[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..b0fbe4c1e52c4c38885567f9cf428301be81d968 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -2067,12 +2067,30 @@ void LCodeGen::DoLoadContextSlot(LLoadContextSlot* instr) {
   Register context = ToRegister(instr->context());
   Register result = ToRegister(instr->result());
   __ movq(result, ContextOperand(context, instr->slot_index()));
+  if (instr->RequiresHoleCheck()) {
+    Label is_not_hole;
+    __ Cmp(result, factory()->the_hole_value());
+    __ j(not_equal, &is_not_hole, Label::kNear);
+
+    __ movq(result, factory()->undefined_value(), RelocInfo::NONE);
+
+    __ bind(&is_not_hole);
+  }
 }
 
 
 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 +2106,8 @@ void LCodeGen::DoStoreContextSlot(LStoreContextSlot* instr) {
                               EMIT_REMEMBERED_SET,
                               check_needed);
   }
+
+  __ bind(&skip_assignment);
 }