enable/improve constant propagation through varargs methods

- Store varargs type information in the InferenceResult object, such that the info can be used during inference/optimization

- Hack in a more precise return type for getfield of a vararg tuple. Ideally, we would handle this by teaching inference to track the types of the individual fields of a Tuple, which would make this unnecessary, but until then, this hack is helpful.

- Spoof parents as well as children during recursion limiting, so that higher degree cycles are appropriately spoofed

- A broadcast test marked as broken is now no longer broken, presumably due to the optimizations in this commit

- Fix relationship between depth/mindepth in limit_type_size/is_derived_type. The relationship should have been inverse over the domain in which they overlap, but was not maintained consistently. An example of problematic case was:

t = Tuple{X,X} where X<:Tuple{Tuple{Int64,Vararg{Int64,N} where N},Tuple{Int64,Vararg{Int64,N} where N}}
c = Tuple{X,X} where X<:Tuple{Int64,Vararg{Int64,N} where N}

because is_derived_type was computing the depth of usage rather than the depth of definition. This change thus makes the depth/mindepth calculations more consistent, and causes the limiting heuristic to return strictly wider types than it did before.

- Move the optimizer's "varargs types to tuple type" rewrite to after cache lookup.Inference is populating the InferenceResult cache using the varargs form, so the optimizer needs to do the lookup before writing the atypes in order to avoid cache misses.

Co-authored-by: Jameson Nash <vtjnash@users.noreply.github.com>
Co-authored-by: Keno Fischer <keno@alumni.harvard.edu>

base/compiler/abstractinterpretation.jl

@@ -116,8 +116,7 @@ function abstract_call_method_with_const_args(@nospecialize(f), argtypes::Vector
     method.isva && (nargs -= 1)
     length(argtypes) >= nargs || return Any # probably limit_tuple_type made this non-matching method apparently match
     haveconst = false
-    for i in 1:nargs
-        a = argtypes[i]
+    for a in argtypes
         if isa(a, Const) && !isdefined(typeof(a.val), :instance) && !(isa(a.val, Type) && issingletontype(a.val))
             # have new information from argtypes that wasn't available from the signature
             haveconst = true
@@ -144,8 +143,7 @@ function abstract_call_method_with_const_args(@nospecialize(f), argtypes::Vector
         tm = _topmod(sv)
         if !istopfunction(tm, f, :getproperty) && !istopfunction(tm, f, :setproperty!)
             # in this case, see if all of the arguments are constants
-            for i in 1:nargs
-                a = argtypes[i]
+            for a in argtypes
                 if !isa(a, Const) && !isconstType(a)
                     return Any
                 end
@@ -156,6 +154,17 @@ function abstract_call_method_with_const_args(@nospecialize(f), argtypes::Vector
     if inf_result === nothing
         inf_result = InferenceResult(code)
         atypes = get_argtypes(inf_result)
+        if method.isva
+            vargs = argtypes[(nargs + 1):end]
+            for i in 1:length(vargs)
+                a = vargs[i]
+                if i > length(inf_result.vargs)
+                    push!(inf_result.vargs, a)
+                elseif a isa Const
+                    inf_result.vargs[i] = a
+                end
+            end
+        end
         for i in 1:nargs
             a = argtypes[i]
             if a isa Const
@@ -187,7 +196,13 @@ function abstract_call_method(method::Method, @nospecialize(sig), sparams::Simpl
     cyclei = 0
     infstate = sv
     edgecycle = false
+    # The `method_for_inference_heuristics` will expand the given method's generator if
+    # necessary in order to retrieve this field from the generated `CodeInfo`, if it exists.
+    # The other `CodeInfo`s we inspect will already have this field inflated, so we just
+    # access it directly instead (to avoid regeneration).
     method2 = method_for_inference_heuristics(method, sig, sparams, sv.params.world) # Union{Method, Nothing}
+    sv_method2 = sv.src.method_for_inference_limit_heuristics # limit only if user token match
+    sv_method2 isa Method || (sv_method2 = nothing) # Union{Method, Nothing}
     while !(infstate === nothing)
         infstate = infstate::InferenceState
         if method === infstate.linfo.def
@@ -208,7 +223,9 @@ function abstract_call_method(method::Method, @nospecialize(sig), sparams::Simpl
                 for parent in infstate.callers_in_cycle
                     # check in the cycle list first
                     # all items in here are mutual parents of all others
-                    if parent.linfo.def === sv.linfo.def
+                    parent_method2 = parent.src.method_for_inference_limit_heuristics # limit only if user token match
+                    parent_method2 isa Method || (parent_method2 = nothing) # Union{Method, Nothing}
+                    if parent.linfo.def === sv.linfo.def && sv_method2 === parent_method2
                         topmost = infstate
                         edgecycle = true
                         break
@@ -218,7 +235,9 @@ function abstract_call_method(method::Method, @nospecialize(sig), sparams::Simpl
                     # then check the parent link
                     if topmost === nothing && parent !== nothing
                         parent = parent::InferenceState
-                        if parent.cached && parent.linfo.def === sv.linfo.def
+                        parent_method2 = parent.src.method_for_inference_limit_heuristics # limit only if user token match
+                        parent_method2 isa Method || (parent_method2 = nothing) # Union{Method, Nothing}
+                        if parent.cached && parent.linfo.def === sv.linfo.def && sv_method2 === parent_method2
                             topmost = infstate
                             edgecycle = true
                         end
@@ -315,8 +334,8 @@ function precise_container_type(@nospecialize(arg), @nospecialize(typ), vtypes::
     end
 
     arg = ssa_def_expr(arg, sv)
-    if is_specializable_vararg_slot(arg, sv)
-        return Any[rewrap_unionall(p, sv.linfo.specTypes) for p in sv.vararg_type_container.parameters]
+    if is_specializable_vararg_slot(arg, sv.nargs, sv.result.vargs)
+        return sv.result.vargs
     end
 
     tti0 = widenconst(typ)
@@ -482,7 +501,13 @@ function abstract_call(@nospecialize(f), fargs::Union{Tuple{},Vector{Any}}, argt
     tm = _topmod(sv)
     if isa(f, Builtin) || isa(f, IntrinsicFunction)
         rt = builtin_tfunction(f, argtypes[2:end], sv)
-        if (rt === Bool || (isa(rt, Const) && isa(rt.val, Bool))) && isa(fargs, Vector{Any})
+        if f === getfield && isa(fargs, Vector{Any}) && length(argtypes) == 3 && isa(argtypes[3], Const) && isa(argtypes[3].val, Int) && argtypes[2] ⊑ Tuple
+            cti = precise_container_type(fargs[2], argtypes[2], vtypes, sv)
+            idx = argtypes[3].val
+            if 1 <= idx <= length(cti)
+                rt = unwrapva(cti[idx])
+            end
+        elseif (rt === Bool || (isa(rt, Const) && isa(rt.val, Bool))) && isa(fargs, Vector{Any})
             # perform very limited back-propagation of type information for `is` and `isa`
             if f === isa
                 a = ssa_def_expr(fargs[2], sv)

base/compiler/inferenceresult.jl

@@ -5,6 +5,7 @@ const EMPTY_VECTOR = Vector{Any}()
 mutable struct InferenceResult
     linfo::MethodInstance
     args::Vector{Any}
+    vargs::Vector{Any}
     result # ::Type, or InferenceState if WIP
     src::Union{CodeInfo, Nothing} # if inferred copy is available
     function InferenceResult(linfo::MethodInstance)
@@ -13,7 +14,7 @@ mutable struct InferenceResult
         else
             result = linfo.rettype
         end
-        return new(linfo, EMPTY_VECTOR, result, nothing)
+        return new(linfo, EMPTY_VECTOR, Any[], result, nothing)
     end
 end
 
@@ -31,7 +32,35 @@ function get_argtypes(result::InferenceResult)
             end
             vararg_type = Tuple
         else
-            vararg_type = rewrap(tupleparam_tail(atypes, nargs), linfo.specTypes)
+            laty = length(atypes)
+            if nargs > laty
+                va = atypes[laty]
+                if isvarargtype(va)
+                    new_va = rewrap_unionall(unconstrain_vararg_length(va), linfo.specTypes)
+                    vararg_type_vec = Any[new_va]
+                    vararg_type = Tuple{new_va}
+                else
+                    vararg_type_vec = Any[]
+                    vararg_type = Tuple{}
+                end
+            else
+                vararg_type_vec = Any[]
+                for p in atypes[nargs:laty]
+                    p = isvarargtype(p) ? unconstrain_vararg_length(p) : p
+                    push!(vararg_type_vec, rewrap_unionall(p, linfo.specTypes))
+                end
+                vararg_type = tuple_tfunc(Tuple{vararg_type_vec...})
+                for i in 1:length(vararg_type_vec)
+                    atyp = vararg_type_vec[i]
+                    if isa(atyp, DataType) && isdefined(atyp, :instance)
+                        # replace singleton types with their equivalent Const object
+                        vararg_type_vec[i] = Const(atyp.instance)
+                    elseif isconstType(atyp)
+                        vararg_type_vec[i] = Const(atyp.parameters[1])
+                    end
+                end
+            end
+            result.vargs = vararg_type_vec
         end
         args[nargs] = vararg_type
         nargs -= 1
@@ -80,19 +109,12 @@ function cache_lookup(code::MethodInstance, argtypes::Vector{Any}, cache::Vector
     for cache_code in cache
         # try to search cache first
         cache_args = cache_code.args
-        if cache_code.linfo === code && length(cache_args) >= nargs
+        cache_vargs = cache_code.vargs
+        if cache_code.linfo === code && length(argtypes) === (length(cache_vargs) + nargs)
             cache_match = true
-            # verify that the trailing args (va) aren't Const
-            for i in (nargs + 1):length(cache_args)
-                if isa(cache_args[i], Const)
-                    cache_match = false
-                    break
-                end
-            end
-            cache_match || continue
-            for i in 1:nargs
+            for i in 1:length(argtypes)
                 a = argtypes[i]
-                ca = cache_args[i]
+                ca = i <= nargs ? cache_args[i] : cache_vargs[i - nargs]
                 # verify that all Const argument types match between the call and cache
                 if (isa(a, Const) || isa(ca, Const)) && !(a === ca)
                     cache_match = false

base/compiler/inferencestate.jl

@@ -30,7 +30,6 @@ mutable struct InferenceState
     # ssavalue sparsity and restart info
     ssavalue_uses::Vector{BitSet}
     ssavalue_defs::Vector{LineNum}
-    vararg_type_container #::Type
 
     backedges::Vector{Tuple{InferenceState, LineNum}} # call-graph backedges connecting from callee to caller
     callers_in_cycle::Vector{InferenceState}
@@ -102,19 +101,11 @@ mutable struct InferenceState
         # initial types
         nslots = length(src.slotnames)
         argtypes = get_argtypes(result)
-        vararg_type_container = nothing
         nargs = length(argtypes)
         s_argtypes = VarTable(undef, nslots)
         src.slottypes = Vector{Any}(undef, nslots)
         for i in 1:nslots
             at = (i > nargs) ? Bottom : argtypes[i]
-            if !toplevel && linfo.def.isva && i == nargs
-                if !(at == Tuple) # would just be a no-op
-                    vararg_type_container = unwrap_unionall(at)
-                    vararg_type = tuple_tfunc(vararg_type_container) # returns a Const object, if applicable
-                    at = rewrap(vararg_type, linfo.specTypes)
-                end
-            end
             s_argtypes[i] = VarState(at, i > nargs)
             src.slottypes[i] = at
         end
@@ -152,7 +143,7 @@ mutable struct InferenceState
             nargs, s_types, s_edges,
             Union{}, W, 1, n,
             cur_hand, handler_at, n_handlers,
-            ssavalue_uses, ssavalue_defs, vararg_type_container,
+            ssavalue_uses, ssavalue_defs,
             Vector{Tuple{InferenceState,LineNum}}(), # backedges
             Vector{InferenceState}(), # callers_in_cycle
             #=parent=#nothing,
@@ -238,9 +229,8 @@ function add_mt_backedge!(mt::Core.MethodTable, @nospecialize(typ), caller::Infe
     nothing
 end
 
-function is_specializable_vararg_slot(@nospecialize(arg), sv::InferenceState)
-    return (isa(arg, Slot) && slot_id(arg) == sv.nargs &&
-            isa(sv.vararg_type_container, DataType))
+function is_specializable_vararg_slot(@nospecialize(arg), nargs, vargs)
+    return (isa(arg, Slot) && slot_id(arg) == nargs && !isempty(vargs))
 end
 
 function print_callstack(sv::InferenceState)

base/compiler/optimize.jl

@@ -6,7 +6,7 @@
 
 mutable struct OptimizationState
     linfo::MethodInstance
-    vararg_type_container #::Type
+    result_vargs::Vector{Any}
     backedges::Vector{Any}
     src::CodeInfo
     mod::Module
@@ -23,7 +23,7 @@ mutable struct OptimizationState
         end
         src = frame.src
         next_label = max(label_counter(src.code), length(src.code)) + 10
-        return new(frame.linfo, frame.vararg_type_container,
+        return new(frame.linfo, frame.result.vargs,
                    s_edges::Vector{Any},
                    src, frame.mod, frame.nargs,
                    next_label, frame.min_valid, frame.max_valid,
@@ -53,8 +53,8 @@ mutable struct OptimizationState
             nargs = 0
         end
         next_label = max(label_counter(src.code), length(src.code)) + 10
-        vararg_type_container = nothing # if you want something more accurate, set it yourself :P
-        return new(linfo, vararg_type_container,
+        result_vargs = Any[] # if you want something more accurate, set it yourself :P
+        return new(linfo, result_vargs,
                    s_edges::Vector{Any},
                    src, inmodule, nargs,
                    next_label,
@@ -100,11 +100,6 @@ function add_backedge!(li::MethodInstance, caller::OptimizationState)
     nothing
 end
 
-function is_specializable_vararg_slot(@nospecialize(arg), sv::OptimizationState)
-    return (isa(arg, Slot) && slot_id(arg) == sv.nargs &&
-            isa(sv.vararg_type_container, DataType))
-end
-
 ###########
 # structs #
 ###########
@@ -1333,22 +1328,30 @@ function inlineable(@nospecialize(f), @nospecialize(ft), e::Expr, atypes::Vector
     if invoke_api(linfo) == 2
         # in this case function can be inlined to a constant
         add_backedge!(linfo, sv)
+        # XXX: @vtjnash thinks this should be `argexprs0`, but doing so exposes a
+        # downstream optimizer problem that breaks tests, so we're going to avoid
+        # changing it for now. ref
+        # https://github.com/JuliaLang/julia/pull/26826#issuecomment-386381103
         return inline_as_constant(linfo.inferred_const, argexprs, sv, invoke_data)
     end
 
-    # see if the method has a InferenceResult in the current cache
+    # See if the method has a InferenceResult in the current cache
     # or an existing inferred code info store in `.inferred`
+    #
+    # Above, we may have rewritten trailing varargs in `atypes` to a tuple type. However,
+    # inference populates the cache with the pre-rewrite version (`atypes0`), so here, we
+    # check against that instead.
     haveconst = false
-    for i in 1:length(atypes)
-        a = atypes[i]
+    for i in 1:length(atypes0)
+        a = atypes0[i]
         if isa(a, Const) && !isdefined(typeof(a.val), :instance) && !(isa(a.val, Type) && issingletontype(a.val))
             # have new information from argtypes that wasn't available from the signature
             haveconst = true
             break
         end
     end
     if haveconst
-        inf_result = cache_lookup(linfo, atypes, sv.params.cache) # Union{Nothing, InferenceResult}
+        inf_result = cache_lookup(linfo, atypes0, sv.params.cache) # Union{Nothing, InferenceResult}
     else
         inf_result = nothing
     end
@@ -2003,8 +2006,8 @@ function inline_call(e::Expr, sv::OptimizationState, stmts::Vector{Any}, boundsc
                         tmpv = newvar!(sv, t)
                         push!(newstmts, Expr(:(=), tmpv, aarg))
                     end
-                    if is_specializable_vararg_slot(aarg, sv)
-                        tp = sv.vararg_type_container.parameters
+                    if is_specializable_vararg_slot(aarg, sv.nargs, sv.result_vargs)
+                        tp = sv.result_vargs
                     else
                         tp = t.parameters
                     end

base/compiler/tfuncs.jl

@@ -223,7 +223,7 @@ add_tfunc(===, 2, 2,
         end
         return Bool
     end, 1)
-function isdefined_tfunc(args...)
+function isdefined_tfunc(@nospecialize(args...))
     arg1 = args[1]
     if isa(arg1, Const)
         a1 = typeof(arg1.val)

base/compiler/typelimits.jl

@@ -50,15 +50,12 @@ function is_derived_type(@nospecialize(t), @nospecialize(c), mindepth::Int)
     if t === c
         return mindepth == 0
     end
-    if isa(c, TypeVar)
-        # see if it is replacing a TypeVar upper bound with something simpler
-        return is_derived_type(t, c.ub, mindepth)
-    elseif isa(c, Union)
+    if isa(c, Union)
         # see if it is one of the elements of the union
         return is_derived_type(t, c.a, mindepth + 1) || is_derived_type(t, c.b, mindepth + 1)
     elseif isa(c, UnionAll)
         # see if it is derived from the body
-        return is_derived_type(t, c.body, mindepth)
+        return is_derived_type(t, c.var.ub, mindepth) || is_derived_type(t, c.body, mindepth + 1)
     elseif isa(c, DataType)
         if isa(t, DataType)
             # see if it is one of the supertypes of a parameter
@@ -96,7 +93,8 @@ function is_derived_type_from_any(@nospecialize(t), sources::SimpleVector, minde
     return false
 end
 
-# type vs. comparison or which was derived from source
+# The goal of this function is to return a type of greater "size" and less "complexity" than
+# both `t` or `c` over the lattice defined by `sources`, `depth`, and `allowed_tuplelen`.
 function _limit_type_size(@nospecialize(t), @nospecialize(c), sources::SimpleVector, depth::Int, allowed_tuplelen::Int)
     if t === c
         return t # quick egal test
@@ -140,9 +138,9 @@ function _limit_type_size(@nospecialize(t), @nospecialize(c), sources::SimpleVec
                 lb = Bottom
             end
             v2 = TypeVar(tv.name, lb, ub)
-            return UnionAll(v2, _limit_type_size(t{v2}, c{v2}, sources, depth + 1, allowed_tuplelen))
+            return UnionAll(v2, _limit_type_size(t{v2}, c{v2}, sources, depth, allowed_tuplelen))
         end
-        tbody = _limit_type_size(t.body, c, sources, depth + 1, allowed_tuplelen)
+        tbody = _limit_type_size(t.body, c, sources, depth, allowed_tuplelen)
         tbody === t.body && return t
         return UnionAll(t.var, tbody)
     elseif isa(c, UnionAll)

base/compiler/typeutils.jl

@@ -99,20 +99,6 @@ function tuple_tail_elem(@nospecialize(init), ct)
     return Vararg{widenconst(foldl((a, b) -> tmerge(a, tvar_extent(unwrapva(b))), init, ct))}
 end
 
-# t[n:end]
-function tupleparam_tail(t::SimpleVector, n)
-    lt = length(t)
-    if n > lt
-        va = t[lt]
-        if isvarargtype(va)
-            # assumes that we should never see Vararg{T, x}, where x is a constant (should be guaranteed by construction)
-            return Tuple{va}
-        end
-        return Tuple{}
-    end
-    return Tuple{t[n:lt]...}
-end
-
 # take a Tuple where one or more parameters are Unions
 # and return an array such that those Unions are removed
 # and `Union{return...} == ty`

base/essentials.jl

@@ -214,6 +214,14 @@ function unwrapva(@nospecialize(t))
     return isvarargtype(t2) ? rewrap_unionall(t2.parameters[1], t) : t
 end
 
+function unconstrain_vararg_length(@nospecialize(va))
+    # construct a new Vararg type where its length is unconstrained,
+    # but its element type still captures any dependencies the input
+    # element type may have had on the input length
+    T = unwrap_unionall(va).parameters[1]
+    return rewrap_unionall(Vararg{T}, va)
+end
+
 typename(a) = error("typename does not apply to this type")
 typename(a::DataType) = a.name
 function typename(a::Union)