Introduce concurrent on-stack replacement.

src/flag-definitions.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // 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 313 matching lines @@
             "safe operations")
 
 DEFINE_bool(concurrent_recompilation, true,
             "optimizing hot functions asynchronously on a separate thread")
 DEFINE_bool(trace_concurrent_recompilation, false,
             "track concurrent recompilation")
 DEFINE_int(concurrent_recompilation_queue_length, 8,
            "the length of the concurrent compilation queue")
 DEFINE_int(concurrent_recompilation_delay, 0,
            "artificial compilation delay in ms")
+DEFINE_bool(concurrent_osr, false,
+            "concurrent on-stack replacement")
 
 DEFINE_bool(omit_map_checks_for_leaf_maps, true,
             "do not emit check maps for constant values that have a leaf map, "
             "deoptimize the optimized code if the layout of the maps changes.")
 
 // Experimental profiler changes.
 DEFINE_bool(experimental_profiler, true, "enable all profiler experiments")
 DEFINE_bool(watch_ic_patching, false, "profiler considers IC stability")
 DEFINE_int(frame_count, 1, "number of stack frames inspected by the profiler")
 DEFINE_bool(self_optimization, false,
@@ skipping 505 matching lines @@
 #undef DEFINE_ALIAS_int
 #undef DEFINE_ALIAS_string
 #undef DEFINE_ALIAS_float
 #undef DEFINE_ALIAS_args
 
 #undef FLAG_MODE_DECLARE
 #undef FLAG_MODE_DEFINE
 #undef FLAG_MODE_DEFINE_DEFAULTS
 #undef FLAG_MODE_META
 #undef FLAG_MODE_DEFINE_IMPLICATIONS