module: Prepare usings array for world age partition (JuliaLang#55357)

This is a relatively independent part of the bindings partition branch,
extending the module usings list to gain `min_world` and `max_world`
`size_t`s. These are always `0` and `(size_t)-1` respectively in this
PR, which handles the GC and serialization implications of this change.
The semantic part will come later.

Author: Keno

src/gc-debug.c

@@ -1125,7 +1125,8 @@ int gc_slot_to_arrayidx(void *obj, void *_slot) JL_NOTSAFEPOINT
     if (vt == jl_module_type) {
         jl_module_t *m = (jl_module_t*)obj;
         start = (char*)m->usings.items;
-        len = m->usings.len;
+        len = module_usings_length(m);
+        elsize = sizeof(struct _jl_module_using);
     }
     else if (vt == jl_simplevector_type) {
         start = (char*)jl_svec_data(obj);

src/gc-stock.c

@@ -2053,16 +2053,18 @@ STATIC_INLINE void gc_mark_module_binding(jl_ptls_t ptls, jl_module_t *mb_parent
     gc_heap_snapshot_record_module_to_binding(mb_parent, bindings, bindingkeyset);
     gc_assert_parent_validity((jl_value_t *)mb_parent, (jl_value_t *)mb_parent->parent);
     gc_try_claim_and_push(mq, (jl_value_t *)mb_parent->parent, &nptr);
-    size_t nusings = mb_parent->usings.len;
+    size_t nusings = module_usings_length(mb_parent);
     if (nusings > 0) {
         // this is only necessary because bindings for "using" modules
         // are added only when accessed. therefore if a module is replaced
         // after "using" it but before accessing it, this array might
         // contain the only reference.
         jl_value_t *obj_parent = (jl_value_t *)mb_parent;
-        jl_value_t **objary_begin = (jl_value_t **)mb_parent->usings.items;
-        jl_value_t **objary_end = objary_begin + nusings;
-        gc_mark_objarray(ptls, obj_parent, objary_begin, objary_end, 1, nptr);
+        struct _jl_module_using *objary_begin = (struct _jl_module_using *)mb_parent->usings.items;
+        struct _jl_module_using *objary_end = objary_begin + nusings;
+        static_assert(sizeof(struct _jl_module_using) == 3*sizeof(void *), "Mismatch in _jl_module_using size");
+        static_assert(offsetof(struct _jl_module_using, mod) == 0, "Expected `mod` at the beginning of _jl_module_using");
+        gc_mark_objarray(ptls, obj_parent, (jl_value_t**)objary_begin, (jl_value_t**)objary_end, 3, nptr);
     }
     else {
         gc_mark_push_remset(ptls, (jl_value_t *)mb_parent, nptr);
@@ -2175,7 +2177,7 @@ FORCE_INLINE void gc_mark_outrefs(jl_ptls_t ptls, jl_gc_markqueue_t *mq, void *_
                 if (update_meta)
                     gc_setmark(ptls, o, bits, sizeof(jl_module_t));
                 jl_module_t *mb_parent = (jl_module_t *)new_obj;
-                uintptr_t nptr = ((mb_parent->usings.len + 1) << 2) | (bits & GC_OLD);
+                uintptr_t nptr = ((module_usings_length(mb_parent) + 1) << 2) | (bits & GC_OLD);
                 gc_mark_module_binding(ptls, mb_parent, nptr, bits);
             }
             else if (vtag == jl_task_tag << 4) {

src/julia.h

@@ -714,7 +714,7 @@ typedef struct _jl_module_t {
     jl_sym_t *file;
     int32_t line;
     // hidden fields:
-    arraylist_t usings;  // modules with all bindings potentially imported
+    arraylist_t usings; /* arraylist of struct jl_module_using */  // modules with all bindings potentially imported
     jl_uuid_t build_id;
     jl_uuid_t uuid;
     _Atomic(uint32_t) counter;
@@ -728,6 +728,12 @@ typedef struct _jl_module_t {
     intptr_t hash;
 } jl_module_t;
 
+struct _jl_module_using {
+    jl_module_t *mod;
+    size_t min_world;
+    size_t max_world;
+};
+
 struct _jl_globalref_t {
     JL_DATA_TYPE
     jl_module_t *mod;

src/julia_internal.h

@@ -819,6 +819,28 @@ void jl_eval_global_expr(jl_module_t *m, jl_expr_t *ex, int set_type);
 JL_DLLEXPORT void jl_declare_global(jl_module_t *m, jl_value_t *arg, jl_value_t *set_type);
 JL_DLLEXPORT jl_value_t *jl_toplevel_eval_flex(jl_module_t *m, jl_value_t *e, int fast, int expanded, const char **toplevel_filename, int *toplevel_lineno);
 
+STATIC_INLINE struct _jl_module_using *module_usings_getidx(jl_module_t *m JL_PROPAGATES_ROOT, size_t i) JL_NOTSAFEPOINT;
+STATIC_INLINE jl_module_t *module_usings_getmod(jl_module_t *m JL_PROPAGATES_ROOT, size_t i) JL_NOTSAFEPOINT;
+
+#ifndef __clang_gcanalyzer__
+// The analyzer doesn't like looking through the arraylist, so just model the
+// access for it using this function
+STATIC_INLINE struct _jl_module_using *module_usings_getidx(jl_module_t *m JL_PROPAGATES_ROOT, size_t i) JL_NOTSAFEPOINT {
+    return (struct _jl_module_using *)&(m->usings.items[3*i]);
+}
+STATIC_INLINE jl_module_t *module_usings_getmod(jl_module_t *m JL_PROPAGATES_ROOT, size_t i) JL_NOTSAFEPOINT {
+    return module_usings_getidx(m, i)->mod;
+}
+#endif
+
+STATIC_INLINE size_t module_usings_length(jl_module_t *m) JL_NOTSAFEPOINT {
+    return m->usings.len/3;
+}
+
+STATIC_INLINE size_t module_usings_max(jl_module_t *m) JL_NOTSAFEPOINT {
+    return m->usings.max/3;
+}
+
 jl_value_t *jl_eval_global_var(jl_module_t *m JL_PROPAGATES_ROOT, jl_sym_t *e);
 jl_value_t *jl_interpret_opaque_closure(jl_opaque_closure_t *clos, jl_value_t **args, size_t nargs);
 jl_value_t *jl_interpret_toplevel_thunk(jl_module_t *m, jl_code_info_t *src);

src/module.c

@@ -373,16 +373,6 @@ JL_DLLEXPORT jl_binding_t *jl_get_binding_for_method_def(jl_module_t *m, jl_sym_
     return b;
 }
 
-static inline jl_module_t *module_usings_getidx(jl_module_t *m JL_PROPAGATES_ROOT, size_t i) JL_NOTSAFEPOINT;
-
-#ifndef __clang_gcanalyzer__
-// The analyzer doesn't like looking through the arraylist, so just model the
-// access for it using this function
-static inline jl_module_t *module_usings_getidx(jl_module_t *m JL_PROPAGATES_ROOT, size_t i) JL_NOTSAFEPOINT {
-    return (jl_module_t*)m->usings.items[i];
-}
-#endif
-
 static int eq_bindings(jl_binding_partition_t *owner, jl_binding_t *alias, size_t world)
 {
     jl_ptr_kind_union_t owner_pku = jl_atomic_load_relaxed(&owner->restriction);
@@ -407,11 +397,11 @@ static jl_binding_t *using_resolve_binding(jl_module_t *m JL_PROPAGATES_ROOT, jl
     jl_binding_partition_t *bpart = NULL;
     jl_module_t *owner = NULL;
     JL_LOCK(&m->lock);
-    int i = (int)m->usings.len - 1;
+    int i = (int)module_usings_length(m) - 1;
     JL_UNLOCK(&m->lock);
     for (; i >= 0; --i) {
         JL_LOCK(&m->lock);
-        jl_module_t *imp = module_usings_getidx(m, i);
+        jl_module_t *imp = module_usings_getmod(m, i);
         JL_UNLOCK(&m->lock);
         jl_binding_t *tempb = jl_get_module_binding(imp, var, 0);
         if (tempb != NULL && tempb->exportp) {
@@ -746,19 +736,24 @@ JL_DLLEXPORT void jl_module_use_as(jl_module_t *to, jl_module_t *from, jl_sym_t
     module_import_(to, from, asname, s, 0);
 }
 
-
 JL_DLLEXPORT void jl_module_using(jl_module_t *to, jl_module_t *from)
 {
     if (to == from)
         return;
     JL_LOCK(&to->lock);
-    for (size_t i = 0; i < to->usings.len; i++) {
-        if (from == to->usings.items[i]) {
+    for (size_t i = 0; i < module_usings_length(to); i++) {
+        if (from == module_usings_getmod(to, i)) {
             JL_UNLOCK(&to->lock);
             return;
         }
     }
-    arraylist_push(&to->usings, from);
+    struct _jl_module_using new_item = {
+        .mod = from,
+        .min_world = 0,
+        .max_world = (size_t)-1
+    };
+    arraylist_grow(&to->usings, sizeof(struct _jl_module_using)/sizeof(void*));
+    memcpy(&to->usings.items[to->usings.len-3], &new_item, sizeof(struct _jl_module_using));
     jl_gc_wb(to, from);
     JL_UNLOCK(&to->lock);
 
@@ -1096,12 +1091,12 @@ JL_DLLEXPORT jl_value_t *jl_checked_assignonce(jl_binding_t *b, jl_module_t *mod
 JL_DLLEXPORT jl_value_t *jl_module_usings(jl_module_t *m)
 {
     JL_LOCK(&m->lock);
-    int j = m->usings.len;
+    int j = module_usings_length(m);
     jl_array_t *a = jl_alloc_array_1d(jl_array_any_type, j);
     JL_GC_PUSH1(&a);
     for (int i = 0; j > 0; i++) {
         j--;
-        jl_module_t *imp = (jl_module_t*)m->usings.items[i];
+        jl_module_t *imp = module_usings_getmod(m, i);
         jl_array_ptr_set(a, j, (jl_value_t*)imp);
     }
     JL_UNLOCK(&m->lock); // may gc
@@ -1156,10 +1151,8 @@ JL_DLLEXPORT jl_value_t *jl_module_names(jl_module_t *m, int all, int imported,
     if (usings) {
         // If `usings` is specified, traverse the list of `using`-ed modules and incorporate
         // the names exported by those modules into the list.
-        for(int i=(int)m->usings.len-1; i >= 0; --i) {
-            jl_module_t *usinged = module_usings_getidx(m, i);
-            append_exported_names(a, usinged, all);
-        }
+        for (int i = module_usings_length(m)-1; i >= 0; i--)
+            append_exported_names(a, module_usings_getmod(m, i), all);
     }
     JL_GC_POP();
     return (jl_value_t*)a;

src/staticdata.c

@@ -811,8 +811,8 @@ static void jl_queue_module_for_serialization(jl_serializer_state *s, jl_module_
         }
     }
 
-    for (size_t i = 0; i < m->usings.len; i++) {
-        jl_queue_for_serialization(s, (jl_value_t*)m->usings.items[i]);
+    for (size_t i = 0; i < module_usings_length(m); i++) {
+        jl_queue_for_serialization(s, module_usings_getmod(m, i));
     }
 }
 
@@ -1266,27 +1266,44 @@ static void jl_write_module(jl_serializer_state *s, uintptr_t item, jl_module_t
     // write out the usings list
     memset(&newm->usings._space, 0, sizeof(newm->usings._space));
     if (m->usings.items == &m->usings._space[0]) {
-        newm->usings.items = (void**)offsetof(jl_module_t, usings._space);
+        // Push these relocations here, to keep them in order. This pairs with the `newm->usings.items = ` below.
         arraylist_push(&s->relocs_list, (void*)(reloc_offset + offsetof(jl_module_t, usings.items)));
         arraylist_push(&s->relocs_list, (void*)(((uintptr_t)DataRef << RELOC_TAG_OFFSET) + item));
         size_t i;
-        for (i = 0; i < m->usings.len; i++) {
-            arraylist_push(&s->relocs_list, (void*)(reloc_offset + offsetof(jl_module_t, usings._space[i])));
-            arraylist_push(&s->relocs_list, (void*)backref_id(s, m->usings._space[i], s->link_ids_relocs));
+        for (i = 0; i < module_usings_length(m); i++) {
+            struct _jl_module_using *newm_data = module_usings_getidx(newm, i);
+            struct _jl_module_using *data = module_usings_getidx(m, i);
+            // TODO: Remove dead entries
+            newm_data->min_world = data->min_world;
+            newm_data->max_world = data->max_world;
+            if (s->incremental) {
+                if (data->max_world != (size_t)-1)
+                    newm_data->max_world = 0;
+                newm_data->min_world = 0;
+            }
+            arraylist_push(&s->relocs_list, (void*)(reloc_offset + offsetof(jl_module_t, usings._space[3*i])));
+            arraylist_push(&s->relocs_list, (void*)backref_id(s, data->mod, s->link_ids_relocs));
         }
+        newm->usings.items = (void**)offsetof(jl_module_t, usings._space);
     }
     else {
         newm->usings.items = (void**)tot;
         arraylist_push(&s->relocs_list, (void*)(reloc_offset + offsetof(jl_module_t, usings.items)));
         arraylist_push(&s->relocs_list, (void*)(((uintptr_t)DataRef << RELOC_TAG_OFFSET) + item));
         size_t i;
-        for (i = 0; i < m->usings.len; i++) {
-            write_pointerfield(s, (jl_value_t*)m->usings.items[i]);
-            tot += sizeof(void*);
-        }
-        for (; i < m->usings.max; i++) {
+        for (i = 0; i < module_usings_length(m); i++) {
+            struct _jl_module_using *data = module_usings_getidx(m, i);
+            write_pointerfield(s, (jl_value_t*)data->mod);
+            write_uint(s->s, data->min_world);
+            write_uint(s->s, data->max_world);
+            static_assert(sizeof(struct _jl_module_using) == 3*sizeof(void*), "_jl_module_using mismatch");
+            tot += sizeof(struct _jl_module_using);
+        }
+        for (; i < module_usings_max(m); i++) {
             write_pointer(s->s);
-            tot += sizeof(void*);
+            write_uint(s->s, 0);
+            write_uint(s->s, 0);
+            tot += sizeof(struct _jl_module_using);
         }
     }
     assert(ios_pos(s->s) - reloc_offset == tot);

test/clangsa/MissingRoots.c

@@ -328,7 +328,7 @@ void scopes() {
 jl_module_t *propagation(jl_module_t *m JL_PROPAGATES_ROOT);
 void module_member(jl_module_t *m)
 {
-    for(int i=(int)m->usings.len-1; i >= 0; --i) {
+    for(int i=(int)m->usings.len-1; i >= 0; i -= 3) {
       jl_module_t *imp = propagation(m);
       jl_gc_safepoint();
       look_at_value((jl_value_t*)imp);