From: Tim Northover Date: Thu, 23 May 2013 19:14:12 +0000 (+0000) Subject: Add caveat to __builtin_readcyclecounter documentation. X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=ef7c6e7703a2968c29e9b5990edcca0406efee3a;p=clang Add caveat to __builtin_readcyclecounter documentation. The ARM cycle-counter can be restricted by the operating system; it's worth warning potential users of this issue. git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182604 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/docs/LanguageExtensions.rst b/docs/LanguageExtensions.rst index 0c56d5eda7..d7e88dfda9 100644 --- a/docs/LanguageExtensions.rst +++ b/docs/LanguageExtensions.rst @@ -1410,7 +1410,9 @@ should only be used for timing small intervals. When not supported by the target, the return value is always zero. This builtin takes no arguments and produces an unsigned long long result. -Query for this feature with ``__has_builtin(__builtin_readcyclecounter)``. +Query for this feature with ``__has_builtin(__builtin_readcyclecounter)``. Note +that even if present, its use may depend on run-time privilege or other OS +controlled state. .. _langext-__builtin_shufflevector: