AbstractInterpreter: enable selective pure/concrete eval for extern…

…al `AbstractInterpreter` with overlayed method table

Built on top of #44511 and #44561, and solves <JuliaGPU/GPUCompiler.jl#309>.
This commit allows external `AbstractInterpreter` to selectively use
pure/concrete evals even if it uses an overlayed method table.
More specifically, such `AbstractInterpreter` can use pure/concrete evals
as far as any callees used in a call in question doesn't come from the
overlayed method table:
```julia
@test Base.return_types((), MTOverlayInterp()) do
    isbitstype(Int) ? nothing : missing
end == Any[Nothing]
Base.@assume_effects :terminates_globally function issue41694(x)
    res = 1
    1 < x < 20 || throw("bad")
    while x > 1
        res *= x
        x -= 1
    end
    return res
end
@test Base.return_types((), MTOverlayInterp()) do
    issue41694(3) == 6 ? nothing : missing
end == Any[Nothing]
```

In order to check if a call is tainted by any overlayed call, our effect
system now additionally tracks `overlayed::Bool` property. This effect
property is required to prevents concrete-eval in the following kind of situation:
```julia
strangesin(x) = sin(x)
@overlay OverlayedMT strangesin(x::Float64) = iszero(x) ? nothing : cos(x)
Base.@assume_effects :total totalcall(f, args...) = f(args...)
@test Base.return_types(; interp=MTOverlayInterp()) do
    # we need to disable partial pure/concrete evaluation when tainted by any overlayed call
    if totalcall(strangesin, 1.0) == cos(1.0)
        return nothing
    else
        return missing
    end
end |> only === Nothing
```

base/compiler/inferencestate.jl

@@ -134,7 +134,7 @@ mutable struct InferenceState
             #=parent=#nothing,
             #=cached=#cache === :global,
             #=inferred=#false, #=dont_work_on_me=#false,
-            #=ipo_effects=#Effects(consistent, ALWAYS_TRUE, ALWAYS_TRUE, ALWAYS_TRUE, inbounds_taints_consistency),
+            #=ipo_effects=#Effects(consistent, ALWAYS_TRUE, ALWAYS_TRUE, ALWAYS_TRUE, false, inbounds_taints_consistency),
             interp)
         result.result = frame
         cache !== :no && push!(get_inference_cache(interp), result)

base/compiler/methodtable.jl

@@ -40,15 +40,18 @@ end
 getindex(result::MethodLookupResult, idx::Int) = getindex(result.matches, idx)::MethodMatch
 
 """
-    findall(sig::Type, view::MethodTableView; limit::Int=typemax(Int)) -> MethodLookupResult or missing
+    findall(sig::Type, view::MethodTableView; limit::Int=typemax(Int)) ->
+        (matches::MethodLookupResult, overlayed::Bool) or missing
 
-Find all methods in the given method table `view` that are applicable to the
-given signature `sig`. If no applicable methods are found, an empty result is
-returned. If the number of applicable methods exceeded the specified limit,
-`missing` is returned.
+Find all methods in the given method table `view` that are applicable to the given signature `sig`.
+If no applicable methods are found, an empty result is returned.
+If the number of applicable methods exceeded the specified limit, `missing` is returned.
+`overlayed` indicates if any matching method is defined in an overlayed method table.
 """
 function findall(@nospecialize(sig::Type), table::InternalMethodTable; limit::Int=Int(typemax(Int32)))
-    return _findall(sig, nothing, table.world, limit)
+    result = _findall(sig, nothing, table.world, limit)
+    result === missing && return missing
+    return result, false
 end
 
 function findall(@nospecialize(sig::Type), table::OverlayMethodTable; limit::Int=Int(typemax(Int32)))
@@ -57,7 +60,7 @@ function findall(@nospecialize(sig::Type), table::OverlayMethodTable; limit::Int
     nr = length(result)
     if nr ≥ 1 && result[nr].fully_covers
         # no need to fall back to the internal method table
-        return result
+        return result, true
     end
     # fall back to the internal method table
     fallback_result = _findall(sig, nothing, table.world, limit)
@@ -68,7 +71,7 @@ function findall(@nospecialize(sig::Type), table::OverlayMethodTable; limit::Int
         WorldRange(
             max(result.valid_worlds.min_world, fallback_result.valid_worlds.min_world),
             min(result.valid_worlds.max_world, fallback_result.valid_worlds.max_world)),
-        result.ambig | fallback_result.ambig)
+        result.ambig | fallback_result.ambig), !isempty(result)
 end
 
 function _findall(@nospecialize(sig::Type), mt::Union{Nothing,Core.MethodTable}, world::UInt, limit::Int)
@@ -83,31 +86,38 @@ function _findall(@nospecialize(sig::Type), mt::Union{Nothing,Core.MethodTable},
 end
 
 """
-    findsup(sig::Type, view::MethodTableView) -> Tuple{MethodMatch, WorldRange} or nothing
-
-Find the (unique) method `m` such that `sig <: m.sig`, while being more
-specific than any other method with the same property. In other words, find
-the method which is the least upper bound (supremum) under the specificity/subtype
-relation of the queried `signature`. If `sig` is concrete, this is equivalent to
-asking for the method that will be called given arguments whose types match the
-given signature. This query is also used to implement `invoke`.
-
-Such a method `m` need not exist. It is possible that no method is an
-upper bound of `sig`, or it is possible that among the upper bounds, there
-is no least element. In both cases `nothing` is returned.
+    findsup(sig::Type, view::MethodTableView) ->
+        (match::MethodMatch, valid_worlds::WorldRange, overlayed::Bool) or nothing
+
+Find the (unique) method such that `sig <: match.method.sig`, while being more
+specific than any other method with the same property. In other words, find the method
+which is the least upper bound (supremum) under the specificity/subtype relation of
+the queried `sig`nature. If `sig` is concrete, this is equivalent to asking for the method
+that will be called given arguments whose types match the given signature.
+Note that this query is also used to implement `invoke`.
+
+Such a matching method `match` doesn't necessarily exist.
+It is possible that no method is an upper bound of `sig`, or
+it is possible that among the upper bounds, there is no least element.
+In both cases `nothing` is returned.
+
+`overlayed` indicates if the matching method is defined in an overlayed method table.
 """
 function findsup(@nospecialize(sig::Type), table::InternalMethodTable)
-    return _findsup(sig, nothing, table.world)
+    return (_findsup(sig, nothing, table.world)..., false)
 end
 
 function findsup(@nospecialize(sig::Type), table::OverlayMethodTable)
     match, valid_worlds = _findsup(sig, table.mt, table.world)
-    match !== nothing && return match, valid_worlds
+    match !== nothing && return match, valid_worlds, true
     # fall back to the internal method table
     fallback_match, fallback_valid_worlds = _findsup(sig, nothing, table.world)
-    return fallback_match, WorldRange(
-        max(valid_worlds.min_world, fallback_valid_worlds.min_world),
-        min(valid_worlds.max_world, fallback_valid_worlds.max_world))
+    return (
+        fallback_match,
+        WorldRange(
+            max(valid_worlds.min_world, fallback_valid_worlds.min_world),
+            min(valid_worlds.max_world, fallback_valid_worlds.max_world)),
+        false)
 end
 
 function _findsup(@nospecialize(sig::Type), mt::Union{Nothing,Core.MethodTable}, world::UInt)

base/compiler/ssair/show.jl

@@ -803,6 +803,7 @@ function Base.show(io::IO, e::Core.Compiler.Effects)
     print(io, ',')
     printstyled(io, string(tristate_letter(e.terminates), 't'); color=tristate_color(e.terminates))
     print(io, ')')
+    e.overlayed && printstyled(io, '′'; color=:red)
 end
 
 @specialize

base/compiler/tfuncs.jl

@@ -1789,11 +1789,11 @@ function builtin_effects(f::Builtin, argtypes::Vector{Any}, rt)
     if (f === Core.getfield || f === Core.isdefined) && length(argtypes) >= 3
         # consistent if the argtype is immutable
         if isvarargtype(argtypes[2])
-            return Effects(Effects(), effect_free=ALWAYS_TRUE, terminates=ALWAYS_TRUE)
+            return Effects(; effect_free=ALWAYS_TRUE, terminates=ALWAYS_TRUE, overlayed=false)
         end
         s = widenconst(argtypes[2])
         if isType(s) || !isa(s, DataType) || isabstracttype(s)
-            return Effects(Effects(), effect_free=ALWAYS_TRUE, terminates=ALWAYS_TRUE)
+            return Effects(; effect_free=ALWAYS_TRUE, terminates=ALWAYS_TRUE, overlayed=false)
         end
         s = s::DataType
         ipo_consistent = !ismutabletype(s)
@@ -1826,7 +1826,9 @@ function builtin_effects(f::Builtin, argtypes::Vector{Any}, rt)
         ipo_consistent ? ALWAYS_TRUE : ALWAYS_FALSE,
         effect_free ? ALWAYS_TRUE : ALWAYS_FALSE,
         nothrow ? ALWAYS_TRUE : TRISTATE_UNKNOWN,
-        ALWAYS_TRUE)
+        #=terminates=#ALWAYS_TRUE,
+        #=overlayed=#false,
+        )
 end
 
 function builtin_nothrow(@nospecialize(f), argtypes::Array{Any, 1}, @nospecialize(rt))
@@ -2007,7 +2009,9 @@ function intrinsic_effects(f::IntrinsicFunction, argtypes::Vector{Any})
         ipo_consistent ? ALWAYS_TRUE : ALWAYS_FALSE,
         effect_free ? ALWAYS_TRUE : ALWAYS_FALSE,
         nothrow ? ALWAYS_TRUE : TRISTATE_UNKNOWN,
-        ALWAYS_TRUE)
+        #=terminates=#ALWAYS_TRUE,
+        #=overlayed=#false,
+        )
 end
 
 # TODO: this function is a very buggy and poor model of the return_type function

base/compiler/typeinfer.jl

@@ -431,7 +431,7 @@ function rt_adjust_effects(@nospecialize(rt), ipo_effects::Effects)
     # but we don't currently model idempontency using dataflow, so we don't notice.
     # Fix that up here to improve precision.
     if !ipo_effects.inbounds_taints_consistency && rt === Union{}
-        return Effects(ipo_effects, consistent=ALWAYS_TRUE)
+        return Effects(ipo_effects; consistent=ALWAYS_TRUE)
     end
     return ipo_effects
 end
@@ -755,11 +755,11 @@ function merge_call_chain!(parent::InferenceState, ancestor::InferenceState, chi
     # and ensure that walking the parent list will get the same result (DAG) from everywhere
     # Also taint the termination effect, because we can no longer guarantee the absence
     # of recursion.
-    tristate_merge!(parent, Effects(EFFECTS_TOTAL, terminates=TRISTATE_UNKNOWN))
+    tristate_merge!(parent, Effects(EFFECTS_TOTAL; terminates=TRISTATE_UNKNOWN))
     while true
         add_cycle_backedge!(child, parent, parent.currpc)
         union_caller_cycle!(ancestor, child)
-        tristate_merge!(child, Effects(EFFECTS_TOTAL, terminates=TRISTATE_UNKNOWN))
+        tristate_merge!(child, Effects(EFFECTS_TOTAL; terminates=TRISTATE_UNKNOWN))
         child = parent
         child === ancestor && break
         parent = child.parent::InferenceState

base/compiler/types.jl

@@ -38,6 +38,7 @@ struct Effects
     effect_free::TriState
     nothrow::TriState
     terminates::TriState
+    overlayed::Bool
     # This effect is currently only tracked in inference and modified
     # :consistent before caching. We may want to track it in the future.
     inbounds_taints_consistency::Bool
@@ -46,27 +47,33 @@ function Effects(
     consistent::TriState,
     effect_free::TriState,
     nothrow::TriState,
-    terminates::TriState)
+    terminates::TriState,
+    overlayed::Bool)
     return Effects(
         consistent,
         effect_free,
         nothrow,
         terminates,
+        overlayed,
         false)
 end
-Effects() = Effects(TRISTATE_UNKNOWN, TRISTATE_UNKNOWN, TRISTATE_UNKNOWN, TRISTATE_UNKNOWN)
 
-function Effects(e::Effects;
+const EFFECTS_TOTAL = Effects(ALWAYS_TRUE, ALWAYS_TRUE, ALWAYS_TRUE, ALWAYS_TRUE, false)
+const EFFECTS_UNKNOWN = Effects(TRISTATE_UNKNOWN, TRISTATE_UNKNOWN, TRISTATE_UNKNOWN, TRISTATE_UNKNOWN, true)
+
+function Effects(e::Effects = EFFECTS_UNKNOWN;
     consistent::TriState = e.consistent,
     effect_free::TriState = e.effect_free,
     nothrow::TriState = e.nothrow,
     terminates::TriState = e.terminates,
+    overlayed::Bool = e.overlayed,
     inbounds_taints_consistency::Bool = e.inbounds_taints_consistency)
     return Effects(
         consistent,
         effect_free,
         nothrow,
         terminates,
+        overlayed,
         inbounds_taints_consistency)
 end
 
@@ -82,20 +89,20 @@ is_removable_if_unused(effects::Effects) =
     effects.terminates === ALWAYS_TRUE &&
     effects.nothrow === ALWAYS_TRUE
 
-const EFFECTS_TOTAL = Effects(ALWAYS_TRUE, ALWAYS_TRUE, ALWAYS_TRUE, ALWAYS_TRUE)
-
 function encode_effects(e::Effects)
-    return e.consistent.state |
-           (e.effect_free.state << 2) |
-           (e.nothrow.state << 4) |
-           (e.terminates.state << 6)
+    return (e.consistent.state << 1) |
+           (e.effect_free.state << 3) |
+           (e.nothrow.state << 5) |
+           (e.terminates.state << 7) |
+           (e.overlayed)
 end
 function decode_effects(e::UInt8)
     return Effects(
-        TriState(e & 0x3),
-        TriState((e >> 2) & 0x3),
-        TriState((e >> 4) & 0x3),
-        TriState((e >> 6) & 0x3),
+        TriState((e >> 1) & 0x03),
+        TriState((e >> 3) & 0x03),
+        TriState((e >> 5) & 0x03),
+        TriState((e >> 7) & 0x03),
+        e & 0x01 ≠ 0x00,
         false)
 end
 
@@ -109,6 +116,7 @@ function tristate_merge(old::Effects, new::Effects)
             old.nothrow, new.nothrow),
         tristate_merge(
             old.terminates, new.terminates),
+        old.overlayed | new.overlayed,
         old.inbounds_taints_consistency | new.inbounds_taints_consistency)
 end
 
@@ -158,7 +166,7 @@ mutable struct InferenceResult
                              arginfo#=::Union{Nothing,Tuple{ArgInfo,InferenceState}}=# = nothing)
         argtypes, overridden_by_const = matching_cache_argtypes(linfo, arginfo)
         return new(linfo, argtypes, overridden_by_const, Any, nothing,
-            WorldRange(), Effects(), Effects(), nothing)
+            WorldRange(), Effects(; overlayed=false), Effects(; overlayed=false), nothing)
     end
 end
 

test/compiler/AbstractInterpreter.jl

@@ -41,25 +41,53 @@ import Base.Experimental: @MethodTable, @overlay
 @MethodTable(OverlayedMT)
 CC.method_table(interp::MTOverlayInterp) = CC.OverlayMethodTable(CC.get_world_counter(interp), OverlayedMT)
 
-@overlay OverlayedMT sin(x::Float64) = 1
-@test Base.return_types((Int,), MTOverlayInterp()) do x
-    sin(x)
-end == Any[Int]
+strangesin(x) = sin(x)
+@overlay OverlayedMT strangesin(x::Float64) = iszero(x) ? nothing : cos(x)
+@test Base.return_types((Float64,), MTOverlayInterp()) do x
+    strangesin(x)
+end |> only === Union{Float64,Nothing}
 @test Base.return_types((Any,), MTOverlayInterp()) do x
-    Base.@invoke sin(x::Float64)
-end == Any[Int]
+    Base.@invoke strangesin(x::Float64)
+end |> only === Union{Float64,Nothing}
 
 # fallback to the internal method table
 @test Base.return_types((Int,), MTOverlayInterp()) do x
     cos(x)
-end == Any[Float64]
+end |> only === Float64
 @test Base.return_types((Any,), MTOverlayInterp()) do x
     Base.@invoke cos(x::Float64)
-end == Any[Float64]
+end |> only === Float64
 
 # not fully covered overlay method match
 overlay_match(::Any) = nothing
 @overlay OverlayedMT overlay_match(::Int) = missing
 @test Base.return_types((Any,), MTOverlayInterp()) do x
     overlay_match(x)
-end == Any[Union{Nothing,Missing}]
+end |> only === Union{Nothing,Missing}
+
+# partial pure/concrete evaluation
+@test Base.return_types((), MTOverlayInterp()) do
+    isbitstype(Int) ? nothing : missing
+end |> only === Nothing
+Base.@assume_effects :terminates_globally function issue41694(x)
+    res = 1
+    1 < x < 20 || throw("bad")
+    while x > 1
+        res *= x
+        x -= 1
+    end
+    return res
+end
+@test Base.return_types((), MTOverlayInterp()) do
+    issue41694(3) == 6 ? nothing : missing
+end |> only === Nothing
+
+# disable partial pure/concrete evaluation when tainted by any overlayed call
+Base.@assume_effects :total totalcall(f, args...) = f(args...)
+@test Base.return_types((), MTOverlayInterp()) do
+    if totalcall(strangesin, 1.0) == cos(1.0)
+        return nothing
+    else
+        return missing
+    end
+end |> only === Nothing