mzolotukhin created this revision. mzolotukhin added reviewers: hfinkel, rsmith. mzolotukhin added a subscriber: cfe-commits.
In r247104 I added the builtins for generating non-temporal memory operations, but now I realized that they lack documentation. This patch adds some. http://reviews.llvm.org/D12785 Files: docs/LanguageExtensions.rst Index: docs/LanguageExtensions.rst =================================================================== --- docs/LanguageExtensions.rst +++ docs/LanguageExtensions.rst @@ -1778,6 +1778,36 @@ For these reasons the higher level atomic primitives should be preferred where possible. +Non-temporal load/store builtins +-------------------------------- + +Clang provides overloaded builtins allowing to generate non-temporal memory +accesses. + +.. code-block:: c + + T __builtin_nontemporal_load(T *addr); + void __builtin_nontemporal_store(T value, T *addr); + +The types ``T`` currently supported are: + +* Integer types. +* Floating-point types +* Vector types. + +Note that the compiler does not guarantee that non-temporal loads or stores +would be used. Also, using non-temporal loads and stores might change program +semantics on some targets, so the builtins should be used with care. + +For example, on AArch64 in the following code:: + + LDR X1, [X2] + LDNP X3, X4, [X1] + +the ``LDNP`` might be executed before the ``LDR``. In this case the load would +be performed from a wrong address (see 6.3.8 in `Programmer's Guide for ARMv8-A +<http://infocenter.arm.com/help/topic/com.arm.doc.den0024a/DEN0024A_v8_architecture_PG.pdf>`_). + Non-standard C++11 Attributes =============================
Index: docs/LanguageExtensions.rst =================================================================== --- docs/LanguageExtensions.rst +++ docs/LanguageExtensions.rst @@ -1778,6 +1778,36 @@ For these reasons the higher level atomic primitives should be preferred where possible. +Non-temporal load/store builtins +-------------------------------- + +Clang provides overloaded builtins allowing to generate non-temporal memory +accesses. + +.. code-block:: c + + T __builtin_nontemporal_load(T *addr); + void __builtin_nontemporal_store(T value, T *addr); + +The types ``T`` currently supported are: + +* Integer types. +* Floating-point types +* Vector types. + +Note that the compiler does not guarantee that non-temporal loads or stores +would be used. Also, using non-temporal loads and stores might change program +semantics on some targets, so the builtins should be used with care. + +For example, on AArch64 in the following code:: + + LDR X1, [X2] + LDNP X3, X4, [X1] + +the ``LDNP`` might be executed before the ``LDR``. In this case the load would +be performed from a wrong address (see 6.3.8 in `Programmer's Guide for ARMv8-A +<http://infocenter.arm.com/help/topic/com.arm.doc.den0024a/DEN0024A_v8_architecture_PG.pdf>`_). + Non-standard C++11 Attributes =============================
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