Revert "Continued fix for 351257. Reusing the feedback vector is too complex."

src/x64/full-codegen-x64.cc

Index: src/x64/full-codegen-x64.cc
diff --git a/src/x64/full-codegen-x64.cc b/src/x64/full-codegen-x64.cc
index b146809a24e19a745a5d3810b97ad4bcff8412d9..b40ee92977a2559281f8ac836222cb7f9cdef770 100644
--- a/src/x64/full-codegen-x64.cc
+++ b/src/x64/full-codegen-x64.cc
@@ -119,6 +119,8 @@ void FullCodeGenerator::Generate() {
   handler_table_ =
       isolate()->factory()->NewFixedArray(function()->handler_count(), TENURED);
 
+  InitializeFeedbackVector();
+
   profiling_counter_ = isolate()->factory()->NewCell(
       Handle<Smi>(Smi::FromInt(FLAG_interrupt_budget), isolate()));
   SetFunctionPosition(function());
@@ -1125,10 +1127,15 @@ void FullCodeGenerator::VisitForInStatement(ForInStatement* stmt) {
   Label non_proxy;
   __ bind(&fixed_array);
 
+  Handle<Object> feedback = Handle<Object>(
+      Smi::FromInt(TypeFeedbackInfo::kForInFastCaseMarker),
+      isolate());
+  StoreFeedbackVectorSlot(slot, feedback);
+
   // No need for a write barrier, we are storing a Smi in the feedback vector.
   __ Move(rbx, FeedbackVector());
   __ Move(FieldOperand(rbx, FixedArray::OffsetOfElementAt(slot)),
-          TypeFeedbackInfo::MegamorphicSentinel(isolate()));
+          Smi::FromInt(TypeFeedbackInfo::kForInSlowCaseMarker));
   __ Move(rbx, Smi::FromInt(1));  // Smi indicates slow check
   __ movp(rcx, Operand(rsp, 0 * kPointerSize));  // Get enumerated object
   STATIC_ASSERT(FIRST_JS_PROXY_TYPE == FIRST_SPEC_OBJECT_TYPE);
@@ -2641,6 +2648,9 @@ void FullCodeGenerator::EmitCallWithStub(Call* expr) {
   // Record source position for debugger.
   SetSourcePosition(expr->position());
 
+  Handle<Object> uninitialized =
+      TypeFeedbackInfo::UninitializedSentinel(isolate());
+  StoreFeedbackVectorSlot(expr->CallFeedbackSlot(), uninitialized);
   __ Move(rbx, FeedbackVector());
   __ Move(rdx, Smi::FromInt(expr->CallFeedbackSlot()));
 
@@ -2818,6 +2828,9 @@ void FullCodeGenerator::VisitCallNew(CallNew* expr) {
   __ movp(rdi, Operand(rsp, arg_count * kPointerSize));
 
   // Record call targets in unoptimized code, but not in the snapshot.
+  Handle<Object> uninitialized =
+      TypeFeedbackInfo::UninitializedSentinel(isolate());
+  StoreFeedbackVectorSlot(expr->CallNewFeedbackSlot(), uninitialized);
   __ Move(rbx, FeedbackVector());
   __ Move(rdx, Smi::FromInt(expr->CallNewFeedbackSlot()));