Improve integer division on IA32 and X64

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
===================================================================
--- src/x64/lithium-x64.cc	(revision 13175)
+++ src/x64/lithium-x64.cc	(working copy)
@@ -1187,6 +1187,13 @@
   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()), NULL);
+      return AssignEnvironment(DefineSameAsFirst(div));
+    }
     // The temporary operand is necessary to ensure that right is not allocated
     // into rdx.
     LOperand* temp = FixedTemp(rdx);