Improve attribution of delayed invalidations (#261)

Improves on #260 by collecting all callees and callers and then doing
the attribution at once (finding at least one identifiable callee).

This also adds the test's Manifest.toml, which was missing on #260 but not
detected because the necessary Julia version had not yet hit nightly.

src/invalidations.jl

@@ -187,7 +187,7 @@ function Base.show(io::IO, methinvs::MethodInvalidations)
                 sig = root.first
                 if isa(sig, MethodInstance)
                     # "insert_backedges_callee"/"insert_backedges" (delayed) invalidations
-                    printstyled(io, which(sig.specTypes), color = :light_cyan)
+                    printstyled(io, try which(sig.specTypes) catch _ "(unavailable)" end, color = :light_cyan)
                     print(io, " (formerly ", sig.def, ')')
                 else
                     # `sig` (immediate) invalidations
@@ -290,27 +290,24 @@ function invalidation_trees(list; exclude_corecompiler::Bool=true)
 
     function handle_insert_backedges(list, i, callee)
         ncovered = 0
+        callees = Any[callee]
         while length(list) >= i+2 && list[i+2] == "insert_backedges_callee"
-            if isa(callee, Type)
-                newcallee = list[i+1]
-                if isa(newcallee, MethodInstance)
-                    callee = newcallee
-                end
-            end
+            push!(callees, list[i+1])
             i += 2
         end
+        callers = MethodInstance[]
         while length(list) >= i+2 && list[i+2] == "insert_backedges"
-            caller = list[i+=1]
-            i += 1
-            push!(delayed, callee => caller)
+            push!(callers, list[i+1])
+            i += 2
             ncovered += 1
         end
+        push!(delayed, callees => callers)
         @assert ncovered > 0
         return i
     end
 
     methodinvs = MethodInvalidations[]
-    delayed = Pair{Any,MethodInstance}[]   # from "insert_backedges" invalidations
+    delayed = Pair{Vector{Any},Vector{MethodInstance}}[]   # from "insert_backedges" invalidations
     leaf = nothing
     mt_backedges, backedges, mt_cache, mt_disable = methinv_storage()
     reason = nothing
@@ -418,20 +415,31 @@ function invalidation_trees(list; exclude_corecompiler::Bool=true)
             end
         end
     end
-    trouble = similar(delayed, 0)
-    for (callee, caller) in delayed
-        if isa(callee, MethodInstance)
-            idx = get(callee2idx, callee.def, nothing)
-            if idx !== nothing
-                push!(methodinvs[idx].mt_backedges, callee => caller)
-                continue
+    solved = Int[]
+    for (i, (callees, callers)) in enumerate(delayed)
+        for callee in callees
+            if isa(callee, MethodInstance)
+                idx = get(callee2idx, callee.def, nothing)
+                if idx !== nothing
+                    for caller in callers
+                        push!(methodinvs[idx].mt_backedges, callee => caller)
+                    end
+                    push!(solved, i)
+                    break
+                end
             end
         end
-        push!(trouble, callee => caller)
     end
-    if !isempty(trouble)
+    deleteat!(delayed, solved)
+    if !isempty(delayed)
         @warn "Could not attribute the following delayed invalidations:"
-        display(trouble)
+        for (callees, callers) in delayed
+            @assert !isempty(callees)   # this shouldn't ever happen
+            printstyled(length(callees) == 1 ? callees[1] : callees; color = :light_cyan)
+            print(" invalidated ")
+            printstyled(length(callers) == 1 ? callers[1] : callers; color = :light_yellow)
+            println()
+        end
     end
     return sort!(methodinvs; by=countchildren)
 end

test/snoopr.jl

@@ -212,3 +212,53 @@ end
     @test isempty(filtermod(Outer, trees))
     @test length(filtermod(Outer, trees; recursive=true)) == 1
 end
+
+@testset "Delayed invalidations" begin
+    if Base.VERSION >= v"1.7.0-DEV.254"   # julia#39132 (redirect to Pipe)
+        # "Natural" tests are performed in the "Stale" testset of "snoopi_deep.jl"
+        # because they are also used for precompile_blockers.
+        # Here we craft them artificially.
+        M = @eval Module() begin
+            fake1(x) = 1
+            fake2(x) = fake1(x)
+            fake3() = nothing
+            foo() = nothing
+            @__MODULE__
+        end
+        M.fake2('a')
+        M.fake3()
+        callee = methodinstance(M.fake1, (Char,))
+        caller = methodinstance(M.fake2, (Char,))
+        othercallee = methodinstance(M.fake3, ())
+        # failed attribution (no invalidations occurred prior to the backedges invalidations)
+        invalidations = Any[callee, "insert_backedges_callee", othercallee, "insert_backedges_callee", caller, "insert_backedges"]
+        pipe = Pipe()
+        redirect_stdout(pipe) do
+            @test_logs (:warn, "Could not attribute the following delayed invalidations:") begin
+                trees = invalidation_trees(invalidations)
+                @test isempty(trees)
+            end
+        end
+        close(pipe.in)
+        str = read(pipe.out, String)
+        @test occursin(r"fake1\(::Char\).*invalidated.*fake2\(::Char\)", str)
+
+        m = which(M.foo, ())
+        invalidations = Any[Any[caller, Int32(1), callee, "jl_method_table_insert", m, "jl_method_table_insert"]; invalidations]
+        tree = @test_nowarn only(invalidation_trees(invalidations))
+        @test tree.method == m
+        @test tree.reason == :inserting
+        mi1, mi2 = tree.mt_backedges[1]
+        @test mi1 == callee
+        @test mi2 == caller
+        @test Core.MethodInstance(tree.backedges[1]) == callee
+        io = IOBuffer()
+        print(io, tree)
+        str = String(take!(io))
+        @test occursin(r"fake1\(x\) in.*formerly fake1\(x\) in", str)
+        Base.delete_method(callee.def)
+        print(io, tree)
+        str = String(take!(io))
+        @test occursin(r"\(unavailable\).*formerly fake1\(x\) in", str)
+    end
+end

test/testmodules/Stale/Manifest.toml

@@ -0,0 +1,21 @@
+# This file is machine-generated - editing it directly is not advised
+
+julia_version = "1.6.3-pre.1"
+manifest_format = "2.0"
+
+[[deps.StaleA]]
+path = "StaleA"
+uuid = "daf834c3-b832-4a67-a95b-01ec1ffe9b4d"
+version = "0.1.0"
+
+[[deps.StaleB]]
+deps = ["StaleA", "StaleC"]
+path = "StaleB"
+uuid = "af730a9e-e668-4d07-a0f0-de54196c2067"
+version = "0.1.0"
+
+[[deps.StaleC]]
+deps = ["StaleA"]
+path = "StaleC"
+uuid = "f6b5ece7-60fa-49fc-ba7e-b783050e37f1"
+version = "0.1.0"