This brings down the size of the struct from 56 to 32 bytes on 64-bit,
and to 16 bytes on 32-bit.
The appended adds macros to prevent us from mistakenly overflowing
the bitfields when more elements are added to the corresponding
enums/macros.
Note that reg/mem_reg need only 6 bits (for ia64) but for performance
is probably better to align them to a byte address.
Given that TCGTemp is used in large arrays this leads to a few KBs
of savings. However, unpacking the bits takes additional code, so
the net effect depends on the target (host is x86_64):
Before:
$ find . -name 'tcg.o' | xargs size
text data bss dec hex filename
41131 29800 88 71019 1156b ./aarch64-softmmu/tcg/tcg.o
37969 29416 96 67481 10799 ./x86_64-linux-user/tcg/tcg.o
39354 28816 96 68266 10aaa ./arm-linux-user/tcg/tcg.o
40802 29096 88 69986 11162 ./arm-softmmu/tcg/tcg.o
39417 29672 88 69177 10e39 ./x86_64-softmmu/tcg/tcg.o
After:
$ find . -name 'tcg.o' | xargs size
text data bss dec hex filename
41187 29800 88 71075 115a3 ./aarch64-softmmu/tcg/tcg.o
37777 29416 96 67289 106d9 ./x86_64-linux-user/tcg/tcg.o
39162 28816 96 68074 109ea ./arm-linux-user/tcg/tcg.o
40858 29096 88 70042 1119a ./arm-softmmu/tcg/tcg.o
39473 29672 88 69233 10e71 ./x86_64-softmmu/tcg/tcg.o
Suggested-by: Stefan Weil <s...@weilnetz.de>
Suggested-by: Richard Henderson <r...@twiddle.net>
Signed-off-by: Emilio G. Cota <c...@braap.org>
---
tcg/tcg.h | 22 +++++++++++++---------
1 file changed, 13 insertions(+), 9 deletions(-)
diff --git a/tcg/tcg.h b/tcg/tcg.h
index add7f75..71ae7b2 100644
--- a/tcg/tcg.h
+++ b/tcg/tcg.h
@@ -193,7 +193,7 @@ typedef struct TCGPool {
typedef enum TCGType {
TCG_TYPE_I32,
TCG_TYPE_I64,
- TCG_TYPE_COUNT, /* number of different types */
+ TCG_TYPE_COUNT, /* number of different types, see TCG_TYPE_NR_BITS */
/* An alias for the size of the host register. */
#if TCG_TARGET_REG_BITS == 32
@@ -217,6 +217,9 @@ typedef enum TCGType {
#endif
} TCGType;
+/* used for bitfield packing to save space */
+#define TCG_TYPE_NR_BITS 1
+
/* Constants for qemu_ld and qemu_st for the Memory Operation field. */
typedef enum TCGMemOp {
MO_8 = 0,
@@ -421,16 +424,14 @@ static inline TCGCond tcg_high_cond(TCGCond c)
#define TEMP_VAL_REG 1
#define TEMP_VAL_MEM 2
#define TEMP_VAL_CONST 3
+#define TEMP_VAL_NR_BITS 2
-/* XXX: optimize memory layout */
typedef struct TCGTemp {
- TCGType base_type;
- TCGType type;
- int val_type;
- int reg;
- tcg_target_long val;
- int mem_reg;
- intptr_t mem_offset;
+ unsigned int reg:8;
+ unsigned int mem_reg:8;
+ unsigned int val_type:TEMP_VAL_NR_BITS;
+ unsigned int base_type:TCG_TYPE_NR_BITS;
+ unsigned int type:TCG_TYPE_NR_BITS;
unsigned int fixed_reg:1;
unsigned int mem_coherent:1;
unsigned int mem_allocated:1;
@@ -438,6 +439,9 @@ typedef struct TCGTemp {
basic blocks. Otherwise, it is not
preserved across basic blocks. */
unsigned int temp_allocated:1; /* never used for code gen */
+
+ tcg_target_long val;
+ intptr_t mem_offset;
const char *name;
} TCGTemp;
--
1.9.1
