Improve integer division on ARM in favor of power of 2 constant divisor

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 1183 matching lines @@
   if (instr->HasNoUses()) return NULL;
   LOperand* value = UseRegisterAtStart(instr->value());
   return DefineAsRegister(new(zone()) LBitNotI(value));
 }
 
 
 LInstruction* LChunkBuilder::DoDiv(HDiv* instr) {
   if (instr->representation().IsDouble()) {
     return DoArithmeticD(Token::DIV, instr);
   } else if (instr->representation().IsInteger32()) {
+    if (instr->HasPowerOf2Divisor()) {
+      ASSERT(!instr->CheckFlag(HValue::kCanBeDivByZero));
+      LOperand* value = UseRegisterAtStart(instr->left());
+      LDivI* div =
+          new(zone()) LDivI(value, UseOrConstant(instr->right()));
+      return AssignEnvironment(DefineSameAsFirst(div));
+    }
     // TODO(1042) The fixed register allocation
     // is needed because we call TypeRecordingBinaryOpStub from
     // the generated code, which requires registers r0
     // and r1 to be used. We should remove that
     // when we provide a native implementation.
     LOperand* dividend = UseFixed(instr->left(), r0);
     LOperand* divisor = UseFixed(instr->right(), r1);
     return AssignEnvironment(AssignPointerMap(
              DefineFixed(new(zone()) LDivI(dividend, divisor), r0)));
   } else {
@@ skipping 1241 matching lines @@
 
 
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseRegister(instr->index());
   return DefineAsRegister(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal