Update ci_table

This newly introduced table is a weak de-duplication table, too, like
fstring_table.

gc.c

@@ -14636,11 +14636,15 @@ rb_mmtk_on_overloaded_cme_delete(st_data_t key, st_data_t value, void *arg)
 void
 rb_mmtk_update_frozen_strings_table(void)
 {
+    // The frozen strings table is a deduplicating table for frozen strings.
+    // Used as a HashSet (key always equals value).
+    // Hashed by string content.
+
 #if USE_RUBY_DEBUG_LOG
     size_t size1 = GET_VM()->frozen_strings->num_entries;
 #endif
 
-    rb_mmtk_st_update_fstring_table(GET_VM()->frozen_strings);
+    rb_mmtk_st_update_dedup_table(GET_VM()->frozen_strings);
 
 #if USE_RUBY_DEBUG_LOG
     size_t size2 = GET_VM()->frozen_strings->num_entries;
@@ -14714,6 +14718,26 @@ rb_mmtk_update_overloaded_cme_table(void)
                               NULL);
 }
 
+void
+rb_mmtk_update_ci_table(void)
+{
+    // The CI table is a deduplicating table for callinfo.
+    // Used as a HashSet (key always equals value).
+    // Compared and hashed by callinfo fields.  Two CIs are equal if all fields are equal.
+
+#if USE_RUBY_DEBUG_LOG
+    size_t size1 = GET_VM()->ci_table->num_entries;
+#endif
+
+    rb_mmtk_st_update_dedup_table(GET_VM()->ci_table);
+
+#if USE_RUBY_DEBUG_LOG
+    size_t size2 = GET_VM()->ci_table->num_entries;
+#endif
+
+    RUBY_DEBUG_LOG("CI table size: %zu -> %zu.  Removed: %zu\n",
+        size1, size2, size1-size2);
+}
 /////////////// END: Global table updating ////////////////
 
 // Workaround private functions

include/ruby/st.h

@@ -188,7 +188,7 @@ CONSTFUNC(st_index_t rb_st_hash_start(st_index_t h));
 void rb_hash_bulk_insert_into_st_table(long, const VALUE *, VALUE);
 
 #if USE_MMTK
-void rb_mmtk_st_update_fstring_table(st_table *tab);
+void rb_mmtk_st_update_dedup_table(st_table *tab);
 #endif
 
 RUBY_SYMBOL_EXPORT_END

internal/mmtk.h

@@ -75,6 +75,7 @@ typedef struct MMTk_RubyUpcalls {
     void (*update_obj_id_tables)(void);
     void (*update_global_symbols_table)(void);
     void (*update_overloaded_cme_table)(void);
+    void (*update_ci_table)(void);
     void *(*get_original_givtbl)(MMTk_ObjectReference object);
     void (*move_givtbl)(MMTk_ObjectReference old_objref, MMTk_ObjectReference new_objref);
     size_t (*vm_live_bytes)(void);

mmtk_support.c

@@ -1528,6 +1528,7 @@ void rb_mmtk_update_finalizer_table(void); // Defined in gc.c
 void rb_mmtk_update_obj_id_tables(void); // Defined in gc.c
 void rb_mmtk_update_global_symbols_table(void); // Defined in gc.c
 void rb_mmtk_update_overloaded_cme_table(void); // Defined in gc.c
+void rb_mmtk_update_ci_table(void); // Defined in gc.c
 
 MMTk_RubyUpcalls ruby_upcalls = {
     rb_mmtk_init_gc_worker_thread,
@@ -1549,6 +1550,7 @@ MMTk_RubyUpcalls ruby_upcalls = {
     rb_mmtk_update_obj_id_tables,
     rb_mmtk_update_global_symbols_table,
     rb_mmtk_update_overloaded_cme_table,
+    rb_mmtk_update_ci_table,
     rb_mmtk_get_original_givtbl,
     rb_mmtk_move_givtbl,
     rb_mmtk_vm_live_bytes,

st.c

@@ -2340,8 +2340,19 @@ rb_st_compact_table(st_table *tab)
 }
 
 #if USE_MMTK
+// Update a deduplication table.
+//
+// This function forwards reachable entries and removes dead entries of deduplication tables.
+// The frozen string table and the CI table are such tables.  We assume keys are always equal to
+// their respective values.
+//
+// This function is intended to be faster than existing updating functions based on st_foreach.
+// This function never attempts to compare elements by value or by hash (which is unsafe during GC
+// because some value-comparing or hash-computing operations may depend on weak tables or fields
+// which are not yet updated), and never touches entries that hold non-reference values
+// (SPECIAL_CONST_P).
 void
-rb_mmtk_st_update_fstring_table(st_table *tab)
+rb_mmtk_st_update_dedup_table(st_table *tab)
 {
     for (st_index_t ind = tab->entries_start; ind < tab->entries_bound; ind++) {
         if (DELETED_ENTRY_P(&tab->entries[ind])) {
@@ -2373,6 +2384,10 @@ rb_mmtk_st_update_fstring_table(st_table *tab)
         }
     }
 
+    if (tab->bins == NULL) {
+        return;
+    }
+
     st_index_t num_bins = get_bins_num(tab);
     unsigned int const size_ind = get_size_ind(tab);