Am 21.03.2015 um 07:27 schrieb Emilio G. Cota:
This brings down the size of the struct from 56 to 48 bytes.
Signed-off-by: Emilio G. Cota <c...@braap.org>
---
tcg/tcg.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tcg/tcg.h b/tcg/tcg.h
index add7f75..3276924 100644
--- a/tcg/tcg.h
+++ b/tcg/tcg.h
@@ -429,8 +429,8 @@ typedef struct TCGTemp {
int val_type;
int reg;
tcg_target_long val;
- int mem_reg;
intptr_t mem_offset;
+ int mem_reg;
unsigned int fixed_reg:1;
unsigned int mem_coherent:1;
unsigned int mem_allocated:1;
Reviewed-by: Stefan Weil <s...@weilnetz.de>
TCGContext includes an array of TCGTemp, so it is even reduced by 4 KiB
(good for caching),
and tcg.o now uses 55364 instead of 56116 bytes (maybe faster, too).
Further optimizations are possible. TCGTemp can be reduced to 32 bytes
as the output
of pahole shows:
struct TCGTemp {
TCGTempVal val_type:8; /* 0:24 4 */
unsigned int reg:8; /* 0:16 4 */
unsigned int mem_reg:8; /* 0: 8 4 */
/* Bitfield combined with next fields */
_Bool fixed_reg:1; /* 3: 7 1 */
_Bool mem_coherent:1; /* 3: 6 1 */
_Bool mem_allocated:1; /* 3: 5 1 */
_Bool temp_local:1; /* 3: 4 1 */
_Bool temp_allocated:1; /* 3: 3 1 */
/* XXX 3 bits hole, try to pack */
TCGType base_type:16; /* 4:16 4 */
TCGType type:16; /* 4: 0 4 */
tcg_target_long val; /* 8 8 */
intptr_t mem_offset; /* 16 8 */
const char * name; /* 24 8 */
/* size: 32, cachelines: 1, members: 13 */
/* bit holes: 1, sum bit holes: 3 bits */
/* last cacheline: 32 bytes */
};
Here I used a new enum type for val_type and reduced some values to 8 or
16 bit.
I also put the two most often used values at the beginning, so they can be
addressed without or with a small offset ("often" in the code, no runtime
data available).
Are such optimizations useful?
Stefan
