Explicitly clear out the IC-data register in ExecuteMatch.

runtime/vm/intrinsifier_x64.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_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intrinsifier.h"
 
 #include "vm/assembler.h"
@@ skipping 1911 matching lines @@
 void Intrinsifier::JSRegExp_ExecuteMatch(Assembler* assembler) {
   if (FLAG_use_jscre) {
     return;
   }
   static const intptr_t kRegExpParamOffset = 3 * kWordSize;
   static const intptr_t kStringParamOffset = 2 * kWordSize;
   // start_index smi is located at offset 1.
 
   // Incoming registers:
   // RAX: Function. (Will be loaded with the specialized matcher function.)
-  // RCX: IC-Data. (Will be preserved.)
+  // RCX: Unknown. (Must be GC safe on tail call.)
   // R10: Arguments descriptor. (Will be preserved.)
 
   // Load the specialized function pointer into RAX. Leverage the fact the
   // string CIDs as well as stored function pointers are in sequence.
   __ movq(RBX, Address(RSP, kRegExpParamOffset));
   __ movq(RDI, Address(RSP, kStringParamOffset));
   __ LoadClassId(RDI, RDI);
   __ SubImmediate(RDI, Immediate(kOneByteStringCid), PP);
   __ movq(RAX, FieldAddress(RBX, RDI, TIMES_8,
                             JSRegExp::function_offset(kOneByteStringCid)));
 
   // Registers are now set up for the lazy compile stub. It expects the function
   // in RAX, the argument descriptor in R10, and IC-Data in RCX.
   static const intptr_t arg_count = RegExpMacroAssembler::kParamCount;
   __ LoadObject(R10, Array::Handle(ArgumentsDescriptor::New(arg_count)), PP);
+  __ xorl(RCX, RCX);

[Vyacheslav Egorov (Google), 2014/11/26 14:26:17]

xor*q*

[zerny-google, 2014/11/26 14:33:55]

Thanks!

 
   // Tail-call the function.
   __ movq(RDI, FieldAddress(RAX, Function::instructions_offset()));
   __ addq(RDI, Immediate(Instructions::HeaderSize() - kHeapObjectTag));
   __ jmp(RDI);
 }
 
 
 // On stack: user tag (+1), return-address (+0).
 void Intrinsifier::UserTag_makeCurrent(Assembler* assembler) {
@@ skipping 38 matching lines @@
   // Set return value to Isolate::current_tag_.
   __ movq(RAX, Address(RBX, Isolate::current_tag_offset()));
   __ ret();
 }
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64