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Diffstat (limited to 'docs')
| -rw-r--r-- | docs/LanguageExtensions.rst | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/docs/LanguageExtensions.rst b/docs/LanguageExtensions.rst index cb72c459c1..5bd234f2bf 100644 --- a/docs/LanguageExtensions.rst +++ b/docs/LanguageExtensions.rst @@ -2946,12 +2946,12 @@ Extensions for loop hint optimizations The ``#pragma clang loop`` directive is used to specify hints for optimizing the subsequent for, while, do-while, or c++11 range-based for loop. The directive -provides options for vectorization, interleaving, unrolling and +provides options for vectorization, interleaving, predication, unrolling and distribution. Loop hints can be specified before any loop and will be ignored if the optimization is not safe to apply. -Vectorization and Interleaving ------------------------------- +Vectorization, Interleaving, and Predication +-------------------------------------------- A vectorized loop performs multiple iterations of the original loop in parallel using vector instructions. The instruction set of the target @@ -2994,6 +2994,21 @@ width/count of the set of target architectures supported by your application. Specifying a width/count of 1 disables the optimization, and is equivalent to ``vectorize(disable)`` or ``interleave(disable)``. +Vector predication is enabled by ``vectorize_predicate(enable)``, for example: + +.. code-block:: c++ + + #pragma clang loop vectorize(enable) + #pragma clang loop vectorize_predicate(enable) + for(...) { + ... + } + +This predicates (masks) all instructions in the loop, which allows the scalar +remainder loop (the tail) to be folded into the main vectorized loop. This +might be more efficient when vector predication is efficiently supported by the +target platform. + Loop Unrolling -------------- |