zlib_deflate/deftree: remove bi_reverse()

Remove bi_reverse() and use generic bitrev32() instead - it should have
better performance on some platforms.

Signed-off-by: yalin wang <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

lib/zlib_deflate/deftree.c

···
 /* #include "deflate.h" */
 
 #include <linux/zutil.h>
+#include <linux/bitrev.h>
 #include "defutil.h"
 
 #ifdef DEBUG_ZLIB
···
 static void compress_block (deflate_state *s, ct_data *ltree,
                            ct_data *dtree);
 static void set_data_type  (deflate_state *s);
-static unsigned bi_reverse (unsigned value, int length);
 static void bi_windup      (deflate_state *s);
 static void bi_flush       (deflate_state *s);
 static void copy_block     (deflate_state *s, char *buf, unsigned len,
···
     /* The static distance tree is trivial: */
     for (n = 0; n < D_CODES; n++) {
         static_dtree[n].Len = 5;
-        static_dtree[n].Code = bi_reverse((unsigned)n, 5);
+        static_dtree[n].Code = bitrev32((u32)n) >> (32 - 5);
     }
     static_init_done = 1;
 }
···
         int len = tree[n].Len;
         if (len == 0) continue;
         /* Now reverse the bits */
-        tree[n].Code = bi_reverse(next_code[len]++, len);
+        tree[n].Code = bitrev32((u32)(next_code[len]++)) >> (32 - len);
 
         Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
              n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));

lib/zlib_deflate/defutil.h

···
 }
 
 /* ===========================================================================
- * Reverse the first len bits of a code, using straightforward code (a faster
- * method would use a table)
- * IN assertion: 1 <= len <= 15
- */
-static inline unsigned bi_reverse(unsigned code, /* the value to invert */
-				  int len)       /* its bit length */
-{
-    register unsigned res = 0;
-    do {
-        res |= code & 1;
-        code >>= 1, res <<= 1;
-    } while (--len > 0);
-    return res >> 1;
-}
-
-/* ===========================================================================
  * Flush the bit buffer, keeping at most 7 bits in it.
  */
 static inline void bi_flush(deflate_state *s)