[GC] Fix code flushing to use bytecode if it exists.

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index bad3495bbe4befe1c583ff680b66bc8a845ff213..7177f88cc6c78b04e33add6ea9e36e58808e0f79 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -904,6 +904,8 @@ void MarkCompactCollector::Finish() {
 
 void CodeFlusher::ProcessJSFunctionCandidates() {
   Code* lazy_compile = isolate_->builtins()->builtin(Builtins::kCompileLazy);
+  Code* interpreter_entry_trampoline =
+      isolate_->builtins()->builtin(Builtins::kInterpreterEntryTrampoline);
   Object* undefined = isolate_->heap()->undefined_value();
 
   JSFunction* candidate = jsfunction_candidates_head_;
@@ -926,8 +928,13 @@ void CodeFlusher::ProcessJSFunctionCandidates() {
       if (!shared->OptimizedCodeMapIsCleared()) {
         shared->ClearOptimizedCodeMap();
       }
-      shared->set_code(lazy_compile);
-      candidate->set_code(lazy_compile);
+      if (shared->HasBytecodeArray()) {

[Michael Starzinger, 2016/11/24 12:14:45]

I have the feeling we will have the same problem in {Runtime_InstantiateAsmJs}
as well. We also unconditionally reset the shared code to the CompileLazy
builtin there. Would it be possible to instead make compiler.cc resilient to
ensure we don't accidentally regenerate bytecode even if the CompileLazy stub is
installed as shared code?

+        shared->set_code(interpreter_entry_trampoline);
+        candidate->set_code(interpreter_entry_trampoline);
+      } else {
+        shared->set_code(lazy_compile);
+        candidate->set_code(lazy_compile);
+      }
     } else {
       DCHECK(Marking::IsBlack(code_mark));
       candidate->set_code(code);
@@ -954,7 +961,8 @@ void CodeFlusher::ProcessJSFunctionCandidates() {
 
 void CodeFlusher::ProcessSharedFunctionInfoCandidates() {
   Code* lazy_compile = isolate_->builtins()->builtin(Builtins::kCompileLazy);
-
+  Code* interpreter_entry_trampoline =
+      isolate_->builtins()->builtin(Builtins::kInterpreterEntryTrampoline);
   SharedFunctionInfo* candidate = shared_function_info_candidates_head_;
   SharedFunctionInfo* next_candidate;
   while (candidate != NULL) {
@@ -973,7 +981,11 @@ void CodeFlusher::ProcessSharedFunctionInfoCandidates() {
       if (!candidate->OptimizedCodeMapIsCleared()) {
         candidate->ClearOptimizedCodeMap();
       }
-      candidate->set_code(lazy_compile);
+      if (candidate->HasBytecodeArray()) {
+        candidate->set_code(interpreter_entry_trampoline);
+      } else {
+        candidate->set_code(lazy_compile);
+      }
     }
 
     Object** code_slot =