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chunker: optimized the barrel shift

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move the modulo out of the barrel shift and use 32bits variables so
that the compiler recognizes it and uses the "rol*" asm instructions.

Before: 245 MiB/s
After: 338 MiB/s

CPU: Intel(R) Core(TM) i5-3320M CPU @ 2.60GHz

Modification by Jonas: commit message formatting and added
Cyril Roussillon to AUTHORS
This commit is contained in:
Cyril Roussillon 2014-05-13 19:52:42 +02:00 committed by Jonas Borgström
parent 7e258c8401
commit 0b4e324af2
2 changed files with 8 additions and 5 deletions
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1
AUTHORS
View file

@ -9,6 +9,7 @@ Development Lead
Patches and Suggestions
```````````````````````
- Brian Johnson
- Cyril Roussillon
- Dan Christensen
- Jeremy Maitin-Shepard
- Johann Klähn

12
attic/_chunker.c
View file

@ -38,7 +38,7 @@ static uint32_t table_base[] =
0xc5ae37bb, 0xa76ce12a, 0x8150d8f3, 0x2ec29218, 0xa35f0984, 0x48c0647e, 0x0b5ff98c, 0x71893f7b
};
#define BARREL_SHIFT(v, shift) ( ((v) << ((shift) & 0x1f)) | ((v) >> (32 - ((shift) & 0x1f))) )
#define BARREL_SHIFT(v, shift) ( ((v) << shift) | ((v) >> (32 - shift)) )
static uint32_t *
@ -56,11 +56,12 @@ buzhash_init_table(uint32_t seed)
static uint32_t
buzhash(const unsigned char *data, size_t len, const uint32_t *h)
{
size_t i;
uint32_t sum = 0;
uint32_t i;
uint32_t sum = 0, imod;
for(i = len - 1; i > 0; i--)
{
sum ^= BARREL_SHIFT(h[*data], i);
imod = i & 0x1f;
sum ^= BARREL_SHIFT(h[*data], imod);
data++;
}
return sum ^ h[*data];
@ -69,7 +70,8 @@ buzhash(const unsigned char *data, size_t len, const uint32_t *h)
static uint32_t
buzhash_update(uint32_t sum, unsigned char remove, unsigned char add, size_t len, const uint32_t *h)
{
return BARREL_SHIFT(sum, 1) ^ BARREL_SHIFT(h[remove], len) ^ h[add];
uint32_t lenmod = len & 0x1f;
return BARREL_SHIFT(sum, 1) ^ BARREL_SHIFT(h[remove], lenmod) ^ h[add];
}
typedef struct {