optimizer: early finalize insertion

Currently, in the finalizer inlining pass, if not all the code between
the finalizer registration and the end of the object’s lifetime (i.e.,
where the finalizer would be inlined) is marked as `:nothrow`, it simply
bails out. However, even in such cases, we can insert a `finalize` call
at the end of the object’s lifetime, allowing us to call the finalizer
early if no exceptions occur.

This commit implements this optimization. To do so, it also moves
`finalize` to `Core`, so the compiler can handle it directly.

Author: aviatesk

base/Base.jl

@@ -271,8 +271,7 @@ end
 
 BUILDROOT::String = ""
 
-baremodule BuildSettings
-end
+baremodule BuildSettings end
 
 let i = 1
     global BUILDROOT

base/boot.jl

@@ -214,7 +214,7 @@ export
     nfields, throw, tuple, ===, isdefined, eval,
     # access to globals
     getglobal, setglobal!, swapglobal!, modifyglobal!, replaceglobal!, setglobalonce!,
-    # ifelse, sizeof    # not exported, to avoid conflicting with Base
+    # ifelse, sizeof, finalize # not exported, to avoid conflicting with Base
     # type reflection
     <:, typeof, isa, typeassert,
     # method reflection

base/compiler/ssair/passes.jl

@@ -1625,19 +1625,18 @@ function try_resolve_finalizer!(ir::IRCode, alloc_idx::Int, finalizer_idx::Int,
     foreach(note_defuse!, defuse.defs)
     insert_bb != 0 || return nothing # verify post-dominator of all uses exists
 
+    # Figure out the exact statement where we're going to inline the finalizer.
+    loc = insert_idx === nothing ? first(ir.cfg.blocks[insert_bb].stmts) : insert_idx::Int
+    attach_after = insert_idx !== nothing
+    flag = info isa FinalizerInfo ? flags_for_effects(info.effects) : IR_FLAG_NULL
+    finalizer_stmt = ir[SSAValue(finalizer_idx)][:stmt]
+
     if !OptimizationParams(inlining.interp).assume_fatal_throw
         # Collect all reachable blocks between the finalizer registration and the
         # insertion point
         blocks = reachable_blocks(ir.cfg, finalizer_bb, insert_bb)
 
         # Check #3
-        function check_range_nothrow(s::Int, e::Int)
-            return all(s:e) do sidx::Int
-                sidx == finalizer_idx && return true
-                sidx == alloc_idx && return true
-                return is_nothrow(ir, SSAValue(sidx))
-            end
-        end
         for bb in blocks
             range = ir.cfg.blocks[bb].stmts
             s, e = first(range), last(range)
@@ -1648,18 +1647,23 @@ function try_resolve_finalizer!(ir::IRCode, alloc_idx::Int, finalizer_idx::Int,
             if bb == finalizer_bb
                 s = finalizer_idx
             end
-            check_range_nothrow(s, e) || return nothing
+            all(s:e) do sidx::Int
+                sidx == finalizer_idx && return true
+                sidx == alloc_idx && return true
+                return is_nothrow(ir, SSAValue(sidx))
+            end && continue
+
+            # A exception may be thrown between the finalizer registration and the point
+            # where the object’s lifetime ends (`insert_idx`): In such cases, we can’t
+            # remove the finalizer registration, but we can still insert a `Core.finalize`
+            # call at `insert_idx` while leaving the registration intact.
+            newinst = add_flag(NewInstruction(Expr(:call, GlobalRef(Core, :finalize), finalizer_stmt.args[3]), Nothing), flag)
+            insert_node!(ir, loc, newinst, attach_after)
+            return nothing
         end
     end
 
-    # Ok, legality check complete. Figure out the exact statement where we're
-    # going to inline the finalizer.
-    loc = insert_idx === nothing ? first(ir.cfg.blocks[insert_bb].stmts) : insert_idx::Int
-    attach_after = insert_idx !== nothing
-
-    finalizer_stmt = ir[SSAValue(finalizer_idx)][:stmt]
     argexprs = Any[finalizer_stmt.args[2], finalizer_stmt.args[3]]
-    flag = info isa FinalizerInfo ? flags_for_effects(info.effects) : IR_FLAG_NULL
     if length(finalizer_stmt.args) >= 4
         inline = finalizer_stmt.args[4]
         if inline === nothing

base/compiler/tfuncs.jl

@@ -743,6 +743,7 @@ add_tfunc(donotdelete, 0, INT_INF, @nospecs((𝕃::AbstractLattice, args...)->No
 end
 add_tfunc(compilerbarrier, 2, 2, compilerbarrier_tfunc, 5)
 add_tfunc(Core.finalizer, 2, 4, @nospecs((𝕃::AbstractLattice, args...)->Nothing), 5)
+add_tfunc(Core.finalize, 1, 1, @nospecs((𝕃::AbstractLattice, o)->Nothing), 100)
 
 @nospecs function compilerbarrier_nothrow(setting, val)
     return isa(setting, Const) && contains_is((:type, :const, :conditional), setting.val)
@@ -2288,8 +2289,11 @@ function _builtin_nothrow(𝕃::AbstractLattice, @nospecialize(f::Builtin), argt
         return true
     elseif f === Core.finalizer
         2 <= na <= 4 || return false
-        # Core.finalizer does no error checking - that's done in Base.finalizer
+        # `Core.finalizer` does no error checking - that's done in Base.finalizer
         return true
+    elseif f === Core.finalize
+        na == 2 || return false
+        return true # `Core.finalize` does no error checking
     elseif f === Core.compilerbarrier
         na == 2 || return false
         return compilerbarrier_nothrow(argtypes[1], nothing)

base/gcutils.jl

@@ -1,6 +1,5 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
-
 """
     WeakRef(x)
 
@@ -99,8 +98,7 @@ end
 
 Immediately run finalizers registered for object `x`.
 """
-finalize(@nospecialize(o)) = ccall(:jl_finalize_th, Cvoid, (Any, Any,),
-                                   current_task(), o)
+finalize(@nospecialize(o)) = Core.finalize(o)
 
 """
     Base.GC

src/builtin_proto.h

@@ -37,6 +37,7 @@ DECLARE_BUILTIN(compilerbarrier);
 DECLARE_BUILTIN(current_scope);
 DECLARE_BUILTIN(donotdelete);
 DECLARE_BUILTIN(fieldtype);
+DECLARE_BUILTIN(finalize);
 DECLARE_BUILTIN(finalizer);
 DECLARE_BUILTIN(getfield);
 DECLARE_BUILTIN(getglobal);

src/builtins.c

@@ -588,6 +588,13 @@ JL_CALLABLE(jl_f_throw_methoderror)
     return jl_nothing;
 }
 
+JL_CALLABLE(jl_f_finalize)
+{
+    JL_NARGS(finalize, 1, 1);
+    jl_finalize(args[0]);
+    return jl_nothing;
+}
+
 JL_CALLABLE(jl_f_ifelse)
 {
     JL_NARGS(ifelse, 3, 3);
@@ -2446,6 +2453,7 @@ void jl_init_primitives(void) JL_GC_DISABLED
     add_builtin_func("_svec_ref", jl_f__svec_ref);
     jl_builtin_current_scope = add_builtin_func("current_scope", jl_f_current_scope);
     add_builtin_func("throw_methoderror", jl_f_throw_methoderror);
+    add_builtin_func("finalize", jl_f_finalize);
 
     // builtin types
     add_builtin("Any", (jl_value_t*)jl_any_type);

src/codegen.cpp

@@ -1621,6 +1621,7 @@ static const auto &builtin_func_map() {
           { jl_f__call_in_world_total_addr, new JuliaFunction<>{XSTR(jl_f__call_in_world_total), get_func_sig, get_func_attrs} },
           { jl_f_throw_addr,              new JuliaFunction<>{XSTR(jl_f_throw), get_func_sig, get_func_attrs} },
           { jl_f_throw_methoderror_addr,  new JuliaFunction<>{XSTR(jl_f_throw_methoderror), get_func_sig, get_func_attrs} },
+          { jl_f_finalize_addr,           new JuliaFunction<>{XSTR(jl_f_finalize), get_func_sig, get_func_attrs} },
           { jl_f_tuple_addr,              jltuple_func },
           { jl_f_svec_addr,               new JuliaFunction<>{XSTR(jl_f_svec), get_func_sig, get_func_attrs} },
           { jl_f_applicable_addr,         new JuliaFunction<>{XSTR(jl_f_applicable), get_func_sig, get_func_attrs} },

src/staticdata.c

@@ -501,7 +501,7 @@ static htable_t relocatable_ext_cis;
 // (reverse of fptr_to_id)
 // This is a manually constructed dual of the fvars array, which would be produced by codegen for Julia code, for C.
 static const jl_fptr_args_t id_to_fptrs[] = {
-    &jl_f_throw, &jl_f_throw_methoderror, &jl_f_is, &jl_f_typeof, &jl_f_issubtype, &jl_f_isa,
+    &jl_f_throw, &jl_f_throw_methoderror, &jl_f_finalize, &jl_f_is, &jl_f_typeof, &jl_f_issubtype, &jl_f_isa,
     &jl_f_typeassert, &jl_f__apply_iterate, &jl_f__apply_pure,
     &jl_f__call_latest, &jl_f__call_in_world, &jl_f__call_in_world_total, &jl_f_isdefined,
     &jl_f_tuple, &jl_f_svec, &jl_f_intrinsic_call,

test/compiler/inline.jl

@@ -1596,6 +1596,19 @@ let
     @test get_finalization_count() == 1000
 end
 
+# early `finalize` insertion
+let src = code_typed1((Int,)) do x
+        xs = finalizer(Ref(x)) do obj
+            Base.@assume_effects :nothrow :notaskstate
+            Core.println("finalizing: ", objectid(obj))
+        end
+        @show xs[]
+        return xs[]
+    end
+    @test count(iscall((src, Core.finalizer)), src.code) == 1
+    @test count(iscall((src, Core.finalize)), src.code) == 1
+end
+
 # optimize `[push!|pushfirst!](::Vector{Any}, x...)`
 @testset "optimize `$f(::Vector{Any}, x...)`" for f = Any[push!, pushfirst!]
     @eval begin