inference: propagate variable changes to all exception frames #42081

aviatesk · vtjnash · aviatesk · commit e3b5d1d56219 · 2021-09-04T02:01:59.000+09:00
cherry-picked from #42081 Co-Authored-By: Jameson Nash <vtjnash+github@gmail.com>
diff --git a/base/compiler/abstractinterpretation.jl b/base/compiler/abstractinterpretation.jl
@@ -1331,19 +1331,18 @@ function typeinf_local(interp::AbstractInterpreter, frame::InferenceState)
     n = frame.nstmts
     while frame.pc´´ <= n
         # make progress on the active ip set
-        local pc::Int = frame.pc´´ # current program-counter
+        local pc::Int = frame.pc´´
         while true # inner loop optimizes the common case where it can run straight from pc to pc + 1
             #print(pc,": ",s[pc],"\n")
             local pc´::Int = pc + 1 # next program-counter (after executing instruction)
             if pc == frame.pc´´
-                # need to update pc´´ to point at the new lowest instruction in W
-                min_pc = _bits_findnext(W.bits, pc + 1)
-                frame.pc´´ = min_pc == -1 ? n + 1 : min_pc
+                # want to update pc´´ to point at the new lowest instruction in W
+                frame.pc´´ = pc´
             end
             delete!(W, pc)
             frame.currpc = pc
-            frame.cur_hand = frame.handler_at[pc]
-            frame.stmt_edges[pc] === nothing || empty!(frame.stmt_edges[pc])
+            edges = frame.stmt_edges[pc]
+            edges === nothing || empty!(edges)
             frame.stmt_info[pc] = nothing
             stmt = frame.src.code[pc]
             changes = s[pc]::VarTable
@@ -1377,7 +1376,6 @@ function typeinf_local(interp::AbstractInterpreter, frame::InferenceState)
                     pc´ = l
                 else
                     # general case
-                    frame.handler_at[l] = frame.cur_hand
                     changes_else = changes
                     if isa(condt, Conditional)
                         if condt.elsetype !== Any && condt.elsetype !== changes[slot_id(condt.var)]
@@ -1425,7 +1423,6 @@ function typeinf_local(interp::AbstractInterpreter, frame::InferenceState)
                 end
             elseif hd === :enter
                 l = stmt.args[1]::Int
-                frame.cur_hand = Pair{Any,Any}(l, frame.cur_hand)
                 # propagate type info to exception handler
                 old = s[l]
                 newstate_catch = stupdate!(old, changes)
@@ -1437,11 +1434,7 @@ function typeinf_local(interp::AbstractInterpreter, frame::InferenceState)
                     s[l] = newstate_catch
                 end
                 typeassert(s[l], VarTable)
-                frame.handler_at[l] = frame.cur_hand
             elseif hd === :leave
-                for i = 1:((stmt.args[1])::Int)
-                    frame.cur_hand = (frame.cur_hand::Pair{Any,Any}).second
-                end
             else
                 if hd === :(=)
                     t = abstract_eval_statement(interp, stmt.args[2], changes, frame)
@@ -1467,16 +1460,22 @@ function typeinf_local(interp::AbstractInterpreter, frame::InferenceState)
                         frame.src.ssavaluetypes[pc] = t
                     end
                 end
-                if frame.cur_hand !== nothing && isa(changes, StateUpdate)
-                    # propagate new type info to exception handler
-                    # the handling for Expr(:enter) propagates all changes from before the try/catch
-                    # so this only needs to propagate any changes
-                    l = frame.cur_hand.first::Int
-                    if stupdate1!(s[l]::VarTable, changes::StateUpdate) !== false
-                        if l < frame.pc´´
-                            frame.pc´´ = l
+                if isa(changes, StateUpdate)
+                    let cur_hand = frame.handler_at[pc], l, enter
+                        while cur_hand != 0
+                            enter = frame.src.code[cur_hand]
+                            l = (enter::Expr).args[1]::Int
+                            # propagate new type info to exception handler
+                            # the handling for Expr(:enter) propagates all changes from before the try/catch
+                            # so this only needs to propagate any changes
+                            if stupdate1!(s[l]::VarTable, changes::StateUpdate) !== false
+                                if l < frame.pc´´
+                                    frame.pc´´ = l
+                                end
+                                push!(W, l)
+                            end
+                            cur_hand = frame.handler_at[cur_hand]
                         end
-                        push!(W, l)
                     end
                 end
             end
@@ -1489,7 +1488,6 @@ function typeinf_local(interp::AbstractInterpreter, frame::InferenceState)
             end
 
             pc´ > n && break # can't proceed with the fast-path fall-through
-            frame.handler_at[pc´] = frame.cur_hand
             newstate = stupdate!(s[pc´], changes)
             if isa(stmt, GotoNode) && frame.pc´´ < pc´
                 # if we are processing a goto node anyways,
@@ -1500,7 +1498,7 @@ function typeinf_local(interp::AbstractInterpreter, frame::InferenceState)
                     s[pc´] = newstate
                 end
                 push!(W, pc´)
-                pc = frame.pc´´
+                break
             elseif newstate !== nothing
                 s[pc´] = newstate
                 pc = pc´
@@ -1510,6 +1508,7 @@ function typeinf_local(interp::AbstractInterpreter, frame::InferenceState)
                 break
             end
         end
+        frame.pc´´ = _bits_findnext(W.bits, frame.pc´´)::Int # next program-counter
     end
     frame.dont_work_on_me = false
     nothing
diff --git a/base/compiler/inferencestate.jl b/base/compiler/inferencestate.jl
@@ -28,9 +28,7 @@ mutable struct InferenceState
     pc´´::LineNum
     nstmts::Int
     # current exception handler info
-    cur_hand #::Union{Nothing, Pair{LineNum, prev_handler}}
-    handler_at::Vector{Any}
-    n_handlers::Int
+    handler_at::Vector{LineNum}
     # ssavalue sparsity and restart info
     ssavalue_uses::Vector{BitSet}
     throw_blocks::BitSet
@@ -57,8 +55,9 @@ mutable struct InferenceState
     function InferenceState(result::InferenceResult, src::CodeInfo,
                             cached::Bool, interp::AbstractInterpreter)
         linfo = result.linfo
+        def = linfo.def
         code = src.code::Array{Any,1}
-        toplevel = !isa(linfo.def, Method)
+        toplevel = !isa(def, Method)
 
         sp = sptypes_from_meth_instance(linfo::MethodInstance)
 
@@ -87,30 +86,21 @@ mutable struct InferenceState
         throw_blocks = find_throw_blocks(code)
 
         # exception handlers
-        cur_hand = nothing
-        handler_at = Any[ nothing for i=1:n ]
-        n_handlers = 0
-
-        W = BitSet()
-        push!(W, 1) #initial pc to visit
-
-        if !toplevel
-            meth = linfo.def
-            inmodule = meth.module
-        else
-            inmodule = linfo.def::Module
-        end
+        ip = BitSet()
+        handler_at = compute_trycatch(src.code, ip)
+        push!(ip, 1)
 
+        mod = isa(def, Method) ? def.module : def
         valid_worlds = WorldRange(src.min_world,
             src.max_world == typemax(UInt) ? get_world_counter() : src.max_world)
+
         frame = new(
             InferenceParams(interp), result, linfo,
-            sp, slottypes, inmodule, 0,
+            sp, slottypes, mod, 0,
             IdSet{InferenceState}(), IdSet{InferenceState}(),
             src, get_world_counter(interp), valid_worlds,
             nargs, s_types, s_edges, stmt_info,
-            Union{}, W, 1, n,
-            cur_hand, handler_at, n_handlers,
+            Union{}, ip, 1, n, handler_at,
             ssavalue_uses, throw_blocks,
             Vector{Tuple{InferenceState,LineNum}}(), # cycle_backedges
             Vector{InferenceState}(), # callers_in_cycle
@@ -124,6 +114,90 @@ mutable struct InferenceState
     end
 end
 
+function compute_trycatch(code::Vector{Any}, ip::BitSet)
+    # The goal initially is to record the frame like this for the state at exit:
+    # 1: (enter 3) # == 0
+    # 3: (expr)    # == 1
+    # 3: (leave 1) # == 1
+    # 4: (expr)    # == 0
+    # then we can find all trys by walking backwards from :enter statements,
+    # and all catches by looking at the statement after the :enter
+    n = length(code)
+    empty!(ip)
+    ip.offset = 0 # for _bits_findnext
+    push!(ip, n + 1)
+    handler_at = fill(0, n)
+
+    # start from all :enter statements and record the location of the try
+    for pc = 1:n
+        stmt = code[pc]
+        if isexpr(stmt, :enter)
+            l = stmt.args[1]::Int
+            handler_at[pc + 1] = pc
+            push!(ip, pc + 1)
+            handler_at[l] = pc
+            push!(ip, l)
+        end
+    end
+
+    # now forward those marks to all :leave statements
+    pc´´ = 0
+    while true
+        # make progress on the active ip set
+        pc = _bits_findnext(ip.bits, pc´´)::Int
+        pc > n && break
+        while true # inner loop optimizes the common case where it can run straight from pc to pc + 1
+            pc´ = pc + 1 # next program-counter (after executing instruction)
+            if pc == pc´´
+                pc´´ = pc´
+            end
+            delete!(ip, pc)
+            cur_hand = handler_at[pc]
+            @assert cur_hand != 0 "unbalanced try/catch"
+            stmt = code[pc]
+            if isa(stmt, GotoNode)
+                pc´ = stmt.label
+            elseif isa(stmt, GotoIfNot)
+                l = stmt.dest::Int
+                if handler_at[l] != cur_hand
+                    @assert handler_at[l] == 0 "unbalanced try/catch"
+                    handler_at[l] = cur_hand
+                    if l < pc´´
+                        pc´´ = l
+                    end
+                    push!(ip, l)
+                end
+            elseif isa(stmt, ReturnNode)
+                @assert !isdefined(stmt, :val) "unbalanced try/catch"
+                break
+            elseif isa(stmt, Expr)
+                head = stmt.head
+                if head === :enter
+                    cur_hand = pc
+                elseif head === :leave
+                    l = stmt.args[1]::Int
+                    for i = 1:l
+                        cur_hand = handler_at[cur_hand]
+                    end
+                    cur_hand == 0 && break
+                end
+            end
+
+            pc´ > n && break # can't proceed with the fast-path fall-through
+            if handler_at[pc´] != cur_hand
+                @assert handler_at[pc´] == 0 "unbalanced try/catch"
+                handler_at[pc´] = cur_hand
+            elseif !in(pc´, ip)
+                break  # already visited
+            end
+            pc = pc´
+        end
+    end
+
+    @assert first(ip) == n + 1
+    return handler_at
+end
+
 method_table(interp::AbstractInterpreter, sv::InferenceState) = sv.method_table
 
 function InferenceState(result::InferenceResult, cached::Bool, interp::AbstractInterpreter)
diff --git a/test/compiler/inference.jl b/test/compiler/inference.jl
@@ -3002,3 +3002,48 @@ Base.return_types((Union{Int,Nothing},)) do x
     end
     x
 end == [Int]
+
+# issue #42022
+let x = Tuple{Int,Any}[
+        #= 1=# (0, Expr(:(=), Core.SlotNumber(3), 1))
+        #= 2=# (0, Expr(:enter, 18))
+        #= 3=# (2, Expr(:(=), Core.SlotNumber(3), 2.0))
+        #= 4=# (2, Expr(:enter, 12))
+        #= 5=# (4, Expr(:(=), Core.SlotNumber(3), '3'))
+        #= 6=# (4, Core.GotoIfNot(Core.SlotNumber(2), 9))
+        #= 7=# (4, Expr(:leave, 2))
+        #= 8=# (0, Core.ReturnNode(1))
+        #= 9=# (4, Expr(:call, GlobalRef(Main, :throw)))
+        #=10=# (4, Expr(:leave, 1))
+        #=11=# (2, Core.GotoNode(16))
+        #=12=# (4, Expr(:leave, 1))
+        #=13=# (2, Expr(:(=), Core.SlotNumber(4), Expr(:the_exception)))
+        #=14=# (2, Expr(:call, GlobalRef(Main, :rethrow)))
+        #=15=# (2, Expr(:pop_exception, Core.SSAValue(4)))
+        #=16=# (2, Expr(:leave, 1))
+        #=17=# (0, Core.GotoNode(22))
+        #=18=# (2, Expr(:leave, 1))
+        #=19=# (0, Expr(:(=), Core.SlotNumber(5), Expr(:the_exception)))
+        #=20=# (0, nothing)
+        #=21=# (0, Expr(:pop_exception, Core.SSAValue(2)))
+        #=22=# (0, Core.ReturnNode(Core.SlotNumber(3)))
+    ]
+    handler_at = Core.Compiler.compute_trycatch(last.(x), Core.Compiler.BitSet())
+    @test handler_at == first.(x)
+end
+
+@test only(Base.return_types((Bool,)) do y
+        x = 1
+        try
+            x = 2.0
+            try
+                x = '3'
+                y ? (return 1) : throw()
+            catch ex1
+                rethrow()
+            end
+        catch ex2
+            nothing
+        end
+        return x
+    end) === Union{Int, Float64, Char}
