Move Maps' back pointers from "transitions" to "constructor" field

src/ia32/macro-assembler-ia32.cc

 // 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.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_IA32
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
@@ skipping 1901 matching lines @@
   Label ok;
   test(result, result);
   j(not_zero, &ok);
   mov(scratch, op1);
   or_(scratch, op2);
   j(sign, then_label);
   bind(&ok);
 }
 
 
+void MacroAssembler::GetMapConstructor(Register result, Register map,
+                                       Register temp) {
+  Label done, loop;
+  mov(result, FieldOperand(map, Map::kConstructorOrBackPointerOffset));
+  bind(&loop);
+  JumpIfSmi(result, &done);
+  CmpObjectType(result, MAP_TYPE, temp);
+  j(not_equal, &done);
+  mov(result, FieldOperand(result, Map::kConstructorOrBackPointerOffset));
+  jmp(&loop);
+  bind(&done);
+}
+
+
 void MacroAssembler::TryGetFunctionPrototype(Register function,
                                              Register result,
                                              Register scratch,
                                              Label* miss,
                                              bool miss_on_bound_function) {
   Label non_instance;
   if (miss_on_bound_function) {
     // Check that the receiver isn't a smi.
     JumpIfSmi(function, miss);
 
@@ skipping 31 matching lines @@
 
   // Get the prototype from the initial map.
   mov(result, FieldOperand(result, Map::kPrototypeOffset));
 
   if (miss_on_bound_function) {
     jmp(&done);
 
     // Non-instance prototype: Fetch prototype from constructor field
     // in initial map.
     bind(&non_instance);
-    mov(result, FieldOperand(result, Map::kConstructorOffset));
+    GetMapConstructor(result, result, scratch);
   }
 
   // All done.
   bind(&done);
 }
 
 
 void MacroAssembler::CallStub(CodeStub* stub, TypeFeedbackId ast_id) {
   DCHECK(AllowThisStubCall(stub));  // Calls are not allowed in some stubs.
   call(stub->GetCode(), RelocInfo::CODE_TARGET, ast_id);
@@ skipping 1299 matching lines @@
   if (mag.shift > 0) sar(edx, mag.shift);
   mov(eax, dividend);
   shr(eax, 31);
   add(edx, eax);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32