SubArray: default to linear indexing when it's fast

base/subarray.jl

@@ -258,10 +258,21 @@ function tailsize(P, d)
     s
 end
 
+stagedfunction linearindexing{T,N,P,I,LD}(A::SubArray{T,N,P,I,LD})
+    length(I) == LD ? (:(LinearFast())) : (:(LinearSlow()))
+end
+stagedfunction linearindexing{A<:SubArray}(::Type{A})
+    T,N,P,I,LD = A.parameters
+    length(I) == LD ? (:(LinearFast())) : (:(LinearSlow()))
+end
+
 getindex(::Colon, ::Colon) = Colon()
 getindex{T}(v::AbstractArray{T,1}, ::Colon) = v
 getindex(::Colon, i) = i
 
+step(::Colon) = 1
+first(::Colon) = 1
+
 ## Strides
 stagedfunction strides{T,N,P,I}(V::SubArray{T,N,P,I})
     all(map(x->x<:Union(RangeIndex,Colon), I)) || error("strides valid only for RangeIndex indexing")
@@ -299,9 +310,6 @@ function stride1expr(Atype::Type, Itypes::Tuple, Aexpr, Inewsym, LD)
     ex
 end
 
-step(::Colon) = 1
-first(::Colon) = 1
-
 first_index(V::SubArray) = first_index(V.parent, V.indexes)
 function first_index(P::AbstractArray, indexes::Tuple)
     f = 1

test/arrayops.jl

@@ -859,13 +859,17 @@ end
 a = [1:5]
 @test isa(Base.linearindexing(a), Base.LinearFast)
 b = sub(a, :)
-@test isa(Base.linearindexing(b), Base.IteratorsMD.LinearSlow)
+@test isa(Base.linearindexing(b), Base.IteratorsMD.LinearFast)
+aa = fill(99, 10)
+aa[1:2:9] = a
 shp = [5]
 for i = 1:10
     A = reshape(a, tuple(shp...))
     @test mdsum(A) == 15
     @test mdsum2(A) == 15
-    B = sub(A, ntuple(i, i->Colon())...)
+    AA = reshape(aa, tuple(2, shp...))
+    B = sub(AA, 1:1, ntuple(i, i->Colon())...)
+    @test isa(Base.linearindexing(B), Base.IteratorsMD.LinearSlow)
     @test mdsum(B) == 15
     @test mdsum2(B) == 15
     unshift!(shp, 1)