Document rdrand effective target

2017-05-23  Tom de Vries  <tom@codesourcery.com>

	* doc/sourcebuild.texi (Effective-Target Keywords, Other hardware
	attributes): Document rdrand effective target.

From-SVN: r248360

gcc/ChangeLog

 2017-05-23  Tom de Vries  <tom@codesourcery.com>
 
 	* doc/sourcebuild.texi (Effective-Target Keywords, Other hardware
+	attributes): Document rdrand effective target.
+
+2017-05-23  Tom de Vries  <tom@codesourcery.com>
+
+	* doc/sourcebuild.texi (Effective-Target Keywords, Other hardware
 	attributes): Sort alphabetically.
 
 2017-05-23  Georg-Johann Lay  <avr@gjlay.de>

gcc/doc/sourcebuild.texi

@@ -1855,6 +1855,9 @@ Target does not require strict alignment.
 @item pie_copyreloc
 The x86-64 target linker supports PIE with copy reloc.
 
+@item rdrand
+Target supports x86 @code{rdrand} instruction.
+
 @item sqrt_insn
 Target has a square root instruction that the compiler can generate.