diff options
Diffstat (limited to 'gcc/doc/extend.texi')
| -rw-r--r-- | gcc/doc/extend.texi | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index 61757f0d4d9..a6853d8206e 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -4442,7 +4442,7 @@ if (__builtin_expect (ptr != NULL, 1)) when testing pointer or floating-point values. @end deftypefn -@deftypefn {Built-in Function} void __builtin_prefetch (void *@var{addr}, int @var{rw}, int @var{locality}) +@deftypefn {Built-in Function} void __builtin_prefetch (void *@var{addr}, ...) This function is used to minimize cache-miss latency by moving data into a cache before it is accessed. You can insert calls to @code{__builtin_prefetch} into code for which @@ -4452,14 +4452,17 @@ If the prefetch is done early enough before the access then the data will be in the cache by the time it is accessed. The value of @var{addr} is the address of the memory to prefetch. +There are two optional arguments, @var{rw} and @var{locality}. The value of @var{rw} is a compile-time constant one or zero; one -means that the prefetch is preparing for a write to the memory address. +means that the prefetch is preparing for a write to the memory address +and zero, the default, means that the prefetch is preparing for a read. The value @var{locality} must be a compile-time constant integer between zero and three. A value of zero means that the data has no temporal locality, so it need not be left in the cache after the access. A value of three means that the data has a high degree of temporal locality and should be left in all levels of cache possible. Values of one and two -mean, respectively, a low or moderate degree of temporal locality. +mean, respectively, a low or moderate degree of temporal locality. The +default is three. @smallexample for (i = 0; i < n; i++) |