Fix exception for assignment to uninitialised const

src/arm64/full-codegen-arm64.cc

Index: src/arm64/full-codegen-arm64.cc
diff --git a/src/arm64/full-codegen-arm64.cc b/src/arm64/full-codegen-arm64.cc
index 083a8350320c0d495ae696b4a4dd8ddda1f7b8a5..6b388437642fab558562c7b3ca5cbd68778d2fda 100644
--- a/src/arm64/full-codegen-arm64.cc
+++ b/src/arm64/full-codegen-arm64.cc
@@ -2447,6 +2447,20 @@ void FullCodeGenerator::EmitVariableAssignment(Variable* var,
     __ Bind(&assign);
     EmitStoreToStackLocalOrContextSlot(var, location);
 
+  } else if (var->mode() == CONST && op != Token::INIT_CONST) {
+    // Assignment to const variable needs a write barrier.
+    DCHECK(!var->IsLookupSlot());
+    DCHECK(var->IsStackAllocated() || var->IsContextSlot());
+    Label const_error;
+    MemOperand location = VarOperand(var, x1);
+    __ Ldr(x10, location);
+    __ JumpIfNotRoot(x10, Heap::kTheHoleValueRootIndex, &const_error);
+    __ Mov(x10, Operand(var->name()));
+    __ Push(x10);
+    __ 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.