Non-idempotent compilation

[maleadt]

Reduced from JuliaGPU/CUDAnative.jl#278, where a simple CUDAnative kernel that calls print_to_string doesn't work anymore since #28876 due to unsupported recursion. Although the recursion itself is problematic, which #25984 is supposed to fix, there seems to be a greater issue here, where multiple invocations of the compiler yield different results. Maybe that falls under the known problem of order-dependent inference, but I'm not sure so putting it out here anyway.

MWE without CUDAnative:

function codegen()
    f = Base.checked_sub
    tt = Tuple{Int,Int}

    # get the method instance
    world = typemax(UInt)
    meth = which(f, tt)
    sig = Base.signature_type(f, tt)::Type
    (ti, env) = ccall(:jl_type_intersection_with_env, Any,
                      (Any, Any), sig, meth.sig)::Core.SimpleVector
    meth = Base.func_for_method_checked(meth, ti)
    linfo = ccall(:jl_specializations_get_linfo, Ref{Core.MethodInstance},
                  (Any, Any, Any, UInt), meth, ti, env, world)

    # set-up hooks
    method_stack = Vector{Core.MethodInstance}()
    function hook_emit_function(method_instance, code, world)
        println("  "^length(method_stack), "emit_function($method_instance)")
        push!(method_stack, method_instance)

        # check for recursion
        if method_instance in method_stack[1:end-1]
            throw("recursion is currently not supported")
        end
    end
    function hook_emitted_function(method_instance, code, world)
        @assert last(method_stack) == method_instance ctx
        pop!(method_stack)
    end

    # set-up params
    params = Base.CodegenParams(cached             = false,
                                track_allocations  = false,
                                code_coverage      = false,
                                static_alloc       = false,
                                prefer_specsig     = true,
                                emit_function      = hook_emit_function,
                                emitted_function   = hook_emitted_function)

    ccall(:jl_get_llvmf_defn, Ptr{Cvoid},
          (Any, UInt, Bool, Bool, Base.CodegenParams),
          linfo, world, #=wrapper=#false, #=optimize=#false, params)

    return
end

Calling codegen() twice yields different results, where the second one results in recursive codegen for print_to_string:

julia> codegen()
emit_function(MethodInstance for checked_sub(::Int64, ::Int64))
  emit_function(MethodInstance for throw_overflowerr_binaryop(::Symbol, ::Int64, ::Int64))

julia> codegen()
emit_function(MethodInstance for checked_sub(::Int64, ::Int64))
  emit_function(MethodInstance for throw_overflowerr_binaryop(::Symbol, ::Int64, ::Int64))
    emit_function(MethodInstance for print_to_string(::Int64, ::Vararg{Any,N} where N))
      emit_function(MethodInstance for getindex(::Tuple{}, ::Int64))
      emit_function(MethodInstance for #IOBuffer#300(::Bool, ::Bool, ::Nothing, ::Bool, ::Int64, ::Int64, ::Type))
        emit_function(MethodInstance for getindex(::Tuple{}, ::Int64))
        emit_function(MethodInstance for throw_inexacterror(::Symbol, ::Any, ::Int64))
          emit_function(MethodInstance for InexactError(::Symbol, ::Any, ::Any))
        emit_function(MethodInstance for getindex(::Tuple{}, ::Int64))
        emit_function(MethodInstance for #IOBuffer#299(::Bool, ::Bool, ::Bool, ::Bool, ::Int64, ::Nothing, ::Type, ::Array{UInt8,1}))
          emit_function(MethodInstance for print_to_string(::String, ::Vararg{Any,N} where N))
            emit_function(MethodInstance for (::getfield(Core, Symbol("#kw#Type")))(::NamedTuple{(:sizehint,),Tuple{Int64}}, ::Type{Base.GenericIOBuffer{Array{UInt8,1}}}))
              emit_function(MethodInstance for getindex(::Tuple{}, ::Int64))
              emit_function(MethodInstance for #IOBuffer#300(::Bool, ::Bool, ::Nothing, ::Bool, ::Int64, ::Int64, ::Type))
ERROR: "recursion is currently not supported"

The part of #28876 that has resulted in this behavior, is the removal of a keyword argument. Adding an unused one back fixes the recursion:

julia> @eval Base begin
          function print_to_string(xs...; whatever=nothing)
              if isempty(xs)
                  return ""
              end
              siz = 0
              for x in xs
                  siz += tostr_sizehint(x)
              end
              # specialized for performance reasons
              s = IOBuffer(sizehint=siz)
              for x in xs
                  print(s, x)
              end
              String(resize!(s.data, s.size))
          end
        end
print_to_string (generic function with 1 method)

julia> codegen()
emit_function(MethodInstance for checked_sub(::Int64, ::Int64))
  emit_function(MethodInstance for throw_overflowerr_binaryop(::Symbol, ::Int64, ::Int64))

julia> codegen()
emit_function(MethodInstance for checked_sub(::Int64, ::Int64))
  emit_function(MethodInstance for throw_overflowerr_binaryop(::Symbol, ::Int64, ::Int64))

This is on latest 1.0.2 (b196720).

Another possible clue:

julia> @eval Base begin
          function print_to_string(xs...; whatever=nothing)
              if isempty(xs)
                  return ""
              end
              siz = 0
              for x in xs
                  siz += tostr_sizehint(x)
              end
              # specialized for performance reasons
              s = IOBuffer(sizehint=siz)
              for x in xs
                  print(s, x)
              end
              String(resize!(s.data, s.size))
          end
        end
print_to_string (generic function with 1 method)

julia> using CUDAnative
julia: /home/tim/Julia/julia-1.0/src/gf.c:157: jl_method_instance_t *jl_specializations_get_linfo(jl_method_t *, jl_value_t *, jl_svec_t *, size_t): Assertion `linfo->min_world <= sf->min_world && linfo->max_world >= sf->max_world' failed.

signal (6): Aborted
in expression starting at no file:0
gsignal at /usr/lib/libc.so.6 (unknown line)
abort at /usr/lib/libc.so.6 (unknown line)
__assert_fail_base.cold.0 at /usr/lib/libc.so.6 (unknown line)
__assert_fail at /usr/lib/libc.so.6 (unknown line)
jl_specializations_get_linfo at /home/tim/Julia/julia-1.0/src/gf.c:157
jl_recache_method_instance at /home/tim/Julia/julia-1.0/src/dump.c:2996 [inlined]
jl_recache_other at /home/tim/Julia/julia-1.0/src/dump.c:3016 [inlined]
_jl_restore_incremental at /home/tim/Julia/julia-1.0/src/dump.c:3104
jl_restore_incremental at /home/tim/Julia/julia-1.0/src/dump.c:3146
_include_from_serialized at ./loading.jl:617
macro expansion at ./logging.jl:310 [inlined]
_require_search_from_serialized at ./loading.jl:704
_tryrequire_from_serialized at ./loading.jl:648
_require_search_from_serialized at ./loading.jl:702
_require at ./loading.jl:937
require at ./loading.jl:858
macro expansion at ./logging.jl:309 [inlined]
require at ./loading.jl:840
jl_fptr_trampoline at /home/tim/Julia/julia-1.0/src/gf.c:1831
jl_apply_generic at /home/tim/Julia/julia-1.0/src/gf.c:2184
jl_apply at /home/tim/Julia/julia-1.0/src/julia.h:1537 [inlined]
call_require at /home/tim/Julia/julia-1.0/src/toplevel.c:441 [inlined]
eval_import_path at /home/tim/Julia/julia-1.0/src/toplevel.c:476
jl_toplevel_eval_flex at /home/tim/Julia/julia-1.0/src/toplevel.c:671
jl_toplevel_eval_in at /home/tim/Julia/julia-1.0/src/builtins.c:622
eval at ./boot.jl:319
jl_apply_generic at /home/tim/Julia/julia-1.0/src/gf.c:2184
eval_user_input at /home/tim/Julia/julia-1.0/build/release/usr/share/julia/stdlib/v1.0/REPL/src/REPL.jl:85
macro expansion at /home/tim/Julia/julia-1.0/build/release/usr/share/julia/stdlib/v1.0/REPL/src/REPL.jl:117 [inlined]
#28 at ./task.jl:259
jl_apply_generic at /home/tim/Julia/julia-1.0/src/gf.c:2184
jl_apply at /home/tim/Julia/julia-1.0/src/julia.h:1537 [inlined]
start_task at /home/tim/Julia/julia-1.0/src/task.c:268
unknown function (ip: 0xffffffffffffffff)
Allocations: 16752583 (Pool: 16747964; Big: 4619); GC: 35
zsh: abort      julia --depwarn=no --color=yes

[maleadt]

Note that with #29957 merged, one needs to revert that change in order to have recursion with the checked_add function as tested in this MWE.

[KristofferC]

Fixed by #29957

Edit: Or well, maybe the non-idempotence is still an issue

[maleadt]

Annoyingly, this seems precompilation/sysimg related. Can't reproduce with similar functions that are defined in the file itself, only by calling eg. Base.checked_sub. Also doesn't reproduce on master, only on release-1.0, and I bisected it to 17a5754...

[maleadt]

Probably not relevant anymore after the codegen refactor.