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innobase/include/univ.i: Added some comments.

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innobase/include/univ.i:
  Replace PRULINT with ULINTPF in a comment.
  Document the macros based on __builtin_expect()
  and __builtin_prefetch().
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unknown 2005-06-10 12:29:35 +03:00
commit 5900f0cd5c
1 changed files with 15 additions and 5 deletions
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innobase/include/univ.i
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@ -181,7 +181,7 @@ management to ensure correct alignment for doubles etc. */
/* Another basic type we use is unsigned long integer which should be equal to
the word size of the machine, that is on a 32-bit platform 32 bits, and on a
64-bit platform 64 bits. We also give the printf format for the type as a
macro PRULINT. */
macro ULINTPF. */
#ifdef _WIN64
typedef unsigned __int64 ulint;
@ -243,19 +243,29 @@ contains the sum of the following flag and the locally stored len. */
#define UNIV_EXTERN_STORAGE_FIELD (UNIV_SQL_NULL - UNIV_PAGE_SIZE)
/* Some macros to improve branch prediction and reduce cache misses */
#if defined(__GNUC__) && (__GNUC__ > 2)
# define UNIV_EXPECT(expr,value) __builtin_expect(expr, value)
# define UNIV_LIKELY_NULL(expr) __builtin_expect((ulint) expr, 0)
/* Tell the compiler that 'expr' probably evaluates to 'constant'. */
# define UNIV_EXPECT(expr,constant) __builtin_expect(expr, constant)
/* Tell the compiler that a pointer is likely to be NULL */
# define UNIV_LIKELY_NULL(ptr) __builtin_expect((ulint) ptr, 0)
/* Minimize cache-miss latency by moving data at addr into a cache before
it is read. */
# define UNIV_PREFETCH_R(addr) __builtin_prefetch(addr, 0, 3)
/* Minimize cache-miss latency by moving data at addr into a cache before
it is read or written. */
# define UNIV_PREFETCH_RW(addr) __builtin_prefetch(addr, 1, 3)
#else
/* Dummy versions of the macros */
# define UNIV_EXPECT(expr,value) (expr)
# define UNIV_LIKELY_NULL(expr) (expr)
# define UNIV_PREFETCH_R(addr) ((void) 0)
# define UNIV_PREFETCH_RW(addr) ((void) 0)
#endif
#define UNIV_LIKELY(expr) UNIV_EXPECT(expr, TRUE)
#define UNIV_UNLIKELY(expr) UNIV_EXPECT(expr, FALSE)
/* Tell the compiler that cond is likely to hold */
#define UNIV_LIKELY(cond) UNIV_EXPECT(cond, TRUE)
/* Tell the compiler that cond is unlikely to hold */
#define UNIV_UNLIKELY(cond) UNIV_EXPECT(cond, FALSE)
#include <stdio.h>
#include "ut0dbg.h"