Change the Hydrogen representation of uses.

src/x64/lithium-x64.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 833 matching lines @@
   LOperand* right = NULL;
   int constant_value = 0;
   if (right_value->IsConstant()) {
     HConstant* constant = HConstant::cast(right_value);
     right = chunk_->DefineConstantOperand(constant);
     constant_value = constant->Integer32Value() & 0x1f;
   } else {
     right = UseFixed(right_value, rcx);
   }
 
-  // Shift operations can only deoptimize if we do a logical shift
-  // by 0 and the result cannot be truncated to int32.
-  bool can_deopt = (op == Token::SHR && constant_value == 0);
-  if (can_deopt) {
-    bool can_truncate = true;
-    for (int i = 0; i < instr->uses()->length(); i++) {
-      if (!instr->uses()->at(i)->CheckFlag(HValue::kTruncatingToInt32)) {
-        can_truncate = false;
+  // Shift operations can only deoptimize if we do a logical shift by 0 and
+  // the result cannot be truncated to int32.
+  bool may_deopt = (op == Token::SHR && constant_value == 0);
+  bool does_deopt = false;
+  if (may_deopt) {
+    for (HUseIterator it(instr->uses()); !it.Done(); it.Advance()) {
+      if (!it.value()->CheckFlag(HValue::kTruncatingToInt32)) {
+        does_deopt = true;
         break;
       }
     }
-    can_deopt = !can_truncate;
   }
 
-  LShiftI* result = new LShiftI(op, left, right, can_deopt);
-  return can_deopt
-      ? AssignEnvironment(DefineSameAsFirst(result))
-      : DefineSameAsFirst(result);
+  LInstruction* result =
+      DefineSameAsFirst(new LShiftI(op, left, right, does_deopt));
+  return does_deopt ? AssignEnvironment(result) : result;
 }
 
 
 LInstruction* LChunkBuilder::DoArithmeticD(Token::Value op,
                                            HArithmeticBinaryOperation* instr) {
   ASSERT(instr->representation().IsDouble());
   ASSERT(instr->left()->representation().IsDouble());
   ASSERT(instr->right()->representation().IsDouble());
   ASSERT(op != Token::MOD);
   LOperand* left = UseRegisterAtStart(instr->left());
@@ skipping 1246 matching lines @@
 
 LInstruction* LChunkBuilder::DoLeaveInlined(HLeaveInlined* instr) {
   HEnvironment* outer = current_block_->last_environment()->outer();
   current_block_->UpdateEnvironment(outer);
   return NULL;
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64