Revert 226920 "Roll Clang 188423:191856."

trunk/src/base/debug/stack_trace_android.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/debug/stack_trace.h"
 
 #include <android/log.h>
 #include <unwind.h>
 
 #include "base/debug/proc_maps_linux.h"
 #include "base/strings/stringprintf.h"
 #include "base/threading/thread_restrictions.h"
 
 namespace {
 
 struct StackCrawlState {
   StackCrawlState(uintptr_t* frames, size_t max_depth)
       : frames(frames),
         frame_count(0),
         max_depth(max_depth),
         have_skipped_self(false) {}
 
   uintptr_t* frames;
   size_t frame_count;
   size_t max_depth;
   bool have_skipped_self;
 };
 
+// Clang's unwind.h doesn't provide _Unwind_GetIP on ARM, refer to
+// http://llvm.org/bugs/show_bug.cgi?id=16564 for details.
+#if defined(__clang__)
+uintptr_t _Unwind_GetIP(_Unwind_Context* context) {
+  uintptr_t ip = 0;
+  _Unwind_VRS_Get(context, _UVRSC_CORE, 15, _UVRSD_UINT32, &ip);
+  return ip & ~static_cast<uintptr_t>(0x1);  // Remove thumb mode bit.
+}
+#endif
+
 _Unwind_Reason_Code TraceStackFrame(_Unwind_Context* context, void* arg) {
   StackCrawlState* state = static_cast<StackCrawlState*>(arg);
   uintptr_t ip = _Unwind_GetIP(context);
 
   // The first stack frame is this function itself.  Skip it.
   if (ip != 0 && !state->have_skipped_self) {
     state->have_skipped_self = true;
     return _URC_NO_REASON;
   }
 
@@ skipping 74 matching lines @@
     } else {
       *os << "<unknown>";
     }
 
     *os << "\n";
   }
 }
 
 }  // namespace debug
 }  // namespace base