De-dup identical callinfo objects

Previously every call to vm_ci_new (when the CI was not packable) would
result in a different callinfo being returned this meant that every
kwarg callsite had its own CI.

When calling, different CIs result in different CCs. These CIs and CCs
both end up persisted on the T_CLASS inside cc_tbl. So in an eval loop
this resulted in a memory leak of both types of object. This also likely
resulted in extra memory used, and extra time searching, in non-eval
cases.

For simplicity in this commit I always allocate a CI object inside
rb_vm_ci_lookup, but ideally we would lazily allocate it only when
needed. I hope to do that as a follow up in the future.

gc.c

@@ -3745,6 +3745,7 @@ obj_free(rb_objspace_t *objspace, VALUE obj)
           case imemo_callinfo:
             {
                 const struct rb_callinfo * ci = ((const struct rb_callinfo *)obj);
+                rb_vm_ci_free(ci);
                 if (ci->kwarg) {
                     ((struct rb_callinfo_kwarg *)ci->kwarg)->references--;
                     if (ci->kwarg->references == 0) xfree((void *)ci->kwarg);

internal/class.h

@@ -44,7 +44,7 @@ struct rb_classext_struct {
     VALUE *iv_ptr;
     struct rb_id_table *const_tbl;
     struct rb_id_table *callable_m_tbl;
-    struct rb_id_table *cc_tbl; /* ID -> [[ci, cc1], cc2, ...] */
+    struct rb_id_table *cc_tbl; /* ID -> [[ci1, cc1], [ci2, cc2] ...] */
     struct rb_id_table *cvc_tbl;
     size_t superclass_depth;
     VALUE *superclasses;

vm.c

@@ -2873,6 +2873,7 @@ rb_vm_update_references(void *ptr)
     if (ptr) {
         rb_vm_t *vm = ptr;
 
+        rb_gc_update_tbl_refs(vm->ci_table);
         rb_gc_update_tbl_refs(vm->frozen_strings);
         vm->mark_object_ary = rb_gc_location(vm->mark_object_ary);
         vm->load_path = rb_gc_location(vm->load_path);
@@ -3119,6 +3120,10 @@ ruby_vm_destruct(rb_vm_t *vm)
             st_free_table(vm->loading_table);
             vm->loading_table = 0;
         }
+        if (vm->ci_table) {
+            st_free_table(vm->ci_table);
+            vm->ci_table = NULL;
+        }
         if (vm->frozen_strings) {
             st_free_table(vm->frozen_strings);
             vm->frozen_strings = 0;
@@ -3209,6 +3214,7 @@ vm_memsize(const void *ptr)
         rb_vm_memsize_workqueue(&vm->workqueue) +
         rb_st_memsize(vm->defined_module_hash) +
         vm_memsize_at_exit_list(vm->at_exit) +
+        rb_st_memsize(vm->ci_table) +
         rb_st_memsize(vm->frozen_strings) +
         vm_memsize_builtin_function_table(vm->builtin_function_table) +
         rb_id_table_memsize(vm->negative_cme_table) +
@@ -4303,6 +4309,7 @@ Init_vm_objects(void)
     /* initialize mark object array, hash */
     vm->mark_object_ary = rb_ary_hidden_new(128);
     vm->loading_table = st_init_strtable();
+    vm->ci_table = st_init_table(&vm_ci_hashtype);
     vm->frozen_strings = st_init_table_with_size(&rb_fstring_hash_type, 10000);
 }
 

vm_callinfo.h

@@ -199,12 +199,13 @@ vm_ci_dump(const struct rb_callinfo *ci)
       (((VALUE)(argc)) << CI_EMBED_ARGC_SHFT) |  \
       RUBY_FIXNUM_FLAG))
 
+// vm_method.c
+const struct rb_callinfo *rb_vm_ci_lookup(ID mid, unsigned int flag, unsigned int argc, const struct rb_callinfo_kwarg *kwarg);
+void rb_vm_ci_free(const struct rb_callinfo *);
+
 static inline const struct rb_callinfo *
 vm_ci_new_(ID mid, unsigned int flag, unsigned int argc, const struct rb_callinfo_kwarg *kwarg, const char *file, int line)
 {
-    if (kwarg) {
-        ((struct rb_callinfo_kwarg *)kwarg)->references++;
-    }
     if (USE_EMBED_CI && VM_CI_EMBEDDABLE_P(mid, flag, argc, kwarg)) {
         RB_DEBUG_COUNTER_INC(ci_packed);
         return vm_ci_new_id(mid, flag, argc, kwarg);
@@ -213,13 +214,7 @@ vm_ci_new_(ID mid, unsigned int flag, unsigned int argc, const struct rb_callinf
     const bool debug = 0;
     if (debug) ruby_debug_printf("%s:%d ", file, line);
 
-    // TODO: dedup
-    const struct rb_callinfo *ci = (const struct rb_callinfo *)
-      rb_imemo_new(imemo_callinfo,
-                   (VALUE)mid,
-                   (VALUE)flag,
-                   (VALUE)argc,
-                   (VALUE)kwarg);
+    const struct rb_callinfo *ci = rb_vm_ci_lookup(mid, flag, argc, kwarg);
     if (debug) rp(ci);
     if (kwarg) {
         RB_DEBUG_COUNTER_INC(ci_kw);

vm_core.h

@@ -752,6 +752,7 @@ typedef struct rb_vm_struct {
 
     const struct rb_builtin_function *builtin_function_table;
 
+    st_table *ci_table;
     struct rb_id_table *negative_cme_table;
     st_table *overloaded_cme_table; // cme -> overloaded_cme
 

vm_method.c

@@ -333,6 +333,120 @@ invalidate_all_refinement_cc(void *vstart, void *vend, size_t stride, void *data
     return 0; // continue to iteration
 }
 
+static st_index_t
+vm_ci_hash(VALUE v)
+{
+    const struct rb_callinfo *ci = (const struct rb_callinfo *)v;
+    st_index_t h;
+    h = rb_hash_start(ci->mid);
+    h = rb_hash_uint(h, ci->flag);
+    h = rb_hash_uint(h, ci->argc);
+    if (ci->kwarg) {
+        for (int i = 0; i < ci->kwarg->keyword_len; i++) {
+            h = rb_hash_uint(h, ci->kwarg->keywords[i]);
+        }
+    }
+    return h;
+}
+
+static int
+vm_ci_hash_cmp(VALUE v1, VALUE v2)
+{
+    const struct rb_callinfo *ci1 = (const struct rb_callinfo *)v1;
+    const struct rb_callinfo *ci2 = (const struct rb_callinfo *)v2;
+    if (ci1->mid != ci2->mid) return 1;
+    if (ci1->flag != ci2->flag) return 1;
+    if (ci1->argc != ci2->argc) return 1;
+    if (ci1->kwarg != NULL) {
+        VM_ASSERT(ci2->kwarg != NULL); // implied by matching flags
+
+        if (ci1->kwarg->keyword_len != ci2->kwarg->keyword_len)
+            return 1;
+
+        for (int i = 0; i < ci1->kwarg->keyword_len; i++) {
+            if (ci1->kwarg->keywords[i] != ci2->kwarg->keywords[i]) {
+                return 1;
+            }
+        }
+    } else {
+        VM_ASSERT(ci2->kwarg == NULL); // implied by matching flags
+    }
+    return 0;
+}
+
+static const struct st_hash_type vm_ci_hashtype = {
+    vm_ci_hash_cmp,
+    vm_ci_hash
+};
+
+static int
+ci_lookup_i(st_data_t *key, st_data_t *value, st_data_t data, int existing)
+{
+    const struct rb_callinfo *ci = (const struct rb_callinfo *)*key;
+    st_data_t *ret = (st_data_t *)data;
+
+    if (existing) {
+        if (rb_objspace_garbage_object_p((VALUE)ci)) {
+            *ret = (st_data_t)NULL;
+            return ST_DELETE;
+        } else {
+            *ret = *key;
+            return ST_STOP;
+        }
+    }
+    else {
+        *key = *value = *ret = (st_data_t)ci;
+        return ST_CONTINUE;
+    }
+}
+
+const struct rb_callinfo *
+rb_vm_ci_lookup(ID mid, unsigned int flag, unsigned int argc, const struct rb_callinfo_kwarg *kwarg)
+{
+    rb_vm_t *vm = GET_VM();
+    const struct rb_callinfo *ci = NULL;
+
+    if (kwarg) {
+        ((struct rb_callinfo_kwarg *)kwarg)->references++;
+    }
+    const struct rb_callinfo *new_ci = (const struct rb_callinfo *)
+        rb_imemo_new(
+                imemo_callinfo,
+                (VALUE)mid,
+                (VALUE)flag,
+                (VALUE)argc,
+                (VALUE)kwarg);
+
+    RB_VM_LOCK_ENTER();
+    {
+        st_table *ci_table = vm->ci_table;
+        VM_ASSERT(ci_table);
+
+        do {
+            st_update(ci_table, (st_data_t)new_ci, ci_lookup_i, (st_data_t)&ci);
+        } while (ci == NULL);
+    }
+    RB_VM_LOCK_LEAVE();
+
+    VM_ASSERT(ci);
+    VM_ASSERT(vm_ci_markable(ci));
+
+    return ci;
+}
+
+void
+rb_vm_ci_free(const struct rb_callinfo *ci)
+{
+    rb_vm_t *vm = GET_VM();
+
+    RB_VM_LOCK_ENTER();
+    {
+        st_data_t key = (st_data_t)ci;
+        st_delete(vm->ci_table, &key, NULL);
+    }
+    RB_VM_LOCK_LEAVE();
+}
+
 void
 rb_clear_all_refinement_method_cache(void)
 {