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tcg: Use bitmaps for free temporaries

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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
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11
tcg/tcg.h
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@ -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;