Restore old SubArray bounds check semantics

That is, don't check bounds and instead let the parent array do the bounds checking.  Due to the abstract fallbacks, it's still advantageous to define both `getindex` and `unsafe_getindex`.  It'd be nice to use metaprogramming here to loop over the two names and define both at once, but it seems like `subarray.jl` lives too early in the bootstrap for the required machinery.

base/subarray.jl

@@ -527,7 +527,30 @@ function parentdims(s::SubArray)
 end
 
 ## Scalar indexing
-getindex(V::SubArray, I::Int...) = (@_inline_meta; checkbounds(V, I...); unsafe_getindex(V, I...))
+
+# While it'd be nice to explicitly check bounds against the SubArray dimensions,
+# the lack of an extensible @inbounds mechanism makes it difficult for users to
+# avoid the cost of the bounds check without rewriting their syntax to use the
+# unwieldy unsafe_getindex/unsafe_setindex! function calls. So instead we define
+# getindex to rely upon the bounds checks in the parent array. It's still
+# advantageous to define the unsafe_ variants without any bounds checks since
+# the abstract indexing fallbacks can make use of them.
+@generated function getindex{T,N,P,IV,LD}(V::SubArray{T,N,P,IV,LD}, I::Int...)
+ ni = length(I)
+ if ni == 1 && length(IV.parameters) == LD # linear indexing
+ meta = Expr(:meta, :inline)
+ if iscontiguous(V)
+ return :($meta; getindex(V.parent, V.first_index + I[1] - 1))
+ end
+ return :($meta; getindex(V.parent, V.first_index + V.stride1*(I[1]-1)))
+ end
+ Isyms = [:(I[$d]) for d = 1:ni]
+ exhead, idxs = index_generate(ndims(P), IV, :V, Isyms)
+ quote
+ $exhead
+ getindex(V.parent, $(idxs...))
+ end
+end
 @generated function unsafe_getindex{T,N,P,IV,LD}(V::SubArray{T,N,P,IV,LD}, I::Int...)
  ni = length(I)
  if ni == 1 && length(IV.parameters) == LD # linear indexing
@@ -544,7 +567,22 @@ getindex(V::SubArray, I::Int...) = (@_inline_meta; checkbounds(V, I...); unsafe_
  unsafe_getindex(V.parent, $(idxs...))
  end
 end
-setindex!(V::SubArray, v, I::Int...) = (@_inline_meta; checkbounds(V, I...); unsafe_setindex!(V, v, I...))
+@generated function setindex!{T,N,P,IV,LD}(V::SubArray{T,N,P,IV,LD}, v, I::Int...)
+ ni = length(I)
+ if ni == 1 && length(IV.parameters) == LD # linear indexing
+ meta = Expr(:meta, :inline)
+ if iscontiguous(V)
+ return :($meta; setindex!(V.parent, v, V.first_index + I[1] - 1))
+ end
+ return :($meta; setindex!(V.parent, v, V.first_index + V.stride1*(I[1]-1)))
+ end
+ Isyms = [:(I[$d]) for d = 1:ni]
+ exhead, idxs = index_generate(ndims(P), IV, :V, Isyms)
+ quote
+ $exhead
+ setindex!(V.parent, v, $(idxs...))
+ end
+end
 @generated function unsafe_setindex!{T,N,P,IV,LD}(V::SubArray{T,N,P,IV,LD}, v, I::Int...)
  ni = length(I)
  if ni == 1 && length(IV.parameters) == LD # linear indexing