Use the previous context link when checking context extension objects.

src/mips/full-codegen-mips.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1110 matching lines @@
 
   Scope* s = scope();
   while (s != NULL) {
     if (s->num_heap_slots() > 0) {
       if (s->calls_eval()) {
         // Check that extension is NULL.
         __ lw(temp, ContextOperand(current, Context::EXTENSION_INDEX));
         __ Branch(slow, ne, temp, Operand(zero_reg));
       }
       // Load next context in chain.
-      __ lw(next, ContextOperand(current, Context::CLOSURE_INDEX));
-      __ lw(next, FieldMemOperand(next, JSFunction::kContextOffset));
+      __ lw(next, ContextOperand(current, Context::PREVIOUS_INDEX));
       // Walk the rest of the chain without clobbering cp.
       current = next;
     }
     // If no outer scope calls eval, we do not need to check more
     // context extensions.
     if (!s->outer_scope_calls_eval() || s->is_eval_scope()) break;
     s = s->outer_scope();
   }
 
   if (s->is_eval_scope()) {
     Label loop, fast;
     if (!current.is(next)) {
       __ Move(next, current);
     }
     __ bind(&loop);
     // Terminate at global context.
     __ lw(temp, FieldMemOperand(next, HeapObject::kMapOffset));
     __ LoadRoot(t0, Heap::kGlobalContextMapRootIndex);
     __ Branch(&fast, eq, temp, Operand(t0));
     // Check that extension is NULL.
     __ lw(temp, ContextOperand(next, Context::EXTENSION_INDEX));
     __ Branch(slow, ne, temp, Operand(zero_reg));
     // Load next context in chain.
-    __ lw(next, ContextOperand(next, Context::CLOSURE_INDEX));
-    __ lw(next, FieldMemOperand(next, JSFunction::kContextOffset));
+    __ lw(next, ContextOperand(next, Context::PREVIOUS_INDEX));
     __ Branch(&loop);
     __ bind(&fast);
   }
 
   __ lw(a0, GlobalObjectOperand());
   __ li(a2, Operand(slot->var()->name()));
   RelocInfo::Mode mode = (typeof_state == INSIDE_TYPEOF)
       ? RelocInfo::CODE_TARGET
       : RelocInfo::CODE_TARGET_CONTEXT;
   Handle<Code> ic = isolate()->builtins()->LoadIC_Initialize();
   EmitCallIC(ic, mode, AstNode::kNoNumber);
 }
 
 
 MemOperand FullCodeGenerator::ContextSlotOperandCheckExtensions(
     Slot* slot,
     Label* slow) {
   ASSERT(slot->type() == Slot::CONTEXT);
   Register context = cp;
   Register next = a3;
   Register temp = t0;
 
   for (Scope* s = scope(); s != slot->var()->scope(); s = s->outer_scope()) {
     if (s->num_heap_slots() > 0) {
       if (s->calls_eval()) {
         // Check that extension is NULL.
         __ lw(temp, ContextOperand(context, Context::EXTENSION_INDEX));
         __ Branch(slow, ne, temp, Operand(zero_reg));
       }
-      __ lw(next, ContextOperand(context, Context::CLOSURE_INDEX));
-      __ lw(next, FieldMemOperand(next, JSFunction::kContextOffset));
+      __ lw(next, ContextOperand(context, Context::PREVIOUS_INDEX));
       // Walk the rest of the chain without clobbering cp.
       context = next;
     }
   }
   // Check that last extension is NULL.
   __ lw(temp, ContextOperand(context, Context::EXTENSION_INDEX));
   __ Branch(slow, ne, temp, Operand(zero_reg));
 
   // This function is used only for loads, not stores, so it's safe to
   // return an cp-based operand (the write barrier cannot be allowed to
@@ skipping 3181 matching lines @@
   __ Addu(at, a1, Operand(masm_->CodeObject()));
   __ Jump(at);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS