optimize a bit further

base/compiler/abstractinterpretation.jl

@@ -2057,7 +2057,7 @@ function abstract_eval_statement(interp::AbstractInterpreter, @nospecialize(e),
         t = Const(t.instance)
     end
     if !isempty(sv.pclimitations)
-        if t isa Const || t === Union{}
+        if t isa Const || t === Bottom
             empty!(sv.pclimitations)
         else
             t = LimitedAccuracy(t, sv.pclimitations)
@@ -2276,7 +2276,6 @@ function typeinf_local(interp::AbstractInterpreter, frame::InferenceState)
 
         for frame.currpc in frame.currpc:bbend
             stmt = frame.src.code[frame.currpc]
-            push!(frame.was_reached, frame.currpc)
             # If we're at the end of the basic block ...
             if frame.currpc == bbend
                 # Handle control flow
@@ -2291,6 +2290,7 @@ function typeinf_local(interp::AbstractInterpreter, frame::InferenceState)
                     condx = stmt.cond
                     condt = abstract_eval_value(interp, condx, currstate, frame)
                     if condt === Bottom
+                        ssavaluetypes[frame.currpc] = Bottom
                         empty!(frame.pclimitations)
                         @goto find_next_bb
                     end
@@ -2402,7 +2402,8 @@ function typeinf_local(interp::AbstractInterpreter, frame::InferenceState)
             # Process non control-flow statements
             (; changes, type) = abstract_eval_basic_statement(interp,
                 stmt, currstate, frame)
-            if type === Union{}
+            if type === Bottom
+                ssavaluetypes[frame.currpc] = Bottom
                 @goto find_next_bb
             end
             if changes !== nothing

base/compiler/inferencestate.jl

@@ -94,7 +94,6 @@ mutable struct InferenceState
     currbb::Int
     currpc::Int
     ip::BitSet#=TODO BoundedMinPrioritySet=# # current active instruction pointers
-    was_reached::BitSet
     handler_at::Vector{Int} # current exception handler info
     ssavalue_uses::Vector{BitSet} # ssavalue sparsity and restart info
     # TODO: Could keep this sparsely by doing structural liveness analysis ahead of time.
@@ -141,7 +140,6 @@ mutable struct InferenceState
 
         currbb = currpc = 1
         ip = BitSet(1) # TODO BitSetBoundedMinPrioritySet(1)
-        was_reached = BitSet()
         handler_at = compute_trycatch(code, BitSet())
         nssavalues = src.ssavaluetypes::Int
         ssavalue_uses = find_ssavalue_uses(code, nssavalues)
@@ -192,7 +190,7 @@ mutable struct InferenceState
 
         frame = new(
             linfo, world, mod, sptypes, slottypes, src, cfg,
-            currbb, currpc, ip, was_reached, handler_at, ssavalue_uses, bb_vartables, stmt_edges, stmt_info,
+            currbb, currpc, ip, handler_at, ssavalue_uses, bb_vartables, stmt_edges, stmt_info,
             pclimitations, limitations, cycle_backedges, callers_in_cycle, dont_work_on_me, parent, inferred,
             result, valid_worlds, bestguess, ipo_effects,
             params, restrict_abstract_call_sites, cached,
@@ -234,7 +232,7 @@ function any_inbounds(code::Vector{Any})
     return false
 end
 
-was_reached((; was_reached)::InferenceState, pc::Int) = pc in was_reached
+was_reached(sv::InferenceState, pc::Int) = sv.src.ssavaluetypes[pc] !== NOT_FOUND
 
 function compute_trycatch(code::Vector{Any}, ip::BitSet)
     # The goal initially is to record the frame like this for the state at exit:

base/compiler/typeinfer.jl

@@ -565,15 +565,6 @@ function widen_all_consts!(src::CodeInfo)
     return src
 end
 
-function widen_ssavaluetypes!(sv::InferenceState)
-    ssavaluetypes = sv.src.ssavaluetypes::Vector{Any}
-    for j = 1:length(ssavaluetypes)
-        t = ssavaluetypes[j]
-        ssavaluetypes[j] = t === NOT_FOUND ? Bottom : widenconditional(t)
-    end
-    return nothing
-end
-
 function record_slot_assign!(sv::InferenceState)
     # look at all assignments to slots
     # and union the set of types stored there
@@ -587,7 +578,9 @@ function record_slot_assign!(sv::InferenceState)
         if was_reached(sv, i) && isexpr(expr, :(=))
             lhs = expr.args[1]
             if isa(lhs, SlotNumber)
-                vt = widenconst(ssavaluetypes[i])
+                typ = ssavaluetypes[i]
+                @assert typ !== NOT_FOUND "active slot in unreached region"
+                vt = widenconst(typ)
                 if vt !== Bottom
                     id = slot_id(lhs)
                     otherTy = slottypes[id]
@@ -627,6 +620,7 @@ function annotate_slot_load!(undefs::Vector{Bool}, idx::Int, sv::InferenceState,
             typ = widenconditional(ignorelimited(vt.typ))
         else
             typ = sv.src.ssavaluetypes[pc]
+            @assert typ !== NOT_FOUND "active slot in unreached region"
         end
         # add type annotations where needed
         if !(sv.slottypes[id] ⊑ typ)
@@ -670,10 +664,16 @@ function find_dominating_assignment(id::Int, idx::Int, sv::InferenceState)
     return nothing
 end
 
+function widen_ssavaluetypes!(ssavaluetypes::Vector{Any})
+    for j = 1:length(ssavaluetypes)
+        t = ssavaluetypes[j]
+        ssavaluetypes[j] = t === NOT_FOUND ? Bottom : widenconditional(t)
+    end
+    return ssavaluetypes
+end
+
 # annotate types of all symbols in AST
 function type_annotate!(sv::InferenceState, run_optimizer::Bool)
-    widen_ssavaluetypes!(sv)
-
     # compute the required type for each slot
     # to hold all of the items assigned into it
     record_slot_assign!(sv)
@@ -722,8 +722,8 @@ function type_annotate!(sv::InferenceState, run_optimizer::Bool)
             # introduce temporary TypedSlot for the later optimization passes
             # and also mark used-undef slots
             body[i] = annotate_slot_load!(undefs, oldidx, sv, expr)
-        else # unreached statement  (see issue #7836)
-            if isa(expr, Expr) && is_meta_expr_head(expr.head)
+        else # unreached statement (see issue #7836)
+            if is_meta_expr(expr)
                 # keep any lexically scoped expressions
             elseif run_optimizer
                 deleteat!(body, i)
@@ -752,7 +752,7 @@ function type_annotate!(sv::InferenceState, run_optimizer::Bool)
     end
 
     src.code = body
-    src.ssavaluetypes = ssavaluetypes
+    src.ssavaluetypes = widen_ssavaluetypes!(ssavaluetypes)
 
     nothing
 end