Explicitly clear out the IC-data register in ExecuteMatch.

runtime/vm/intrinsifier_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"  // Needed here to get TARGET_ARCH_MIPS.
 #if defined(TARGET_ARCH_MIPS)
 
 #include "vm/intrinsifier.h"
 
 #include "vm/assembler.h"
@@ skipping 2062 matching lines @@
   if (FLAG_use_jscre) {
     return;
   }
   static const intptr_t kRegExpParamOffset = 2 * kWordSize;
   static const intptr_t kStringParamOffset = 1 * kWordSize;
   // start_index smi is located at 0.
 
   // Incoming registers:
   // T0: Function. (Will be reloaded with the specialized matcher function.)
   // S4: Arguments descriptor. (Will be preserved.)
-  // S5: IC-Data. (Will be preserved.)
+  // S5: Unknown. (Must be GC safe on tail call.)
 
   // Load the specialized function pointer into T0. Leverage the fact the
   // string CIDs as well as stored function pointers are in sequence.
   __ lw(T1, Address(SP, kRegExpParamOffset));
   __ lw(T3, Address(SP, kStringParamOffset));
   __ LoadClassId(T2, T3);
   __ AddImmediate(T2, -kOneByteStringCid);
   __ sll(T2, T2, kWordSizeLog2);
   __ addu(T2, T2, T1);
   __ lw(T0, FieldAddress(T2, JSRegExp::function_offset(kOneByteStringCid)));
 
   // Registers are now set up for the lazy compile stub. It expects the function
   // in T0, the argument descriptor in S4, and IC-Data in S5.
   static const intptr_t arg_count = RegExpMacroAssembler::kParamCount;
   __ LoadObject(S4, Array::Handle(ArgumentsDescriptor::New(arg_count)));
+  __ mov(S5, ZR);
 
   // Tail-call the function.
   __ lw(T3, FieldAddress(T0, Function::instructions_offset()));
   __ AddImmediate(T3, Instructions::HeaderSize() - kHeapObjectTag);
   __ jr(T3);
 }
 
 
 // On stack: user tag (+0).
 void Intrinsifier::UserTag_makeCurrent(Assembler* assembler) {
@@ skipping 30 matching lines @@
   Isolate* isolate = Isolate::Current();
   __ LoadImmediate(V0, reinterpret_cast<uword>(isolate));
   // Set return value.
   __ Ret();
   __ delay_slot()->lw(V0, Address(V0, Isolate::current_tag_offset()));
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_MIPS