Commit 34184b07 authored by Emilio G. Cota's avatar Emilio G. Cota Committed by Richard Henderson
Browse files

tcg: allocate optimizer temps with tcg_malloc 



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: default avatarRichard Henderson <rth@twiddle.net>
Signed-off-by: default avatarEmilio G. Cota <cota@braap.org>
Signed-off-by: default avatarRichard Henderson <richard.henderson@linaro.org>
parent c3fac113

tcg/optimize.c

+19 −23
Original line number Diff line number Diff line
@@ -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;
@@ -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)
@@ -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.
@@ -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;
@@ -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]);

            }

        }
@@ -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 {
@@ -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 {
@@ -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];
@@ -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];
@@ -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++) {