Accelerate isless(::T,::T) where {T<:CartesianIndex} (#43395)

Author: N5N3

base/multidimensional.jl

@@ -124,13 +124,7 @@ module IteratorsMD
     @inline (*)(index::CartesianIndex, a::Integer) = *(a,index)
 
     # comparison
-    @inline isless(I1::CartesianIndex{N}, I2::CartesianIndex{N}) where {N} = _isless(0, I1.I, I2.I)
-    @inline function _isless(ret, I1::Tuple{Int,Vararg{Int}}, I2::Tuple{Int,Vararg{Int}})
-        newret = ifelse(ret==0, icmp(last(I1), last(I2)), ret)
-        return _isless(newret, Base.front(I1), Base.front(I2))
-    end
-    _isless(ret, ::Tuple{}, ::Tuple{}) = ifelse(ret==1, true, false)
-    icmp(a, b) = ifelse(isless(a,b), 1, ifelse(a==b, 0, -1))
+    isless(I1::CartesianIndex{N}, I2::CartesianIndex{N}) where {N} = isless(reverse(I1.I), reverse(I2.I))
 
     # conversions
     convert(::Type{T}, index::CartesianIndex{1}) where {T<:Number} = convert(T, index[1])