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improve long-range decoder speed

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on enwik9 at level 22 (which is almost a worst case scenario),
speed improves by +7% on my laptop (415 -> 445 MB/s)
This commit is contained in:
Yann Collet
2018-11-08 12:47:46 -08:00
parent 8bed4012bd
commit 9126da5b5c
3 changed files with 14 additions and 12 deletions
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lib/common/compiler.h
+8 -10
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@@ -89,23 +89,21 @@
#endif
/* prefetch
* can be disabled, by declaring NO_PREFETCH macro
* All prefetch invocations use a single default locality 2,
* generating instruction prefetcht1,
* which, according to Intel, means "load data into L2 cache".
* This is a good enough "middle ground" for the time being,
* though in theory, it would be better to specialize locality depending on data being prefetched.
* Tests could not determine any sensible difference based on locality value. */
* can be disabled, by declaring NO_PREFETCH build macro */
#if defined(NO_PREFETCH)
# define PREFETCH_L1(ptr) (void)(ptr) /* disabled */
# define PREFETCH(ptr) (void)(ptr) /* disabled */
#else
# if defined(_MSC_VER) && (defined(_M_X64) || defined(_M_I86)) /* _mm_prefetch() is not defined outside of x86/x64 */
# include <mmintrin.h> /* https://msdn.microsoft.com/fr-fr/library/84szxsww(v=vs.90).aspx */
# define PREFETCH(ptr) _mm_prefetch((const char*)(ptr), _MM_HINT_T1)
# define PREFETCH_L1(ptr) _mm_prefetch((const char*)(ptr), _MM_HINT_T0)
# define PREFETCH(ptr) _mm_prefetch((const char*)(ptr), _MM_HINT_T1)
# elif defined(__GNUC__) && ( (__GNUC__ >= 4) || ( (__GNUC__ == 3) && (__GNUC_MINOR__ >= 1) ) )
# define PREFETCH(ptr) __builtin_prefetch((ptr), 0 /* rw==read */, 2 /* locality */)
# define PREFETCH_L1(ptr) __builtin_prefetch((ptr), 0 /* rw==read */, 3 /* locality */)
# define PREFETCH(ptr) __builtin_prefetch((ptr), 0 /* rw==read */, 2 /* locality */)
# else
# define PREFETCH(ptr) (void)(ptr) /* disabled */
# define PREFETCH_L1(ptr) (void)(ptr) /* disabled */
# define PREFETCH(ptr) (void)(ptr) /* disabled */
# endif
#endif /* NO_PREFETCH */