enable toplevel optimization and eliminate some toplevel special casings

Better to work with <JuliaLang/julia#42013>, but
I also added an hacky fallback that makes use of the existing method
definition pipeline.

src/JET.jl

@@ -842,30 +842,32 @@ function report_text(text::AbstractString,
     return JETToplevelResult(analyzer′, res, source; analyzer, jetconfigs...)
 end
 
+# we have to go on hacks; see `transform_abstract_global_symbols!` and `resolve_toplevel_symbols`
 function analyze_toplevel!(analyzer::AbstractAnalyzer, src::CodeInfo)
     # construct toplevel `MethodInstance`
     mi = ccall(:jl_new_method_instance_uninit, Ref{Core.MethodInstance}, ());
-    mi.uninferred = src
     mi.specTypes = Tuple{}
 
-    transform_abstract_global_symbols!(analyzer, src)
-    mi.def = get_toplevelmod(analyzer)
+    mi.def = mod = get_toplevelmod(analyzer)
+    src = transform_abstract_global_symbols!(analyzer, src)
+    src = resolve_toplevel_symbols(mod, src)
+    mi.uninferred = src
 
     result = InferenceResult(mi);
-    # toplevel frame doesn't need to be cached (and so it won't be optimized), nor should
-    # go through JET's code generation error check
-    frame = InferenceState(result, src, #=cached=# false, analyzer);
+    # toplevel frames don't really need to be cached, but still better to be optimized
+    # in order to get reasonable `LocalUndefVarErrorReport` and `UncaughtExceptionReport`
+    frame = InferenceState(result, src, #=cached=# true, analyzer);
 
     return analyze_frame!(analyzer, frame)
 end
 
-# HACK this is an native hack to re-use `AbstractInterpreter`'s approximated slot types for
+# HACK this is very naive hack to re-use `AbstractInterpreter`'s slot type approximation for
 # assignments of abstract global variables, which are represented as toplevel symbols at this point;
-# the idea is just to transform them into slots from symbols and use their approximated type
-# on their assignment.
+# the idea is just to transform them into slot from symbol and use their approximated type
+# on their assignment (see `finish(::InferenceState, ::AbstractAnalyzer)`).
 # NOTE that `transform_abstract_global_symbols!` will produce really invalid code for
 # actual interpretation or execution, but all the statements won't be interpreted anymore
-# by `ConcreteInterpreter` nor executed anyway since toplevel frames aren't cached
+# by `ConcreteInterpreter` nor executed by the native compilation pipeline anyway
 function transform_abstract_global_symbols!(analyzer::AbstractAnalyzer, src::CodeInfo)
     nslots = length(src.slotnames)
     abstrct_global_variables = Dict{Symbol,Int}()
@@ -901,6 +903,35 @@ function transform_abstract_global_symbols!(analyzer::AbstractAnalyzer, src::Cod
     end
 
     set_global_slots!(analyzer, Dict(idx => slotname for (slotname, idx) in abstrct_global_variables))
+
+    return src
+end
+
+# resolve toplevel symbols (and other expressions like `:foreigncall`)
+# so that the returned `CodeInfo` is eligible for abstractintepret and optimization
+@static if VERSION ≥ v"1.8.0-DEV.420"
+    function resolve_toplevel_symbols(mod::Module, src::CodeInfo)
+        newsrc = copy(src)
+        @ccall jl_resolve_globals_in_ir(newsrc.code::Any, mod::Any, svec()::Any, 1::Any)::Cvoid
+        return newsrc
+    end
+else
+    # HACK before https://github.com/JuliaLang/julia/pull/42013, we need to go through
+    # the method definition pipeline to get the effect of `jl_resolve_globals_in_ir`
+    function resolve_toplevel_symbols(mod::Module, src::CodeInfo)
+        sig = Core.svec(
+            svec(typeof(__toplevelf__)),
+            svec(),
+            QuoteNode(LineNumberNode(@__LINE__, @__FILE__)))
+        # branching on https://github.com/JuliaLang/julia/pull/41137
+        method = (@static if isdefined(Core.Compiler, :OverlayMethodTable)
+            ccall(:jl_method_def, Any, (Any, Ptr{Cvoid}, Any, Any), sig, C_NULL, src, mod)
+        else
+            ccall(:jl_method_def, Any, (Any, Any, Any), sig, src, mod)
+        end)::Method
+        return CC.uncompressed_ir(method)
+    end
+    function __toplevelf__ end
 end
 
 # TODO `analyze_builtin!` ?

src/abstractinterpretation.jl

@@ -385,9 +385,6 @@ function CC.abstract_eval_special_value(analyzer::AbstractAnalyzer, @nospecializ
                 # if it's really not defined, the error will be generated later anyway
                 e = GlobalRef(get_toplevelmod(analyzer), get_slotname(sv, e))
             end
-        elseif isa(e, Symbol)
-            # (already concretized) toplevel global symbols
-            e = GlobalRef(get_toplevelmod(analyzer), e)
         end
     end
 
@@ -749,7 +746,7 @@ function is_constant_declared(name::Symbol, sv::InferenceState)
     return any(sv.src.code) do @nospecialize(x)
         if @isexpr(x, :const)
             arg = first(x.args)
-            # `transform_global_symbols!` replaces all the global symbols in this toplevel frame with `Slot`s
+            # `transform_abstract_global_symbols!` replaces all the global symbols in this toplevel frame with `Slot`s
             if isa(arg, Slot)
                 return get_slotname(sv, arg) === name
             end

src/analyzer.jl

@@ -482,8 +482,7 @@ function maybe_initialize_caches!(analyzer::AbstractAnalyzer)
 end
 
 # check if we're in a toplevel module
-@inline istoplevel(sv::InferenceState)    = istoplevel(sv.linfo)
-@inline istoplevel(::OptimizationState)   = false # optimization never happen for top-level code
+@inline istoplevel(sv::State)             = istoplevel(sv.linfo)
 @inline istoplevel(linfo::MethodInstance) = isa(linfo.def, Module)
 
 is_global_slot(analyzer::AbstractAnalyzer, slot::Int)   = slot in keys(get_global_slots(analyzer))

src/locinfo.jl

@@ -160,15 +160,7 @@ function _get_sig_type((sv, _)::StateAtPC, arg::Argument)
     return Any[sig, typ], typ
 end
 _get_sig_type(_::StateAtPC, gr::GlobalRef) = Any[string(gr.mod, '.', gr.name)], nothing
-function _get_sig_type(s::StateAtPC, name::Symbol)
-    sv = first(s)
-    if istoplevel(sv)
-        # this is concrete global variable, form the global reference
-        return _get_sig_type(s, GlobalRef(sv.linfo.def, name))
-    else
-        return Any[repr(name; context = :compact => true)], nothing
-    end
-end
+_get_sig_type(_::StateAtPC, name::Symbol) = Any[repr(name; context = :compact => true)], nothing
 function _get_sig_type(s::StateAtPC, gotoifnot::GotoIfNot)
     sig  = Any[string("goto %", gotoifnot.dest, " if not "), _get_sig(s, gotoifnot.cond)...]
     return sig, nothing

src/typeinfer.jl

@@ -287,7 +287,8 @@ function (::SoundBasicPass)(::Type{UncaughtExceptionReport}, analyzer::AbstractA
         throw_locs  = get_throw_locs(analyzer)
         throw_calls = Tuple{Int,Expr}[]
         for (pc, stmt) in enumerate(stmts)
-            is_throw_call_expr(analyzer, frame, stmt) || continue
+            isa(stmt, Expr) || continue
+            is_throw_call(stmt) || continue
             # if this `throw` is already reported, don't duplciate
             linetable[codelocs[pc]]::LineInfoNode in throw_locs && continue
             push!(throw_calls, (pc, stmt))
@@ -303,22 +304,3 @@ function (::SoundBasicPass)(::Type{UncaughtExceptionReport}, analyzer::AbstractA
         empty!(get_uncaught_exceptions(analyzer))
     end
 end
-
-# basically same as `is_throw_call`, but also toplevel module handling added
-function is_throw_call_expr(analyzer::AbstractAnalyzer, frame::InferenceState, @nospecialize(e))
-    if isa(e, Expr)
-        if e.head === :call
-            f = e.args[1]
-            if istoplevel(frame) && isa(f, Symbol)
-                f = GlobalRef(get_toplevelmod(analyzer), f)
-            end
-            if isa(f, GlobalRef)
-                ff = CC.abstract_eval_global(f.mod, f.name)
-                if isa(ff, Const) && ff.val === Core.throw
-                    return true
-                end
-            end
-        end
-    end
-    return false
-end

test/test_abstractinterpretation.jl

@@ -134,9 +134,7 @@ end
         @test isempty(get_reports(analyzer))
     end
 
-    # with the current approach, local undefined variables in toplevel frame can't be found
-    # since we don't cache toplevel frame and thus it won't be optimized
-    let
+    let # should work for top-level analysis
         res = @analyze_toplevel begin
             foo = let
                 if rand(Bool)
@@ -146,7 +144,9 @@ end
                 end
             end
         end
-        @test_broken !isempty(res.inference_error_reports)
+        @test length(res.inference_error_reports) === 1 &&
+              first(res.inference_error_reports) isa LocalUndefVarErrorReport &&
+              first(res.inference_error_reports).name === :bar
     end
 end