[hydrogen] don't bailout assignments to consts

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 2b31f22247156d34b6452e90cd7f3dfaae9f4d7b..ea466469884a7ff819025797ea90e89acc412834 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -2073,6 +2073,15 @@ void LCodeGen::DoLoadContextSlot(LLoadContextSlot* instr) {
 void LCodeGen::DoStoreContextSlot(LStoreContextSlot* instr) {
   Register context = ToRegister(instr->context());
   Register value = ToRegister(instr->value());
+
+  Label skip_assignment;
+
+  if (instr->RequiresHoleCheck()) {
+    __ Cmp(ContextOperand(context, instr->slot_index()),
+           factory()->the_hole_value());
+    __ j(not_equal, &skip_assignment, Label::kNear);
+  }
+
   __ movq(ContextOperand(context, instr->slot_index()), value);
   if (instr->hydrogen()->NeedsWriteBarrier()) {
     HType type = instr->hydrogen()->value()->type();
@@ -2088,6 +2097,8 @@ void LCodeGen::DoStoreContextSlot(LStoreContextSlot* instr) {
                               EMIT_REMEMBERED_SET,
                               check_needed);
   }
+
+  __ bind(&skip_assignment);
 }