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tcg: allocate optimizer temps with tcg_malloc
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Groundwork for supporting multiple TCG contexts.

While at it, also allocate temps_used directly as a bitmap of the
required size, instead of using a bitmap of TCG_MAX_TEMPS via
TCGTempSet.

Performance-wise we lose about 1.12% in a translation-heavy workload
such as booting+shutting down debian-arm:

Performance counter stats for 'taskset -c 0 arm-softmmu/qemu-system-arm \
	-machine type=virt -nographic -smp 1 -m 4096 \
	-netdev user,id=unet,hostfwd=tcp::2222-:22 \
	-device virtio-net-device,netdev=unet \
	-drive file=die-on-boot.qcow2,id=myblock,index=0,if=none \
	-device virtio-blk-device,drive=myblock \
	-kernel kernel.img -append console=ttyAMA0 root=/dev/vda1 \
	-name arm,debug-threads=on -smp 1' (10 runs):

             exec time (s)  Relative slowdown wrt original (%)
---------------------------------------------------------------
 original     20.213321616                                  0.
 tcg_malloc   20.441130078                           1.1270214
 TCGContext   20.477846517                           1.3086662
 g_malloc     20.780527895                           2.8061013

The other two alternatives shown in the table are:
- TCGContext: embed temps[TCG_MAX_TEMPS] and TCGTempSet used_temps
  in TCGContext. This is simple enough but it isn't faster than using
  tcg_malloc; moreover, it wastes memory.
- g_malloc: allocate/deallocate both temps and used_temps every time
  tcg_optimize is executed.

Suggested-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
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@cota @rth7680
cota authored and rth7680 committed Oct 24, 2017
1 parent c3fac11 commit 34184b0
Showing 1 changed file with 19 additions and 23 deletions.
42 changes: 19 additions & 23 deletions tcg/optimize.c
View file
Expand Up @@ -40,9 +40,6 @@ struct tcg_temp_info {
tcg_target_ulong mask;
};

static struct tcg_temp_info temps[TCG_MAX_TEMPS];
static TCGTempSet temps_used;

static inline struct tcg_temp_info *ts_info(TCGTemp *ts)
{
return ts->state_ptr;
Expand Down Expand Up @@ -88,31 +85,27 @@ static void reset_temp(TCGArg arg)
reset_ts(arg_temp(arg));
}

/* Reset all temporaries, given that there are NB_TEMPS of them. */
static void reset_all_temps(int nb_temps)
{
bitmap_zero(temps_used.l, nb_temps);
}

/* Initialize and activate a temporary. */
static void init_ts_info(TCGTemp *ts)
static void init_ts_info(struct tcg_temp_info *infos,
TCGTempSet *temps_used, TCGTemp *ts)
{
size_t idx = temp_idx(ts);
if (!test_bit(idx, temps_used.l)) {
struct tcg_temp_info *ti = &temps[idx];
if (!test_bit(idx, temps_used->l)) {
struct tcg_temp_info *ti = &infos[idx];

ts->state_ptr = ti;
ti->next_copy = ts;
ti->prev_copy = ts;
ti->is_const = false;
ti->mask = -1;
set_bit(idx, temps_used.l);
set_bit(idx, temps_used->l);
}
}

static void init_arg_info(TCGArg arg)
static void init_arg_info(struct tcg_temp_info *infos,
TCGTempSet *temps_used, TCGArg arg)
{
init_ts_info(arg_temp(arg));
init_ts_info(infos, temps_used, arg_temp(arg));
}

static int op_bits(TCGOpcode op)
Expand Down Expand Up @@ -611,6 +604,8 @@ void tcg_optimize(TCGContext *s)
{
int oi, oi_next, nb_temps, nb_globals;
TCGOp *prev_mb = NULL;
struct tcg_temp_info *infos;
TCGTempSet temps_used;

/* Array VALS has an element for each temp.
If this temp holds a constant then its value is kept in VALS' element.
Expand All @@ -619,7 +614,8 @@ void tcg_optimize(TCGContext *s)

nb_temps = s->nb_temps;
nb_globals = s->nb_globals;
reset_all_temps(nb_temps);
bitmap_zero(temps_used.l, nb_temps);
infos = tcg_malloc(sizeof(struct tcg_temp_info) * nb_temps);

for (oi = s->gen_op_buf[0].next; oi != 0; oi = oi_next) {
tcg_target_ulong mask, partmask, affected;
Expand All @@ -640,14 +636,14 @@ void tcg_optimize(TCGContext *s)
for (i = 0; i < nb_oargs + nb_iargs; i++) {
TCGTemp *ts = arg_temp(op->args[i]);
if (ts) {
init_ts_info(ts);
init_ts_info(infos, &temps_used, ts);
}
}
} else {
nb_oargs = def->nb_oargs;
nb_iargs = def->nb_iargs;
for (i = 0; i < nb_oargs + nb_iargs; i++) {
init_arg_info(op->args[i]);
init_arg_info(infos, &temps_used, op->args[i]);
}
}

Expand Down Expand Up @@ -1208,7 +1204,7 @@ void tcg_optimize(TCGContext *s)
op->args[1], op->args[2]);
if (tmp != 2) {
if (tmp) {
reset_all_temps(nb_temps);
bitmap_zero(temps_used.l, nb_temps);
op->opc = INDEX_op_br;
op->args[0] = op->args[3];
} else {
Expand Down Expand Up @@ -1297,7 +1293,7 @@ void tcg_optimize(TCGContext *s)
if (tmp != 2) {
if (tmp) {
do_brcond_true:
reset_all_temps(nb_temps);
bitmap_zero(temps_used.l, nb_temps);
op->opc = INDEX_op_br;
op->args[0] = op->args[5];
} else {
Expand All @@ -1313,7 +1309,7 @@ void tcg_optimize(TCGContext *s)
/* Simplify LT/GE comparisons vs zero to a single compare
vs the high word of the input. */
do_brcond_high:
reset_all_temps(nb_temps);
bitmap_zero(temps_used.l, nb_temps);
op->opc = INDEX_op_brcond_i32;
op->args[0] = op->args[1];
op->args[1] = op->args[3];
Expand All @@ -1339,7 +1335,7 @@ void tcg_optimize(TCGContext *s)
goto do_default;
}
do_brcond_low:
reset_all_temps(nb_temps);
bitmap_zero(temps_used.l, nb_temps);
op->opc = INDEX_op_brcond_i32;
op->args[1] = op->args[2];
op->args[2] = op->args[4];
Expand Down Expand Up @@ -1459,7 +1455,7 @@ void tcg_optimize(TCGContext *s)
block, otherwise we only trash the output args. "mask" is
the non-zero bits mask for the first output arg. */
if (def->flags & TCG_OPF_BB_END) {
reset_all_temps(nb_temps);
bitmap_zero(temps_used.l, nb_temps);
} else {
do_reset_output:
for (i = 0; i < nb_oargs; i++) {
Expand Down

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