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Fix serialization of code instances. #46373

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Sep 27, 2022
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Fix serialization of code instances. #46373

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14 changes: 8 additions & 6 deletions src/dump.c
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Original file line number Diff line number Diff line change
Expand Up @@ -653,13 +653,15 @@ static int jl_serialize_generic(jl_serializer_state *s, jl_value_t *v) JL_GC_DIS
return 0;
}

static void jl_serialize_code_instance(jl_serializer_state *s, jl_code_instance_t *codeinst, int skip_partial_opaque, int internal) JL_GC_DISABLED
static void jl_serialize_code_instance(jl_serializer_state *s, jl_code_instance_t *codeinst,
int skip_partial_opaque, int internal,
int force) JL_GC_DISABLED
{
if (internal > 2) {
while (codeinst && !codeinst->relocatability)
codeinst = codeinst->next;
}
if (jl_serialize_generic(s, (jl_value_t*)codeinst)) {
if (!force && jl_serialize_generic(s, (jl_value_t*)codeinst)) {
return;
}
assert(codeinst != NULL); // handle by jl_serialize_generic, but this makes clang-sa happy
Expand All @@ -680,7 +682,7 @@ static void jl_serialize_code_instance(jl_serializer_state *s, jl_code_instance_
if (write_ret_type && codeinst->rettype_const &&
jl_typeis(codeinst->rettype_const, jl_partial_opaque_type)) {
if (skip_partial_opaque) {
jl_serialize_code_instance(s, codeinst->next, skip_partial_opaque, internal);
jl_serialize_code_instance(s, codeinst->next, skip_partial_opaque, internal, 0);
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Why not pass force here?

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I'm just preserving how this function worked before. Presumably there was a reason that jl_serialize_code_instance didn't serialize CIs with backref entries on recursive calls to jl_serialize_code_instance, so I'm just preserving that behavior. Instead, I'm only forcing the CIs to be serialized when I know that the backref table initialization doesn't mean that the object has been serialized, i.e., from the jl_is_code_instance branch in jl_serialize_value.

return;
}
else {
Expand All @@ -707,7 +709,7 @@ static void jl_serialize_code_instance(jl_serializer_state *s, jl_code_instance_
jl_serialize_value(s, jl_nothing);
}
write_uint8(s->s, codeinst->relocatability);
jl_serialize_code_instance(s, codeinst->next, skip_partial_opaque, internal);
jl_serialize_code_instance(s, codeinst->next, skip_partial_opaque, internal, 0);
}

enum METHOD_SERIALIZATION_MODE {
Expand Down Expand Up @@ -968,10 +970,10 @@ static void jl_serialize_value_(jl_serializer_state *s, jl_value_t *v, int as_li
}
jl_serialize_value(s, (jl_value_t*)backedges);
jl_serialize_value(s, (jl_value_t*)NULL); //callbacks
jl_serialize_code_instance(s, mi->cache, 1, internal);
jl_serialize_code_instance(s, mi->cache, 1, internal, 0);
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What if a MethodInstance is a code-object? Would you want to serialize the CodeInstances that it points to? If so...we might have to keep track at a higher level of how we got here: if by traversing a module, then don't force, but if we're caching code, then force.

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Not setting force=0 doesn't mean that the CI won't be serialized, it only means that it can't have a backref table entry. Since we're calling jl_serialize_code_instance here on a field that wasn't the direct input to jl_serialize_value (which populates the backref table), IIUC that means we will either serialize it for the first time, or the backref table will have an entry point to a successfully serialized CI.

And this does indeed seem to work as expected. With your example above, I can successfully precompile the array of MIs and inspect the CI in the cache:

module CodeInstancePrecompile

const some_mis = [first(methods(identity)).specializations[1]]

__init__() = @show some_mis[].cache

end
❯ JULIA_LOAD_PATH=. jl --startup-file=no -e 'using CodeInstancePrecompile'
(some_mis[]).cache = Core.CodeInstance(MethodInstance for identity(::Base.BottomRF{typeof(Base.add_sum)}), #undef, 0x0000000000000001, 0xffffffffffffffff, Base.BottomRF{typeof(Base.add_sum)}, Base.BottomRF{typeof(Base.add_sum)}(Base.add_sum), nothing, 0x00000155, 0x00000155, nothing, false, false, Ptr{Nothing} @0x00000001034d3a08, Ptr{Nothing} @0x0000000000000000, 0x00)

}
else if (jl_is_code_instance(v)) {
jl_serialize_code_instance(s, (jl_code_instance_t*)v, 0, 2);
jl_serialize_code_instance(s, (jl_code_instance_t*)v, 0, 2, 1);
}
else if (jl_typeis(v, jl_module_type)) {
jl_serialize_module(s, (jl_module_t*)v);
Expand Down
17 changes: 17 additions & 0 deletions test/precompile.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -1488,5 +1488,22 @@ precompile_test_harness("Issue #46558") do load_path
@test (@eval $Foo.foo(1)) == 2
end

precompile_test_harness("issue #46296") do load_path
write(joinpath(load_path, "CodeInstancePrecompile.jl"),
"""
module CodeInstancePrecompile

mi = first(methods(identity)).specializations[1]
ci = Core.CodeInstance(mi, Any, nothing, nothing, zero(Int32), typemin(UInt64),
typemax(UInt64), zero(UInt32), zero(UInt32), nothing, 0x00)

__init__() = @assert ci isa Core.CodeInstance

end
""")
Base.compilecache(Base.PkgId("CodeInstancePrecompile"))
(@eval (using CodeInstancePrecompile))
end

empty!(Base.DEPOT_PATH)
append!(Base.DEPOT_PATH, original_depot_path)