Remove the fcontext field from all contexts.

src/x64/full-codegen-x64.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 662 matching lines @@
         } else if (function != NULL) {
           VisitForAccumulatorValue(function);
           __ movq(Operand(rbp, SlotOffset(slot)), result_register());
         }
         break;
 
       case Slot::CONTEXT:
         // We bypass the general EmitSlotSearch because we know more about
         // this specific context.
 
-        // The variable in the decl always resides in the current context.
+        // The variable in the decl always resides in the current function
+        // context.
         ASSERT_EQ(0, scope()->ContextChainLength(variable->scope()));
         if (FLAG_debug_code) {
-          // Check if we have the correct context pointer.
-          __ movq(rbx, ContextOperand(rsi, Context::FCONTEXT_INDEX));
-          __ cmpq(rbx, rsi);
-          __ Check(equal, "Unexpected declaration in current context.");
+          // Check that we're not inside a with or catch context.
+          __ movq(rbx, FieldOperand(rsi, HeapObject::kMapOffset));
+          __ CompareRoot(rbx, Heap::kWithContextMapRootIndex);
+          __ Check(not_equal, "Declaration in with context.");
+          __ CompareRoot(rbx, Heap::kCatchContextMapRootIndex);
+          __ Check(not_equal, "Declaration in catch context.");
         }
         if (mode == Variable::CONST) {
           __ LoadRoot(kScratchRegister, Heap::kTheHoleValueRootIndex);
           __ movq(ContextOperand(rsi, slot->index()), kScratchRegister);
           // No write barrier since the hole value is in old space.
         } else if (function != NULL) {
           VisitForAccumulatorValue(function);
           __ movq(ContextOperand(rsi, slot->index()), result_register());
           int offset = Context::SlotOffset(slot->index());
           __ movq(rbx, rsi);
@@ skipping 1071 matching lines @@
       case Slot::PARAMETER:
         // No const parameters.
         UNREACHABLE();
         break;
       case Slot::LOCAL:
         __ movq(rdx, Operand(rbp, SlotOffset(slot)));
         __ CompareRoot(rdx, Heap::kTheHoleValueRootIndex);
         __ j(not_equal, &skip);
         __ movq(Operand(rbp, SlotOffset(slot)), rax);
         break;
-      case Slot::CONTEXT: {
-        __ movq(rcx, ContextOperand(rsi, Context::FCONTEXT_INDEX));
-        __ movq(rdx, ContextOperand(rcx, slot->index()));
-        __ CompareRoot(rdx, Heap::kTheHoleValueRootIndex);
-        __ j(not_equal, &skip);
-        __ movq(ContextOperand(rcx, slot->index()), rax);
-        int offset = Context::SlotOffset(slot->index());
-        __ movq(rdx, rax);  // Preserve the stored value in eax.
-        __ RecordWrite(rcx, offset, rdx, rbx);
-        break;
-      }
+      case Slot::CONTEXT:
       case Slot::LOOKUP:
         __ push(rax);
         __ push(rsi);
         __ Push(var->name());
         __ CallRuntime(Runtime::kInitializeConstContextSlot, 3);
         break;
     }
     __ bind(&skip);
 
   } else if (var->mode() != Variable::CONST) {
@@ skipping 2428 matching lines @@
   __ ret(0);
 }
 
 
 #undef __
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64