changeset 14402:c4fa801257f9

8155795: Optimize Integer/Long.reverse by using reverseBytes Reviewed-by: redestad, shade Contributed-by: jaroslav@kamenik.cz
author redestad
date Tue, 10 May 2016 13:28:00 +0200
parents f2553c90dbc2
children b2f12e28d97b
files src/java.base/share/classes/java/lang/Integer.java src/java.base/share/classes/java/lang/Long.java test/java/lang/Integer/BitTwiddle.java test/java/lang/Long/BitTwiddle.java
diffstat 4 files changed, 54 insertions(+), 11 deletions(-) [+]
line wrap: on
line diff
--- a/src/java.base/share/classes/java/lang/Integer.java	Tue May 10 15:12:04 2016 +0800
+++ b/src/java.base/share/classes/java/lang/Integer.java	Tue May 10 13:28:00 2016 +0200
@@ -1790,9 +1790,8 @@
         i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
         i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
         i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
-        i = (i << 24) | ((i & 0xff00) << 8) |
-            ((i >>> 8) & 0xff00) | (i >>> 24);
-        return i;
+
+        return reverseBytes(i);
     }
 
     /**
@@ -1820,10 +1819,10 @@
      */
     @HotSpotIntrinsicCandidate
     public static int reverseBytes(int i) {
-        return ((i >>> 24)           ) |
-               ((i >>   8) &   0xFF00) |
-               ((i <<   8) & 0xFF0000) |
-               ((i << 24));
+        return (i << 24)            |
+               ((i & 0xff00) << 8)  |
+               ((i >>> 8) & 0xff00) |
+               (i >>> 24);
     }
 
     /**
--- a/src/java.base/share/classes/java/lang/Long.java	Tue May 10 15:12:04 2016 +0800
+++ b/src/java.base/share/classes/java/lang/Long.java	Tue May 10 13:28:00 2016 +0200
@@ -1952,10 +1952,8 @@
         i = (i & 0x5555555555555555L) << 1 | (i >>> 1) & 0x5555555555555555L;
         i = (i & 0x3333333333333333L) << 2 | (i >>> 2) & 0x3333333333333333L;
         i = (i & 0x0f0f0f0f0f0f0f0fL) << 4 | (i >>> 4) & 0x0f0f0f0f0f0f0f0fL;
-        i = (i & 0x00ff00ff00ff00ffL) << 8 | (i >>> 8) & 0x00ff00ff00ff00ffL;
-        i = (i << 48) | ((i & 0xffff0000L) << 16) |
-            ((i >>> 16) & 0xffff0000L) | (i >>> 48);
-        return i;
+
+        return reverseBytes(i);
     }
 
     /**
--- a/test/java/lang/Integer/BitTwiddle.java	Tue May 10 15:12:04 2016 +0800
+++ b/test/java/lang/Integer/BitTwiddle.java	Tue May 10 13:28:00 2016 +0200
@@ -58,6 +58,21 @@
 
         for (int i = 0; i < N; i++) {
             int x = rnd.nextInt();
+
+            String expected = new StringBuilder()
+                .append(leftpad(toBinaryString(x), 32))
+                .reverse().toString();
+
+            String actual = leftpad(toBinaryString(reverse(x)), 32);
+
+            if (!expected.equals(actual)) {
+                throw new RuntimeException("reverse: \n" +
+                        expected + " \n" + actual);
+            }
+        }
+
+        for (int i = 0; i < N; i++) {
+            int x = rnd.nextInt();
             if (highestOneBit(x) != reverse(lowestOneBit(reverse(x))))
                 throw new RuntimeException("g: " + toHexString(x));
         }
@@ -136,4 +151,12 @@
                 throw new RuntimeException("z: " + toHexString(x));
         }
     }
+
+    private static String leftpad(String s, int width) {
+        String r = s;
+        for (int c = 0; c < width - s.length(); c++) {
+            r = "0" + r;
+        }
+        return r;
+    }
 }
--- a/test/java/lang/Long/BitTwiddle.java	Tue May 10 15:12:04 2016 +0800
+++ b/test/java/lang/Long/BitTwiddle.java	Tue May 10 13:28:00 2016 +0200
@@ -58,6 +58,21 @@
 
         for (int i = 0; i < N; i++) {
             long x = rnd.nextLong();
+
+            String expected = new StringBuilder()
+                .append(leftpad(toBinaryString(x), 64))
+                .reverse().toString();
+
+            String actual = leftpad(toBinaryString(reverse(x)), 64);
+
+            if (!expected.equals(actual)) {
+                throw new RuntimeException("reverse: \n" +
+                        expected + " \n" + actual);
+            }
+        }
+
+        for (int i = 0; i < N; i++) {
+            long x = rnd.nextLong();
             if (highestOneBit(x) != reverse(lowestOneBit(reverse(x))))
                 throw new RuntimeException("g: " + toHexString(x));
         }
@@ -136,4 +151,12 @@
                 throw new RuntimeException("z: " + toHexString(x));
         }
     }
+
+    private static String leftpad(String s, int width) {
+        String r = s;
+        for (int c = 0; c < width - s.length(); c++) {
+            r = "0" + r;
+        }
+        return r;
+    }
 }