Ensure that BoxInt32 input is correctly preserved on the slow-path.

runtime/vm/flow_graph_compiler_arm64.cc

 // Copyright (c) 2014, 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_ARM64.
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 1386 matching lines @@
     __ Pop(left);
   } else {
     __ CompareRegisters(left, right);
   }
 }
 
 
 // This function must be in sync with FlowGraphCompiler::RecordSafepoint and
 // FlowGraphCompiler::SlowPathEnvironmentFor.
 void FlowGraphCompiler::SaveLiveRegisters(LocationSummary* locs) {
+#if defined(DEBUG)
+  locs->CheckWritableInputs();
+#endif
+
   // TODO(vegorov): consider saving only caller save (volatile) registers.
   const intptr_t fpu_regs_count = locs->live_registers()->FpuRegisterCount();
   if (fpu_regs_count > 0) {
     // Store fpu registers with the lowest register number at the lowest
     // address.
     for (intptr_t reg_idx = kNumberOfVRegisters - 1;
                   reg_idx >= 0; --reg_idx) {
       VRegister fpu_reg = static_cast<VRegister>(reg_idx);
       if (locs->live_registers()->ContainsFpuRegister(fpu_reg)) {
         __ PushQuad(fpu_reg);
@@ skipping 315 matching lines @@
 void ParallelMoveResolver::RestoreFpuScratch(FpuRegister reg) {
   UNIMPLEMENTED();
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64