Explicitly clear out the IC-data register in ExecuteMatch.

runtime/vm/intrinsifier_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/intrinsifier.h"
 
 #include "vm/assembler.h"
@@ skipping 1928 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 offset 0.
 
   // Incoming registers:
   // R0: Function. (Will be reloaded with the specialized matcher function.)
   // R4: Arguments descriptor. (Will be preserved.)
-  // R5: IC-Data. (Will be preserved.)
+  // R5: Unknown. (Must be GC safe on tail call.)
 
   // Load the specialized function pointer into R0. Leverage the fact the
   // string CIDs as well as stored function pointers are in sequence.
   __ ldr(R2, Address(SP, kRegExpParamOffset));
   __ ldr(R1, Address(SP, kStringParamOffset));
   __ LoadClassId(R1, R1, kNoPP);
   __ AddImmediate(R1, R1, -kOneByteStringCid, kNoPP);
   __ add(R1, R2, Operand(R1, LSL, kWordSizeLog2));
   __ ldr(R0, FieldAddress(R1, JSRegExp::function_offset(kOneByteStringCid)));
 
   // Registers are now set up for the lazy compile stub. It expects the function
   // in R0, the argument descriptor in R4, and IC-Data in R5.
   static const intptr_t arg_count = RegExpMacroAssembler::kParamCount;
   __ LoadObject(R4, Array::Handle(ArgumentsDescriptor::New(arg_count)), kNoPP);
+  __ eor(R5, R5, Operand(R5));
 
   // Tail-call the function.
   __ ldr(R1, FieldAddress(R0, Function::instructions_offset()));
   __ AddImmediate(R1, R1, Instructions::HeaderSize() - kHeapObjectTag, kNoPP);
   __ br(R1);
 }
 
 
 // On stack: user tag (+0).
 void Intrinsifier::UserTag_makeCurrent(Assembler* assembler) {
@@ skipping 30 matching lines @@
   Isolate* isolate = Isolate::Current();
   __ LoadImmediate(R1, reinterpret_cast<uword>(isolate), kNoPP);
   // Set return value to Isolate::current_tag_.
   __ ldr(R0, Address(R1, Isolate::current_tag_offset()));
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64