Commit 5900f0cd authored by unknown's avatar unknown
Browse files

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


innobase/include/univ.i:
  Replace PRULINT with ULINTPF in a comment.
  Document the macros based on __builtin_expect()
  and __builtin_prefetch().
parent 7256cdaa

innobase/include/univ.i

+15 −5
Original line number Diff line number Diff line
@@ -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"