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| author | Tim Northover <t.p.northover@gmail.com> | 2013-05-23 19:14:12 +0000 |
|---|---|---|
| committer | Tim Northover <t.p.northover@gmail.com> | 2013-05-23 19:14:12 +0000 |
| commit | bfe2e5f778a13057d1b26cb05e58bea63f03ade3 (patch) | |
| tree | db262f966e7c6928789d9aa00459209fe1bb8f5e /clang/docs/LanguageExtensions.rst | |
| parent | bc93308489b5513ef3d4e56bad28b7ab4bce7303 (diff) | |
| download | bcm5719-llvm-bfe2e5f778a13057d1b26cb05e58bea63f03ade3.tar.gz bcm5719-llvm-bfe2e5f778a13057d1b26cb05e58bea63f03ade3.zip | |
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.
llvm-svn: 182604
Diffstat (limited to 'clang/docs/LanguageExtensions.rst')
| -rw-r--r-- | clang/docs/LanguageExtensions.rst | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/clang/docs/LanguageExtensions.rst b/clang/docs/LanguageExtensions.rst index 0c56d5eda77..d7e88dfda9a 100644 --- a/clang/docs/LanguageExtensions.rst +++ b/clang/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: |
