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| author | Sandra Loosemore <sandra@codesourcery.com> | 2018-11-11 13:39:10 -0500 |
|---|---|---|
| committer | Sandra Loosemore <sandra@gcc.gnu.org> | 2018-11-11 13:39:10 -0500 |
| commit | 6157c37500dd889e46ded9a8eb357de9a71de0eb (patch) | |
| tree | 54aa4fde74a1eb33fa069880fbdef3764ff7f680 | |
| parent | bd5d3961572e2d65ed0e612235f0c7a28305cf98 (diff) | |
| download | gcc-6157c37500dd889e46ded9a8eb357de9a71de0eb.zip gcc-6157c37500dd889e46ded9a8eb357de9a71de0eb.tar.gz gcc-6157c37500dd889e46ded9a8eb357de9a71de0eb.tar.bz2 | |
re PR c/26366 (__builtin_expect needs better documentation)
2018-11-11 Sandra Loosemore <sandra@codesourcery.com>
PR c/26366
gcc/
* doc/extend.texi (Other Builtins): Document probability associated
with __builtin_expect.
From-SVN: r266017
| -rw-r--r-- | gcc/ChangeLog | 6 | ||||
| -rw-r--r-- | gcc/doc/extend.texi | 6 |
2 files changed, 12 insertions, 0 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 67a6b80..4a8293f 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2018-11-11 Sandra Loosemore <sandra@codesourcery.com> + + PR c/26366 + * doc/extend.texi (Other Builtins): Document probability associated + with __builtin_expect. + 2018-11-11 Uros Bizjak <ubizjak@gmail.com> PR target/87928 diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index 5ce5069..022d0e0 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -12121,6 +12121,12 @@ if (__builtin_expect (ptr != NULL, 1)) @noindent when testing pointer or floating-point values. + +For the purposes of branch prediction optimizations, the probability that +a @code{__builtin_expect} expression is true is controlled by GCC's +@code{builtin-expect-probability} parameter, which defaults to 90%. +You can also use @code{__builtin_expect_with_probability} to explicitly +assign a probability value to individual expressions. @end deftypefn @deftypefn {Built-in Function} long __builtin_expect_with_probability |