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inferencestate.jl
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inferencestate.jl
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# This file is a part of Julia. License is MIT: https://julialang.org/license
const LineNum = Int
mutable struct InferenceState
params::InferenceParams
result::InferenceResult # remember where to put the result
linfo::MethodInstance
sptypes::Vector{Any} # types of static parameter
slottypes::Vector{Any}
mod::Module
currpc::LineNum
# info on the state of inference and the linfo
src::CodeInfo
world::UInt
valid_worlds::WorldRange
nargs::Int
stmt_types::Vector{Any}
stmt_edges::Vector{Any}
stmt_info::Vector{Any}
# return type
bestguess #::Type
# current active instruction pointers
ip::BitSet
pc´´::LineNum
nstmts::Int
# current exception handler info
cur_hand #::Union{Nothing, Pair{LineNum, prev_handler}}
handler_at::Vector{Any}
n_handlers::Int
# ssavalue sparsity and restart info
ssavalue_uses::Vector{BitSet}
throw_blocks::BitSet
cycle_backedges::Vector{Tuple{InferenceState, LineNum}} # call-graph backedges connecting from callee to caller
callers_in_cycle::Vector{InferenceState}
parent::Union{Nothing, InferenceState}
# TODO: move these to InferenceResult / Params?
cached::Bool
limited::Bool
inferred::Bool
dont_work_on_me::Bool
# The place to look up methods while working on this function.
# In particular, we cache method lookup results for the same function to
# fast path repeated queries.
method_table::CachedMethodTable{InternalMethodTable}
# The interpreter that created this inference state. Not looked at by
# NativeInterpreter. But other interpreters may use this to detect cycles
interp::AbstractInterpreter
# src is assumed to be a newly-allocated CodeInfo, that can be modified in-place to contain intermediate results
function InferenceState(result::InferenceResult, src::CodeInfo,
cached::Bool, interp::AbstractInterpreter)
linfo = result.linfo
code = src.code::Array{Any,1}
toplevel = !isa(linfo.def, Method)
sp = sptypes_from_meth_instance(linfo::MethodInstance)
nssavalues = src.ssavaluetypes::Int
src.ssavaluetypes = Any[ NOT_FOUND for i = 1:nssavalues ]
stmt_info = Any[ nothing for i = 1:length(code) ]
n = length(code)
s_edges = Any[ nothing for i = 1:n ]
s_types = Any[ nothing for i = 1:n ]
# initial types
nslots = length(src.slotflags)
argtypes = result.argtypes
nargs = length(argtypes)
s_argtypes = VarTable(undef, nslots)
slottypes = Vector{Any}(undef, nslots)
for i in 1:nslots
at = (i > nargs) ? Bottom : argtypes[i]
s_argtypes[i] = VarState(at, i > nargs)
slottypes[i] = at
end
s_types[1] = s_argtypes
ssavalue_uses = find_ssavalue_uses(code, nssavalues)
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
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,
src, get_world_counter(interp), valid_worlds,
nargs, s_types, s_edges, stmt_info,
Union{}, W, 1, n,
cur_hand, handler_at, n_handlers,
ssavalue_uses, throw_blocks,
Vector{Tuple{InferenceState,LineNum}}(), # cycle_backedges
Vector{InferenceState}(), # callers_in_cycle
#=parent=#nothing,
cached, false, false, false,
CachedMethodTable(method_table(interp)),
interp)
result.result = frame
cached && push!(get_inference_cache(interp), result)
return frame
end
end
method_table(interp::AbstractInterpreter, sv::InferenceState) = sv.method_table
function InferenceState(result::InferenceResult, cached::Bool, interp::AbstractInterpreter)
# prepare an InferenceState object for inferring lambda
src = retrieve_code_info(result.linfo)
src === nothing && return nothing
validate_code_in_debug_mode(result.linfo, src, "lowered")
return InferenceState(result, src, cached, interp)
end
function sptypes_from_meth_instance(linfo::MethodInstance)
toplevel = !isa(linfo.def, Method)
if !toplevel && isempty(linfo.sparam_vals) && isa(linfo.def.sig, UnionAll)
# linfo is unspecialized
sp = Any[]
sig = linfo.def.sig
while isa(sig, UnionAll)
push!(sp, sig.var)
sig = sig.body
end
else
sp = collect(Any, linfo.sparam_vals)
end
for i = 1:length(sp)
v = sp[i]
if v isa TypeVar
fromArg = 0
# if this parameter came from arg::Type{T}, then `arg` is more precise than
# Type{T} where lb<:T<:ub
sig = linfo.def.sig
temp = sig
for j = 1:i-1
temp = temp.body
end
Pi = temp.var
while temp isa UnionAll
temp = temp.body
end
sigtypes = temp.parameters
for j = 1:length(sigtypes)
tj = sigtypes[j]
if isType(tj) && tj.parameters[1] === Pi
fromArg = j
break
end
end
if fromArg > 0
ty = fieldtype(linfo.specTypes, fromArg)
else
ub = v.ub
while ub isa TypeVar
ub = ub.ub
end
if has_free_typevars(ub)
ub = Any
end
lb = v.lb
while lb isa TypeVar
lb = lb.lb
end
if has_free_typevars(lb)
lb = Bottom
end
if Any <: ub && lb <: Bottom
ty = Any
else
tv = TypeVar(v.name, lb, ub)
ty = UnionAll(tv, Type{tv})
end
end
else
ty = Const(v)
end
sp[i] = ty
end
return sp
end
_topmod(sv::InferenceState) = _topmod(sv.mod)
# work towards converging the valid age range for sv
function update_valid_age!(sv::InferenceState, worlds::WorldRange)
sv.valid_worlds = intersect(worlds, sv.valid_worlds)
@assert(sv.world in sv.valid_worlds, "invalid age range update")
nothing
end
update_valid_age!(edge::InferenceState, sv::InferenceState) = update_valid_age!(sv, edge.valid_worlds)
function record_ssa_assign(ssa_id::Int, @nospecialize(new), frame::InferenceState)
old = frame.src.ssavaluetypes[ssa_id]
if old === NOT_FOUND || !(new ⊑ old)
# typically, we expect that old ⊑ new (that output information only
# gets less precise with worse input information), but to actually
# guarantee convergence we need to use tmerge here to ensure that is true
frame.src.ssavaluetypes[ssa_id] = old === NOT_FOUND ? new : tmerge(old, new)
W = frame.ip
s = frame.stmt_types
for r in frame.ssavalue_uses[ssa_id]
if s[r] !== nothing # s[r] === nothing => unreached statement
if r < frame.pc´´
frame.pc´´ = r
end
push!(W, r)
end
end
end
nothing
end
function add_cycle_backedge!(frame::InferenceState, caller::InferenceState, currpc::Int)
update_valid_age!(frame, caller)
backedge = (caller, currpc)
contains_is(frame.cycle_backedges, backedge) || push!(frame.cycle_backedges, backedge)
add_backedge!(frame.linfo, caller)
return frame
end
# temporarily accumulate our edges to later add as backedges in the callee
function add_backedge!(li::MethodInstance, caller::InferenceState)
isa(caller.linfo.def, Method) || return # don't add backedges to toplevel exprs
if caller.stmt_edges[caller.currpc] === nothing
caller.stmt_edges[caller.currpc] = []
end
push!(caller.stmt_edges[caller.currpc], li)
nothing
end
# used to temporarily accumulate our no method errors to later add as backedges in the callee method table
function add_mt_backedge!(mt::Core.MethodTable, @nospecialize(typ), caller::InferenceState)
isa(caller.linfo.def, Method) || return # don't add backedges to toplevel exprs
if caller.stmt_edges[caller.currpc] === nothing
caller.stmt_edges[caller.currpc] = []
end
push!(caller.stmt_edges[caller.currpc], mt)
push!(caller.stmt_edges[caller.currpc], typ)
nothing
end
function poison_callstack(infstate::InferenceState, topmost::InferenceState, poison_topmost::Bool)
poison_topmost && (topmost = topmost.parent)
while !(infstate === topmost)
if call_result_unused(infstate)
# If we won't propagate the result any further (since it's typically unused),
# it's OK that we keep and cache the "limited" result in the parents
# (non-typically, this means that we lose the ability to detect a guaranteed StackOverflow in some cases)
# TODO: we might be able to halt progress much more strongly here,
# since now we know we won't be able to keep anything much that we learned.
# We were mainly only here to compute the calling convention return type,
# but in most situations now, we are unlikely to be able to use that information.
break
end
infstate.limited = true
for infstate_cycle in infstate.callers_in_cycle
infstate_cycle.limited = true
end
infstate = infstate.parent
infstate === nothing && return
end
end
function is_specializable_vararg_slot(@nospecialize(arg), nargs::Int, vargs::Vector{Any})
return (isa(arg, Slot) && slot_id(arg) == nargs && !isempty(vargs))
end
function print_callstack(sv::InferenceState)
while sv !== nothing
print(sv.linfo)
sv.limited && print(" [limited]")
!sv.cached && print(" [uncached]")
println()
for cycle in sv.callers_in_cycle
print(' ', cycle.linfo)
cycle.limited && print(" [limited]")
println()
end
sv = sv.parent
end
end