Reland - Arm64: Ensure that csp is always aligned to 16 byte values even if jssp is not.

src/flag-definitions.h

 // Copyright 2012 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.
 
 // This file defines all of the flags.  It is separated into different section,
 // for Debug, Release, Logging and Profiling, etc.  To add a new flag, find the
 // correct section, and use one of the DEFINE_ macros, without a trailing ';'.
 //
 // This include does not have a guard, because it is a template-style include,
 // which can be included multiple times in different modes.  It expects to have
@@ skipping 362 matching lines @@
             "instruction pairs (ARM only)")
 DEFINE_bool(enable_unaligned_accesses, true,
             "enable unaligned accesses for ARMv7 (ARM only)")
 DEFINE_bool(enable_32dregs, ENABLE_32DREGS_DEFAULT,
             "enable use of d16-d31 registers on ARM - this requires VFP3")
 DEFINE_bool(enable_vldr_imm, false,
             "enable use of constant pools for double immediate (ARM only)")
 DEFINE_bool(force_long_branches, false,
             "force all emitted branches to be in long mode (MIPS only)")
 
+// cpu-arm64.cc
+DEFINE_bool(enable_always_align_csp, true,
+            "enable alignment of csp to 16 bytes on platforms which prefer "
+            "the register to always be aligned (ARM64 only)")
+
 // bootstrapper.cc
 DEFINE_string(expose_natives_as, NULL, "expose natives in global object")
 DEFINE_string(expose_debug_as, NULL, "expose debug in global object")
 DEFINE_bool(expose_free_buffer, false, "expose freeBuffer extension")
 DEFINE_bool(expose_gc, false, "expose gc extension")
 DEFINE_string(expose_gc_as, NULL,
               "expose gc extension under the specified name")
 DEFINE_implication(expose_gc_as, expose_gc)
 DEFINE_bool(expose_externalize_string, false,
             "expose externalize string extension")
@@ skipping 506 matching lines @@
 #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
 
 #undef COMMA