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tcg: Use bitmaps for free temporaries 

We previously allocated 32-bits per temp for the next_free_temp entry.
We now allocate 4 bits per temp across the 4 bitmaps.

Using a linked list meant that if a translator is tweeked, resulting in
temps being freed in a different order, that would have follow-on effects
throughout the TB.  Always allocating the lowest free temp means that
follow-on effects are minimized, which can make it easier to diff output
when debugging the translators.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Richard Henderson 2013-09-19 12:16:45 -07:00
parent 8f84271da8
commit 0ec9eabc7f
2 changed files with 21 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
tcg/tcg.c
View File

@ -357,11 +357,12 @@ void tcg_set_frame(TCGContext *s, int reg, intptr_t start, intptr_t size)
void tcg_func_start(TCGContext *s)
{
int i;
tcg_pool_reset(s);
s->nb_temps = s->nb_globals;
for(i = 0; i < (TCG_TYPE_COUNT * 2); i++)
s->first_free_temp[i] = -1;
/* No temps have been previously allocated for size or locality. */
memset(s->free_temps, 0, sizeof(s->free_temps));
s->labels = tcg_malloc(sizeof(TCGLabel) * TCG_MAX_LABELS);
s->nb_labels = 0;
s->current_frame_offset = s->frame_start;
@ -503,16 +504,15 @@ static inline int tcg_temp_new_internal(TCGType type, int temp_local)
TCGTemp *ts;
int idx, k;
k = type;
if (temp_local)
k += TCG_TYPE_COUNT;
idx = s->first_free_temp[k];
if (idx != -1) {
/* There is already an available temp with the
right type */
k = type + (temp_local ? TCG_TYPE_COUNT : 0);
idx = find_first_bit(s->free_temps[k].l, TCG_MAX_TEMPS);
if (idx < TCG_MAX_TEMPS) {
/* There is already an available temp with the right type. */
clear_bit(idx, s->free_temps[k].l);
ts = &s->temps[idx];
s->first_free_temp[k] = ts->next_free_temp;
ts->temp_allocated = 1;
assert(ts->base_type == type);
assert(ts->temp_local == temp_local);
} else {
idx = s->nb_temps;
@ -568,7 +568,7 @@ TCGv_i64 tcg_temp_new_internal_i64(int temp_local)
return MAKE_TCGV_I64(idx);
}
static inline void tcg_temp_free_internal(int idx)
static void tcg_temp_free_internal(int idx)
{
TCGContext *s = &tcg_ctx;
TCGTemp *ts;
@ -585,11 +585,9 @@ static inline void tcg_temp_free_internal(int idx)
ts = &s->temps[idx];
assert(ts->temp_allocated != 0);
ts->temp_allocated = 0;
k = ts->base_type;
if (ts->temp_local)
k += TCG_TYPE_COUNT;
ts->next_free_temp = s->first_free_temp[k];
s->first_free_temp[k] = idx;
k = ts->type + (ts->temp_local ? TCG_TYPE_COUNT : 0);
set_bit(idx, s->free_temps[k].l);
}
void tcg_temp_free_i32(TCGv_i32 arg)

11
tcg/tcg.h
View File

@ -26,7 +26,7 @@
#define TCG_H
#include "qemu-common.h"
#include "qemu/bitops.h"
#include "tcg-target.h"
/* Default target word size to pointer size. */
@ -436,13 +436,15 @@ typedef struct TCGTemp {
basic blocks. Otherwise, it is not
preserved across basic blocks. */
unsigned int temp_allocated:1; /* never used for code gen */
/* index of next free temp of same base type, -1 if end */
int next_free_temp;
const char *name;
} TCGTemp;
typedef struct TCGContext TCGContext;
typedef struct TCGTempSet {
unsigned long l[BITS_TO_LONGS(TCG_MAX_TEMPS)];
} TCGTempSet;
struct TCGContext {
uint8_t *pool_cur, *pool_end;
TCGPool *pool_first, *pool_current, *pool_first_large;
@ -450,8 +452,6 @@ struct TCGContext {
int nb_labels;
int nb_globals;
int nb_temps;
/* index of free temps, -1 if none */
int first_free_temp[TCG_TYPE_COUNT * 2];
/* goto_tb support */
uint8_t *code_buf;
@ -477,6 +477,7 @@ struct TCGContext {
uint8_t *code_ptr;
TCGTemp temps[TCG_MAX_TEMPS]; /* globals first, temps after */
TCGTempSet free_temps[TCG_TYPE_COUNT * 2];
GHashTable *helpers;