Fix exception for assignment to uninitialised const

src/ia32/full-codegen-ia32.cc

Index: src/ia32/full-codegen-ia32.cc
diff --git a/src/ia32/full-codegen-ia32.cc b/src/ia32/full-codegen-ia32.cc
index ce36f9ed07b0beac8bba413711da7b42473d44a1..d17137042a5d407b7c68c4bbd446f4a163058f4a 100644
--- a/src/ia32/full-codegen-ia32.cc
+++ b/src/ia32/full-codegen-ia32.cc
@@ -2664,6 +2664,19 @@ void FullCodeGenerator::EmitVariableAssignment(Variable* var,
     __ CallRuntime(Runtime::kThrowReferenceError, 1);
     __ bind(&assign);
     EmitStoreToStackLocalOrContextSlot(var, location);
+  } else if (var->mode() == CONST && op != Token::INIT_CONST) {
+    // Assignment to let variable needs a write barrier.
+    DCHECK(!var->IsLookupSlot());
+    DCHECK(var->IsStackAllocated() || var->IsContextSlot());
+    Label const_error;
+    MemOperand location = VarOperand(var, ecx);
+    __ mov(edx, location);
+    __ cmp(edx, isolate()->factory()->the_hole_value());
+    __ j(not_equal, &const_error, Label::kNear);
+    __ push(Immediate(var->name()));
+    __ CallRuntime(Runtime::kThrowReferenceError, 1);
+    __ bind(&const_error);
+    __ CallRuntime(Runtime::kThrowConstAssignError, 0);
   } else if (!var->is_const_mode() || op == Token::INIT_CONST) {
     if (var->IsLookupSlot()) {
       // Assignment to var.