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Add copy and constant propagation.

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Make tcg_constant_folding do copy and constant propagation. It is a
preparational work before actual constant folding.

Signed-off-by: Kirill Batuzov <batuzovk@ispras.ru>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
This commit is contained in:
Kirill Batuzov 2011-07-07 16:37:13 +04:00 committed by Blue Swirl
parent 8f2e8c07a6
commit 22613af4a6
1 changed files with 180 additions and 2 deletions
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182
tcg/optimize.c
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@ -40,24 +40,196 @@
glue(glue(case INDEX_op_, x), _i32)
#endif
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(int op)
{
switch (op) {
case INDEX_op_mov_i32:
return 32;
#if TCG_TARGET_REG_BITS == 64
case INDEX_op_mov_i64:
return 64;
#endif
default:
fprintf(stderr, "Unrecognized operation %d in op_bits.\n", op);
tcg_abort();
}
}
static int op_to_movi(int op)
{
switch (op_bits(op)) {
case 32:
return INDEX_op_movi_i32;
#if TCG_TARGET_REG_BITS == 64
case 64:
return INDEX_op_movi_i64;
#endif
default:
fprintf(stderr, "op_to_movi: unexpected return value of "
"function op_bits.\n");
tcg_abort();
}
}
static void tcg_opt_gen_mov(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);
if (src >= nb_globals) {
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;
}
/* 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, op, nb_temps, nb_globals;
int i, nb_ops, op_index, op, nb_temps, nb_globals, nb_call_args;
const TCGOpDef *def;
TCGArg *gen_args;
/* 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;
}
}
}
/* 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(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 INDEX_op_call:
i = (args[0] >> 16) + (args[0] & 0xffff) + 3;
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++;
@ -69,6 +241,7 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
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++;
@ -76,6 +249,11 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
}
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];
}