enable constant cache on ractors

constant cache `IC` is accessed by non-atomic manner and there are
thread-safety issues, so Ruby 3.0 disables to use const cache on
non-main ractors.

This patch enables it by introducing `imemo_constcache` and allocates
it by every re-fill of const cache like `imemo_callcache`.
[Bug #17510]

Now `IC` only has one entry `IC::entry` and it points to
`iseq_inline_constant_cache_entry`, managed by T_IMEMO object.

`IC` is atomic data structure so `rb_mjit_before_vm_ic_update()` and
`rb_mjit_after_vm_ic_update()` is not needed.

bootstraptest/test_ractor.rb

@@ -967,6 +967,18 @@ assert_equal 'can not access non-shareable objects in constant C::CONST by non-m
   end
 }
 
+# Constant cache should care about non-sharable constants
+assert_equal "can not access non-shareable objects in constant Object::STR by non-main Ractor.", %q{
+  STR = "hello"
+  def str; STR; end
+  s = str() # fill const cache
+  begin
+    Ractor.new{ str() }.take
+  rescue Ractor::RemoteError => e
+    e.cause.message
+  end
+}
+
 # Setting non-shareable objects into constants by other Ractors is not allowed
 assert_equal 'can not set constants with non-shareable objects by non-main Ractors', %q{
   class C

compile.c

@@ -2359,11 +2359,8 @@ iseq_set_sequence(rb_iseq_t *iseq, LINK_ANCHOR *const anchor)
 			    }
 			    break;
 			}
-		      case TS_ISE: /* inline storage entry */
-			/* Treated as an IC, but may contain a markable VALUE */
-                        FL_SET(iseqv, ISEQ_MARKABLE_ISEQ);
-                        /* fall through */
 		      case TS_IC: /* inline cache */
+		      case TS_ISE: /* inline storage entry */
 		      case TS_IVC: /* inline ivar cache */
 			{
 			    unsigned int ic_index = FIX2UINT(operands[j]);
@@ -2375,8 +2372,7 @@ iseq_set_sequence(rb_iseq_t *iseq, LINK_ANCHOR *const anchor)
                                               ic_index, body->is_size);
 			    }
 			    generated_iseq[code_index + 1 + j] = (VALUE)ic;
-
-                            if (type == TS_IVC) FL_SET(iseqv, ISEQ_MARKABLE_ISEQ);
+                            FL_SET(iseqv, ISEQ_MARKABLE_ISEQ);
 			    break;
 			}
                         case TS_CALLDATA:
@@ -9481,14 +9477,13 @@ iseq_build_from_ary_body(rb_iseq_t *iseq, LINK_ANCHOR *const anchor,
 			}
 			break;
 		      case TS_ISE:
-                        FL_SET((VALUE)iseq, ISEQ_MARKABLE_ISEQ);
-                        /* fall through */
 		      case TS_IC:
                       case TS_IVC:  /* inline ivar cache */
 			argv[j] = op;
 			if (NUM2UINT(op) >= iseq->body->is_size) {
 			    iseq->body->is_size = NUM2INT(op) + 1;
 			}
+                        FL_SET((VALUE)iseq, ISEQ_MARKABLE_ISEQ);
 			break;
                       case TS_CALLDATA:
 			argv[j] = iseq_build_callinfo_from_hash(iseq, op);
@@ -10466,14 +10461,13 @@ ibf_load_code(const struct ibf_load *load, rb_iseq_t *iseq, ibf_offset_t bytecod
                     break;
                 }
               case TS_ISE:
-                FL_SET(iseqv, ISEQ_MARKABLE_ISEQ);
-                /* fall through */
               case TS_IC:
               case TS_IVC:
                 {
                     VALUE op = ibf_load_small_value(load, &reading_pos);
                     code[code_index] = (VALUE)&is_entries[op];
                 }
+                FL_SET(iseqv, ISEQ_MARKABLE_ISEQ);
                 break;
               case TS_CALLDATA:
                 {

debug_counter.h

@@ -309,6 +309,7 @@ RB_DEBUG_COUNTER(obj_imemo_memo)
 RB_DEBUG_COUNTER(obj_imemo_parser_strterm)
 RB_DEBUG_COUNTER(obj_imemo_callinfo)
 RB_DEBUG_COUNTER(obj_imemo_callcache)
+RB_DEBUG_COUNTER(obj_imemo_constcache)
 
 /* ar_table */
 RB_DEBUG_COUNTER(artable_hint_hit)

ext/objspace/objspace.c

@@ -650,6 +650,7 @@ count_imemo_objects(int argc, VALUE *argv, VALUE self)
         imemo_type_ids[10] = rb_intern("imemo_parser_strterm");
         imemo_type_ids[11] = rb_intern("imemo_callinfo");
         imemo_type_ids[12] = rb_intern("imemo_callcache");
+        imemo_type_ids[13] = rb_intern("imemo_constcache");
     }
 
     each_object_with_flags(count_imemo_objects_i, (void *)hash);

gc.c

@@ -2398,6 +2398,7 @@ rb_imemo_name(enum imemo_type type)
         IMEMO_NAME(parser_strterm);
         IMEMO_NAME(callinfo);
         IMEMO_NAME(callcache);
+        IMEMO_NAME(constcache);
 #undef IMEMO_NAME
     }
     return "unknown";
@@ -3102,9 +3103,9 @@ obj_free(rb_objspace_t *objspace, VALUE obj)
           case imemo_callcache:
             RB_DEBUG_COUNTER_INC(obj_imemo_callcache);
             break;
-	  default:
-            /* unreachable */
-	    break;
+          case imemo_constcache:
+            RB_DEBUG_COUNTER_INC(obj_imemo_constcache);
+            break;
 	}
 	return 0;
 
@@ -6260,6 +6261,12 @@ gc_mark_imemo(rb_objspace_t *objspace, VALUE obj)
             gc_mark(objspace, (VALUE)vm_cc_cme(cc));
         }
         return;
+      case imemo_constcache:
+        {
+            const struct iseq_inline_constant_cache_entry *ice = (struct iseq_inline_constant_cache_entry *)obj;
+            gc_mark(objspace, ice->value);
+        }
+        return;
 #if VM_CHECK_MODE > 0
       default:
 	VM_UNREACHABLE(gc_mark_imemo);
@@ -8985,6 +8992,12 @@ gc_ref_update_imemo(rb_objspace_t *objspace, VALUE obj)
             }
         }
         break;
+      case imemo_constcache:
+        {
+            const struct iseq_inline_constant_cache_entry *ice = (struct iseq_inline_constant_cache_entry *)obj;
+            UPDATE_IF_MOVED(objspace, ice->value);
+        }
+        break;
       case imemo_parser_strterm:
       case imemo_tmpbuf:
       case imemo_callinfo:

insns.def

@@ -1023,9 +1023,10 @@ opt_getinlinecache
 ()
 (VALUE val)
 {
-    if (vm_ic_hit_p(ic->ic_serial, ic->ic_cref, GET_EP())) {
-	val = ic->value;
-	JUMP(dst);
+    struct iseq_inline_constant_cache_entry *ice = ic->entry;
+    if (ice && vm_ic_hit_p(ice, GET_EP())) {
+        val = ice->value;
+        JUMP(dst);
     }
     else {
 	val = Qnil;
@@ -1039,7 +1040,7 @@ opt_setinlinecache
 (VALUE val)
 (VALUE val)
 {
-    vm_ic_update(ic, val, GET_EP());
+    vm_ic_update(GET_ISEQ(), ic, val, GET_EP());
 }
 
 /* run iseq only once */

internal/imemo.h

@@ -45,6 +45,7 @@ enum imemo_type {
     imemo_parser_strterm = 10,
     imemo_callinfo       = 11,
     imemo_callcache      = 12,
+    imemo_constcache     = 13,
 };
 
 /* CREF (Class REFerence) is defined in method.h */

iseq.c

@@ -182,6 +182,17 @@ iseq_extract_values(VALUE *code, size_t pos, iseq_value_itr_t * func, void *data
               }
             }
             break;
+          case TS_IC:
+            {
+                IC ic = (IC)code[pos + op_no + 1];
+                if (ic->entry) {
+                    VALUE nv = func(data, (VALUE)ic->entry);
+                    if ((VALUE)ic->entry != nv) {
+                        ic->entry = (void *)nv;
+                    }
+                }
+            }
+            break;
           case TS_IVC:
             {
                 IVC ivc = (IVC)code[pos + op_no + 1];

mjit.c

@@ -82,24 +82,6 @@ mjit_gc_exit_hook(void)
     CRITICAL_SECTION_FINISH(4, "mjit_gc_exit_hook");
 }
 
-// Lock setinlinecache
-void
-rb_mjit_before_vm_ic_update(void)
-{
-    if (!mjit_enabled)
-        return;
-    CRITICAL_SECTION_START(3, "before vm_ic_update");
-}
-
-// Unlock setinlinecache
-void
-rb_mjit_after_vm_ic_update(void)
-{
-    if (!mjit_enabled)
-        return;
-    CRITICAL_SECTION_FINISH(3, "after vm_ic_update");
-}
-
 // Deal with ISeq movement from compactor
 void
 mjit_update_references(const rb_iseq_t *iseq)

mjit.h

@@ -83,8 +83,6 @@ RUBY_EXTERN bool mjit_call_p;
 extern void rb_mjit_add_iseq_to_process(const rb_iseq_t *iseq);
 extern VALUE rb_mjit_wait_call(rb_execution_context_t *ec, struct rb_iseq_constant_body *body);
 extern struct rb_mjit_compile_info* rb_mjit_iseq_compile_info(const struct rb_iseq_constant_body *body);
-extern void rb_mjit_before_vm_ic_update(void);
-extern void rb_mjit_after_vm_ic_update(void);
 extern void rb_mjit_recompile_send(const rb_iseq_t *iseq);
 extern void rb_mjit_recompile_ivar(const rb_iseq_t *iseq);
 extern void rb_mjit_recompile_exivar(const rb_iseq_t *iseq);
@@ -187,8 +185,6 @@ void mjit_finish(bool close_handle_p);
 
 # else // USE_MJIT
 
-static inline void rb_mjit_before_vm_ic_update(void){}
-static inline void rb_mjit_after_vm_ic_update(void){}
 static inline struct mjit_cont *mjit_cont_new(rb_execution_context_t *ec){return NULL;}
 static inline void mjit_cont_free(struct mjit_cont *cont){}
 static inline void mjit_gc_start_hook(void){}

test/ruby/test_gc.rb

@@ -92,19 +92,23 @@ class TestGc < Test::Unit::TestCase
     assert_kind_of(Integer, res[:count])
 
     stat, count = {}, {}
-    GC.start
-    GC.stat(stat)
-    ObjectSpace.count_objects(count)
-    # repeat same methods invocation for cache object creation.
-    GC.stat(stat)
-    ObjectSpace.count_objects(count)
+    2.times{ # to ignore const cache imemo creation
+      GC.start
+      GC.stat(stat)
+      ObjectSpace.count_objects(count)
+      # repeat same methods invocation for cache object creation.
+      GC.stat(stat)
+      ObjectSpace.count_objects(count)
+    }
     assert_equal(count[:TOTAL]-count[:FREE], stat[:heap_live_slots])
     assert_equal(count[:FREE], stat[:heap_free_slots])
 
     # measure again without GC.start
-    1000.times{ "a" + "b" }
-    GC.stat(stat)
-    ObjectSpace.count_objects(count)
+    2.times{ # to ignore const cache imemo creation
+      1000.times{ "a" + "b" }
+      GC.stat(stat)
+      ObjectSpace.count_objects(count)
+    }
     assert_equal(count[:FREE], stat[:heap_free_slots])
   end
 

tool/ruby_vm/views/_mjit_compile_getinlinecache.erb

@@ -12,11 +12,13 @@
 % end
 
 % # compiler: Capture IC values, locking getinlinecache
-    rb_mjit_before_vm_ic_update();
-    rb_serial_t ic_serial = ic->ic_serial;
-    const rb_cref_t *ic_cref = ic->ic_cref;
-    VALUE ic_value = ic->value;
-    rb_mjit_after_vm_ic_update();
+    struct iseq_inline_constant_cache_entry *ice = ic->entry;
+    if (ice == NULL) {
+        goto getinlinecache_cancel;
+    }
+    rb_serial_t ic_serial = ice->ic_serial;
+    const rb_cref_t *ic_cref = ice->ic_cref;
+    VALUE ic_value = ice->value;
 
     if (ic_serial && !status->compile_info->disable_const_cache) {
 %       # JIT: Inline everything in IC, and cancel the slow path
@@ -34,3 +36,4 @@
         b->stack_size += <%= insn.call_attribute('sp_inc') %>;
         break;
     }
+    getinlinecache_cancel:;

vm_core.h

@@ -218,10 +218,18 @@ struct rb_control_frame_struct;
 /* iseq data type */
 typedef struct rb_compile_option_struct rb_compile_option_t;
 
-struct iseq_inline_cache_entry {
-    rb_serial_t ic_serial;
-    const rb_cref_t *ic_cref;
-    VALUE value;
+// imemo_constcache
+struct iseq_inline_constant_cache_entry {
+    VALUE flags;
+
+    VALUE value;              // v0
+    const rb_cref_t *ic_cref; // v1
+    rb_serial_t ic_serial;    // v2
+                              // v3
+};
+
+struct iseq_inline_constant_cache {
+    struct iseq_inline_constant_cache_entry *entry;
 };
 
 struct iseq_inline_iv_cache_entry {
@@ -233,7 +241,7 @@ union iseq_inline_storage_entry {
 	struct rb_thread_struct *running_thread;
 	VALUE value;
     } once;
-    struct iseq_inline_cache_entry cache;
+    struct iseq_inline_constant_cache ic_cache;
     struct iseq_inline_iv_cache_entry iv_cache;
 };
 
@@ -1126,7 +1134,7 @@ enum vm_svar_index {
 };
 
 /* inline cache */
-typedef struct iseq_inline_cache_entry *IC;
+typedef struct iseq_inline_constant_cache *IC;
 typedef struct iseq_inline_iv_cache_entry *IVC;
 typedef union iseq_inline_storage_entry *ISE;
 typedef const struct rb_callinfo *CALL_INFO;

vm_insnhelper.c

@@ -4611,26 +4611,34 @@ vm_opt_newarray_min(rb_num_t num, const VALUE *ptr)
 
 #undef id_cmp
 
+#define IMEMO_CONST_CACHE_SHAREABLE IMEMO_FL_USER0
+
 static int
-vm_ic_hit_p(const rb_serial_t ic_serial, const rb_cref_t *ic_cref, const VALUE *reg_ep)
+vm_ic_hit_p(const struct iseq_inline_constant_cache_entry *ice, const VALUE *reg_ep)
 {
-    if (ic_serial == GET_GLOBAL_CONSTANT_STATE() && rb_ractor_main_p()) {
-        return (ic_cref == NULL || // no need to check CREF
-                ic_cref == vm_get_cref(reg_ep));
+    VM_ASSERT(IMEMO_TYPE_P(ice, imemo_constcache));
+    if (ice->ic_serial == GET_GLOBAL_CONSTANT_STATE() &&
+        (FL_TEST_RAW((VALUE)ice, IMEMO_CONST_CACHE_SHAREABLE) || rb_ractor_main_p())) {
+
+        VM_ASSERT(FL_TEST_RAW((VALUE)ice, IMEMO_CONST_CACHE_SHAREABLE) ? rb_ractor_shareable_p(ice->value) : true);
+
+        return (ice->ic_cref == NULL || // no need to check CREF
+                ice->ic_cref == vm_get_cref(reg_ep));
     }
     return FALSE;
 }
 
 static void
-vm_ic_update(IC ic, VALUE val, const VALUE *reg_ep)
+vm_ic_update(const rb_iseq_t *iseq, IC ic, VALUE val, const VALUE *reg_ep)
 {
-    VM_ASSERT(ic->value != Qundef);
-    rb_mjit_before_vm_ic_update();
-    ic->value = val;
-    ic->ic_serial = GET_GLOBAL_CONSTANT_STATE() - ruby_vm_const_missing_count;
-    ic->ic_cref = vm_get_const_key_cref(reg_ep);
-    rb_mjit_after_vm_ic_update();
+
+    struct iseq_inline_constant_cache_entry *ice = (struct iseq_inline_constant_cache_entry *)rb_imemo_new(imemo_constcache, 0, 0, 0, 0);
+    RB_OBJ_WRITE(ice, &ice->value, val);
+    ice->ic_cref = vm_get_const_key_cref(reg_ep);
+    ice->ic_serial = GET_GLOBAL_CONSTANT_STATE() - ruby_vm_const_missing_count;
+    if (rb_ractor_shareable_p(val)) ice->flags |= IMEMO_CONST_CACHE_SHAREABLE;
     ruby_vm_const_missing_count = 0;
+    RB_OBJ_WRITE(iseq, &ic->entry, ice);
 }
 
 static VALUE