SIMD Support
Type VecElement{T}
is intended for building libraries of SIMD operations. Practical use of it requires using llvmcall
. The type is defined as:
struct 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 primitive bits type.
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:
const 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
.