data_reference_p a, b;
tree ca = bb_predicate (gimple_bb (stmt));
for (i = 0; VEC_iterate (data_reference_p, drs, i, a); i++)
if (DR_STMT (a) == stmt
&& DR_IS_WRITE (a))
{
bool found = false;
int x = DR_WRITTEN_AT_LEAST_ONCE (a);
if (x == 0)
return false;
if (x == 1)
continue;
for (j = 0; VEC_iterate (data_reference_p, drs, j, b); j++)
if (DR_STMT (b) != stmt
&& DR_IS_WRITE (b)
&& same_data_refs_base_objects (a, b))
{
tree cb = bb_predicate (gimple_bb (DR_STMT (b)));
if (DR_WRITTEN_AT_LEAST_ONCE (b) == 1
|| is_true_predicate (cb)
|| is_true_predicate (ca = fold_or_predicates (EXPR_LOCATION (cb),
ca, cb)))
{
DR_WRITTEN_AT_LEAST_ONCE (a) = 1;
DR_WRITTEN_AT_LEAST_ONCE (b) = 1;
found = true;
break;
}
}
if (!found)
{
DR_WRITTEN_AT_LEAST_ONCE (a) = 0;
return false;
}
}
return true;
}
/* Return true when the memory references of STMT won't trap in the
if-converted code. There are two things that we have to check for:
- writes to memory occur to writable memory: if-conversion of
memory writes transforms the conditional memory writes into
unconditional writes, i.e. "if (cond) A[i] = foo" is transformed
into "A[i] = cond ? foo : A[i]", and as the write to memory may not
be executed at all in the original code, it may be a readonly
memory. To check that A is not const-qualified, we check that
there exists at least an unconditional write to A in the current
function.
- reads or writes to memory are valid memory accesses for every
iteration. To check that the memory accesses are correctly formed
and that we are allowed to read and write in these locations, we
check that the memory accesses to be if-converted occur at every
iteration unconditionally. */
static bool
ifcvt_memrefs_wont_trap (gimple stmt, VEC (data_reference_p, heap) *refs)
{
return write_memrefs_written_at_least_once (stmt, refs)
&& memrefs_read_or_written_unconditionally (stmt, refs);
}
/* Wrapper around gimple_could_trap_p refined for the needs of the
if-conversion. Try to prove that the memory accesses of STMT could
not trap in the innermost loop containing STMT. */
static bool
ifcvt_could_trap_p (gimple stmt, VEC (data_reference_p, heap) *refs)
{
if (gimple_vuse (stmt)
&& !gimple_could_trap_p_1 (stmt, false, false)
&& ifcvt_memrefs_wont_trap (stmt, refs))
return false;
return gimple_could_trap_p (stmt);
}
/* Return true when STMT is if-convertible.
GIMPLE_ASSIGN statement is not if-convertible if,
- it is not movable,
- it could trap,
- LHS is not var decl. */
static bool
if_convertible_gimple_assign_stmt_p (gimple stmt,
VEC (data_reference_p, heap) *refs)
{
tree lhs = gimple_assign_lhs (stmt);
basic_block bb;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "-------------------------\n");
print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
}
if (!is_gimple_reg_type (TREE_TYPE (lhs)))
return false;
/* Some of these constrains might be too conservative. */
if (stmt_ends_bb_p (stmt)
|| gimple_has_volatile_ops (stmt)
|| (TREE_CODE (lhs) == SSA_NAME
&& SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs))
|| gimple_has_side_effects (stmt))
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "stmt not suitable for ifcvt\n");
return false;
}
if (flag_tree_loop_if_convert_stores)
{
if (ifcvt_could_trap_p (stmt, refs))
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "tree could trap...\n");
return false;
}
return true;
}
if (gimple_assign_rhs_could_trap_p (stmt))
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "tree could trap...\n");
return false;
}
bb = gimple_bb (stmt);
if (TREE_CODE (lhs) != SSA_NAME
&& bb != bb->loop_father->header
&& !bb_with_exit_edge_p (bb->loop_father, bb))
{
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "LHS is not var\n");
print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
}
return false;
}
return true;
}
/* Return true when STMT is if-convertible.
A statement is if-convertible if:
- it is an if-convertible GIMPLE_ASSGIN,
- it is a GIMPLE_LABEL or a GIMPLE_COND. */
static bool
if_convertible_stmt_p (gimple stmt, VEC (data_reference_p, heap) *refs)
{
switch (gimple_code (stmt))
{
case GIMPLE_LABEL:
case GIMPLE_DEBUG:
case GIMPLE_COND:
return true;
case GIMPLE_ASSIGN:
return if_convertible_gimple_assign_stmt_p (stmt, refs);
case GIMPLE_CALL:
{
tree fndecl = gimple_call_fndecl (stmt);
if (fndecl)
{
int flags = gimple_call_flags (stmt);
if ((flags & ECF_CONST)
&& !(flags & ECF_LOOPING_CONST_OR_PURE)
/* We can only vectorize some builtins at the moment,
so restrict if-conversion to those. */
&& DECL_BUILT_IN (fndecl))
return true;
}
return false;
}
default:
/* Don't know what to do with 'em so don't do anything. */
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "don't know what to do\n");
print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
}
return false;
break;
}
return true;
}
/* Return true when BB post-dominates all its predecessors. */
static bool
bb_postdominates_preds (basic_block bb)
{
unsigned i;
for (i = 0; i < EDGE_COUNT (bb->preds); i++)
if (!dominated_by_p (CDI_POST_DOMINATORS, EDGE_PRED (bb, i)->src, bb))
return false;
return true;
}
/* Return true when BB is if-convertible. This routine does not check
basic block's statements and phis.
A basic block is not if-convertible if:
- it is non-empty and it is after the exit block (in BFS order),
- it is after the exit block but before the latch,
- its edges are not normal.
EXIT_BB is the basic block containing the exit of the LOOP. BB is
inside LOOP. */
static bool
if_convertible_bb_p (struct loop *loop, basic_block bb, basic_block exit_bb)
{
edge e;
edge_iterator ei;
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "----------[%d]-------------\n", bb->index);
if (EDGE_COUNT (bb->preds) > 2
|| EDGE_COUNT (bb->succs) > 2)
return false;
if (exit_bb)
{
if (bb != loop->latch)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "basic block after exit bb but before latch\n");
return false;
}
else if (!empty_block_p (bb))
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "non empty basic block after exit bb\n");
return false;
}
else if (bb == loop->latch
&& bb != exit_bb
&& !dominated_by_p (CDI_DOMINATORS, bb, exit_bb))
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "latch is not dominated by exit_block\n");
return false;
}
}
/* Be less adventurous and handle only normal edges. */
FOR_EACH_EDGE (e, ei, bb->succs)
if (e->flags &
(EDGE_ABNORMAL_CALL | EDGE_EH | EDGE_ABNORMAL | EDGE_IRREDUCIBLE_LOOP))
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Difficult to handle edges\n");
return false;
}
if (EDGE_COUNT (bb->preds) == 2
&& bb != loop->header
&& !bb_postdominates_preds (bb))
return false;
return true;
}
/* Return true when all predecessor blocks of BB are visited. The
VISITED bitmap keeps track of the visited blocks. */
static bool
pred_blocks_visited_p (basic_block bb, bitmap *visited)
{
edge e;
edge_iterator ei;
FOR_EACH_EDGE (e, ei, bb->preds)
if (!bitmap_bit_p (*visited, e->src->index))
return false;
return true;
}
/* Get body of a LOOP in suitable order for if-conversion. It is
caller's responsibility to deallocate basic block list.
If-conversion suitable order is, breadth first sort (BFS) order
with an additional constraint: select a block only if all its
predecessors are already selected. */
static basic_block *
get_loop_body_in_if_conv_order (const struct loop *loop)
{
basic_block *blocks, *blocks_in_bfs_order;
basic_block bb;
bitmap visited;
unsigned int index = 0;
unsigned int visited_count = 0;
gcc_assert (loop->num_nodes);
gcc_assert (loop->latch != EXIT_BLOCK_PTR);
blocks = XCNEWVEC (basic_block, loop->num_nodes);
visited = BITMAP_ALLOC (NULL);
blocks_in_bfs_order = get_loop_body_in_bfs_order (loop);
index = 0;
while (index < loop->num_nodes)
{
bb = blocks_in_bfs_order [index];
if (bb->flags & BB_IRREDUCIBLE_LOOP)
{
free (blocks_in_bfs_order);
BITMAP_FREE (visited);
free (blocks);
return NULL;
}
if (!bitmap_bit_p (visited, bb->index))
{
if (pred_blocks_visited_p (bb, &visited)
|| bb == loop->header)
{
/* This block is now visited. */
bitmap_set_bit (visited, bb->index);
blocks[visited_count++] = bb;
}
}
index++;
if (index == loop->num_nodes
&& visited_count != loop->num_nodes)
/* Not done yet. */
index = 0;
}
free (blocks_in_bfs_order);
BITMAP_FREE (visited);
return blocks;
}
/* Returns true when the analysis of the predicates for all the basic
blocks in LOOP succeeded.
predicate_bbs first allocates the predicates of the basic blocks.
These fields are then initialized with the tree expressions
representing the predicates under which a basic block is executed
in the LOOP. As the loop->header is executed at each iteration, it
has the "true" predicate. Other statements executed under a
condition are predicated with that condition, for example
| if (x)
| S1;
| else
| S2;
S1 will be predicated with "x", and
S2 will be predicated with "!x". */
static bool
predicate_bbs (loop_p loop)
{
unsigned int i;
for (i = 0; i < loop->num_nodes; i++)
init_bb_predicate (ifc_bbs[i]);
for (i = 0; i < loop->num_nodes; i++)
{
basic_block bb = ifc_bbs[i];
tree cond;
gimple_stmt_iterator itr;
/* The loop latch is always executed and has no extra conditions
to be processed: skip it. */
if (bb == loop->latch)
{
reset_bb_predicate (loop->latch);
continue;
}
cond = bb_predicate (bb);
for (itr = gsi_start_bb (bb); !gsi_end_p (itr); gsi_next (&itr))
{
gimple stmt = gsi_stmt (itr);
switch (gimple_code (stmt))
{
case GIMPLE_LABEL:
case GIMPLE_ASSIGN:
case GIMPLE_CALL:
case GIMPLE_DEBUG:
break;
case GIMPLE_COND:
{
tree c2, tem;
edge true_edge, false_edge;
location_t loc = gimple_location (stmt);
tree c = fold_build2_loc (loc, gimple_cond_code (stmt),
boolean_type_node,
gimple_cond_lhs (stmt),
gimple_cond_rhs (stmt));
/* Add new condition into destination's predicate list. */
extract_true_false_edges_from_block (gimple_bb (stmt),
&true_edge, &false_edge);
/* If C is true, then TRUE_EDGE is taken. */
add_to_dst_predicate_list (loop, true_edge,
unshare_expr (cond),
unshare_expr (c));
/* If C is false, then FALSE_EDGE is taken. */
c2 = invert_truthvalue_loc (loc, unshare_expr (c));
tem = canonicalize_cond_expr_cond (c2);
if (tem)
c2 = tem;
add_to_dst_predicate_list (loop, false_edge,
unshare_expr (cond), c2);
cond = NULL_TREE;
break;
}
default: