inference: re-enable inference overload for basic statements (#58027)

After #55575, inference for basic statements got inlined
into `typeinf_local`. But external abstract interpreters like JET.jl
need to overload this inference to customize this behavior. So this
commit extracts the inlined inference logic back out into a separate
`abstract_eval_basic_statement` method.

Author: aviatesk

Compiler/src/abstractinterpretation.jl

@@ -3659,6 +3659,107 @@ function abstract_eval_ssavalue(s::SSAValue, ssavaluetypes::Vector{Any})
     return typ
 end
 
+struct AbstractEvalBasicStatementResult
+    rt
+    exct
+    effects::Union{Nothing,Effects}
+    changes::Union{Nothing,StateUpdate}
+    refinements # ::Union{Nothing,SlotRefinement,Vector{Any}}
+    currsaw_latestworld::Bool
+    function AbstractEvalBasicStatementResult(rt, exct, effects::Union{Nothing,Effects},
+        changes::Union{Nothing,StateUpdate}, refinements, currsaw_latestworld::Bool)
+        @nospecialize rt exct refinements
+        return new(rt, exct, effects, changes, refinements, currsaw_latestworld)
+    end
+end
+
+function abstract_eval_basic_statement(interp::AbstractInterpreter, @nospecialize(stmt), sstate::StatementState, frame::InferenceState,
+                                       result::Union{Nothing,Future{RTEffects}}=nothing)
+    rt = nothing
+    exct = Bottom
+    changes = nothing
+    refinements = nothing
+    effects = nothing
+    currsaw_latestworld = sstate.saw_latestworld
+    if result !== nothing
+        @goto injectresult
+    end
+    if isa(stmt, NewvarNode)
+        changes = StateUpdate(stmt.slot, VarState(Bottom, true))
+    elseif isa(stmt, PhiNode)
+        add_curr_ssaflag!(frame, IR_FLAGS_REMOVABLE)
+        # Implement convergence for PhiNodes. In particular, PhiNodes need to tmerge over
+        # the incoming values from all iterations, but `abstract_eval_phi` will only tmerge
+        # over the first and last iterations. By tmerging in the current old_rt, we ensure that
+        # we will not lose an intermediate value.
+        rt = abstract_eval_phi(interp, stmt, sstate, frame)
+        old_rt = frame.ssavaluetypes[frame.currpc]
+        rt = old_rt === NOT_FOUND ? rt : tmerge(typeinf_lattice(interp), old_rt, rt)
+    else
+        lhs = nothing
+        if isexpr(stmt, :(=))
+            lhs = stmt.args[1]
+            stmt = stmt.args[2]
+        end
+        if !isa(stmt, Expr)
+            (; rt, exct, effects, refinements) = abstract_eval_special_value(interp, stmt, sstate, frame)
+        else
+            hd = stmt.head
+            if hd === :method
+                fname = stmt.args[1]
+                if isa(fname, SlotNumber)
+                    changes = StateUpdate(fname, VarState(Any, false))
+                end
+            elseif (hd === :code_coverage_effect ||
+                    # :boundscheck can be narrowed to Bool
+                    (hd !== :boundscheck && is_meta_expr(stmt)))
+                rt = Nothing
+            elseif hd === :latestworld
+                currsaw_latestworld = true
+                rt = Nothing
+            else
+                result = abstract_eval_statement_expr(interp, stmt, sstate, frame)::Future{RTEffects}
+                if !isready(result) || !isempty(frame.tasks)
+                    return result
+
+                    @label injectresult
+                    # reload local variables
+                    lhs = nothing
+                    if isexpr(stmt, :(=))
+                        lhs = stmt.args[1]
+                        stmt = stmt.args[2]
+                    end
+                end
+                result = result[]
+                (; rt, exct, effects, refinements) = result
+                if effects.noub === NOUB_IF_NOINBOUNDS
+                    if has_curr_ssaflag(frame, IR_FLAG_INBOUNDS)
+                        effects = Effects(effects; noub=ALWAYS_FALSE)
+                    elseif !propagate_inbounds(frame)
+                        # The callee read our inbounds flag, but unless we propagate inbounds,
+                        # we ourselves don't read our parent's inbounds.
+                        effects = Effects(effects; noub=ALWAYS_TRUE)
+                    end
+                end
+                @assert !isa(rt, TypeVar) "unhandled TypeVar"
+                rt = maybe_singleton_const(rt)
+                if !isempty(frame.pclimitations)
+                    if rt isa Const || rt === Union{}
+                        empty!(frame.pclimitations)
+                    else
+                        rt = LimitedAccuracy(rt, frame.pclimitations)
+                        frame.pclimitations = IdSet{InferenceState}()
+                    end
+                end
+            end
+        end
+        if lhs !== nothing && rt !== Bottom
+            changes = StateUpdate(lhs::SlotNumber, VarState(rt, false))
+        end
+    end
+    return AbstractEvalBasicStatementResult(rt, exct, effects, changes, refinements, currsaw_latestworld)
+end
+
 struct BestguessInfo{Interp<:AbstractInterpreter}
     interp::Interp
     bestguess
@@ -3940,14 +4041,16 @@ end
 
 # make as much progress on `frame` as possible (without handling cycles)
 struct CurrentState
-    result::Future
+    result::Future{RTEffects}
     currstate::VarTable
     currsaw_latestworld::Bool
     bbstart::Int
     bbend::Int
-    CurrentState(result::Future, currstate::VarTable, currsaw_latestworld::Bool, bbstart::Int, bbend::Int) = new(result, currstate, currsaw_latestworld, bbstart, bbend)
+    CurrentState(result::Future{RTEffects}, currstate::VarTable, currsaw_latestworld::Bool, bbstart::Int, bbend::Int) =
+        new(result, currstate, currsaw_latestworld, bbstart, bbend)
     CurrentState() = new()
 end
+
 function typeinf_local(interp::AbstractInterpreter, frame::InferenceState, nextresult::CurrentState)
     @assert !is_inferred(frame)
     W = frame.ip
@@ -3966,7 +4069,9 @@ function typeinf_local(interp::AbstractInterpreter, frame::InferenceState, nextr
         bbend = nextresult.bbend
         currstate = nextresult.currstate
         currsaw_latestworld = nextresult.currsaw_latestworld
-        @goto injectresult
+        stmt = frame.src.code[currpc]
+        result = abstract_eval_basic_statement(interp, stmt, StatementState(currstate, currsaw_latestworld), frame, nextresult.result)
+        @goto injected_result
     end
 
     if currbb != 1
@@ -4119,87 +4224,15 @@ function typeinf_local(interp::AbstractInterpreter, frame::InferenceState, nextr
             end
             # Process non control-flow statements
             @assert isempty(frame.tasks)
-            rt = nothing
-            exct = Bottom
-            changes = nothing
-            refinements = nothing
-            effects = nothing
-            if isa(stmt, NewvarNode)
-                changes = StateUpdate(stmt.slot, VarState(Bottom, true))
-            elseif isa(stmt, PhiNode)
-                add_curr_ssaflag!(frame, IR_FLAGS_REMOVABLE)
-                # Implement convergence for PhiNodes. In particular, PhiNodes need to tmerge over
-                # the incoming values from all iterations, but `abstract_eval_phi` will only tmerge
-                # over the first and last iterations. By tmerging in the current old_rt, we ensure that
-                # we will not lose an intermediate value.
-                rt = abstract_eval_phi(interp, stmt, StatementState(currstate, currsaw_latestworld), frame)
-                old_rt = frame.ssavaluetypes[currpc]
-                rt = old_rt === NOT_FOUND ? rt : tmerge(typeinf_lattice(interp), old_rt, rt)
+            sstate = StatementState(currstate, currsaw_latestworld)
+            result = abstract_eval_basic_statement(interp, stmt, sstate, frame)
+            if result isa Future{RTEffects}
+                return CurrentState(result, currstate, currsaw_latestworld, bbstart, bbend)
             else
-                lhs = nothing
-                if isexpr(stmt, :(=))
-                    lhs = stmt.args[1]
-                    stmt = stmt.args[2]
-                end
-                if !isa(stmt, Expr)
-                    (; rt, exct, effects, refinements) = abstract_eval_special_value(interp, stmt, StatementState(currstate, currsaw_latestworld), frame)
-                else
-                    hd = stmt.head
-                    if hd === :method
-                        fname = stmt.args[1]
-                        if isa(fname, SlotNumber)
-                            changes = StateUpdate(fname, VarState(Any, false))
-                        end
-                    elseif (hd === :code_coverage_effect || (
-                            hd !== :boundscheck && # :boundscheck can be narrowed to Bool
-                            is_meta_expr(stmt)))
-                        rt = Nothing
-                    elseif hd === :latestworld
-                        currsaw_latestworld = true
-                        rt = Nothing
-                    else
-                        result = abstract_eval_statement_expr(interp, stmt, StatementState(currstate, currsaw_latestworld), frame)::Future
-                        if !isready(result) || !isempty(frame.tasks)
-                            return CurrentState(result, currstate, currsaw_latestworld, bbstart, bbend)
-                            @label injectresult
-                            # reload local variables
-                            stmt = frame.src.code[currpc]
-                            changes = nothing
-                            lhs = nothing
-                            if isexpr(stmt, :(=))
-                                lhs = stmt.args[1]
-                                stmt = stmt.args[2]
-                            end
-                            result = nextresult.result::Future{RTEffects}
-                        end
-                        result = result[]
-                        (; rt, exct, effects, refinements) = result
-                        if effects.noub === NOUB_IF_NOINBOUNDS
-                            if has_curr_ssaflag(frame, IR_FLAG_INBOUNDS)
-                                effects = Effects(effects; noub=ALWAYS_FALSE)
-                            elseif !propagate_inbounds(frame)
-                                # The callee read our inbounds flag, but unless we propagate inbounds,
-                                # we ourselves don't read our parent's inbounds.
-                                effects = Effects(effects; noub=ALWAYS_TRUE)
-                            end
-                        end
-                        @assert !isa(rt, TypeVar) "unhandled TypeVar"
-                        rt = maybe_singleton_const(rt)
-                        if !isempty(frame.pclimitations)
-                            if rt isa Const || rt === Union{}
-                                empty!(frame.pclimitations)
-                            else
-                                rt = LimitedAccuracy(rt, frame.pclimitations)
-                                frame.pclimitations = IdSet{InferenceState}()
-                            end
-                        end
-                    end
-                end
-                effects === nothing || merge_override_effects!(interp, effects, frame)
-                if lhs !== nothing && rt !== Bottom
-                    changes = StateUpdate(lhs::SlotNumber, VarState(rt, false))
-                end
+                @label injected_result
+                (; rt, exct, effects, changes, refinements, currsaw_latestworld) = result
             end
+            effects === nothing || merge_override_effects!(interp, effects, frame)
             if !has_curr_ssaflag(frame, IR_FLAG_NOTHROW)
                 if exct !== Union{}
                     update_exc_bestguess!(interp, exct, frame)