inference: refine exct information if :nothrow is proven

Author: aviatesk

base/compiler/abstractinterpretation.jl

@@ -1196,13 +1196,14 @@ function semi_concrete_eval_call(interp::AbstractInterpreter,
                 # state = InliningState(interp)
                 # ir = ssa_inlining_pass!(irsv.ir, state, propagate_inbounds(irsv))
                 effects = result.effects
-                if !is_nothrow(effects)
-                    effects = Effects(effects; nothrow)
+                if nothrow
+                    effects = Effects(effects; nothrow=true)
                 end
                 if noub
-                    effects = Effects(effects; noub = ALWAYS_TRUE)
+                    effects = Effects(effects; noub=ALWAYS_TRUE)
                 end
-                return ConstCallResults(rt, result.exct, SemiConcreteResult(mi, ir, effects), effects, mi)
+                exct = refine_exception_type(result.exct, effects)
+                return ConstCallResults(rt, exct, SemiConcreteResult(mi, ir, effects), effects, mi)
             end
         end
     end

base/compiler/typeinfer.jl

@@ -503,6 +503,11 @@ function adjust_effects(sv::InferenceState)
     return ipo_effects
 end
 
+function refine_exception_type(@nospecialize(exc_bestguess), ipo_effects::Effects)
+    ipo_effects.nothrow && return Bottom
+    return exc_bestguess
+end
+
 # inference completed on `me`
 # update the MethodInstance
 function finish(me::InferenceState, interp::AbstractInterpreter)
@@ -539,8 +544,8 @@ function finish(me::InferenceState, interp::AbstractInterpreter)
     end
     me.result.valid_worlds = me.valid_worlds
     me.result.result = bestguess
-    me.result.ipo_effects = me.ipo_effects = adjust_effects(me)
-    me.result.exc_result = exc_bestguess
+    ipo_effects = me.result.ipo_effects = me.ipo_effects = adjust_effects(me)
+    me.result.exc_result = me.exc_bestguess = refine_exception_type(me.exc_bestguess, ipo_effects)
 
     if limited_ret
         # a parent may be cached still, but not this intermediate work:
@@ -862,20 +867,23 @@ function typeinf_edge(interp::AbstractInterpreter, method::Method, @nospecialize
         isinferred = is_inferred(frame)
         edge = isinferred ? mi : nothing
         effects = isinferred ? frame.result.ipo_effects : adjust_effects(Effects(), method) # effects are adjusted already within `finish` for ipo_effects
+        exc_bestguess = refine_exception_type(frame.exc_bestguess, effects)
         # propagate newly inferred source to the inliner, allowing efficient inlining w/o deserialization:
         # note that this result is cached globally exclusively, we can use this local result destructively
         volatile_inf_result = isinferred && let inferred_src = result.src
                 isa(inferred_src, CodeInfo) && (is_inlineable(inferred_src) || force_inline)
             end ? VolatileInferenceResult(result) : nothing
-        return EdgeCallResult(frame.bestguess, frame.exc_bestguess, edge, effects, volatile_inf_result)
+        return EdgeCallResult(frame.bestguess, exc_bestguess, edge, effects, volatile_inf_result)
     elseif frame === true
         # unresolvable cycle
         return EdgeCallResult(Any, Any, nothing, Effects())
     end
     # return the current knowledge about this cycle
     frame = frame::InferenceState
     update_valid_age!(caller, frame.valid_worlds)
-    return EdgeCallResult(frame.bestguess, frame.exc_bestguess, nothing, adjust_effects(Effects(), method))
+    effects = adjust_effects(Effects(), method)
+    exc_bestguess = refine_exception_type(frame.exc_bestguess, effects)
+    return EdgeCallResult(frame.bestguess, exc_bestguess, nothing, effects)
 end
 
 function cached_return_type(code::CodeInstance)

test/compiler/inference.jl

@@ -5558,3 +5558,32 @@ function foo_typed_throw_metherr()
     return 1
 end
 @test Base.return_types(foo_typed_throw_metherr) |> only === Float64
+
+# using `exct` information if `:nothrow` is proven
+Base.@assume_effects :nothrow function sin_nothrow(x::Float64)
+    x == Inf && return zero(x)
+    return sin(x)
+end
+@test Base.infer_exception_type(sin_nothrow, (Float64,)) == Union{}
+@test Base.return_types((Float64,)) do x
+    try
+        return sin_nothrow(x)
+    catch err
+        return err
+    end
+end |> only === Float64
+# for semi-concrete interpretation result too
+Base.@constprop :aggressive function sin_maythrow(x::Float64, maythrow::Bool)
+    if maythrow
+        return sin(x)
+    else
+        return @noinline sin_nothrow(x)
+    end
+end
+@test Base.return_types((Float64,)) do x
+    try
+        return sin_maythrow(x, false)
+    catch err
+        return err
+    end
+end |> only === Float64