Replace multiplication with shift

Since the multiplier is a power-of-two, we should avoid relying on the
compiler noticing that and perform the optimization directly. Of course,
the JIT does realize this in C2, but ideally we don't write code making
those assumptions as easy to regress.

Author: ben-manes

caffeine/src/jmh/java/com/github/benmanes/caffeine/cache/TimerWheelBenchmark.java

@@ -80,6 +80,11 @@ public void expire(ThreadState threadState) {
     timerWheel.schedule(timer);
   }
 
+  @Benchmark
+  public long getExpirationDelay() {
+    return timerWheel.getExpirationDelay();
+  }
+
   static final class Timer extends Node<Integer, Integer> {
     Node<Integer, Integer> prev;
     Node<Integer, Integer> next;

caffeine/src/main/java/com/github/benmanes/caffeine/cache/TimerWheel.java

@@ -234,6 +234,7 @@ void unlink(Node<K, V> node) {
   }
 
   /** Returns the duration until the next bucket expires, or {@link Long.MAX_VALUE} if none. */
+  @SuppressWarnings("IntLongMath")
   public long getExpirationDelay() {
     for (int i = 0; i < SHIFT.length; i++) {
       Node<K, V>[] timerWheel = wheel[i];
@@ -247,7 +248,8 @@ public long getExpirationDelay() {
         Node<K, V> sentinel = timerWheel[(j & mask)];
         Node<K, V> next = sentinel.getNextInVariableOrder();
         if (sentinel != next) {
-          long delay = ((j - start) * SPANS[i]) - (nanos & spanMask);
+          long buckets = (j - start);
+          long delay = (buckets << SHIFT[i]) - (nanos & spanMask);
           return (delay > 0) ? delay : SPANS[i];
         }
       }