Becuase of cross-context calls, hydrogen-based Array constructor needs to ensure

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 234 matching lines @@
             "perform array bounds checks elimination")
 DEFINE_bool(array_index_dehoisting, true,
             "perform array index dehoisting")
 DEFINE_bool(dead_code_elimination, true, "use dead code elimination")
 DEFINE_bool(fold_constants, true, "use constant folding")
 DEFINE_bool(trace_dead_code_elimination, false, "trace dead code elimination")
 DEFINE_bool(unreachable_code_elimination, false,
             "eliminate unreachable code (hidden behind soft deopts)")
 DEFINE_bool(track_allocation_sites, true,
             "Use allocation site info to reduce transitions")
-DEFINE_bool(optimize_constructed_arrays, false,
+DEFINE_bool(optimize_constructed_arrays, true,
             "Use allocation site info on constructed arrays")
 DEFINE_bool(trace_osr, false, "trace on-stack replacement")
 DEFINE_int(stress_runs, 0, "number of stress runs")
 DEFINE_bool(optimize_closures, true, "optimize closures")
 DEFINE_bool(lookup_sample_by_shared, true,
             "when picking a function to optimize, watch for shared function "
             "info, not JSFunction itself")
 DEFINE_bool(cache_optimized_code, true,
             "cache optimized code for closures")
 DEFINE_bool(inline_construct, true, "inline constructor calls")
@@ skipping 512 matching lines @@
 #undef DEFINE_bool
 #undef DEFINE_int
 #undef DEFINE_string
 #undef DEFINE_implication
 
 #undef FLAG_MODE_DECLARE
 #undef FLAG_MODE_DEFINE
 #undef FLAG_MODE_DEFINE_DEFAULTS
 #undef FLAG_MODE_META
 #undef FLAG_MODE_DEFINE_IMPLICATIONS