[Interpreter] Collect feedback about Oddballs in Subtract Stub.

src/globals.h

 // Copyright 2012 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.
 
 #ifndef V8_GLOBALS_H_
 #define V8_GLOBALS_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 1190 matching lines @@
 inline uint32_t ObjectHash(Address address) {
   // All objects are at least pointer aligned, so we can remove the trailing
   // zeros.
   return static_cast<uint32_t>(bit_cast<uintptr_t>(address) >>
                                kPointerSizeLog2);
 }
 
 // Type feedback is encoded in such a way that, we can combine the feedback
 // at different points by performing an 'OR' operation. Type feedback moves
 // to a more generic type when we combine feedback.
-// kSignedSmall -> kNumber  -> kAny
-//                 kString  -> kAny
+// kSignedSmall -> kNumber  -> kNumberOrOddball -> kAny
+//                             kString          -> kAny
+// TODO(mythria): Remove kNumber type when crankshaft can handle Oddballs
+// similar to Numbers. We don't need kNumber feedback for Turbofan. Extra
+// information about Number might reduce few instructions but causes more
+// deopts. We collect Number only because crankshaft does not handle all
+// cases of oddballs.
 class BinaryOperationFeedback {
  public:
   enum {
     kNone = 0x0,
     kSignedSmall = 0x1,
     kNumber = 0x3,
-    kString = 0x4,
+    kNumberOrOddball = 0x7,
+    kString = 0x8,
     kAny = 0xF

[Leszek Swirski, 2016/10/10 11:57:22]

Should kAny change to 0x1F, so that it has a value beyond kNumberOrOddball |
kString (i.e. so that it has a bit set for non-number, non-strings)?

[mythria, 2016/10/10 13:26:00]

Good point. Done.

   };
 };
 
 // TODO(epertoso): consider unifying this with BinaryOperationFeedback.
 class CompareOperationFeedback {
  public:
   enum { kNone = 0x00, kSignedSmall = 0x01, kNumber = 0x3, kAny = 0x7 };
 };
 
 // Describes how exactly a frame has been dropped from stack.
@@ skipping 30 matching lines @@
   UNREACHABLE();
   return os;
 }
 
 }  // namespace internal
 }  // namespace v8
 
 namespace i = v8::internal;
 
 #endif  // V8_GLOBALS_H_