Frees up LR on arm for use by the register allocator.

runtime/vm/flow_graph_compiler_arm.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"  // Needed here to get TARGET_ARCH_ARM.
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 166 matching lines @@
 #define __ assem->
   __ Comment("%s", Name());
   __ Bind(entry_label());
   if (FLAG_trap_on_deoptimization) {
     __ bkpt(0);
   }
 
   ASSERT(deopt_env() != NULL);
 
   StubCode* stub_code = compiler->isolate()->stub_code();
+  // LR may be live. It will be clobbered by BranchLink, so cache it in IP.
+  // It will be restored at the top of the deoptimization stub, specifically in
+  // GenerateDeoptimizationSequence in stub_code_arm.cc.
+  __ mov(IP, Operand(LR));
   __ BranchLink(&stub_code->DeoptimizeLabel());
   set_pc_offset(assem->CodeSize());
 #undef __
 }
 
 
 #define __ assembler()->
 
 
 // Fall through if bool_register contains null.
@@ skipping 1605 matching lines @@
   DRegister dreg = EvenDRegisterOf(reg);
   __ vldrd(dreg, Address(SP, kDoubleSize, Address::PostIndex));
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM