BoundsCheck should be extended to support array_bounds_checks_elimination

src/x64/lithium-x64.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 1583 matching lines @@
 
 
 LInstruction* LChunkBuilder::DoDateField(HDateField* instr) {
   LOperand* object = UseFixed(instr->value(), rax);
   LDateField* result = new(zone()) LDateField(object, instr->index());
   return MarkAsCall(DefineFixed(result, rax), instr);
 }
 
 
 LInstruction* LChunkBuilder::DoBoundsCheck(HBoundsCheck* instr) {
-  LOperand* value = UseRegisterOrConstantAtStart(instr->index());
-  LOperand* length = Use(instr->length());
-  return AssignEnvironment(new(zone()) LBoundsCheck(value, length));
+  if (instr->index()->IsConstant() ||
+      (instr->lower_offset() == 0 && instr->upper_offset() == 0)) {
+    return AssignEnvironment(new(zone()) LBoundsCheck(
+                UseRegisterOrConstantAtStart(instr->index()),
+                Use(instr->length()), NULL));
+  } else {
+    return AssignEnvironment(new(zone()) LBoundsCheck(
+                UseRegisterOrConstant(instr->index()),
+                Use(instr->length()), TempRegister()));
+  }
 }
 
 
 LInstruction* LChunkBuilder::DoAbnormalExit(HAbnormalExit* instr) {
   // The control instruction marking the end of a block that completed
   // abruptly (e.g., threw an exception).  There is nothing specific to do.
   return NULL;
 }
 
 
@@ skipping 709 matching lines @@
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
   return DefineSameAsFirst(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64