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Diffstat (limited to 'gcc/doc/extend.texi')
| -rw-r--r-- | gcc/doc/extend.texi | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index bfe9c21..8711745 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -11849,6 +11849,34 @@ to and from other datatypes of the same size). You cannot operate between vectors of different lengths or different signedness without a cast. +@findex __builtin_shufflevector +Vector shuffling is available using the +@code{__builtin_shufflevector (vec1, vec2, index...)} +function. @var{vec1} and @var{vec2} must be expressions with +vector type with a compatible element type. The result of +@code{__builtin_shufflevector} is a vector with the same element type +as @var{vec1} and @var{vec2} but that has an element count equal to +the number of indices specified. + +The @var{index} arguments are a list of integers that 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. +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 freely chosen to optimized +the generated code sequence performing the shuffle operation. + +Consider the following example, +@smallexample +typedef int v4si __attribute__ ((vector_size (16))); +typedef int v8si __attribute__ ((vector_size (32))); + +v8si a = @{1,-2,3,-4,5,-6,7,-8@}; +v4si b = __builtin_shufflevector (a, a, 0, 2, 4, 6); /* b is @{1,3,5,7@} */ +v4si c = @{-2,-4,-6,-8@}; +v8si d = __builtin_shufflevector (c, b, 4, 0, 5, 1, 6, 2, 7, 3); /* d is a */ +@end smallexample + @findex __builtin_convertvector Vector conversion is available using the @code{__builtin_convertvector (vec, vectype)} |