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>

1 files changed, 6 insertions, 5 deletions

diff --git a/tcg/tcg.h b/tcg/tcg.h
index 0d9bd293b5..c72af6cfb7 100644
--- a/tcg/tcg.h
+++ b/tcg/tcg.h
@@ -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;