Make Snapshot::EnsureBuiltinIsDeserialized more robust.

Also unskip test that has already been fixed in f1b1ec70.

R=jgruber@chromium.org

Bug: v8:178
Change-Id: I9cd2156ef41146b0dd58a974088726f5cbda8058
Reviewed-on: https://chromium-review.googlesource.com/970243Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52050}

src/runtime/runtime-internal.cc

@@ -458,6 +458,19 @@ RUNTIME_FUNCTION(Runtime_DeserializeLazy) {
   DCHECK(FLAG_lazy_deserialization);
 
   Handle<SharedFunctionInfo> shared(function->shared(), isolate);
+
+#ifdef DEBUG
+  int builtin_id = shared->lazy_deserialization_builtin_id();
+  // At this point, the builtins table should definitely have DeserializeLazy
+  // set at the position of the target builtin.
+  CHECK_EQ(Builtins::kDeserializeLazy,
+           isolate->builtins()->builtin(builtin_id)->builtin_index());
+  // The DeserializeLazy builtin tail-calls the deserialized builtin. This only
+  // works with JS-linkage.
+  CHECK(Builtins::IsLazy(builtin_id));
+  CHECK_EQ(Builtins::TFJ, Builtins::KindOf(builtin_id));
+#endif  // DEBUG
+
   Snapshot::EnsureBuiltinIsDeserialized(isolate, shared);
 
   function->set_code(shared->code());

src/snapshot/snapshot-common.cc

@@ -147,22 +147,19 @@ void Snapshot::EnsureBuiltinIsDeserialized(Isolate* isolate,
 
   int builtin_id = shared->lazy_deserialization_builtin_id();
 
-  // At this point, the builtins table should definitely have DeserializeLazy
-  // set at the position of the target builtin. Also, we should never lazily
-  // deserialize DeserializeLazy.
-
+  // We should never lazily deserialize DeserializeLazy.
   DCHECK_NE(Builtins::kDeserializeLazy, builtin_id);
-  DCHECK_EQ(Builtins::kDeserializeLazy,
-            isolate->builtins()->builtin(builtin_id)->builtin_index());
 
-  // The DeserializeLazy builtin tail-calls the deserialized builtin. This only
-  // works with JS-linkage.
-  DCHECK(Builtins::IsLazy(builtin_id));
-  DCHECK_EQ(Builtins::TFJ, Builtins::KindOf(builtin_id));
+  // Look up code from builtins list.
+  Code* code = isolate->builtins()->builtin(builtin_id);
 
-  Code* code = Snapshot::DeserializeBuiltin(isolate, builtin_id);
+  // Deserialize if builtin is not on the list.
+  if (code->builtin_index() != builtin_id) {
+    DCHECK_EQ(code->builtin_index(), Builtins::kDeserializeLazy);
+    code = Snapshot::DeserializeBuiltin(isolate, builtin_id);
     DCHECK_EQ(builtin_id, code->builtin_index());
     DCHECK_EQ(code, isolate->builtins()->builtin(builtin_id));
+  }
   shared->set_code(code);
 }
 

test/cctest/cctest.status

@@ -136,7 +136,6 @@
 
   # https://crbug.com/v8/7543
   'test-debug/BreakPointJSBuiltin': [SKIP],
-  'test-debug/BreakPointBuiltin': [SKIP],
 }],  # ALWAYS
 
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