Implemented the ctz Turbo Fan operator for x64.

src/compiler/machine-operator.h

Index: src/compiler/machine-operator.h
diff --git a/src/compiler/machine-operator.h b/src/compiler/machine-operator.h
index 14ad9e03d11e74722230e080458d6e0673c3aa06..ea92ae0aa3e9302d7879a277cd73a944aa07a427 100644
--- a/src/compiler/machine-operator.h
+++ b/src/compiler/machine-operator.h
@@ -119,9 +119,11 @@ class MachineOperatorBuilder final : public ZoneObject {
     kWord32ShiftIsSafe = 1u << 9,
     kWord32Ctz = 1u << 10,
     kWord32Popcnt = 1u << 11,
+    kWord64Ctz = 1u << 12,
     kAllOptionalOps = kFloat32Max | kFloat32Min | kFloat64Max | kFloat64Min |
                       kFloat64RoundDown | kFloat64RoundTruncate |
-                      kFloat64RoundTiesAway | kWord32Ctz | kWord32Popcnt
+                      kFloat64RoundTiesAway | kWord32Ctz | kWord32Popcnt |
+                      kWord64Ctz
   };
   typedef base::Flags<Flag, unsigned> Flags;
 
@@ -149,6 +151,7 @@ class MachineOperatorBuilder final : public ZoneObject {
   const Operator* Word64Sar();
   const Operator* Word64Ror();
   const Operator* Word64Clz();
+  const OptionalOperator Word64Ctz();
   const Operator* Word64Equal();
 
   const Operator* Int32Add();