Bounds error debugging @avx from LoopVectorization

[baggepinnen]

The code below runs fine normally, but causes a bounds error when run using the debugger

julia> using LoopVectorization

julia> function debugfun(x)
           s = 0.0
           @avx for i in eachindex(x)
               s += x[i]
           end
           s
       end
debugfun (generic function with 1 method)

julia> @run debugfun(randn(3))
ERROR: BoundsError: attempt to access 4-element Array{Any,1} at index [5]
Stacktrace:
 [1] getindex at ./array.jl:788 [inlined]
 [2] build_compiled_call!(::Expr, ::Function, ::Core.CodeInfo, ::Int64, ::Int64, ::Array{Symbol,1}, ::Module) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/optimize.jl:327
 [3] optimize!(::Core.CodeInfo, ::Method) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/optimize.jl:168
 [4] JuliaInterpreter.FrameCode(::Method, ::Core.CodeInfo; generator::Bool, optimize::Bool) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/types.jl:88
 [5] prepare_framecode(::Method, ::Any; enter_generated::Bool) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/construct.jl:189
 [6] prepare_call(::Any, ::Array{Any,1}; enter_generated::Bool) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/construct.jl:260
 [7] get_call_framecode(::Array{Any,1}, ::JuliaInterpreter.FrameCode, ::Int64; enter_generated::Bool) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/localmethtable.jl:63
 [8] evaluate_call_recurse!(::Any, ::JuliaInterpreter.Frame, ::Expr; enter_generated::Bool) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/interpret.jl:225
 [9] evaluate_call_recurse! at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/interpret.jl:202 [inlined]
 [10] eval_rhs(::Any, ::JuliaInterpreter.Frame, ::Expr) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/interpret.jl:387
 [11] step_expr!(::Any, ::JuliaInterpreter.Frame, ::Any, ::Bool) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/interpret.jl:443
 [12] step_expr!(::Any, ::JuliaInterpreter.Frame, ::Bool) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/interpret.jl:566
 [13] finish!(::Any, ::JuliaInterpreter.Frame, ::Bool) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/commands.jl:14
 [14] finish_and_return! at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/commands.jl:29 [inlined]
 [15] evaluate_call_recurse!(::Any, ::JuliaInterpreter.Frame, ::Expr; enter_generated::Bool) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/interpret.jl:240
 [16] evaluate_call_recurse! at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/interpret.jl:202 [inlined]
 [17] eval_rhs(::Any, ::JuliaInterpreter.Frame, ::Expr) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/interpret.jl:387
 [18] step_expr!(::Any, ::JuliaInterpreter.Frame, ::Any, ::Bool) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/interpret.jl:522
 [19] step_expr!(::Any, ::JuliaInterpreter.Frame, ::Bool) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/interpret.jl:566
 [20] finish!(::Any, ::JuliaInterpreter.Frame, ::Bool) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/commands.jl:14
 [21] finish_and_return!(::Any, ::JuliaInterpreter.Frame, ::Bool) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/commands.jl:29
 [22] finish_stack!(::Any, ::JuliaInterpreter.Frame, ::Bool) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/commands.jl:59
 [23] debug_command(::Any, ::JuliaInterpreter.Frame, ::Symbol, ::Bool; line::Nothing) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/commands.jl:449
 [24] debug_command(::Any, ::JuliaInterpreter.Frame, ::Symbol, ::Bool) at /home/fredrikb/.julia/packages/JuliaInterpreter/R1LXQ/src/commands.jl:391
 [25] (::Atom.JunoDebugger.var"#54#56"{Bool,Bool,Bool})() at /home/fredrikb/.julia/packages/Atom/9h5Up/src/debugger/stepper.jl:153
 [26] evalscope(::Atom.JunoDebugger.var"#54#56"{Bool,Bool,Bool}) at /home/fredrikb/.julia/packages/Atom/9h5Up/src/debugger/stepper.jl:386
 [27] startdebugging(::JuliaInterpreter.Frame, ::Bool; istoplevel::Bool, toggle_ui::Bool) at /home/fredrikb/.julia/packages/Atom/9h5Up/src/debugger/stepper.jl:151
 [28] startdebugging(::JuliaInterpreter.Frame, ::Bool) at /home/fredrikb/.julia/packages/Atom/9h5Up/src/debugger/stepper.jl:137
 [29] top-level scope at /home/fredrikb/.julia/packages/Atom/9h5Up/src/debugger/stepper.jl:50

[KristofferC]

Would help a lot with expanding the macro and try to reduce things a bit.

[baggepinnen]

I have no idea what to make of this, but maybe @chriselrod does?

julia> @macroexpand @avx for i in eachindex(x)
           s += x[i]
       end
quote
    begin
    end
    if LoopVectorization.check_args(x)
        var"##loopi#771" = LoopVectorization.maybestaticrange(eachindex(x))
        var"##i_loop_lower_bound#772" = LoopVectorization.maybestaticfirst(var"##loopi#771")
        var"##i_loop_upper_bound#773" = LoopVectorization.maybestaticlast(var"##loopi#771")
        var"##vptr##_x" = LoopVectorization.stridedpointer(x)
        local var"##s_0"
        begin
            $(Expr(:gc_preserve, :(var"##s_0" = LoopVectorization._avx_!(Val{(0, 0, 0)}(), Tuple{:LoopVectorization, :LOOPCONSTANTINSTRUCTION, LoopVectorization.OperationStruct(0x0000000000000000, 0x0000000000000000, 0x0000000000000001, 0x0000000000000000, LoopVectorization.constant, 0x00, 0x01), :LoopVectorization, :getindex, LoopVectorization.OperationStruct(0x0000000000000001, 0x0000000000000000, 0x0000000000000000, 0x0000000000000000, LoopVectorization.memload, 0x01, 0x02), :LoopVectorization, :vadd, LoopVectorization.OperationStruct(0x0000000000000001, 0x0000000000000001, 0x0000000000000000, 0x0000000000000102, LoopVectorization.compute, 0x00, 0x01)}, Tuple{LoopVectorization.ArrayRefStruct{:x,Symbol("##vptr##_x")}(0x0000000000000001, 0x0000000000000001, 0x0000000000000000)}, Tuple{0, Tuple{3}, Tuple{1}, Tuple{}, Tuple{}, Tuple{}, Tuple{}}, Tuple{:i}, (var"##i_loop_lower_bound#772":var"##i_loop_upper_bound#773",), var"##vptr##_x", s)), :x))
        end
        s = LoopVectorization.reduced_add(var"##s_0", s)
    else
        $(Expr(:inbounds, true))
        local var"#758#val" = for i = eachindex(x)
                    #= none:2 =#
                    s = Base.FastMath.add_fast(s, x[i])
                end
        $(Expr(:inbounds, :pop))
        var"#758#val"
    end
end

[timholy]

I'm not certain about the source of the error, but that's just the call to the generated function _avx_!. You'll have to step in to that call in generated mode. This may work well or may not, but certainty it is not well-tested, see #163. If you want to try to fix this yourself (I am too busy to tackle it), I seem to remember that Rebugger might do something closer to the right thing here. (It just uses JuliaInterpreter so we could conceivably port whatever it does to Debugger.)

[timholy]

This seems fixed on the current release.