6935172: Optimize bit-twiddling in Bits.java

Summary: Transformations to reduce size of bytecode
Reviewed-by: sherman
Contributed-by: NBased on an idea by Ulf Zibis <ulf.zibis@gmx.de>

jdk/src/share/classes/java/io/Bits.java

@@ -41,51 +41,39 @@ class Bits {
     }
 
     static char getChar(byte[] b, int off) {
-        return (char) (((b[off + 1] & 0xFF) << 0) +
-                       ((b[off + 0]) << 8));
+        return (char) ((b[off + 1] & 0xFF) +
+                       (b[off] << 8));
     }
 
     static short getShort(byte[] b, int off) {
-        return (short) (((b[off + 1] & 0xFF) << 0) +
-                        ((b[off + 0]) << 8));
+        return (short) ((b[off + 1] & 0xFF) +
+                        (b[off] << 8));
     }
 
     static int getInt(byte[] b, int off) {
-        return ((b[off + 3] & 0xFF) << 0) +
-               ((b[off + 2] & 0xFF) << 8) +
+        return ((b[off + 3] & 0xFF)      ) +
+               ((b[off + 2] & 0xFF) <<  8) +
                ((b[off + 1] & 0xFF) << 16) +
-               ((b[off + 0]) << 24);
+               ((b[off    ]       ) << 24);
     }
 
     static float getFloat(byte[] b, int off) {
-        int i = ((b[off + 3] & 0xFF) << 0) +
-                ((b[off + 2] & 0xFF) << 8) +
-                ((b[off + 1] & 0xFF) << 16) +
-                ((b[off + 0]) << 24);
-        return Float.intBitsToFloat(i);
+        return Float.intBitsToFloat(getInt(b, off));
     }
 
     static long getLong(byte[] b, int off) {
-        return ((b[off + 7] & 0xFFL) << 0) +
-               ((b[off + 6] & 0xFFL) << 8) +
+        return ((b[off + 7] & 0xFFL)      ) +
+               ((b[off + 6] & 0xFFL) <<  8) +
                ((b[off + 5] & 0xFFL) << 16) +
                ((b[off + 4] & 0xFFL) << 24) +
                ((b[off + 3] & 0xFFL) << 32) +
                ((b[off + 2] & 0xFFL) << 40) +
                ((b[off + 1] & 0xFFL) << 48) +
-               (((long) b[off + 0]) << 56);
+               (((long) b[off])      << 56);
     }
 
     static double getDouble(byte[] b, int off) {
-        long j = ((b[off + 7] & 0xFFL) << 0) +
-                 ((b[off + 6] & 0xFFL) << 8) +
-                 ((b[off + 5] & 0xFFL) << 16) +
-                 ((b[off + 4] & 0xFFL) << 24) +
-                 ((b[off + 3] & 0xFFL) << 32) +
-                 ((b[off + 2] & 0xFFL) << 40) +
-                 ((b[off + 1] & 0xFFL) << 48) +
-                 (((long) b[off + 0]) << 56);
-        return Double.longBitsToDouble(j);
+        return Double.longBitsToDouble(getLong(b, off));
     }
 
     /*
@@ -98,50 +86,38 @@ class Bits {
     }
 
     static void putChar(byte[] b, int off, char val) {
-        b[off + 1] = (byte) (val >>> 0);
-        b[off + 0] = (byte) (val >>> 8);
+        b[off + 1] = (byte) (val      );
+        b[off    ] = (byte) (val >>> 8);
     }
 
     static void putShort(byte[] b, int off, short val) {
-        b[off + 1] = (byte) (val >>> 0);
-        b[off + 0] = (byte) (val >>> 8);
+        b[off + 1] = (byte) (val      );
+        b[off    ] = (byte) (val >>> 8);
     }
 
     static void putInt(byte[] b, int off, int val) {
-        b[off + 3] = (byte) (val >>> 0);
-        b[off + 2] = (byte) (val >>> 8);
+        b[off + 3] = (byte) (val       );
+        b[off + 2] = (byte) (val >>>  8);
         b[off + 1] = (byte) (val >>> 16);
-        b[off + 0] = (byte) (val >>> 24);
+        b[off    ] = (byte) (val >>> 24);
     }
 
     static void putFloat(byte[] b, int off, float val) {
-        int i = Float.floatToIntBits(val);
-        b[off + 3] = (byte) (i >>> 0);
-        b[off + 2] = (byte) (i >>> 8);
-        b[off + 1] = (byte) (i >>> 16);
-        b[off + 0] = (byte) (i >>> 24);
+        putInt(b, off,  Float.floatToIntBits(val));
     }
 
     static void putLong(byte[] b, int off, long val) {
-        b[off + 7] = (byte) (val >>> 0);
-        b[off + 6] = (byte) (val >>> 8);
+        b[off + 7] = (byte) (val       );
+        b[off + 6] = (byte) (val >>>  8);
         b[off + 5] = (byte) (val >>> 16);
         b[off + 4] = (byte) (val >>> 24);
         b[off + 3] = (byte) (val >>> 32);
         b[off + 2] = (byte) (val >>> 40);
         b[off + 1] = (byte) (val >>> 48);
-        b[off + 0] = (byte) (val >>> 56);
+        b[off    ] = (byte) (val >>> 56);
     }
 
     static void putDouble(byte[] b, int off, double val) {
-        long j = Double.doubleToLongBits(val);
-        b[off + 7] = (byte) (j >>> 0);
-        b[off + 6] = (byte) (j >>> 8);
-        b[off + 5] = (byte) (j >>> 16);
-        b[off + 4] = (byte) (j >>> 24);
-        b[off + 3] = (byte) (j >>> 32);
-        b[off + 2] = (byte) (j >>> 40);
-        b[off + 1] = (byte) (j >>> 48);
-        b[off + 0] = (byte) (j >>> 56);
+        putLong(b, off, Double.doubleToLongBits(val));
     }
 }