.==(_:_:)
A vector mask with the result of a pointwise equality comparison.
static func .== (a: SIMDMask<Storage>, b: SIMDMask<Storage>) -> SIMDMask<Storage>
Equivalent to:
var result = SIMDMask<SIMD2<Int16>>()
for i in result.indices {
result[i] = a[i] == b[i]
}