Type VecElement{T}
is intended for building libraries of SIMD operations. Practical use of it requires using llvmcall
. The type is defined as:
immutable VecElement{T} value::T end
It has a special compilation rule: a homogeneous tuple of VecElement{T}
maps to an LLVM vector
type when T
is a bitstype and the tuple length is in the set {2-6,8-10,16}.
At -O3
, the compiler might automatically vectorize operations on such tuples. For example, the following program, when compiled with julia -O3
generates two SIMD addition instructions (addps
) on x86 systems:
typealias m128 NTuple{4,VecElement{Float32}} function add(a::m128, b::m128) (VecElement(a[1].value+b[1].value), VecElement(a[2].value+b[2].value), VecElement(a[3].value+b[3].value), VecElement(a[4].value+b[4].value)) end triple(c::m128) = add(add(c,c),c) code_native(triple,(m128,))
However, since the automatic vectorization cannot be relied upon, future use will mostly be via libraries that use llvmcall
.
© 2009–2016 Jeff Bezanson, Stefan Karpinski, Viral B. Shah, and other contributors
Licensed under the MIT License.
http://docs.julialang.org/en/release-0.5/stdlib/simd-types/