#37611

Committed 05 Sep 2023 05:43AM UTC coverage: 86.055% (-0.4%) from 86.433%

Build # #37611

Build Type

push

local

Committed by

web-flow

Commit Message

optimizer: Do not run if we know the function is ConstABI eligible (#51143)

If we can determine that a function is sufficiently pure and returns a
constant, we have special ABI that lets us throw away the code for it
and just return the constant. However, we were still going through all
the steps of actually computing the code, including running the
optimizer on it, compressing it in preparation for caching, etc. We can
just stop doing that and bypass the optimizer entirely.

The actual change to do this is pretty tiny, but there's some unexpected
fallout which this needs to cleanup:
1. Various tests expect code_* queries of things inferred to ConstABI to
still return reasonable code. Fix this by manually emitting a ReturnNode
at the end of inference if the caller is a reflection function.
2. This kinda wreaks havoc on the EscapeAnalysis tests, which work by
using a side-effect of the optimizer, but a lot of the functions are
ConstABI eligible, so the optimizer doesn't run any more. Fortunately,
I'm in the middle of looking at overhauling EscapeAnalysis, so I'll have
some chance to figure out how to change the test system to actually do
this properly, rather than exfiltrating side effects. That said, since
EscapeAnalysis is not in the default pipeline, I don't think we should
hold the perf improvement until that is done.

Benchmarked to be about 10% faster locally, but we'll see what
nanosoldier thinks.

---------

Co-authored-by: Shuhei Kadowaki <40514306+aviatesk@users.noreply.github.com>

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76.54

/base/subarray.jl

# This file is a part of Julia. License is MIT: https://julialang.org/license

abstract type AbstractCartesianIndex{N} end # This is a hacky forward declaration for CartesianIndex
const ViewIndex = Union{Real, AbstractArray}
const ScalarIndex = Real

"""
    SubArray{T,N,P,I,L} <: AbstractArray{T,N}

`N`-dimensional view into a parent array (of type `P`) with an element type `T`, restricted by a tuple of indices (of type `I`). `L` is true for types that support fast linear indexing, and `false` otherwise.

Construct `SubArray`s using the [`view`](@ref) function.
"""
struct SubArray{T,N,P,I,L} <: AbstractArray{T,N}
    parent::P
    indices::I
    offset1::Int       # for linear indexing and pointer, only valid when L==true
    stride1::Int       # used only for linear indexing
    function SubArray{T,N,P,I,L}(parent, indices, offset1, stride1) where {T,N,P,I,L}
        @inline
        check_parent_index_match(parent, indices)
        new(parent, indices, offset1, stride1)
    end
end
# Compute the linear indexability of the indices, and combine it with the linear indexing of the parent
function SubArray(parent::AbstractArray, indices::Tuple)
    @inline
    SubArray(IndexStyle(viewindexing(indices), IndexStyle(parent)), parent, ensure_indexable(indices), index_dimsum(indices...))
end
function SubArray(::IndexCartesian, parent::P, indices::I, ::NTuple{N,Any}) where {P,I,N}
    @inline
    SubArray{eltype(P), N, P, I, false}(parent, indices, 0, 0)
end
function SubArray(::IndexLinear, parent::P, indices::I, ::NTuple{N,Any}) where {P,I,N}
    @inline
    # Compute the stride and offset
    stride1 = compute_stride1(parent, indices)
    SubArray{eltype(P), N, P, I, true}(parent, indices, compute_offset1(parent, stride1, indices), stride1)
end

check_parent_index_match(parent, indices) = check_parent_index_match(parent, index_ndims(indices...))
check_parent_index_match(parent::AbstractArray{T,N}, ::NTuple{N, Bool}) where {T,N} = nothing
check_parent_index_match(parent, ::NTuple{N, Bool}) where {N} =
    throw(ArgumentError("number of indices ($N) must match the parent dimensionality ($(ndims(parent)))"))

# This computes the linear indexing compatibility for a given tuple of indices
viewindexing(I::Tuple{}) = IndexLinear()
# Leading scalar indices simply increase the stride
viewindexing(I::Tuple{ScalarIndex, Vararg{Any}}) = (@inline; viewindexing(tail(I)))
# Slices may begin a section which may be followed by any number of Slices
viewindexing(I::Tuple{Slice, Slice, Vararg{Any}}) = (@inline; viewindexing(tail(I)))
# A UnitRange can follow Slices, but only if all other indices are scalar
viewindexing(I::Tuple{Slice, AbstractUnitRange, Vararg{ScalarIndex}}) = IndexLinear()
viewindexing(I::Tuple{Slice, Slice, Vararg{ScalarIndex}}) = IndexLinear() # disambiguate
# In general, ranges are only fast if all other indices are scalar
viewindexing(I::Tuple{AbstractRange, Vararg{ScalarIndex}}) = IndexLinear()
# All other index combinations are slow
viewindexing(I::Tuple{Vararg{Any}}) = IndexCartesian()
# Of course, all other array types are slow
viewindexing(I::Tuple{AbstractArray, Vararg{Any}}) = IndexCartesian()

# Simple utilities
size(V::SubArray) = (@inline; map(length, axes(V)))

similar(V::SubArray, T::Type, dims::Dims) = similar(V.parent, T, dims)

sizeof(V::SubArray) = length(V) * sizeof(eltype(V))
sizeof(V::SubArray{<:Any,<:Any,<:Array}) = length(V) * elsize(V.parent)

function Base.copy(V::SubArray)
    v = V.parent[V.indices...]
    ndims(V) == 0 || return v
    x = similar(V) # ensure proper type of x
    x[] = v
    return x
end

parent(V::SubArray) = V.parent
parentindices(V::SubArray) = V.indices

"""
    parentindices(A)

Return the indices in the [`parent`](@ref) which correspond to the view `A`.

# Examples
```jldoctest
julia> A = [1 2; 3 4];

julia> V = view(A, 1, :)
2-element view(::Matrix{Int64}, 1, :) with eltype Int64:
 1
 2

julia> parentindices(V)
(1, Base.Slice(Base.OneTo(2)))
```
"""
function parentindices end

parentindices(a::AbstractArray) = map(oneto, size(a))

## Aliasing detection
dataids(A::SubArray) = (dataids(A.parent)..., _splatmap(dataids, A.indices)...)
_splatmap(f, ::Tuple{}) = ()
_splatmap(f, t::Tuple) = (f(t[1])..., _splatmap(f, tail(t))...)
unaliascopy(A::SubArray) = typeof(A)(unaliascopy(A.parent), map(unaliascopy, A.indices), A.offset1, A.stride1)

# When the parent is an Array we can trim the size down a bit. In the future this
# could possibly be extended to any mutable array.
function unaliascopy(V::SubArray{T,N,A,I,LD}) where {T,N,A<:Array,I<:Tuple{Vararg{Union{Real,AbstractRange,Array}}},LD}
    dest = Array{T}(undef, index_lengths(V.indices...))
    copyto!(dest, V)
    SubArray{T,N,A,I,LD}(dest, map(_trimmedindex, V.indices), 0, Int(LD))
end
# Transform indices to be "dense"
_trimmedindex(i::Real) = oftype(i, 1)
_trimmedindex(i::AbstractUnitRange) = oftype(i, oneto(length(i)))
_trimmedindex(i::AbstractArray) = oftype(i, reshape(eachindex(IndexLinear(), i), axes(i)))

## SubArray creation
# We always assume that the dimensionality of the parent matches the number of
# indices that end up getting passed to it, so we store the parent as a
# ReshapedArray view if necessary. The trouble is that arrays of `CartesianIndex`
# can make the number of effective indices not equal to length(I).
_maybe_reshape_parent(A::AbstractArray, ::NTuple{1, Bool}) = reshape(A, Val(1))
_maybe_reshape_parent(A::AbstractArray{<:Any,1}, ::NTuple{1, Bool}) = reshape(A, Val(1))
_maybe_reshape_parent(A::AbstractArray{<:Any,N}, ::NTuple{N, Bool}) where {N} = A
_maybe_reshape_parent(A::AbstractArray, ::NTuple{N, Bool}) where {N} = reshape(A, Val(N))
"""
    view(A, inds...)

Like [`getindex`](@ref), but returns a lightweight array that lazily references
(or is effectively a _view_ into) the parent array `A` at the given index or indices
`inds` instead of eagerly extracting elements or constructing a copied subset.
Calling [`getindex`](@ref) or [`setindex!`](@ref) on the returned value
(often a [`SubArray`](@ref)) computes the indices to access or modify the
parent array on the fly.  The behavior is undefined if the shape of the parent array is
changed after `view` is called because there is no bound check for the parent array; e.g.,
it may cause a segmentation fault.

Some immutable parent arrays (like ranges) may choose to simply
recompute a new array in some circumstances instead of returning
a `SubArray` if doing so is efficient and provides compatible semantics.

!!! compat "Julia 1.6"
    In Julia 1.6 or later, `view` can be called on an `AbstractString`, returning a
    `SubString`.

# Examples
```jldoctest
julia> A = [1 2; 3 4]
2×2 Matrix{Int64}:
 1  2
 3  4

julia> b = view(A, :, 1)
2-element view(::Matrix{Int64}, :, 1) with eltype Int64:
 1
 3

julia> fill!(b, 0)
2-element view(::Matrix{Int64}, :, 1) with eltype Int64:
 0
 0

julia> A # Note A has changed even though we modified b
2×2 Matrix{Int64}:
 0  2
 0  4

julia> view(2:5, 2:3) # returns a range as type is immutable
3:4
```
"""
function view(A::AbstractArray{<:Any,N}, I::Vararg{Any,M}) where {N,M}
    @inline
    J = map(i->unalias(A,i), to_indices(A, I))
    @boundscheck checkbounds(A, J...)
    if length(J) > ndims(A) && J[N+1:end] isa Tuple{Vararg{Int}}
        # view([1,2,3], :, 1) does not need to reshape
        return unsafe_view(A, J[1:N]...)
    end
    unsafe_view(_maybe_reshape_parent(A, index_ndims(J...)), J...)
end

# Ranges implement getindex to return recomputed ranges; use that for views, too (when possible)
function view(r1::OneTo, r2::OneTo)
    @_propagate_inbounds_meta
    getindex(r1, r2)
end
function view(r1::AbstractUnitRange, r2::AbstractUnitRange{<:Integer})
    @_propagate_inbounds_meta
    getindex(r1, r2)
end
function view(r1::AbstractUnitRange, r2::StepRange{<:Integer})
    @_propagate_inbounds_meta
    getindex(r1, r2)
end
function view(r1::StepRange, r2::AbstractRange{<:Integer})
    @_propagate_inbounds_meta
    getindex(r1, r2)
end
function view(r1::StepRangeLen, r2::OrdinalRange{<:Integer})
    @_propagate_inbounds_meta
    getindex(r1, r2)
end
function view(r1::LinRange, r2::OrdinalRange{<:Integer})
    @_propagate_inbounds_meta
    getindex(r1, r2)
end

# getindex(r::AbstractRange, ::Colon) returns a copy of the range, and we may do the same for a view
function view(r1::AbstractRange, c::Colon)
    @_propagate_inbounds_meta
    getindex(r1, c)
end

function unsafe_view(A::AbstractArray, I::Vararg{ViewIndex,N}) where {N}
    @inline
    SubArray(A, I)
end
# When we take the view of a view, it's often possible to "reindex" the parent
# view's indices such that we can "pop" the parent view and keep just one layer
# of indirection. But we can't always do this because arrays of `CartesianIndex`
# might span multiple parent indices, making the reindex calculation very hard.
# So we use _maybe_reindex to figure out if there are any arrays of
# `CartesianIndex`, and if so, we punt and keep two layers of indirection.
unsafe_view(V::SubArray, I::Vararg{ViewIndex,N}) where {N} =
    (@inline; _maybe_reindex(V, I))
_maybe_reindex(V, I) = (@inline; _maybe_reindex(V, I, I))
_maybe_reindex(V, I, ::Tuple{AbstractArray{<:AbstractCartesianIndex}, Vararg{Any}}) =
    (@inline; SubArray(V, I))
# But allow arrays of CartesianIndex{1}; they behave just like arrays of Ints
_maybe_reindex(V, I, A::Tuple{AbstractArray{<:AbstractCartesianIndex{1}}, Vararg{Any}}) =
    (@inline; _maybe_reindex(V, I, tail(A)))
_maybe_reindex(V, I, A::Tuple{Any, Vararg{Any}}) = (@inline; _maybe_reindex(V, I, tail(A)))
function _maybe_reindex(V, I, ::Tuple{})
    @inline
    @inbounds idxs = to_indices(V.parent, reindex(V.indices, I))
    SubArray(V.parent, idxs)
end

## Re-indexing is the heart of a view, transforming A[i, j][x, y] to A[i[x], j[y]]
#
# Recursively look through the heads of the parent- and sub-indices, considering
# the following cases:
# * Parent index is array  -> re-index that with one or more sub-indices (one per dimension)
# * Parent index is Colon  -> just use the sub-index as provided
# * Parent index is scalar -> that dimension was dropped, so skip the sub-index and use the index as is

AbstractZeroDimArray{T} = AbstractArray{T, 0}

reindex(::Tuple{}, ::Tuple{}) = ()

# Skip dropped scalars, so simply peel them off the parent indices and continue
reindex(idxs::Tuple{ScalarIndex, Vararg{Any}}, subidxs::Tuple{Vararg{Any}}) =
    (@_propagate_inbounds_meta; (idxs[1], reindex(tail(idxs), subidxs)...))

# Slices simply pass their subindices straight through
reindex(idxs::Tuple{Slice, Vararg{Any}}, subidxs::Tuple{Any, Vararg{Any}}) =
    (@_propagate_inbounds_meta; (subidxs[1], reindex(tail(idxs), tail(subidxs))...))

# Re-index into parent vectors with one subindex
reindex(idxs::Tuple{AbstractVector, Vararg{Any}}, subidxs::Tuple{Any, Vararg{Any}}) =
    (@_propagate_inbounds_meta; (idxs[1][subidxs[1]], reindex(tail(idxs), tail(subidxs))...))

# Parent matrices are re-indexed with two sub-indices
reindex(idxs::Tuple{AbstractMatrix, Vararg{Any}}, subidxs::Tuple{Any, Any, Vararg{Any}}) =
    (@_propagate_inbounds_meta; (idxs[1][subidxs[1], subidxs[2]], reindex(tail(idxs), tail(tail(subidxs)))...))

# In general, we index N-dimensional parent arrays with N indices
@generated function reindex(idxs::Tuple{AbstractArray{T,N}, Vararg{Any}}, subidxs::Tuple{Vararg{Any}}) where {T,N}
    if length(subidxs.parameters) >= N
        subs = [:(subidxs[$d]) for d in 1:N]
        tail = [:(subidxs[$d]) for d in N+1:length(subidxs.parameters)]
        :(@_propagate_inbounds_meta; (idxs[1][$(subs...)], reindex(tail(idxs), ($(tail...),))...))
    else
        :(throw(ArgumentError("cannot re-index SubArray with fewer indices than dimensions\nThis should not occur; please submit a bug report.")))
    end
end

# In general, we simply re-index the parent indices by the provided ones
SlowSubArray{T,N,P,I} = SubArray{T,N,P,I,false}
function getindex(V::SubArray{T,N}, I::Vararg{Int,N}) where {T,N}
    @inline
    @boundscheck checkbounds(V, I...)
    @inbounds r = V.parent[reindex(V.indices, I)...]
    r
end

# But SubArrays with fast linear indexing pre-compute a stride and offset
FastSubArray{T,N,P,I} = SubArray{T,N,P,I,true}
function getindex(V::FastSubArray, i::Int)
    @inline
    @boundscheck checkbounds(V, i)
    @inbounds r = V.parent[V.offset1 + V.stride1*i]
    r
end
# We can avoid a multiplication if the first parent index is a Colon or AbstractUnitRange,
# or if all the indices are scalars, i.e. the view is for a single value only
FastContiguousSubArray{T,N,P,I<:Union{Tuple{Union{Slice, AbstractUnitRange}, Vararg{Any}},
                                      Tuple{Vararg{ScalarIndex}}}} = SubArray{T,N,P,I,true}
function getindex(V::FastContiguousSubArray, i::Int)
    @inline
    @boundscheck checkbounds(V, i)
    @inbounds r = V.parent[V.offset1 + i]
    r
end
# For vector views with linear indexing, we disambiguate to favor the stride/offset
# computation as that'll generally be faster than (or just as fast as) re-indexing into a range.
function getindex(V::FastSubArray{<:Any, 1}, i::Int)
    @inline
    @boundscheck checkbounds(V, i)
    @inbounds r = V.parent[V.offset1 + V.stride1*i]
    r
end
function getindex(V::FastContiguousSubArray{<:Any, 1}, i::Int)
    @inline
    @boundscheck checkbounds(V, i)
    @inbounds r = V.parent[V.offset1 + i]
    r
end

# Indexed assignment follows the same pattern as `getindex` above
function setindex!(V::SubArray{T,N}, x, I::Vararg{Int,N}) where {T,N}
    @inline
    @boundscheck checkbounds(V, I...)
    @inbounds V.parent[reindex(V.indices, I)...] = x
    V
end
function setindex!(V::FastSubArray, x, i::Int)
    @inline
    @boundscheck checkbounds(V, i)
    @inbounds V.parent[V.offset1 + V.stride1*i] = x
    V
end
function setindex!(V::FastContiguousSubArray, x, i::Int)
    @inline
    @boundscheck checkbounds(V, i)
    @inbounds V.parent[V.offset1 + i] = x
    V
end
function setindex!(V::FastSubArray{<:Any, 1}, x, i::Int)
    @inline
    @boundscheck checkbounds(V, i)
    @inbounds V.parent[V.offset1 + V.stride1*i] = x
    V
end
function setindex!(V::FastContiguousSubArray{<:Any, 1}, x, i::Int)
    @inline
    @boundscheck checkbounds(V, i)
    @inbounds V.parent[V.offset1 + i] = x
    V
end

function isassigned(V::SubArray{T,N}, I::Vararg{Int,N}) where {T,N}
    @inline
    @boundscheck checkbounds(Bool, V, I...) || return false
    @inbounds r = isassigned(V.parent, reindex(V.indices, I)...)
    r
end
function isassigned(V::FastSubArray, i::Int)
    @inline
    @boundscheck checkbounds(Bool, V, i) || return false
    @inbounds r = isassigned(V.parent, V.offset1 + V.stride1*i)
    r
end
function isassigned(V::FastContiguousSubArray, i::Int)
    @inline
    @boundscheck checkbounds(Bool, V, i) || return false
    @inbounds r = isassigned(V.parent, V.offset1 + i)
    r
end
function isassigned(V::FastSubArray{<:Any, 1}, i::Int)
    @inline
    @boundscheck checkbounds(Bool, V, i) || return false
    @inbounds r = isassigned(V.parent, V.offset1 + V.stride1*i)
    r
end
function isassigned(V::FastContiguousSubArray{<:Any, 1}, i::Int)
    @inline
    @boundscheck checkbounds(Bool, V, i) || return false
    @inbounds r = isassigned(V.parent, V.offset1 + i)
    r
end

IndexStyle(::Type{<:FastSubArray}) = IndexLinear()
IndexStyle(::Type{<:SubArray}) = IndexCartesian()

# Strides are the distance in memory between adjacent elements in a given dimension
# which we determine from the strides of the parent
strides(V::SubArray) = substrides(strides(V.parent), V.indices)

substrides(strds::Tuple{}, ::Tuple{}) = ()
substrides(strds::NTuple{N,Int}, I::Tuple{ScalarIndex, Vararg{Any}}) where N = (substrides(tail(strds), tail(I))...,)
substrides(strds::NTuple{N,Int}, I::Tuple{Slice, Vararg{Any}}) where N = (first(strds), substrides(tail(strds), tail(I))...)
substrides(strds::NTuple{N,Int}, I::Tuple{AbstractRange, Vararg{Any}}) where N = (first(strds)*step(I[1]), substrides(tail(strds), tail(I))...)
substrides(strds, I::Tuple{Any, Vararg{Any}}) = throw(ArgumentError("strides is invalid for SubArrays with indices of type $(typeof(I[1]))"))

stride(V::SubArray, d::Integer) = d <= ndims(V) ? strides(V)[d] : strides(V)[end] * size(V)[end]

compute_stride1(parent::AbstractArray, I::NTuple{N,Any}) where {N} =
    (@inline; compute_stride1(1, fill_to_length(axes(parent), OneTo(1), Val(N)), I))
compute_stride1(s, inds, I::Tuple{}) = s
compute_stride1(s, inds, I::Tuple{Vararg{ScalarIndex}}) = s
compute_stride1(s, inds, I::Tuple{ScalarIndex, Vararg{Any}}) =
    (@inline; compute_stride1(s*length(inds[1]), tail(inds), tail(I)))
compute_stride1(s, inds, I::Tuple{AbstractRange, Vararg{Any}}) = s*step(I[1])
compute_stride1(s, inds, I::Tuple{Slice, Vararg{Any}}) = s
compute_stride1(s, inds, I::Tuple{Any, Vararg{Any}}) = throw(ArgumentError("invalid strided index type $(typeof(I[1]))"))

elsize(::Type{<:SubArray{<:Any,<:Any,P}}) where {P} = elsize(P)

iscontiguous(A::SubArray) = iscontiguous(typeof(A))
iscontiguous(::Type{<:SubArray}) = false
iscontiguous(::Type{<:FastContiguousSubArray}) = true

first_index(V::FastSubArray) = V.offset1 + V.stride1 # cached for fast linear SubArrays
function first_index(V::SubArray)
    P, I = parent(V), V.indices
    s1 = compute_stride1(P, I)
    s1 + compute_offset1(P, s1, I)
end

# Computing the first index simply steps through the indices, accumulating the
# sum of index each multiplied by the parent's stride.
# The running sum is `f`; the cumulative stride product is `s`.
# If the parent is a vector, then we offset the parent's own indices with parameters of I
compute_offset1(parent::AbstractVector, stride1::Integer, I::Tuple{AbstractRange}) =
    (@inline; first(I[1]) - stride1*first(axes1(I[1])))
# If the result is one-dimensional and it's a Colon, then linear
# indexing uses the indices along the given dimension.
# If the result is one-dimensional and it's a range, then linear
# indexing might be offset if the index itself is offset
# Otherwise linear indexing always matches the parent.
compute_offset1(parent, stride1::Integer, I::Tuple) =
    (@inline; compute_offset1(parent, stride1, find_extended_dims(1, I...), find_extended_inds(I...), I))
compute_offset1(parent, stride1::Integer, dims::Tuple{Int}, inds::Tuple{Slice}, I::Tuple) =
    (@inline; compute_linindex(parent, I) - stride1*first(axes(parent, dims[1])))  # index-preserving case
compute_offset1(parent, stride1::Integer, dims, inds::Tuple{AbstractRange}, I::Tuple) =
    (@inline; compute_linindex(parent, I) - stride1*first(axes1(inds[1]))) # potentially index-offsetting case
compute_offset1(parent, stride1::Integer, dims, inds, I::Tuple) =
    (@inline; compute_linindex(parent, I) - stride1)
function compute_linindex(parent, I::NTuple{N,Any}) where N
    @inline
    IP = fill_to_length(axes(parent), OneTo(1), Val(N))
    compute_linindex(first(LinearIndices(parent)), 1, IP, I)
end
function compute_linindex(f, s, IP::Tuple, I::Tuple{ScalarIndex, Vararg{Any}})
    @inline
    Δi = I[1]-first(IP[1])
    compute_linindex(f + Δi*s, s*length(IP[1]), tail(IP), tail(I))
end
function compute_linindex(f, s, IP::Tuple, I::Tuple{Any, Vararg{Any}})
    @inline
    Δi = first(I[1])-first(IP[1])
    compute_linindex(f + Δi*s, s*length(IP[1]), tail(IP), tail(I))
end
compute_linindex(f, s, IP::Tuple, I::Tuple{}) = f

find_extended_dims(dim, ::ScalarIndex, I...) = (@inline; find_extended_dims(dim + 1, I...))
find_extended_dims(dim, i1, I...) = (@inline; (dim, find_extended_dims(dim + 1, I...)...))
find_extended_dims(dim) = ()
find_extended_inds(::ScalarIndex, I...) = (@inline; find_extended_inds(I...))
find_extended_inds(i1, I...) = (@inline; (i1, find_extended_inds(I...)...))
find_extended_inds() = ()

function unsafe_convert(::Type{Ptr{T}}, V::SubArray{T,N,P,<:Tuple{Vararg{RangeIndex}}}) where {T,N,P}
    return unsafe_convert(Ptr{T}, V.parent) + _memory_offset(V.parent, map(first, V.indices)...)
end

pointer(V::FastSubArray, i::Int) = pointer(V.parent, V.offset1 + V.stride1*i)
pointer(V::FastContiguousSubArray, i::Int) = pointer(V.parent, V.offset1 + i)

function pointer(V::SubArray{<:Any,<:Any,<:Array,<:Tuple{Vararg{RangeIndex}}}, is::AbstractCartesianIndex{N}) where {N}
    index = first_index(V)
    strds = strides(V)
    for d = 1:N
        index += (is[d]-1)*strds[d]
    end
    return pointer(V.parent, index)
end

# indices are taken from the range/vector
# Since bounds-checking is performance-critical and uses
# indices, it's worth optimizing these implementations thoroughly
axes(S::SubArray) = (@inline; _indices_sub(S.indices...))
_indices_sub(::Real, I...) = (@inline; _indices_sub(I...))
_indices_sub() = ()
function _indices_sub(i1::AbstractArray, I...)
    @inline
    (axes(i1)..., _indices_sub(I...)...)
end

has_offset_axes(S::SubArray) = has_offset_axes(S.indices...)

JuliaLang / julia / #37611

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