[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 293a1db6150d5825390f27df9c5bb67062f0aa82..24431402c68ac68b1ced62ee31e37cc6228bce4d 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -2069,7 +2069,14 @@ void LCodeGen::DoLoadContextSlot(LLoadContextSlot* instr) {
   __ movq(result, ContextOperand(context, instr->slot_index()));
   if (instr->hydrogen()->RequiresHoleCheck()) {
     __ CompareRoot(result, Heap::kTheHoleValueRootIndex);
-    DeoptimizeIf(equal, instr->environment());
+    if (instr->hydrogen()->DeoptimizesOnHole()) {
+      DeoptimizeIf(equal, instr->environment());
+    } else {
+      Label is_not_hole;
+      __ j(not_equal, &is_not_hole, Label::kNear);
+      __ movq(result, factory()->undefined_value(), RelocInfo::NONE);
+      __ bind(&is_not_hole);
+    }
   }
 }
 
@@ -2077,12 +2084,20 @@ void LCodeGen::DoLoadContextSlot(LLoadContextSlot* instr) {
 void LCodeGen::DoStoreContextSlot(LStoreContextSlot* instr) {
   Register context = ToRegister(instr->context());
   Register value = ToRegister(instr->value());
+
   Operand target = ContextOperand(context, instr->slot_index());
+
+  Label skip_assignment;
   if (instr->hydrogen()->RequiresHoleCheck()) {
     __ CompareRoot(target, Heap::kTheHoleValueRootIndex);
-    DeoptimizeIf(equal, instr->environment());
+    if (instr->hydrogen()->DeoptimizesOnHole()) {
+      DeoptimizeIf(equal, instr->environment());
+    } else {
+      __ j(not_equal, &skip_assignment, Label::kNear);
+    }
   }
   __ movq(target, value);
+
   if (instr->hydrogen()->NeedsWriteBarrier()) {
     HType type = instr->hydrogen()->value()->type();
     SmiCheck check_needed =
@@ -2097,6 +2112,8 @@ void LCodeGen::DoStoreContextSlot(LStoreContextSlot* instr) {
                               EMIT_REMEMBERED_SET,
                               check_needed);
   }
+
+  __ bind(&skip_assignment);
 }