vector-based ICs did not update type feedback counts correctly.

src/x64/code-stubs-x64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 2091 matching lines @@
   __ bind(&extra_checks_or_miss);
   Label miss;
 
   __ movp(rcx, FieldOperand(rbx, rdx, times_pointer_size,
                             FixedArray::kHeaderSize));
   __ Cmp(rcx, TypeFeedbackVector::MegamorphicSentinel(isolate));
   __ j(equal, &slow_start);
   __ Cmp(rcx, TypeFeedbackVector::UninitializedSentinel(isolate));
   __ j(equal, &miss);
 
-  if (!FLAG_trace_ic) {
-    // We are going megamorphic. If the feedback is a JSFunction, it is fine
-    // to handle it here. More complex cases are dealt with in the runtime.
-    __ AssertNotSmi(rcx);
-    __ CmpObjectType(rcx, JS_FUNCTION_TYPE, rcx);
-    __ j(not_equal, &miss);
-    __ Move(FieldOperand(rbx, rdx, times_pointer_size, FixedArray::kHeaderSize),
-            TypeFeedbackVector::MegamorphicSentinel(isolate));
-    __ jmp(&slow_start);
-  }
-
   // We are here because tracing is on or we are going monomorphic.
   __ bind(&miss);
   GenerateMiss(masm);
 
   // the slow case
   __ bind(&slow_start);
   // Check that function is not a smi.
   __ JumpIfSmi(rdi, &non_function);
   // Check that function is a JSFunction.
   __ CmpObjectType(rdi, JS_FUNCTION_TYPE, rcx);
@@ skipping 2536 matching lines @@
                               return_value_operand,
                               NULL);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64