2008-07-01 Christian Thalinger <twisti@complang.tuwien.ac.at>

	* java/lang/Integer.java (signum): Implemented properly as
	described in Hacker's Delight Section 2-7, plus Andrew Haley's
	explanation.

2 files changed, 14 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index af13d4968..84ebad90d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2008-07-01  Christian Thalinger  <twisti@complang.tuwien.ac.at>
+
+	* java/lang/Integer.java (signum): Implemented properly as
+	described in Hacker's Delight Section 2-7, plus Andrew Haley's
+	explanation.
+
 2008-07-01  Andrew Haley  <aph@redhat.com>
 
 	* java/lang/Long.java: Comment change only.
diff --git a/java/lang/Integer.java b/java/lang/Integer.java
index 83161b4bf..e5ca4b342 100644
--- a/java/lang/Integer.java
+++ b/java/lang/Integer.java
@@ -687,7 +687,14 @@ public final class Integer extends Number implements Comparable<Integer>
    */
   public static int signum(int x)
   {
-    return (x >> 31) - (-x >> 31);
+    return (x >> 31) | (-x >>> 31);
+
+    // The LHS propagates the sign bit through every bit in the word;
+    // if X < 0, every bit is set to 1, else 0.  if X > 0, the RHS
+    // negates x and shifts the resulting 1 in the sign bit to the
+    // LSB, leaving every other bit 0.
+
+    // Hacker's Delight, Section 2-7
   }
 
   /**