I've checked in this patch to fix PR26366, another small but ancient documentation bug.

-Sandra
2018-11-11  Sandra Loosemore  <san...@codesourcery.com>

	PR c/26366

	gcc/
	* doc/extend.texi (Other Builtins): Document probability associated
	with __builtin_expect.
Index: gcc/doc/extend.texi
===================================================================
--- gcc/doc/extend.texi	(revision 266016)
+++ gcc/doc/extend.texi	(working copy)
@@ -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

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