Small simplification of indexmanipulations (#383)

* simplify indexmanipulations

* remove unnecessarily specialized code

Author: lkdvos

src/auxiliary/auxiliary.jl

@@ -57,30 +57,6 @@ function _interleave(a::NTuple{N}, b::NTuple{N}) where {N}
     return (a[1], b[1], _interleave(tail(a), tail(b))...)
 end
 
-# Low-overhead implementation of `copyto!` for specific case of `stride(B, 1) < stride(B, 2)`
-# used in indexmanipulations: avoids the overhead of Strided.jl
-function _copyto!(A::StridedView{<:Any, 1}, B::StridedView{<:Any, 2})
-    length(A) == length(B) || throw(DimensionMismatch())
-
-    Adata = parent(A)
-    Astr = stride(A, 1)
-    IA = A.offset
-
-    Bdata = parent(B)
-    Bstr = strides(B)
-
-    IB_1 = B.offset
-    @inbounds for _ in axes(B, 2)
-        IB = IB_1
-        for _ in axes(B, 1)
-            Adata[IA += Astr] = Bdata[IB += Bstr[1]]
-        end
-        IB_1 += Bstr[2]
-    end
-
-    return A
-end
-
 @static if VERSION < v"1.11" # TODO: remove once support for v1.10 is dropped
     _allequal(f, xs) = allequal(Base.Generator(f, xs))
 else

src/tensors/indexmanipulations.jl

@@ -701,7 +701,8 @@ function _add_transform_multi!(
     buffer_src = StridedView(buffer2, (blocksize, cols), (1, blocksize), 0)
     for (i, struct_src) in enumerate(structs_src)
         subblock_src = sreshape(StridedView(tsrc.data, sz_src, struct_src...), matsize)
-        _copyto!(buffer_src[:, i], subblock_src)
+        bufblock_src = sreshape(buffer_src[:, i], matsize)
+        copy!(bufblock_src, subblock_src)
     end
 
     # Resummation into a second buffer using BLAS