Setup R10/EDX to be valid Oops before stub calls

runtime/vm/stub_code_mips.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_MIPS)
 
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
 #include "vm/compiler.h"
@@ skipping 16 matching lines @@
 DECLARE_FLAG(bool, trace_optimized_ic_calls);
 
 DECLARE_FLAG(bool, enable_debugger);
 
 // Input parameters:
 //   RA : return address.
 //   SP : address of last argument in argument array.
 //   SP + 4*S4 - 4 : address of first argument in argument array.
 //   SP + 4*S4 : address of return value.
 //   S5 : address of the runtime function to call.
-//   S4 : number of arguments to the call.
+//   S4 : number of arguments to the call as Smi.
 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;
 
   __ SetPrologueOffset();
   __ TraceSimMsg("CallToRuntimeStub");
   __ addiu(SP, SP, Immediate(-3 * kWordSize));
   __ sw(ZR, Address(SP, 2 * kWordSize));  // Push 0 for the PC marker
   __ sw(RA, Address(SP, 1 * kWordSize));
   __ sw(FP, Address(SP, 0 * kWordSize));
   __ mov(FP, SP);
+  __ SmiUntag(S4);
 
   // Load current Isolate pointer from Context structure into A0.
   __ lw(A0, FieldAddress(CTX, Context::isolate_offset()));
 
   // Save exit frame information to enable stack walking as we are about
   // to transition to Dart VM C++ code.
   __ sw(SP, Address(A0, Isolate::top_exit_frame_info_offset()));
 
   // Save current Context pointer into Isolate structure.
   __ sw(CTX, Address(A0, Isolate::top_context_offset()));
@@ skipping 1999 matching lines @@
   const Register right = T0;
   __ lw(left, Address(SP, 1 * kWordSize));
   __ lw(right, Address(SP, 0 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right, temp1, temp2);
   __ Ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_MIPS