Revert remove dead hole check logic

src/crankshaft/mips/lithium-codegen-mips.cc

 // Copyright 2012 the V8 project authors. All rights reserved.7
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2466 matching lines @@
 
   __ Jump(ra);
 }
 
 
 void LCodeGen::DoLoadContextSlot(LLoadContextSlot* instr) {
   Register context = ToRegister(instr->context());
   Register result = ToRegister(instr->result());
 
   __ lw(result, ContextMemOperand(context, instr->slot_index()));
+  if (instr->hydrogen()->RequiresHoleCheck()) {
+    __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
+
+    if (instr->hydrogen()->DeoptimizesOnHole()) {
+      DeoptimizeIf(eq, instr, DeoptimizeReason::kHole, result, Operand(at));
+    } else {
+      Label is_not_hole;
+      __ Branch(&is_not_hole, ne, result, Operand(at));
+      __ LoadRoot(result, Heap::kUndefinedValueRootIndex);
+      __ bind(&is_not_hole);
+    }
+  }
 }
 
 
 void LCodeGen::DoStoreContextSlot(LStoreContextSlot* instr) {
   Register context = ToRegister(instr->context());
   Register value = ToRegister(instr->value());
+  Register scratch = scratch0();
   MemOperand target = ContextMemOperand(context, instr->slot_index());
 
+  Label skip_assignment;
+
+  if (instr->hydrogen()->RequiresHoleCheck()) {
+    __ lw(scratch, target);
+    __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
+
+    if (instr->hydrogen()->DeoptimizesOnHole()) {
+      DeoptimizeIf(eq, instr, DeoptimizeReason::kHole, scratch, Operand(at));
+    } else {
+      __ Branch(&skip_assignment, ne, scratch, Operand(at));
+    }
+  }
+
   __ sw(value, target);
   if (instr->hydrogen()->NeedsWriteBarrier()) {
     SmiCheck check_needed =
         instr->hydrogen()->value()->type().IsHeapObject()
             ? OMIT_SMI_CHECK : INLINE_SMI_CHECK;
     __ RecordWriteContextSlot(context,
                               target.offset(),
                               value,
                               scratch0(),
                               GetRAState(),
                               kSaveFPRegs,
                               EMIT_REMEMBERED_SET,
                               check_needed);
   }
+
+  __ bind(&skip_assignment);
 }
 
 
 void LCodeGen::DoLoadNamedField(LLoadNamedField* instr) {
   HObjectAccess access = instr->hydrogen()->access();
   int offset = access.offset();
   Register object = ToRegister(instr->object());
 
   if (access.IsExternalMemory()) {
     Register result = ToRegister(instr->result());
@@ skipping 2871 matching lines @@
   __ lw(result, FieldMemOperand(scratch,
                                 FixedArray::kHeaderSize - kPointerSize));
   __ bind(deferred->exit());
   __ bind(&done);
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8