Inference hang when inlining is off

[timholy]

If you check out the master branch of AxisArrays.jl (currently, this is commit 4d2f8ccc08d582adcf0a029d28f5ccd12b72f406), then the following script succeeds with normal inlining but hangs during inference with --inline=no:

using AxisArrays

Base.reduced_indices(A::AxisArray, region)  = reduced_indices(axes(A), region)

@inline reduced_indices{Ax<:Axis}(axs::Tuple{Vararg{Axis}}, region::Type{Ax}) =
    _reduced_indices(reduced_axis, (), region, axs...)

@inline _reduced_indices{name}(f, out, chosen::Type{Axis{name}}, ax::Axis{name}, axs...) =
    _reduced_indices(f, (out..., f(ax)), chosen, axs...)
@inline _reduced_indices{name}(f, out, chosen::Axis{name}, ax::Axis{name}, axs...) =
    _reduced_indices(f, (out..., f(ax)), chosen, axs...)
@inline _reduced_indices(f, out, chosen, ax::Axis, axs...) =
    _reduced_indices(f, (out..., ax), chosen, axs...)
_reduced_indices(f, out, chosen) = out

reduced_axis(ax) = ax(oftype(ax.val, Base.OneTo(1)))

C = AxisArray(collect(reshape(1:15,3,5)), :y, :x)
sum(C, Axis{:x})

Observed in JuliaArrays/AxisArrays.jl#56.

[timholy]

Note that this is not a regression, because it also affects julia-0.5.

[timholy]

Here's a completely self-contained reproducer; it also doesn't require setting --inline=no, but note the comment about changing a @noinline to an @inline.

This reproduces the hang for both 0.5 and 0.6.

immutable Axis{name,T}
    val::T
end
(::Type{Axis{name}}){name,T}(val::T) = Axis{name,T}(val)

(A::Axis{name}){name}(i) = Axis{name}(i)

immutable AxisArray{T,N,D,Ax} <: AbstractArray{T,N}
    data::D
    axes::Ax
    (::Type{AxisArray{T,N,D,Ax}}){T,N,D,Ax}(data::AbstractArray{T,N}, axs::Tuple{Vararg{Axis,N}}) = new{T,N,D,Ax}(data, axs)
end
function AxisArray{T,N}(A::AbstractArray{T,N}, axs::NTuple{N,Axis})
    AxisArray{T,N,typeof(A),typeof(axs)}(A, axs)
end

Base.reduced_indices(A::AxisArray, region)  = reduced_indices(A.axes, region)

@inline reduced_indices{Ax<:Axis}(axs::Tuple{Vararg{Axis}}, region::Type{Ax}) =
    _reduced_indices(reduced_axis, (), region, axs...)

@noinline _reduced_indices{name}(f, out, chosen::Type{Axis{name}}, ax::Axis{name}, axs...) =
    _reduced_indices(f, (out..., f(ax)), chosen, axs...)
@noinline _reduced_indices{name}(f, out, chosen::Axis{name}, ax::Axis{name}, axs...) =
    _reduced_indices(f, (out..., f(ax)), chosen, axs...)
# If you change this next line to @inline, then it works fine
@noinline _reduced_indices(f, out, chosen, ax::Axis, axs...) =
    _reduced_indices(f, (out..., ax), chosen, axs...)
_reduced_indices(f, out, chosen) = out

reduced_axis(ax) = ax(oftype(ax.val, Base.OneTo(1)))

Base.similar{T,S,N}(A::AxisArray{T,N}, ::Type{S}, axs::Tuple{Axis,Vararg{Axis}}) =
    AxisArray(similar(A.data, S, map(ax->length(ax.val), axs)), axs)
Base.size(A::AxisArray) = size(A.data)
Base.getindex(A::AxisArray, i::Int, j::Int) = A.data[i, j]
Base.setindex!(A::AxisArray, val, i::Int, j::Int) = A.data[i, j] = val

C = AxisArray(collect(reshape(1:15,3,5)), (Axis{:y}(1:3), Axis{:x}(1:5)))
D = sum(C, Axis{:x})

For 0.6 I'm on

julia> versioninfo()
Julia Version 0.6.0-pre.alpha.229
Commit cc917b5 (2017-03-22 21:53 UTC)
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: Intel(R) Core(TM) i7-5500U CPU @ 2.40GHz
  WORD_SIZE: 64
  BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Haswell)
  LAPACK: libopenblas64_
  LIBM: libopenlibm
  LLVM: libLLVM-3.9.1 (ORCJIT, broadwell)

[timholy]

Even simpler:

julia> include("hang2.jl")
reduced_axis (generic function with 1 method)

julia> reduced_indices((Axis{:y}(1:3), Axis{:x}(1:5)), Axis{:y})
(Axis{:y,UnitRange{Int64}}(1:1), Axis{:x,UnitRange{Int64}}(1:5))

julia> reduced_indices((Axis{:y}(1:3), Axis{:x}(1:5)), Axis{:x})
^C^C^C^C^CWARNING: Force throwing a SIGINT
WARNING: An error occurred during inference. Type inference is now partially disabled.
InterruptException()
unknown function (ip: 0x7fdf07cdd19f)
(Axis{:y,UnitRange{Int64}}(1:3), Axis{:x,UnitRange{Int64}}(1:1))

julia> ^C

with hang2.jl:

immutable Axis{name,T}
    val::T
end
(::Type{Axis{name}}){name,T}(val::T) = Axis{name,T}(val)

(A::Axis{name}){name}(i) = Axis{name}(i)

@inline reduced_indices{Ax<:Axis}(axs::Tuple{Vararg{Axis}}, region::Type{Ax}) =
    _reduced_indices(reduced_axis, (), region, axs...)

@noinline _reduced_indices{name}(f, out, chosen::Type{Axis{name}}, ax::Axis{name}, axs...) =
    _reduced_indices(f, (out..., f(ax)), chosen, axs...)
@noinline _reduced_indices{name}(f, out, chosen::Axis{name}, ax::Axis{name}, axs...) =
    _reduced_indices(f, (out..., f(ax)), chosen, axs...)
# If you change this next line to @inline, then it works fine
@noinline _reduced_indices(f, out, chosen, ax::Axis, axs...) =
    _reduced_indices(f, (out..., ax), chosen, axs...)
_reduced_indices(f, out, chosen) = out

reduced_axis(ax) = ax(oftype(ax.val, Base.OneTo(1)))