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65a7cce17d
qemu/tcg/optimize.c
Aurelien Jarno 65a7cce17d tcg/optimize: swap brcond/setcond arguments when possible 
brcond and setcond ops are not commutative, but it's easy to compute the
new condition after swapping the arguments. Try to always put the constant
argument in second position like for commutative ops, to help backends to
generate better code.

Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
2012-09-11 18:05:59 +02:00

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/*
* Optimizations for Tiny Code Generator for QEMU
*
* Copyright (c) 2010 Samsung Electronics.
* Contributed by Kirill Batuzov <batuzovk@ispras.ru>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "config.h"
#include <stdlib.h>
#include <stdio.h>
#include "qemu-common.h"
#include "tcg-op.h"
#define CASE_OP_32_64(x) \
glue(glue(case INDEX_op_, x), _i32): \
glue(glue(case INDEX_op_, x), _i64)
typedef enum {
TCG_TEMP_UNDEF = 0,
TCG_TEMP_CONST,
TCG_TEMP_COPY,
TCG_TEMP_HAS_COPY,
TCG_TEMP_ANY
} tcg_temp_state;
struct tcg_temp_info {
tcg_temp_state state;
uint16_t prev_copy;
uint16_t next_copy;
tcg_target_ulong val;
};
static struct tcg_temp_info temps[TCG_MAX_TEMPS];
/* Reset TEMP's state to TCG_TEMP_ANY. If TEMP was a representative of some
class of equivalent temp's, a new representative should be chosen in this
class. */
static void reset_temp(TCGArg temp, int nb_temps, int nb_globals)
{
int i;
TCGArg new_base = (TCGArg)-1;
if (temps[temp].state == TCG_TEMP_HAS_COPY) {
for (i = temps[temp].next_copy; i != temp; i = temps[i].next_copy) {
if (i >= nb_globals) {
temps[i].state = TCG_TEMP_HAS_COPY;
new_base = i;
break;
}
}
for (i = temps[temp].next_copy; i != temp; i = temps[i].next_copy) {
if (new_base == (TCGArg)-1) {
temps[i].state = TCG_TEMP_ANY;
} else {
temps[i].val = new_base;
}
}
temps[temps[temp].next_copy].prev_copy = temps[temp].prev_copy;
temps[temps[temp].prev_copy].next_copy = temps[temp].next_copy;
} else if (temps[temp].state == TCG_TEMP_COPY) {
temps[temps[temp].next_copy].prev_copy = temps[temp].prev_copy;
temps[temps[temp].prev_copy].next_copy = temps[temp].next_copy;
new_base = temps[temp].val;
}
temps[temp].state = TCG_TEMP_ANY;
if (new_base != (TCGArg)-1 && temps[new_base].next_copy == new_base) {
temps[new_base].state = TCG_TEMP_ANY;
}
}
static int op_bits(TCGOpcode op)
{
const TCGOpDef *def = &tcg_op_defs[op];
return def->flags & TCG_OPF_64BIT ? 64 : 32;
}
static TCGOpcode op_to_movi(TCGOpcode op)
{
switch (op_bits(op)) {
case 32:
return INDEX_op_movi_i32;
case 64:
return INDEX_op_movi_i64;
default:
fprintf(stderr, "op_to_movi: unexpected return value of "
"function op_bits.\n");
tcg_abort();
}
}
static void tcg_opt_gen_mov(TCGContext *s, TCGArg *gen_args, TCGArg dst,
TCGArg src, int nb_temps, int nb_globals)
{
reset_temp(dst, nb_temps, nb_globals);
assert(temps[src].state != TCG_TEMP_COPY);
/* Don't try to copy if one of temps is a global or either one
is local and another is register */
if (src >= nb_globals && dst >= nb_globals &&
tcg_arg_is_local(s, src) == tcg_arg_is_local(s, dst)) {
assert(temps[src].state != TCG_TEMP_CONST);
if (temps[src].state != TCG_TEMP_HAS_COPY) {
temps[src].state = TCG_TEMP_HAS_COPY;
temps[src].next_copy = src;
temps[src].prev_copy = src;
}
temps[dst].state = TCG_TEMP_COPY;
temps[dst].val = src;
temps[dst].next_copy = temps[src].next_copy;
temps[dst].prev_copy = src;
temps[temps[dst].next_copy].prev_copy = dst;
temps[src].next_copy = dst;
}
gen_args[0] = dst;
gen_args[1] = src;
}
static void tcg_opt_gen_movi(TCGArg *gen_args, TCGArg dst, TCGArg val,
int nb_temps, int nb_globals)
{
reset_temp(dst, nb_temps, nb_globals);
temps[dst].state = TCG_TEMP_CONST;
temps[dst].val = val;
gen_args[0] = dst;
gen_args[1] = val;
}
static TCGOpcode op_to_mov(TCGOpcode op)
{
switch (op_bits(op)) {
case 32:
return INDEX_op_mov_i32;
case 64:
return INDEX_op_mov_i64;
default:
fprintf(stderr, "op_to_mov: unexpected return value of "
"function op_bits.\n");
tcg_abort();
}
}
static TCGArg do_constant_folding_2(TCGOpcode op, TCGArg x, TCGArg y)
{
switch (op) {
CASE_OP_32_64(add):
return x + y;
CASE_OP_32_64(sub):
return x - y;
CASE_OP_32_64(mul):
return x * y;
CASE_OP_32_64(and):
return x & y;
CASE_OP_32_64(or):
return x | y;
CASE_OP_32_64(xor):
return x ^ y;
case INDEX_op_shl_i32:
return (uint32_t)x << (uint32_t)y;
case INDEX_op_shl_i64:
return (uint64_t)x << (uint64_t)y;
case INDEX_op_shr_i32:
return (uint32_t)x >> (uint32_t)y;
case INDEX_op_shr_i64:
return (uint64_t)x >> (uint64_t)y;
case INDEX_op_sar_i32:
return (int32_t)x >> (int32_t)y;
case INDEX_op_sar_i64:
return (int64_t)x >> (int64_t)y;
case INDEX_op_rotr_i32:
x = ((uint32_t)x << (32 - y)) | ((uint32_t)x >> y);
return x;
case INDEX_op_rotr_i64:
x = ((uint64_t)x << (64 - y)) | ((uint64_t)x >> y);
return x;
case INDEX_op_rotl_i32:
x = ((uint32_t)x << y) | ((uint32_t)x >> (32 - y));
return x;
case INDEX_op_rotl_i64:
x = ((uint64_t)x << y) | ((uint64_t)x >> (64 - y));
return x;
CASE_OP_32_64(not):
return ~x;
CASE_OP_32_64(neg):
return -x;
CASE_OP_32_64(andc):
return x & ~y;
CASE_OP_32_64(orc):
return x | ~y;
CASE_OP_32_64(eqv):
return ~(x ^ y);
CASE_OP_32_64(nand):
return ~(x & y);
CASE_OP_32_64(nor):
return ~(x | y);
CASE_OP_32_64(ext8s):
return (int8_t)x;
CASE_OP_32_64(ext16s):
return (int16_t)x;
CASE_OP_32_64(ext8u):
return (uint8_t)x;
CASE_OP_32_64(ext16u):
return (uint16_t)x;
case INDEX_op_ext32s_i64:
return (int32_t)x;
case INDEX_op_ext32u_i64:
return (uint32_t)x;
default:
fprintf(stderr,
"Unrecognized operation %d in do_constant_folding.\n", op);
tcg_abort();
}
}
static TCGArg do_constant_folding(TCGOpcode op, TCGArg x, TCGArg y)
{
TCGArg res = do_constant_folding_2(op, x, y);
if (op_bits(op) == 32) {
res &= 0xffffffff;
}
return res;
}
/* Propagate constants and copies, fold constant expressions. */
static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
TCGArg *args, TCGOpDef *tcg_op_defs)
{
int i, nb_ops, op_index, nb_temps, nb_globals, nb_call_args;
TCGOpcode op;
const TCGOpDef *def;
TCGArg *gen_args;
TCGArg tmp;
/* Array VALS has an element for each temp.
If this temp holds a constant then its value is kept in VALS' element.
If this temp is a copy of other ones then this equivalence class'
representative is kept in VALS' element.
If this temp is neither copy nor constant then corresponding VALS'
element is unused. */
nb_temps = s->nb_temps;
nb_globals = s->nb_globals;
memset(temps, 0, nb_temps * sizeof(struct tcg_temp_info));
nb_ops = tcg_opc_ptr - gen_opc_buf;
gen_args = args;
for (op_index = 0; op_index < nb_ops; op_index++) {
op = gen_opc_buf[op_index];
def = &tcg_op_defs[op];
/* Do copy propagation */
if (!(def->flags & (TCG_OPF_CALL_CLOBBER | TCG_OPF_SIDE_EFFECTS))) {
assert(op != INDEX_op_call);
for (i = def->nb_oargs; i < def->nb_oargs + def->nb_iargs; i++) {
if (temps[args[i]].state == TCG_TEMP_COPY) {
args[i] = temps[args[i]].val;
}
}
}
/* For commutative operations make constant second argument */
switch (op) {
CASE_OP_32_64(add):
CASE_OP_32_64(mul):
CASE_OP_32_64(and):
CASE_OP_32_64(or):
CASE_OP_32_64(xor):
CASE_OP_32_64(eqv):
CASE_OP_32_64(nand):
CASE_OP_32_64(nor):
if (temps[args[1]].state == TCG_TEMP_CONST) {
tmp = args[1];
args[1] = args[2];
args[2] = tmp;
}
break;
CASE_OP_32_64(brcond):
if (temps[args[0]].state == TCG_TEMP_CONST
&& temps[args[1]].state != TCG_TEMP_CONST) {
tmp = args[0];
args[0] = args[1];
args[1] = tmp;
args[2] = tcg_swap_cond(args[2]);
}
break;
CASE_OP_32_64(setcond):
if (temps[args[1]].state == TCG_TEMP_CONST
&& temps[args[2]].state != TCG_TEMP_CONST) {
tmp = args[1];
args[1] = args[2];
args[2] = tmp;
args[3] = tcg_swap_cond(args[3]);
}
break;
default:
break;
}
/* Simplify expressions for "shift/rot r, 0, a => movi r, 0" */
switch (op) {
CASE_OP_32_64(shl):
CASE_OP_32_64(shr):
CASE_OP_32_64(sar):
CASE_OP_32_64(rotl):
CASE_OP_32_64(rotr):
if (temps[args[1]].state == TCG_TEMP_CONST
&& temps[args[1]].val == 0) {
gen_opc_buf[op_index] = op_to_movi(op);
tcg_opt_gen_movi(gen_args, args[0], 0, nb_temps, nb_globals);
args += 3;
gen_args += 2;
continue;
}
break;
default:
break;
}
/* Simplify expression for "op r, a, 0 => mov r, a" cases */
switch (op) {
CASE_OP_32_64(add):
CASE_OP_32_64(sub):
CASE_OP_32_64(shl):
CASE_OP_32_64(shr):
CASE_OP_32_64(sar):
CASE_OP_32_64(rotl):
CASE_OP_32_64(rotr):
CASE_OP_32_64(or):
CASE_OP_32_64(xor):
if (temps[args[1]].state == TCG_TEMP_CONST) {
/* Proceed with possible constant folding. */
break;
}
if (temps[args[2]].state == TCG_TEMP_CONST
&& temps[args[2]].val == 0) {
if ((temps[args[0]].state == TCG_TEMP_COPY
&& temps[args[0]].val == args[1])
|| args[0] == args[1]) {
args += 3;
gen_opc_buf[op_index] = INDEX_op_nop;
} else {
gen_opc_buf[op_index] = op_to_mov(op);
tcg_opt_gen_mov(s, gen_args, args[0], args[1],
nb_temps, nb_globals);
gen_args += 2;
args += 3;
}
continue;
}
break;
default:
break;
}
/* Simplify expression for "op r, a, 0 => movi r, 0" cases */
switch (op) {
CASE_OP_32_64(and):
CASE_OP_32_64(mul):
if ((temps[args[2]].state == TCG_TEMP_CONST
&& temps[args[2]].val == 0)) {
gen_opc_buf[op_index] = op_to_movi(op);
tcg_opt_gen_movi(gen_args, args[0], 0, nb_temps, nb_globals);
args += 3;
gen_args += 2;
continue;
}
break;
default:
break;
}
/* Simplify expression for "op r, a, a => mov r, a" cases */
switch (op) {
CASE_OP_32_64(or):
CASE_OP_32_64(and):
if (args[1] == args[2]) {
if (args[1] == args[0]) {
args += 3;
gen_opc_buf[op_index] = INDEX_op_nop;
} else {
gen_opc_buf[op_index] = op_to_mov(op);
tcg_opt_gen_mov(s, gen_args, args[0], args[1], nb_temps,
nb_globals);
gen_args += 2;
args += 3;
}
continue;
}
break;
default:
break;
}
/* Propagate constants through copy operations and do constant
folding. Constants will be substituted to arguments by register
allocator where needed and possible. Also detect copies. */
switch (op) {
CASE_OP_32_64(mov):
if ((temps[args[1]].state == TCG_TEMP_COPY
&& temps[args[1]].val == args[0])
|| args[0] == args[1]) {
args += 2;
gen_opc_buf[op_index] = INDEX_op_nop;
break;
}
if (temps[args[1]].state != TCG_TEMP_CONST) {
tcg_opt_gen_mov(s, gen_args, args[0], args[1],
nb_temps, nb_globals);
gen_args += 2;
args += 2;
break;
}
/* Source argument is constant. Rewrite the operation and
let movi case handle it. */
op = op_to_movi(op);
gen_opc_buf[op_index] = op;
args[1] = temps[args[1]].val;
/* fallthrough */
CASE_OP_32_64(movi):
tcg_opt_gen_movi(gen_args, args[0], args[1], nb_temps, nb_globals);
gen_args += 2;
args += 2;
break;
CASE_OP_32_64(not):
CASE_OP_32_64(neg):
CASE_OP_32_64(ext8s):
CASE_OP_32_64(ext8u):
CASE_OP_32_64(ext16s):
CASE_OP_32_64(ext16u):
case INDEX_op_ext32s_i64:
case INDEX_op_ext32u_i64:
if (temps[args[1]].state == TCG_TEMP_CONST) {
gen_opc_buf[op_index] = op_to_movi(op);
tmp = do_constant_folding(op, temps[args[1]].val, 0);
tcg_opt_gen_movi(gen_args, args[0], tmp, nb_temps, nb_globals);
gen_args += 2;
args += 2;
break;
} else {
reset_temp(args[0], nb_temps, nb_globals);
gen_args[0] = args[0];
gen_args[1] = args[1];
gen_args += 2;
args += 2;
break;
}
CASE_OP_32_64(add):
CASE_OP_32_64(sub):
CASE_OP_32_64(mul):
CASE_OP_32_64(or):
CASE_OP_32_64(and):
CASE_OP_32_64(xor):
CASE_OP_32_64(shl):
CASE_OP_32_64(shr):
CASE_OP_32_64(sar):
CASE_OP_32_64(rotl):
CASE_OP_32_64(rotr):
CASE_OP_32_64(andc):
CASE_OP_32_64(orc):
CASE_OP_32_64(eqv):
CASE_OP_32_64(nand):
CASE_OP_32_64(nor):
if (temps[args[1]].state == TCG_TEMP_CONST
&& temps[args[2]].state == TCG_TEMP_CONST) {
gen_opc_buf[op_index] = op_to_movi(op);
tmp = do_constant_folding(op, temps[args[1]].val,
temps[args[2]].val);
tcg_opt_gen_movi(gen_args, args[0], tmp, nb_temps, nb_globals);
gen_args += 2;
args += 3;
break;
} else {
reset_temp(args[0], nb_temps, nb_globals);
gen_args[0] = args[0];
gen_args[1] = args[1];
gen_args[2] = args[2];
gen_args += 3;
args += 3;
break;
}
case INDEX_op_call:
nb_call_args = (args[0] >> 16) + (args[0] & 0xffff);
if (!(args[nb_call_args + 1] & (TCG_CALL_CONST | TCG_CALL_PURE))) {
for (i = 0; i < nb_globals; i++) {
reset_temp(i, nb_temps, nb_globals);
}
}
for (i = 0; i < (args[0] >> 16); i++) {
reset_temp(args[i + 1], nb_temps, nb_globals);
}
i = nb_call_args + 3;
while (i) {
*gen_args = *args;
args++;
gen_args++;
i--;
}
break;
case INDEX_op_set_label:
case INDEX_op_jmp:
case INDEX_op_br:
CASE_OP_32_64(brcond):
memset(temps, 0, nb_temps * sizeof(struct tcg_temp_info));
for (i = 0; i < def->nb_args; i++) {
*gen_args = *args;
args++;
gen_args++;
}
break;
default:
/* Default case: we do know nothing about operation so no
propagation is done. We only trash output args. */
for (i = 0; i < def->nb_oargs; i++) {
reset_temp(args[i], nb_temps, nb_globals);
}
for (i = 0; i < def->nb_args; i++) {
gen_args[i] = args[i];
}
args += def->nb_args;
gen_args += def->nb_args;
break;
}
}
return gen_args;
}
TCGArg *tcg_optimize(TCGContext *s, uint16_t *tcg_opc_ptr,
TCGArg *args, TCGOpDef *tcg_op_defs)
{
TCGArg *res;
res = tcg_constant_folding(s, tcg_opc_ptr, args, tcg_op_defs);
return res;
}
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