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

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index f81f5f0667f83289c946547758452e852e24ba5c..49f1eec931a30bcac2dacab916f8f403d63151d7 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -416,6 +416,7 @@ void HValue::Kill() {
   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();
@@ -608,6 +609,7 @@ void HInstruction::Verify() {
   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()) {