Eliminate redundant array bound checks (checks already performed earlier in the DT).

src/hydrogen-instructions.cc

 // Copyright 2012 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 398 matching lines @@
 }
 
 
 void HValue::Kill() {
   // Instead of going through the entire use list of each operand, we only
   // check the first item in each use list and rely on the tail() method to
   // skip dead items, removing them lazily next time we traverse the list.
   SetFlag(kIsDead);
   for (int i = 0; i < OperandCount(); ++i) {
     HValue* operand = OperandAt(i);
+    if (operand == NULL) continue;
     HUseListNode* first = operand->use_list_;
     if (first != NULL && first->value() == this && first->index() == i) {
       operand->use_list_ = first->tail();
     }
   }
 }
 
 
 void HValue::SetBlock(HBasicBlock* block) {
   ASSERT(block_ == NULL || block == NULL);
@@ skipping 172 matching lines @@
   if (next != NULL) next->previous_ = this;
 }
 
 
 #ifdef DEBUG
 void HInstruction::Verify() {
   // Verify that input operands are defined before use.
   HBasicBlock* cur_block = block();
   for (int i = 0; i < OperandCount(); ++i) {
     HValue* other_operand = OperandAt(i);
+    if (other_operand == NULL) continue;
     HBasicBlock* other_block = other_operand->block();
     if (cur_block == other_block) {
       if (!other_operand->IsPhi()) {
         HInstruction* cur = this->previous();
         while (cur != NULL) {
           if (cur == other_operand) break;
           cur = cur->previous();
         }
         // Must reach other operand in the same block!
         ASSERT(cur == other_operand);
@@ skipping 1713 matching lines @@
 
 
 void HCheckPrototypeMaps::Verify() {
   HInstruction::Verify();
   ASSERT(HasNoUses());
 }
 
 #endif
 
 } }  // namespace v8::internal