Fix profiling on ARM64.

runtime/vm/signal_handler_android.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #include "vm/simulator.h"
 #include "vm/signal_handler.h"
 #if defined(TARGET_OS_ANDROID)
 
 namespace dart {
@@ skipping 48 matching lines @@
 
 
 uintptr_t SignalHandler::GetDartStackPointer(const mcontext_t& mcontext) {
   uintptr_t sp = 0;
 
 #if defined(HOST_ARCH_IA32)
   sp = static_cast<uintptr_t>(mcontext.gregs[REG_ESP]);
 #elif defined(HOST_ARCH_ARM)
   sp = static_cast<uintptr_t>(mcontext.arm_sp);
 #elif defined(HOST_ARCH_ARM64)
-  sp = static_cast<uintptr_t>(mcontext.regs[18]);
+  sp = static_cast<uintptr_t>(mcontext.regs[19]);

[Cutch, 2015/10/30 02:29:57]

Could we add #define for the register in constants_??.h  and use that here
instead of the number?

[rmacnak, 2015/10/30 16:17:41]

constants_??.h is included for the target architecture, but not host.

 #else
 #error Unsupported architecture.
 #endif  // HOST_ARCH_...
   return sp;
 }
 
 
 uintptr_t SignalHandler::GetLinkRegister(const mcontext_t& mcontext) {
   uintptr_t lr = 0;
 
@@ skipping 29 matching lines @@
   act.sa_handler = SIG_IGN;
   sigemptyset(&act.sa_mask);
   int r = sigaction(SIGPROF, &act, NULL);
   ASSERT(r == 0);
 }
 
 
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_ANDROID)