[hydrogen] don't bailout assignments to consts

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index b35dc7c145d884c074bd6582419293f7015fd954..7e09682656180801d68dbeebadcdb976b5f52ef2 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -2303,13 +2303,32 @@ void LCodeGen::DoLoadContextSlot(LLoadContextSlot* instr) {
   Register context = ToRegister(instr->context());
   Register result = ToRegister(instr->result());
   __ ldr(result, ContextOperand(context, instr->slot_index()));
+  if (instr->RequiresHoleCheck()) {
+    Label is_not_hole;
+    __ cmp(result, Operand(factory()->the_hole_value()));
+    __ b(ne, &is_not_hole);
+
+    __ mov(result, Operand(factory()->undefined_value()));
+
+    __ bind(&is_not_hole);
+  }
 }
 
 
 void LCodeGen::DoStoreContextSlot(LStoreContextSlot* instr) {
   Register context = ToRegister(instr->context());
   Register value = ToRegister(instr->value());
+  Register scratch = scratch0();
   MemOperand target = ContextOperand(context, instr->slot_index());
+
+  Label skip_assignment;
+
+  if (instr->RequiresHoleCheck()) {
+    __ ldr(scratch, target);
+    __ cmp(scratch, Operand(factory()->the_hole_value()));
+    __ b(ne, &skip_assignment);
+  }
+
   __ str(value, target);
   if (instr->hydrogen()->NeedsWriteBarrier()) {
     HType type = instr->hydrogen()->value()->type();
@@ -2318,12 +2337,14 @@ void LCodeGen::DoStoreContextSlot(LStoreContextSlot* instr) {
     __ RecordWriteContextSlot(context,
                               target.offset(),
                               value,
-                              scratch0(),
+                              scratch,
                               kLRHasBeenSaved,
                               kSaveFPRegs,
                               EMIT_REMEMBERED_SET,
                               check_needed);
   }
+
+  __ bind(&skip_assignment);
 }