inference: always bail out const-prop' with non-const result limited

base/compiler/abstractinterpretation.jl

@@ -814,12 +814,7 @@ end
 function abstract_call_method_with_const_args(interp::AbstractInterpreter,
     result::MethodCallResult, @nospecialize(f), arginfo::ArgInfo, si::StmtInfo,
     match::MethodMatch, sv::AbsIntState, invokecall::Union{Nothing,InvokeCall}=nothing)
-
-    if !const_prop_enabled(interp, sv, match)
-        return nothing
-    end
-    if bail_out_const_call(interp, result, si)
-        add_remark!(interp, sv, "[constprop] No more information to be gained")
+    if !const_prop_enabled(interp, match, sv) || bail_out_const_call(interp, result, si, sv)
         return nothing
     end
     eligibility = concrete_eval_eligible(interp, f, result, arginfo, sv)
@@ -852,7 +847,7 @@ function abstract_call_method_with_const_args(interp::AbstractInterpreter,
     return const_prop_call(interp, mi, result, arginfo, sv, concrete_eval_result)
 end
 
-function const_prop_enabled(interp::AbstractInterpreter, sv::AbsIntState, match::MethodMatch)
+function const_prop_enabled(interp::AbstractInterpreter, match::MethodMatch, sv::AbsIntState)
     if !InferenceParams(interp).ipo_constant_propagation
         add_remark!(interp, sv, "[constprop] Disabled by parameter")
         return false
@@ -864,9 +859,11 @@ function const_prop_enabled(interp::AbstractInterpreter, sv::AbsIntState, match:
     return true
 end
 
-function bail_out_const_call(interp::AbstractInterpreter, result::MethodCallResult, si::StmtInfo)
+function bail_out_const_call(interp::AbstractInterpreter, result::MethodCallResult,
+                             si::StmtInfo, sv::AbsIntState)
     if is_removable_if_unused(result.effects)
         if isa(result.rt, Const) || call_result_unused(si)
+            add_remark!(interp, sv, "[constprop] No more information to be gained (const)")
             return true
         end
     elseif result.rt === Bottom
@@ -876,6 +873,7 @@ function bail_out_const_call(interp::AbstractInterpreter, result::MethodCallResu
             # precise enough to let us determine :consistency of `exct`, so we
             # would have to force constprop just to determine this, which is too
             # expensive.
+            add_remark!(interp, sv, "[constprop] No more information to be gained (bottom)")
             return true
         end
     end
@@ -974,7 +972,10 @@ function maybe_get_const_prop_profitable(interp::AbstractInterpreter,
     match::MethodMatch, sv::AbsIntState)
     method = match.method
     force = force_const_prop(interp, f, method)
-    force || const_prop_entry_heuristic(interp, result, si, sv) || return nothing
+    if !const_prop_entry_heuristic(interp, result, si, sv, force)
+        # N.B. remarks are emitted within `const_prop_entry_heuristic`
+        return nothing
+    end
     nargs::Int = method.nargs
     method.isva && (nargs -= 1)
     length(arginfo.argtypes) < nargs && return nothing
@@ -1001,8 +1002,17 @@ function maybe_get_const_prop_profitable(interp::AbstractInterpreter,
     return mi
 end
 
-function const_prop_entry_heuristic(interp::AbstractInterpreter, result::MethodCallResult, si::StmtInfo, sv::AbsIntState)
-    if call_result_unused(si) && result.edgecycle
+function const_prop_entry_heuristic(interp::AbstractInterpreter, result::MethodCallResult,
+                                    si::StmtInfo, sv::AbsIntState, force::Bool)
+    if result.rt isa LimitedAccuracy
+        # optimizations like inlining are disabled for limited frames,
+        # thus there won't be much benefit in constant-prop' here
+        # N.B. don't allow forced constprop' for safety (xref #52763)
+        add_remark!(interp, sv, "[constprop] Disabled by entry heuristic (limited accuracy)")
+        return false
+    elseif force
+        return true
+    elseif call_result_unused(si) && result.edgecycle
         add_remark!(interp, sv, "[constprop] Disabled by entry heuristic (edgecycle with unused result)")
         return false
     end
@@ -1015,27 +1025,21 @@ function const_prop_entry_heuristic(interp::AbstractInterpreter, result::MethodC
         if rt === Bottom
             add_remark!(interp, sv, "[constprop] Disabled by entry heuristic (erroneous result)")
             return false
-        else
-            return true
         end
+        return true
     elseif isa(rt, PartialStruct) || isa(rt, InterConditional) || isa(rt, InterMustAlias)
         # could be improved to `Const` or a more precise wrapper
         return true
-    elseif isa(rt, LimitedAccuracy)
-        # optimizations like inlining are disabled for limited frames,
-        # thus there won't be much benefit in constant-prop' here
-        add_remark!(interp, sv, "[constprop] Disabled by entry heuristic (limited accuracy)")
-        return false
-    else
-        if isa(rt, Const)
-            if !is_nothrow(result.effects)
-                # Could still be improved to Bottom (or at least could see the effects improved)
-                return true
-            end
+    elseif isa(rt, Const)
+        if is_nothrow(result.effects)
+            add_remark!(interp, sv, "[constprop] Disabled by entry heuristic (nothrow const)")
+            return false
         end
-        add_remark!(interp, sv, "[constprop] Disabled by entry heuristic (unimprovable result)")
-        return false
+        # Could still be improved to Bottom (or at least could see the effects improved)
+        return true
     end
+    add_remark!(interp, sv, "[constprop] Disabled by entry heuristic (unimprovable result)")
+    return false
 end
 
 # determines heuristically whether if constant propagation can be worthwhile

test/compiler/inference.jl

@@ -4937,10 +4937,21 @@ g() = empty_nt_values(Base.inferencebarrier(Tuple{}))
 # This is somewhat sensitive to the exact recursion level that inference is willing to do, but the intention
 # is to test the case where inference limited a recursion, but then a forced constprop nevertheless managed
 # to terminate the call.
+@newinterp RecurseInterpreter
+let CC = Core.Compiler
+    function CC.const_prop_entry_heuristic(interp::RecurseInterpreter, result::CC.MethodCallResult,
+                                           si::CC.StmtInfo, sv::CC.AbsIntState, force::Bool)
+        if result.rt isa CC.LimitedAccuracy
+            return force # allow forced constprop to recurse into unresolved cycles
+        end
+        return @invoke CC.const_prop_entry_heuristic(interp::CC.AbstractInterpreter, result::CC.MethodCallResult,
+                                                     si::CC.StmtInfo, sv::CC.AbsIntState, force::Bool)
+    end
+end
 Base.@constprop :aggressive type_level_recurse1(x...) = x[1] == 2 ? 1 : (length(x) > 100 ? x : type_level_recurse2(x[1] + 1, x..., x...))
 Base.@constprop :aggressive type_level_recurse2(x...) = type_level_recurse1(x...)
 type_level_recurse_entry() = Val{type_level_recurse1(1)}()
-@test Base.return_types(type_level_recurse_entry, ()) |> only == Val{1}
+@test Base.infer_return_type(type_level_recurse_entry, (); interp=RecurseInterpreter()) == Val{1}
 
 # Test that inference doesn't give up if it can potentially refine effects,
 # even if the return type is Any.