Improve code generation for bounds checks.

src/arm/lithium-arm.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 1812 matching lines @@
   LOperand* index = FLAG_debug_code
       ? UseRegisterAtStart(instr->index())
       : UseRegisterOrConstantAtStart(instr->index());
   LOperand* value = UseRegisterAtStart(instr->value());
   LOperand* context = FLAG_debug_code ? UseFixed(instr->context(), cp) : NULL;
   return new(zone()) LSeqStringSetChar(context, string, index, value);
 }
 
 
 LInstruction* LChunkBuilder::DoBoundsCheck(HBoundsCheck* instr) {
-  LOperand* value = UseRegisterOrConstantAtStart(instr->index());
-  LOperand* length = UseRegister(instr->length());
-  return AssignEnvironment(new(zone()) LBoundsCheck(value, length));
+  if (!FLAG_debug_code && instr->skip_check()) return NULL;
+  LOperand* index = UseRegisterOrConstantAtStart(instr->index());
+  LOperand* length = !index->IsConstantOperand()
+      ? UseRegisterOrConstantAtStart(instr->length())
+      : UseRegisterAtStart(instr->length());
+  LInstruction* result = new(zone()) LBoundsCheck(index, length);
+  if (!FLAG_debug_code || !instr->skip_check()) {
+    result = AssignEnvironment(result);
+  }
+  return result;
 }
 
 
 LInstruction* LChunkBuilder::DoBoundsCheckBaseIndexInformation(
     HBoundsCheckBaseIndexInformation* instr) {
   UNREACHABLE();
   return NULL;
 }
 
 
@@ skipping 725 matching lines @@
 
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseRegister(instr->index());
   LLoadFieldByIndex* load = new(zone()) LLoadFieldByIndex(object, index);
   LInstruction* result = DefineSameAsFirst(load);
   return AssignPointerMap(result);
 }
 
 } }  // namespace v8::internal