Allow bailing out of the register allocator when running out of virtual registers.

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 112 matching lines @@
             true,
             "Optimize object size, Array shift, DOM strings and string +")
 
 // Flags for data representation optimizations
 DEFINE_bool(unbox_double_arrays, true, "automatically unbox arrays of doubles")
 DEFINE_bool(string_slices, true, "use string slices")
 
 // Flags for Crankshaft.
 DEFINE_bool(crankshaft, true, "use crankshaft")
 DEFINE_string(hydrogen_filter, "", "hydrogen use/trace filter")
-DEFINE_bool(use_hydrogen, true, "use generated hydrogen for compilation")
-DEFINE_bool(build_lithium, true, "use lithium chunk builder")
-DEFINE_bool(alloc_lithium, true, "use lithium register allocator")
-DEFINE_bool(use_lithium, true, "use lithium code generator")
 DEFINE_bool(use_range, true, "use hydrogen range analysis")
 DEFINE_bool(eliminate_dead_phis, true, "eliminate dead phis")
 DEFINE_bool(use_gvn, true, "use hydrogen global value numbering")
 DEFINE_bool(use_canonicalizing, true, "use hydrogen instruction canonicalizing")
 DEFINE_bool(use_inlining, true, "use function inlining")
 DEFINE_bool(limit_inlining, true, "limit code size growth from inlining")
 DEFINE_bool(eliminate_empty_blocks, true, "eliminate empty blocks")
 DEFINE_bool(loop_invariant_code_motion, true, "loop invariant code motion")
 DEFINE_bool(collect_megamorphic_maps_from_stub_cache,
             true,
@@ skipping 436 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