delena updated this revision to Diff 146462. delena added a comment. Added a line about *load-store* semantics of these two intrinsics. Removed the common description of memory modeling.
Repository: rC Clang https://reviews.llvm.org/D46386 Files: LanguageExtensions.rst Index: LanguageExtensions.rst =================================================================== --- LanguageExtensions.rst +++ LanguageExtensions.rst @@ -1975,6 +1975,32 @@ Support for constant expression evaluation for the above builtins be detected with ``__has_feature(cxx_constexpr_string_builtins)``. +Atomic Min/Max builtins with memory ordering +-------------------------------------------- + +There are two atomic builtins with min/max in-memory comparison and swap. +The syntax and semantics are similar to GCC-compatible __atomic_* builtins. + +* ``__atomic_fetch_min`` +* ``__atomic_fetch_max`` + +The builtins work with signed and unsigned integers and require to specify memory ordering. +The return value is the original value that was stored in memory before comparison. + +Example: + +.. code-block:: c + + unsigned int val = __atomic_fetch_min(unsigned int *pi, unsigned int ui, __ATOMIC_RELAXED); + +The third argument is one of the memory ordering specifiers ``__ATOMIC_RELAXED``, +``__ATOMIC_CONSUME``, ``__ATOMIC_ACQUIRE``, ``__ATOMIC_RELEASE``, +``__ATOMIC_ACQ_REL``, or ``__ATOMIC_SEQ_CST`` following C++11 memory model semantics. + +In terms or aquire-release ordering barriers these two operations are always +considered as operations with *load-store* semantics, even when the original value +is not actually modified after comparison. + .. _langext-__c11_atomic: __c11_atomic builtins @@ -2734,4 +2760,3 @@ The ``#pragma comment(lib, ...)`` directive is supported on all ELF targets. The second parameter is the library name (without the traditional Unix prefix of ``lib``). This allows you to provide an implicit link of dependent libraries. -
Index: LanguageExtensions.rst =================================================================== --- LanguageExtensions.rst +++ LanguageExtensions.rst @@ -1975,6 +1975,32 @@ Support for constant expression evaluation for the above builtins be detected with ``__has_feature(cxx_constexpr_string_builtins)``. +Atomic Min/Max builtins with memory ordering +-------------------------------------------- + +There are two atomic builtins with min/max in-memory comparison and swap. +The syntax and semantics are similar to GCC-compatible __atomic_* builtins. + +* ``__atomic_fetch_min`` +* ``__atomic_fetch_max`` + +The builtins work with signed and unsigned integers and require to specify memory ordering. +The return value is the original value that was stored in memory before comparison. + +Example: + +.. code-block:: c + + unsigned int val = __atomic_fetch_min(unsigned int *pi, unsigned int ui, __ATOMIC_RELAXED); + +The third argument is one of the memory ordering specifiers ``__ATOMIC_RELAXED``, +``__ATOMIC_CONSUME``, ``__ATOMIC_ACQUIRE``, ``__ATOMIC_RELEASE``, +``__ATOMIC_ACQ_REL``, or ``__ATOMIC_SEQ_CST`` following C++11 memory model semantics. + +In terms or aquire-release ordering barriers these two operations are always +considered as operations with *load-store* semantics, even when the original value +is not actually modified after comparison. + .. _langext-__c11_atomic: __c11_atomic builtins @@ -2734,4 +2760,3 @@ The ``#pragma comment(lib, ...)`` directive is supported on all ELF targets. The second parameter is the library name (without the traditional Unix prefix of ``lib``). This allows you to provide an implicit link of dependent libraries. -
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