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Re: [Qemu-devel] [PATCH 10/16] tcg: Avoid loops against variable bounds
From: |
Alex Bennée |
Subject: |
Re: [Qemu-devel] [PATCH 10/16] tcg: Avoid loops against variable bounds |
Date: |
Tue, 27 Jun 2017 10:01:21 +0100 |
User-agent: |
mu4e 0.9.19; emacs 25.2.50.3 |
Richard Henderson <address@hidden> writes:
> Copy s->nb_globals or s->nb_temps to a local variable for the purposes
> of iteration. This should allow the compiler to use low-overhead
> looping constructs on some hosts.
>
> Signed-off-by: Richard Henderson <address@hidden>
> ---
> tcg/tcg.c | 27 ++++++++++-----------------
> 1 file changed, 10 insertions(+), 17 deletions(-)
>
> diff --git a/tcg/tcg.c b/tcg/tcg.c
> index e78140b..c228f1e 100644
> --- a/tcg/tcg.c
> +++ b/tcg/tcg.c
> @@ -943,23 +943,16 @@ void tcg_gen_callN(TCGContext *s, void *func, TCGArg
> ret,
>
> static void tcg_reg_alloc_start(TCGContext *s)
> {
> - int i;
> + int i, n;
> TCGTemp *ts;
> - for(i = 0; i < s->nb_globals; i++) {
> +
> + for (i = 0, n = s->nb_globals; i < n; i++) {
> ts = &s->temps[i];
> - if (ts->fixed_reg) {
> - ts->val_type = TEMP_VAL_REG;
> - } else {
> - ts->val_type = TEMP_VAL_MEM;
> - }
> + ts->val_type = (ts->fixed_reg ? TEMP_VAL_REG : TEMP_VAL_MEM);
> }
> - for(i = s->nb_globals; i < s->nb_temps; i++) {
> + for (n = s->nb_temps; i < n; i++) {
A one line comment like /* i continues on from s->nb_globals above */
might prevent a momentary confusion when reading through.
> ts = &s->temps[i];
> - if (ts->temp_local) {
> - ts->val_type = TEMP_VAL_MEM;
> - } else {
> - ts->val_type = TEMP_VAL_DEAD;
> - }
> + ts->val_type = (ts->temp_local ? TEMP_VAL_MEM : TEMP_VAL_DEAD);
> ts->mem_allocated = 0;
> ts->fixed_reg = 0;
> }
> @@ -2050,9 +2043,9 @@ static void temp_save(TCGContext *s, TCGTemp *ts,
> TCGRegSet allocated_regs)
> temporary registers needs to be allocated to store a constant. */
> static void save_globals(TCGContext *s, TCGRegSet allocated_regs)
> {
> - int i;
> + int i, n;
>
> - for (i = 0; i < s->nb_globals; i++) {
> + for (i = 0, n = s->nb_globals; i < n; i++) {
> temp_save(s, &s->temps[i], allocated_regs);
> }
> }
> @@ -2062,9 +2055,9 @@ static void save_globals(TCGContext *s, TCGRegSet
> allocated_regs)
> temporary registers needs to be allocated to store a constant. */
> static void sync_globals(TCGContext *s, TCGRegSet allocated_regs)
> {
> - int i;
> + int i, n;
>
> - for (i = 0; i < s->nb_globals; i++) {
> + for (i = 0, n = s->nb_globals; i < n; i++) {
> TCGTemp *ts = &s->temps[i];
> tcg_debug_assert(ts->val_type != TEMP_VAL_REG
> || ts->fixed_reg
Otherwise:
Reviewed-by: Alex Bennée <address@hidden>
--
Alex Bennée
- Re: [Qemu-devel] [PATCH 06/16] tcg: Add temp_global bit to TCGTemp, (continued)
- [Qemu-devel] [PATCH 07/16] tcg: Return NULL temp for TCG_CALL_DUMMY_ARG, Richard Henderson, 2017/06/20
- [Qemu-devel] [PATCH 02/16] tcg: Propagate args to op->args in optimizer, Richard Henderson, 2017/06/20
- [Qemu-devel] [PATCH 05/16] tcg: Introduce arg_temp, Richard Henderson, 2017/06/20
- [Qemu-devel] [PATCH 10/16] tcg: Avoid loops against variable bounds, Richard Henderson, 2017/06/20
- Re: [Qemu-devel] [PATCH 10/16] tcg: Avoid loops against variable bounds,
Alex Bennée <=
- [Qemu-devel] [PATCH 11/16] tcg: Change temp_allocate_frame arg to TCGTemp, Richard Henderson, 2017/06/20
- [Qemu-devel] [PATCH 09/16] tcg: Use per-temp state data in liveness, Richard Henderson, 2017/06/20
- [Qemu-devel] [PATCH 08/16] tcg: Introduce temp_arg, Richard Henderson, 2017/06/20
- [Qemu-devel] [PATCH 12/16] tcg: Remove unused TCG_CALL_DUMMY_TCGV, Richard Henderson, 2017/06/20
- [Qemu-devel] [PATCH 13/16] tcg: Export temp_idx, Richard Henderson, 2017/06/20