Setup R10/EDX to be valid Oops before stub calls

runtime/vm/stub_code_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"
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
 #include "vm/cpu.h"
@@ skipping 28 matching lines @@
 void StubCode::GenerateCallToRuntimeStub(Assembler* assembler) {
   const intptr_t isolate_offset = NativeArguments::isolate_offset();
   const intptr_t argc_tag_offset = NativeArguments::argc_tag_offset();
   const intptr_t argv_offset = NativeArguments::argv_offset();
   const intptr_t retval_offset = NativeArguments::retval_offset();
   const intptr_t exitframe_last_param_slot_from_fp = 2;
 
   __ mov(IP, Operand(0));
   __ Push(IP);  // Push 0 for the PC marker.
   __ EnterFrame((1 << FP) | (1 << LR), 0);
+  __ SmiUntag(R4);
 
   // Load current Isolate pointer from Context structure into R0.
   __ ldr(R0, FieldAddress(CTX, Context::isolate_offset()));
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to Dart VM C++ code.
   __ StoreToOffset(kWord, SP, R0, Isolate::top_exit_frame_info_offset());
 
   // Save current Context pointer into Isolate structure.
   __ StoreToOffset(kWord, CTX, R0, Isolate::top_context_offset());
@@ skipping 1771 matching lines @@
   const Register right = R0;
   __ ldr(left, Address(SP, 1 * kWordSize));
   __ ldr(right, Address(SP, 0 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right, temp);
   __ Ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM