Reland and fix r21225 and r21226

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 029e80d9bb96e075f39c14c7d9d93566fc5d4321..00cd62e818346c16b60fcddb03c6fef5d1ca200f 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -4033,12 +4033,12 @@ bool Map::has_non_instance_prototype() {
 
 
 void Map::set_function_with_prototype(bool value) {
-  set_bit_field3(FunctionWithPrototype::update(bit_field3(), value));
+  set_bit_field(FunctionWithPrototype::update(bit_field(), value));
 }
 
 
 bool Map::function_with_prototype() {
-  return FunctionWithPrototype::decode(bit_field3());
+  return FunctionWithPrototype::decode(bit_field());
 }
 
 
@@ -4753,16 +4753,15 @@ ACCESSORS(Map, instance_descriptors, DescriptorArray, kDescriptorsOffset)
 
 
 void Map::set_bit_field3(uint32_t bits) {
-  // Ensure the upper 2 bits have the same value by sign extending it. This is
-  // necessary to be able to use the 31st bit.
-  int value = bits << 1;
-  WRITE_FIELD(this, kBitField3Offset, Smi::FromInt(value >> 1));
+  if (kInt32Size != kPointerSize) {
+    WRITE_UINT32_FIELD(this, kBitField3Offset + kInt32Size, 0);
+  }
+  WRITE_UINT32_FIELD(this, kBitField3Offset, bits);
 }
 
 
 uint32_t Map::bit_field3() {
-  Object* value = READ_FIELD(this, kBitField3Offset);
-  return Smi::cast(value)->value();
+  return READ_UINT32_FIELD(this, kBitField3Offset);
 }