diff options
Diffstat (limited to 'clang/docs')
| -rw-r--r-- | clang/docs/LanguageExtensions.rst | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/clang/docs/LanguageExtensions.rst b/clang/docs/LanguageExtensions.rst index e8826b5b360..37a587ecb42 100644 --- a/clang/docs/LanguageExtensions.rst +++ b/clang/docs/LanguageExtensions.rst @@ -1455,8 +1455,8 @@ for the implementation of various target-specific header files like .. code-block:: c++ - // Identity operation - return 4-element vector V1. - __builtin_shufflevector(V1, V1, 0, 1, 2, 3) + // identity operation - return 4-element vector v1. + __builtin_shufflevector(v1, v1, 0, 1, 2, 3) // "Splat" element 0 of V1 into a 4-element result. __builtin_shufflevector(V1, V1, 0, 0, 0, 0) @@ -1470,6 +1470,9 @@ for the implementation of various target-specific header files like // Concatenate every other element of 8-element vectors V1 and V2. __builtin_shufflevector(V1, V2, 0, 2, 4, 6, 8, 10, 12, 14) + // Shuffle v1 with some elements being undefined + __builtin_shufflevector(v1, v1, 3, -1, 1, -1) + **Description**: The first two arguments to ``__builtin_shufflevector`` are vectors that have @@ -1478,7 +1481,8 @@ specify the elements indices of the first two vectors that should be extracted and returned in a new vector. These element indices are numbered sequentially starting with the first vector, continuing into the second vector. Thus, if ``vec1`` is a 4-element vector, index 5 would refer to the second element of -``vec2``. +``vec2``. An index of -1 can be used to indicate that the corresponding element +in the returned vector is a don't care and can be optimized by the backend. The result of ``__builtin_shufflevector`` is a vector with the same element type as ``vec1``/``vec2`` but that has an element count equal to the number of |
