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/* This pass tries to simplify conditional expression made of a couple of
conditional/unconditional branches if one of the two outgoing paths falls
through to the next basic block.
Copyright (C) 2006-2010 Free Software Foundation, Inc.
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 2, 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 COPYING. If not, write to the Free
Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301, USA.
Authors:
Andrea Ornstein
Erven Rohou
Gabriele Svelto
Thierry Lafage
Contact information at STMicroelectronics:
Andrea C. Ornstein <andrea.ornstein@st.com>
Contact information at INRIA:
Erven Rohou <erven.rohou@inria.fr>
Thierry Lafage <thierry.lafage@inria.fr>
*/
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "flags.h"
#include "timevar.h"
#include "tree.h"
#include "tree-flow.h"
#include "tree-pass.h"
#include "cil-stack.h"
#include "cil-stmt.h"
#include "cil-types.h"
/* These 2 lines avoid including options.h */
extern int flag_cil32_simp_cond;
extern int flag_cil32_simp_cond_float;
/******************************************************************************
* Local functions prototypes *
******************************************************************************/
static inline enum cil_opcode int_condbr_invert (enum cil_opcode);
static inline enum cil_opcode float_condbr_invert (enum cil_opcode);
static void simplify_cond_branch (cil_stmt_iterator *, cil_stack);
static unsigned int simp_cond (void);
static bool simp_cond_gate (void);
/******************************************************************************
* Pass implementation *
******************************************************************************/
static inline enum cil_opcode
int_condbr_invert (enum cil_opcode condbr)
{
switch (condbr)
{
case CIL_BEQ: return CIL_BNE_UN;
case CIL_BGE: return CIL_BLT;
case CIL_BGE_UN: return CIL_BLT_UN;
case CIL_BGT: return CIL_BLE;
case CIL_BGT_UN: return CIL_BLE_UN;
case CIL_BLE: return CIL_BGT;
case CIL_BLE_UN: return CIL_BGT_UN;
case CIL_BLT: return CIL_BGE;
case CIL_BLT_UN: return CIL_BGE_UN;
case CIL_BNE_UN: return CIL_BEQ;
case CIL_BRTRUE: return CIL_BRFALSE;
case CIL_BRFALSE: return CIL_BRTRUE;
default:
return condbr; /* Do nothing, we cannot change this branch. */
}
}
static inline enum cil_opcode
float_condbr_invert (enum cil_opcode condbr)
{
switch (condbr)
{
case CIL_BEQ: return CIL_BNE_UN;
case CIL_BGE: return CIL_BLT_UN;
case CIL_BGE_UN: return CIL_BLT;
case CIL_BGT: return CIL_BLE_UN;
case CIL_BGT_UN: return CIL_BLE;
case CIL_BLE: return CIL_BGT_UN;
case CIL_BLE_UN: return CIL_BGT;
case CIL_BLT: return CIL_BGE_UN;
case CIL_BLT_UN: return CIL_BGE;
case CIL_BNE_UN: return CIL_BEQ;
default:
return condbr; /* Do nothing, we cannot change this branch. */
}
}
static void
simplify_cond_branch (cil_stmt_iterator *csi, cil_stack stack)
{
cil_stmt stmt;
cil_type_t type;
enum cil_opcode opcode, condbr;
tree label_then, label_else;
basic_block then_bb;
edge true_edge, false_edge;
/* Extract the condition's edges. */
extract_true_false_edges_from_block (csi_bb (*csi), &true_edge, &false_edge);
label_then = gimple_block_label (true_edge->dest);
label_else = gimple_block_label (false_edge->dest);
then_bb = label_to_block (label_then);
/* Simplify the condition only if the 'then' edge can be turned into a
fall through to the next basic block. */
if (csi_bb (*csi)->next_bb == then_bb)
{
type = cil_stack_top (stack);
opcode = condbr = cil_opcode (csi_stmt (*csi));
if (flag_cil32_simp_cond && (cil_integer_p (type) || cil_pointer_p (type)))
opcode = int_condbr_invert (condbr);
else if (flag_cil32_simp_cond_float && cil_float_p (type))
opcode = float_condbr_invert (condbr);
if (opcode == condbr)
return; /* No opcode change */
stmt = cil_build_stmt_arg (opcode, label_else);
csi_replace (csi, stmt);
csi_next (csi);
csi_remove (csi);
/* Invert the out-going edges */
true_edge->flags ^= (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
false_edge->flags ^= (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
}
}
/* Main function of this pass. Looks for conditional expressions and
inverts their condition if it allows removing the unconditional branch
following it. */
static unsigned int
simp_cond (void)
{
basic_block bb;
cil_stmt_iterator csi;
cil_stmt stmt;
enum cil_opcode opcode;
cil_bb_stacks bbs;
cil_stack stack;
edge_iterator ei;
edge e;
bbs = cil_bb_stacks_create ();
FOR_EACH_BB (bb)
{
stack = cil_stack_for_bb (bbs, bb);
csi = csi_start_bb (bb);
while (!csi_end_p (csi))
{
stmt = csi_stmt (csi);
opcode = cil_opcode (stmt);
if (cil_cond_branch_p (stmt) && !csi_one_before_end_p (csi))
{
csi_next (&csi);
if (cil_opcode (csi_stmt (csi)) == CIL_BR)
{
csi_prev (&csi);
simplify_cond_branch (&csi, stack);
break;
}
}
cil_stack_after_stmt (stack, stmt);
csi_next (&csi);
}
FOR_EACH_EDGE (e, ei, bb->succs)
{
cil_set_stack_for_bb (bbs, e->dest, stack);
}
}
cil_bb_stacks_destroy (bbs);
return 0;
}
/* Gate function of the peephole-optimizations pass. */
static bool
simp_cond_gate (void)
{
return flag_cil32_simp_cond != 0 || flag_cil32_simp_cond_float != 0;
}
/* Define the parameters of the cond-simp pass. */
struct gimple_opt_pass pass_simp_cond =
{
{
GIMPLE_PASS, /* type */
"cond_simp", /* name */
simp_cond_gate, /* gate */
simp_cond, /* execute */
NULL, /* sub */
NULL, /* next */
0, /* static_pass_number */
TV_SIMP_COND, /* tv_id */
PROP_cfg|PROP_cil, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
TODO_ggc_collect|TODO_dump_func /* todo_flags_finish */
}
};
/*
* Local variables:
* eval: (c-set-style "gnu")
* End:
*/
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