append_c_digits: typeassert Int to improve inference

[nsajko]

Makes the sysimage more resistant to method invalidation, when defining a new Integer subtype with a right bitshift method.

[nsajko]

Eliminates all (47 on current master) invalidations that arise when running the following:

struct I <: Integer end
function Base.:(>>)(::I, ::UInt8) end
function Base.:(>>)(::I, ::Int) end

Reproduce with:

./julia -E 'using SnoopCompileCore; i = (@snoop_invalidations (struct I <: Integer end; function Base.:(>>)(::I, ::UInt8) end; function Base.:(>>)(::I, ::Int) end)); using SnoopCompile; length(uinvalidated(i))'

The eliminated invalidations:

{
    "method": ">>(::Main.RawInvalidations.I, ::Int64) @ Main.RawInvalidations ~/invalidations/script/reproducer.jl:34",
    "reason": "inserting",
    "mt_backedges": [
    ],
    "backedges": [
        {
            "method_instance": {
                "method": ">>(x::Integer, c::Int64) @ Base operators.jl:761",
                "method_instance": "MethodInstance for >>(::Integer, ::Int64)"
            },
            "children": [
                {
                    "method_instance": {
                        "method": ">>(x::Integer, c::Integer) @ Base operators.jl:752",
                        "method_instance": "MethodInstance for >>(::Integer, ::UInt8)"
                    },
                    "children": [
                    ]
                },
                {
                    "method_instance": {
                        "method": ">>(x::Integer, c::Integer) @ Base operators.jl:752",
                        "method_instance": "MethodInstance for >>(::Integer, ::UInt8)"
                    },
                    "children": [
                    ]
                }
            ]
        }
    ],
    "mt_cache": [
    ],
    "mt_disable": [
    ]
}

{
    "method": ">>(::Main.RawInvalidations.I, ::UInt8) @ Main.RawInvalidations ~/invalidations/script/reproducer.jl:34",
    "reason": "inserting",
    "mt_backedges": [
        {
            "type": "Tuple{typeof(>>), Any, UInt8}",
            "tree": {
                "method_instance": {
                    "method": "append_c_digits(olength::Int64, digits::Unsigned, buf, pos::Int64) @ Base intfuncs.jl:843",
                    "method_instance": "MethodInstance for Base.append_c_digits(::Int64, ::Unsigned, ::Memory{UInt8}, ::Int64)"
                },
                "children": [
                    {
                        "method_instance": {
                            "method": "append_c_digits_fast(olength::Int64, digits::Unsigned, buf, pos::Int64) @ Base intfuncs.jl:871",
                            "method_instance": "MethodInstance for Base.append_c_digits_fast(::Int64, ::Unsigned, ::Memory{UInt8}, ::Int64)"
                        },
                        "children": [
                        ]
                    },
                    {
                        "method_instance": {
                            "method": "append_nine_digits(digits::Unsigned, buf, pos::Int64) @ Base intfuncs.jl:860",
                            "method_instance": "MethodInstance for Base.append_nine_digits(::Unsigned, ::Memory{UInt8}, ::Int64)"
                        },
                        "children": [
                            {
                                "method_instance": {
                                    "method": "append_c_digits_fast(olength::Int64, digits::Unsigned, buf, pos::Int64) @ Base intfuncs.jl:871",
                                    "method_instance": "MethodInstance for Base.append_c_digits_fast(::Int64, ::Unsigned, ::Memory{UInt8}, ::Int64)"
                                },
                                "children": [
                                    {
                                        "method_instance": {
                                            "method": "dec(x::Unsigned, pad::Int64, neg::Bool) @ Base intfuncs.jl:889",
                                            "method_instance": "MethodInstance for Base.dec(::Unsigned, ::Int64, ::Bool)"
                                        },
                                        "children": [
                                        ]
                                    }
                                ]
                            }
                        ]
                    }
                ]
            }
        }
    ],
    "backedges": [
        {
            "method_instance": {
                "method": ">>(x::Integer, c::Integer) @ Base operators.jl:752",
                "method_instance": "MethodInstance for >>(::Integer, ::UInt8)"
            },
            "children": [
                {
                    "method_instance": {
                        "method": "append_c_digits(olength::Int64, digits::Unsigned, buf, pos::Int64) @ Base intfuncs.jl:843",
                        "method_instance": "MethodInstance for Base.append_c_digits(::Int64, ::Unsigned, ::Memory{UInt8}, ::Int64)"
                    },
                    "children": [
                    ]
                }
            ]
        }
    ],
    "mt_cache": [
    ],
    "mt_disable": [
    ]
}

[KristofferC]

Why can't this be inferred?

[topolarity]

Why can't this be inferred?

divrem infers poorly:

julia> code_typed(Base.divrem, (Unsigned, typeof(0x64)))
1-element Vector{Any}:
 CodeInfo(
1 ─ %1 = Base.divrem(x, y, Base.RoundToZero)::Tuple{Any, Any}
└──      return %1
) => Tuple{Any, Any}

[oscardssmith]

Unsigned is an abstract type.

[KristofferC]

Unsigned is an abstract type.

Yes, a lot of inference runs with abstract types.