[turbofan] put spill slot reuse behind a flag

src/compiler/pipeline.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/pipeline.h"
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
 
 #include "src/base/platform/elapsed-timer.h"
@@ skipping 926 matching lines @@
   Run<AllocateGeneralRegistersPhase>();
   if (!data->register_allocator()->AllocationOk()) {
     data->set_compilation_failed();
     return;
   }
   Run<AllocateDoubleRegistersPhase>();
   if (!data->register_allocator()->AllocationOk()) {
     data->set_compilation_failed();
     return;
   }
-  Run<ReuseSpillSlotsPhase>();
+  if (FLAG_turbo_reuse_spill_slots) {
+    Run<ReuseSpillSlotsPhase>();
+  }
   Run<PopulatePointerMapsPhase>();
   Run<ConnectRangesPhase>();
   Run<ResolveControlFlowPhase>();
 
   if (FLAG_trace_turbo) {
     OFStream os(stdout);
     PrintableInstructionSequence printable = {config, data->sequence()};
     os << "----- Instruction sequence after register allocation -----\n"
        << printable;
   }
@@ skipping 15 matching lines @@
 }
 
 
 void Pipeline::TearDown() {
   InstructionOperand::TearDownCaches();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8