BoundsError in `dce!`

[YingboMa]

MWE:

using BandedMatrices, BlockArrays, BlockBandedMatrices, Cthulhu
A = BandedBlockBandedMatrix(Ones(10000, 10000), (fill(100, 100), fill(100, 100)), (1, 1), (1, 1))
λ,μ = subblockbandwidths(A)
J=Block.(1:nblocks(A,2))[1]; K=BlockBandedMatrices.blockcolrange(A,J)[1]
V = view(A,K,J)
data = BlockBandedMatrices.bandeddata(V)
@descend data[1]

julia> @descend data[1]
ERROR: BoundsError: attempt to access 0-element Array{Core.Compiler.NewNode,1} at index [7]
Stacktrace:
 [1] getindex at ./array.jl:742 [inlined]
 [2] getindex at ./compiler/ssair/ir.jl:738 [inlined]
 [3] abstract_eval_ssavalue at ./compiler/ssair/queries.jl:68 [inlined]
 [4] argextype(::Any, ::Core.Compiler.IncrementalCompact, ::Array{Any,1}, ::Array{Any,1}) at ./compiler/utilities.jl:173
 [5] argextype at ./compiler/utilities.jl:159 [inlined]
 [6] stmt_effect_free(::Any, ::Any, ::Core.Compiler.IncrementalCompact, ::Array{Any,1}) at ./compiler/ssair/queries.jl:37
 [7] maybe_erase_unused!(::Array{Int64,1}, ::Core.Compiler.IncrementalCompact, ::Int64, ::getfield(Core.Compiler, Symbol("##224#225"))) at ./compiler/ssair/ir.jl:1175
 [8] maybe_erase_unused! at ./compiler/ssair/ir.jl:1170 [inlined]
 [9] simple_dce!(::Core.Compiler.IncrementalCompact) at ./compiler/ssair/ir.jl:1262
 [10] finish at ./compiler/ssair/ir.jl:1285 [inlined]
 [11] dce!(::Core.CodeInfo, ::Core.MethodInstance) at /home/scheme/.julia/dev/Cthulhu/src/reflection.jl:164
 [12] preprocess_ci!(::Core.CodeInfo, ::Core.MethodInstance, ::Bool) at /home/scheme/.julia/dev/Cthulhu/src/reflection.jl:192
 [13] #_descend#38(::Bool, ::Core.Compiler.Params, ::Bool, ::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::typeof(Cthulhu._descend), ::Core.MethodInstance) at /home/scheme/.julia/dev/Cthulhu/src/Cthulhu.jl:122
 [14] #_descend at ./none:0 [inlined]
 [15] #_descend#43(::Core.Compiler.Params, ::Base.Iterators.Pairs{Symbol,Bool,Tuple{Symbol},NamedTuple{(:iswarn,),Tuple{Bool}}}, ::typeof(Cthulhu._descend), ::Any, ::Any) at /home/scheme/.julia/dev/Cthulhu/src/Cthulhu.jl:211
 [16] #_descend at ./none:0 [inlined]
 [17] #_descend_with_error_handling#37(::Base.Iterators.Pairs{Symbol,Bool,Tuple{Symbol},NamedTuple{(:iswarn,),Tuple{Bool}}}, ::typeof(Cthulhu._descend_with_error_handling), ::Function, ::Any) at /home/scheme/.julia/dev/Cthulhu/src/Cthulhu.jl:88
 [18] #_descend_with_error_handling at ./none:0 [inlined]
 [19] #descend_code_typed#35 at /home/scheme/.julia/dev/Cthulhu/src/Cthulhu.jl:62 [inlined]
 [20] descend_code_typed(::Function, ::Any) at /home/scheme/.julia/dev/Cthulhu/src/Cthulhu.jl:62
 [21] top-level scope at REPL[21]:1

[mateuszbaran]

I have accidentally found an easier way to reproduce this (or something very similar):

julia> using Cthulhu

julia> a = rand(10,6,5);

julia> av = view(a, 1:2:7, [1,4], 1)
4×2 view(::Array{Float64,3}, 1:2:7, [1, 4], 1) with eltype Float64:
 0.951176  0.75598 
 0.359306  0.967705
 0.803392  0.366854
 0.167082  0.925235

julia> @descend av[1] = 10
ERROR: BoundsError: attempt to access 0-element Array{Core.Compiler.NewNode,1} at index [3]
Stacktrace:
 [1] getindex at ./array.jl:728 [inlined]
 [2] getindex at ./compiler/ssair/ir.jl:738 [inlined]
 [3] abstract_eval_ssavalue at ./compiler/ssair/queries.jl:68 [inlined]
 [4] argextype(::Any, ::Core.Compiler.IncrementalCompact, ::Array{Any,1}, ::Array{Any,1}) at ./compiler/utilities.jl:175
 [5] argextype at ./compiler/utilities.jl:161 [inlined]
 [6] stmt_effect_free(::Any, ::Any, ::Core.Compiler.IncrementalCompact, ::Array{Any,1}) at ./compiler/ssair/queries.jl:37
 [7] maybe_erase_unused!(::Array{Int64,1}, ::Core.Compiler.IncrementalCompact, ::Int64, ::getfield(Core.Compiler, Symbol("##226#227"))) at ./compiler/ssair/ir.jl:1175
 [8] maybe_erase_unused! at ./compiler/ssair/ir.jl:1170 [inlined]
 [9] simple_dce!(::Core.Compiler.IncrementalCompact) at ./compiler/ssair/ir.jl:1262
 [10] finish at ./compiler/ssair/ir.jl:1285 [inlined]
 [11] dce!(::Core.CodeInfo, ::Core.MethodInstance) at /home/mateusz/.julia/packages/Cthulhu/FuE2s/src/reflection.jl:164
 [12] preprocess_ci!(::Core.CodeInfo, ::Core.MethodInstance, ::Bool) at /home/mateusz/.julia/packages/Cthulhu/FuE2s/src/reflection.jl:192
 [13] #_descend#38(::Bool, ::Core.Compiler.Params, ::Bool, ::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::typeof(Cthulhu._descend), ::Core.MethodInstance) at /home/mateusz/.julia/packages/Cthulhu/FuE2s/src/Cthulhu.jl:122
 [14] #_descend at ./none:0 [inlined]
 [15] #_descend#43(::Core.Compiler.Params, ::Base.Iterators.Pairs{Symbol,Bool,Tuple{Symbol},NamedTuple{(:iswarn,),Tuple{Bool}}}, ::typeof(Cthulhu._descend), ::Any, ::Any) at /home/mateusz/.julia/packages/Cthulhu/FuE2s/src/Cthulhu.jl:211
 [16] #_descend at ./none:0 [inlined]
 [17] #_descend_with_error_handling#37(::Base.Iterators.Pairs{Symbol,Bool,Tuple{Symbol},NamedTuple{(:iswarn,),Tuple{Bool}}}, ::typeof(Cthulhu._descend_with_error_handling), ::Function, ::Any) at /home/mateusz/.julia/packages/Cthulhu/FuE2s/src/Cthulhu.jl:88
 [18] #_descend_with_error_handling at ./none:0 [inlined]
 [19] #descend_code_typed#35 at /home/mateusz/.julia/packages/Cthulhu/FuE2s/src/Cthulhu.jl:62 [inlined]
 [20] descend_code_typed(::Function, ::Any) at /home/mateusz/.julia/packages/Cthulhu/FuE2s/src/Cthulhu.jl:62
 [21] top-level scope at REPL[4]:1

And a second similar case:

julia> using Cthulhu

julia> a = rand(10,6);

julia> av = view(a, 1:2:7, [1,4]);

julia> @descend av[1] = 10
ERROR: BoundsError: attempt to access 111-element Array{Any,1} at index [115]
Stacktrace:
 [1] getindex(::Array{Any,1}, ::Int64) at ./array.jl:728
 [2] abstract_eval_ssavalue(::Core.SSAValue, ::Core.CodeInfo) at ./compiler/abstractinterpretation.jl:1036
 [3] argextype at ./compiler/utilities.jl:175 [inlined]
 [4] (::getfield(Cthulhu, Symbol("##16#20")){Core.CodeInfo,Array{Any,1},Array{Any,1}})(::Core.SSAValue) at /home/mateusz/.julia/packages/Cthulhu/FuE2s/src/reflection.jl:91
 [5] iterate at ./generator.jl:47 [inlined]
 [6] collect_to!(::Array{DataType,1}, ::Base.Generator{Array{Any,1},getfield(Cthulhu, Symbol("##16#20")){Core.CodeInfo,Array{Any,1},Array{Any,1}}}, ::Int64, ::Int64) at ./array.jl:651
 [7] collect_to_with_first!(::Array{DataType,1}, ::Type, ::Base.Generator{Array{Any,1},getfield(Cthulhu, Symbol("##16#20")){Core.CodeInfo,Array{Any,1},Array{Any,1}}}, ::Int64) at ./array.jl:630
 [8] _collect(::Array{Any,1}, ::Base.Generator{Array{Any,1},getfield(Cthulhu, Symbol("##16#20")){Core.CodeInfo,Array{Any,1},Array{Any,1}}}, ::Base.EltypeUnknown, ::Base.HasShape{1}) at ./array.jl:624
 [9] map at ./array.jl:548 [inlined]
 [10] #find_callsites#15(::Core.Compiler.Params, ::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::typeof(Cthulhu.find_callsites), ::Core.CodeInfo, ::Core.MethodInstance, ::Array{Any,1}) at /home/mateusz/.julia/packages/Cthulhu/FuE2s/src/reflection.jl:91
 [11] (::getfield(Cthulhu, Symbol("#kw##find_callsites")))(::NamedTuple{(:params,),Tuple{Core.Compiler.Params}}, ::typeof(Cthulhu.find_callsites), ::Core.CodeInfo, ::Core.MethodInstance, ::Array{Any,1}) at ./none:0
 [12] #_descend#38(::Bool, ::Core.Compiler.Params, ::Bool, ::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::typeof(Cthulhu._descend), ::Core.MethodInstance) at /home/mateusz/.julia/packages/Cthulhu/FuE2s/src/Cthulhu.jl:123
 [13] #_descend at ./none:0 [inlined]
 [14] #_descend#43(::Core.Compiler.Params, ::Base.Iterators.Pairs{Symbol,Bool,Tuple{Symbol},NamedTuple{(:iswarn,),Tuple{Bool}}}, ::typeof(Cthulhu._descend), ::Any, ::Any) at /home/mateusz/.julia/packages/Cthulhu/FuE2s/src/Cthulhu.jl:211
 [15] #_descend at ./none:0 [inlined]
 [16] #_descend_with_error_handling#37(::Base.Iterators.Pairs{Symbol,Bool,Tuple{Symbol},NamedTuple{(:iswarn,),Tuple{Bool}}}, ::typeof(Cthulhu._descend_with_error_handling), ::Function, ::Any) at /home/mateusz/.julia/packages/Cthulhu/FuE2s/src/Cthulhu.jl:88
 [17] #_descend_with_error_handling at ./none:0 [inlined]
 [18] #descend_code_typed#35 at /home/mateusz/.julia/packages/Cthulhu/FuE2s/src/Cthulhu.jl:62 [inlined]
 [19] descend_code_typed(::Function, ::Any) at /home/mateusz/.julia/packages/Cthulhu/FuE2s/src/Cthulhu.jl:62
 [20] top-level scope at REPL[4]:1

[vchuravy]

Note that you now can set: Cthulhu.CONFIG.dead_code_elimination = false to disable DCE.

[YingboMa]

I can confirm that JuliaLang/julia#33368 fixes this