Fix load of potentially eval-shadowed let bindings.

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 1166 matching lines @@
   // eval-introduced variables.  Eval is used a lot without
   // introducing variables.  In those cases, we do not want to
   // perform a runtime call for all variables in the scope
   // containing the eval.
   if (var->mode() == Variable::DYNAMIC_GLOBAL) {
     EmitLoadGlobalCheckExtensions(var, typeof_state, slow);
     __ jmp(done);
   } else if (var->mode() == Variable::DYNAMIC_LOCAL) {
     Variable* local = var->local_if_not_shadowed();
     __ movq(rax, ContextSlotOperandCheckExtensions(local, slow));
-    if (local->mode() == Variable::CONST) {
+    if (local->mode() == Variable::CONST ||
+        local->mode() == Variable::LET) {
       __ CompareRoot(rax, Heap::kTheHoleValueRootIndex);
       __ j(not_equal, done);
-      __ LoadRoot(rax, Heap::kUndefinedValueRootIndex);
+      if (local->mode() == Variable::CONST) {
+        __ LoadRoot(rax, Heap::kUndefinedValueRootIndex);
+      } else {  // Variable::LET
+        __ Push(var->name());
+        __ CallRuntime(Runtime::kThrowReferenceError, 1);
+      }
     }
     __ jmp(done);
   }
 }
 
 
 void FullCodeGenerator::EmitVariableLoad(VariableProxy* proxy) {
   // Record position before possible IC call.
   SetSourcePosition(proxy->position());
   Variable* var = proxy->var();
@@ skipping 2995 matching lines @@
   *context_length = 0;
   return previous_;
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64