Make maps in monomorphic IC stubs weak.

src/ic.cc

Index: src/ic.cc
diff --git a/src/ic.cc b/src/ic.cc
index 36c7e5a30a9f1a1795c54faa2c639b8f6b80f263..6ffe192de42bdca98627984a8cf804799b48c0e8 100644
--- a/src/ic.cc
+++ b/src/ic.cc
@@ -435,6 +435,86 @@ void IC::PostPatching(Address address, Code* target, Code* old_target) {
 }
 
 
+void IC::RegisterWeakMapDependency(Handle<Code> stub) {
+  if (FLAG_collect_maps && FLAG_weak_embedded_maps_in_ic) {
+    if (stub->is_weak_stub()) {
+      MapHandleList maps;
+      int mode_mask = RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT);
+      for (RelocIterator it(*stub, mode_mask); !it.done(); it.next()) {
+        if (it.rinfo()->target_object()->IsMap()) {
+          Handle<Map> map(Map::cast(it.rinfo()->target_object()));
+          if (stub->IsWeakObject(*map)) {
+            maps.Add(map);
+          }
+        }
+      }
+#ifdef VERIFY_HEAP
+      // This disables verification of weak embedded maps after full GC.
+      // AddDependentCode can cause a GC, which would observe the state where
+      // this code is not yet in the depended code lists of the embedded maps.
+      NoWeakObjectVerificationScope disable_verification_of_objects;
+#endif
+      for (int i = 0; i < maps.length(); i++) {
+        maps.at(i)->AddDependentCode(DependentCode::kWeaklyEmbeddedGroup, stub);

[Toon Verwaest, 2014/04/03 15:18:36]

This means that all maps have 2 pointers to monomorphic ICs, once in the code
cache, and once in the dependency list. Can we unify?

Can we avoid clearing the code cache now that those pointers are weak?

[ulan, 2014/04/03 15:40:26]

As discussed offline, we can probably do that if linear search time is ok.

+      }
+    }
+  }
+}
+
+
+Code* IC::MissBuiltin(Isolate* isolate, Code* stub) {
+  switch (stub->kind()) {
+    case Code::LOAD_IC:
+    case Code::STORE_IC:
+    case Code::KEYED_LOAD_IC:
+    case Code::KEYED_STORE_IC: {
+      return isolate->builtins()->builtin(
+                BaseLoadStoreStubCompiler::MissBuiltin(stub->kind()));

[Toon Verwaest, 2014/04/03 15:18:36]

4-space indent

[ulan, 2014/04/03 15:40:26]

Done.

+    }
+    case Code::COMPARE_NIL_IC: {
+      ExtraICState state = stub->extra_ic_state();
+      CompareNilICStub stub(state, HydrogenCodeStub::UNINITIALIZED);
+      stub.ClearState();
+      Code* code = NULL;
+      CHECK(stub.FindCodeInCache(&code, isolate));
+      return code;
+    }
+    default:
+      UNREACHABLE();
+  }
+  return NULL;
+}
+
+
+void IC::InvalidateMapsAndHandlers(Code* stub) {
+  ASSERT(stub->is_weak_stub());
+  Isolate* isolate = stub->GetIsolate();
+  Heap* heap = isolate->heap();
+  Code* miss = MissBuiltin(isolate, stub);
+  Object* undefined = heap->undefined_value();
+  int mode_mask = RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT) |
+                  RelocInfo::ModeMask(RelocInfo::CODE_TARGET);
+  // Set every map to undefined and every code target to the miss builtin.
+  for (RelocIterator it(stub, mode_mask); !it.done(); it.next()) {
+    RelocInfo::Mode mode = it.rinfo()->rmode();
+    if (mode == RelocInfo::EMBEDDED_OBJECT &&
+        it.rinfo()->target_object()->IsMap()) {
+      it.rinfo()->set_target_object(undefined, SKIP_WRITE_BARRIER);
+    } else if (mode == RelocInfo::CODE_TARGET) {
+      Address address = it.rinfo()->pc();
+      Assembler::set_target_address_at(
+          address, stub, miss->instruction_start());
+      if (heap->gc_state() == Heap::MARK_COMPACT) {
+        heap->mark_compact_collector()->RecordCodeTargetPatch(address, miss);
+      } else {
+        heap->incremental_marking()->RecordCodeTargetPatch(address, miss);
+      }
+    }
+  }
+  CPU::FlushICache(stub->instruction_start(), stub->instruction_size());
+}
+
+
 void IC::Clear(Isolate* isolate, Address address,
     ConstantPoolArray* constant_pool) {
   Code* target = GetTargetAtAddress(address, constant_pool);