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Diffstat (limited to 'gcc/doc/extend.texi')
| -rw-r--r-- | gcc/doc/extend.texi | 37 |
1 files changed, 14 insertions, 23 deletions
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index c3ebf095fd0..11118edc1d6 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -6586,16 +6586,18 @@ c = a == b; /* The result would be @{0,-1, 0,-1@} */ Vector shuffling is available using functions @code{__builtin_shuffle (vec, mask)} and -@code{__builtin_shuffle (vec0, vec1, mask)}. Both functions construct -a permutation of elements from one or two vectors and return a vector -of the same type as input vector(s). The mask is a vector of -integer-typed elements. The size of each element of the mask must be -the same as the size of each input vector element. The number of -elements in input vector(s) and mask must be the same. +@code{__builtin_shuffle (vec0, vec1, mask)}. +Both functions construct a permutation of elements from one or two +vectors and return a vector of the same type as the input vector(s). +The @var{mask} is an integral vector with the same width (@var{W}) +and element count (@var{N}) as the output vector. -The elements of the input vectors are numbered from left to right across -one or both of the vectors. Each element in the mask specifies a number -of element from the input vector(s). Consider the following example. +The elements of the input vectors are numbered in memory ordering of +@var{vec0} beginning at 0 and @var{vec1} beginning at @var{N}. The +elements of @var{mask} are considered modulo @var{N} in the single-operand +case and modulo @math{2*@var{N}} in the two-operand case. + +Consider the following example, @smallexample typedef int v4si __attribute__ ((vector_size (16))); @@ -6610,6 +6612,9 @@ res = __builtin_shuffle (a, mask1); /* res is @{1,2,2,4@} */ res = __builtin_shuffle (a, b, mask2); /* res is @{1,5,3,6@} */ @end smallexample +Note that @code{__builtin_shuffle} is intentionally semantically +compatible with the OpenCL @code{shuffle} and @code{shuffle2} functions. + You can declare variables and use them in function calls and returns, as well as in assignments and some casts. You can specify a vector type as a return type for a function. Vector types can also be used as function @@ -6620,20 +6625,6 @@ to and from other datatypes of the same size). You cannot operate between vectors of different lengths or different signedness without a cast. -A port that supports hardware vector operations, usually provides a set -of built-in functions that can be used to operate on vectors. For -example, a function to add two vectors and multiply the result by a -third could look like this: - -@smallexample -v4si f (v4si a, v4si b, v4si c) -@{ - v4si tmp = __builtin_addv4si (a, b); - return __builtin_mulv4si (tmp, c); -@} - -@end smallexample - @node Offsetof @section Offsetof @findex __builtin_offsetof |