crc32: minor optimizations and cleanup

Move common crc body to new function crc32_body() cleaup and micro
optimize crc32_body for speed and less size.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/crc32.c b/lib/crc32.c
index 49d1c9e..02e3b31 100644 (file)
--- a/lib/crc32.c
+++ b/lib/crc32.c
@@ -42,6 +42,48 @@ MODULE_AUTHOR("Matt Domsch <Matt_Domsch@dell.com>");
 MODULE_DESCRIPTION("Ethernet CRC32 calculations");
 MODULE_LICENSE("GPL");
 
+#if CRC_LE_BITS == 8 || CRC_BE_BITS == 8
+
+static inline u32
+crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 *tab)
+{
+# ifdef __LITTLE_ENDIAN
+#  define DO_CRC(x) crc = tab[(crc ^ (x)) & 255 ] ^ (crc >> 8)
+# else
+#  define DO_CRC(x) crc = tab[((crc >> 24) ^ (x)) & 255] ^ (crc << 8)
+# endif
+       const u32 *b = (const u32 *)buf;
+       size_t    rem_len;
+
+       /* Align it */
+       if (unlikely((long)b & 3 && len)) {
+               u8 *p = (u8 *)b;
+               do {
+                       DO_CRC(*p++);
+               } while ((--len) && ((long)p)&3);
+               b = (u32 *)p;
+       }
+       rem_len = len & 3;
+       /* load data 32 bits wide, xor data 32 bits wide. */
+       len = len >> 2;
+       for (--b; len; --len) {
+               crc ^= *++b; /* use pre increment for speed */
+               DO_CRC(0);
+               DO_CRC(0);
+               DO_CRC(0);
+               DO_CRC(0);
+       }
+       len = rem_len;
+       /* And the last few bytes */
+       if (len) {
+               u8 *p = (u8 *)(b + 1) - 1;
+               do {
+                       DO_CRC(*++p); /* use pre increment for speed */
+               } while (--len);
+       }
+       return crc;
+}
+#endif
 /**
  * crc32_le() - Calculate bitwise little-endian Ethernet AUTODIN II CRC32
  * @crc: seed value for computation.  ~0 for Ethernet, sometimes 0 for
@@ -72,48 +114,10 @@ u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len)
 u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len)
 {
 # if CRC_LE_BITS == 8
-       const u32      *b =(u32 *)p;
        const u32      *tab = crc32table_le;
 
-# ifdef __LITTLE_ENDIAN
-#  define DO_CRC(x) crc = tab[ (crc ^ (x)) & 255 ] ^ (crc>>8)
-# else
-#  define DO_CRC(x) crc = tab[ ((crc >> 24) ^ (x)) & 255] ^ (crc<<8)
-# endif
-
        crc = __cpu_to_le32(crc);
-       /* Align it */
-       if(unlikely(((long)b)&3 && len)){
-               do {
-                       u8 *p = (u8 *)b;
-                       DO_CRC(*p++);
-                       b = (void *)p;
-               } while ((--len) && ((long)b)&3 );
-       }
-       if(likely(len >= 4)){
-               /* load data 32 bits wide, xor data 32 bits wide. */
-               size_t save_len = len & 3;
-               len = len >> 2;
-               --b; /* use pre increment below(*++b) for speed */
-               do {
-                       crc ^= *++b;
-                       DO_CRC(0);
-                       DO_CRC(0);
-                       DO_CRC(0);
-                       DO_CRC(0);
-               } while (--len);
-               b++; /* point to next byte(s) */
-               len = save_len;
-       }
-       /* And the last few bytes */
-       if(len){
-               do {
-                       u8 *p = (u8 *)b;
-                       DO_CRC(*p++);
-                       b = (void *)p;
-               } while (--len);
-       }
-
+       crc = crc32_body(crc, p, len, tab);
        return __le32_to_cpu(crc);
 #undef ENDIAN_SHIFT
 #undef DO_CRC
@@ -170,47 +174,10 @@ u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
 u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
 {
 # if CRC_BE_BITS == 8
-       const u32      *b =(u32 *)p;
        const u32      *tab = crc32table_be;
 
-# ifdef __LITTLE_ENDIAN
-#  define DO_CRC(x) crc = tab[ (crc ^ (x)) & 255 ] ^ (crc>>8)
-# else
-#  define DO_CRC(x) crc = tab[ ((crc >> 24) ^ (x)) & 255] ^ (crc<<8)
-# endif
-
        crc = __cpu_to_be32(crc);
-       /* Align it */
-       if(unlikely(((long)b)&3 && len)){
-               do {
-                       u8 *p = (u8 *)b;
-                       DO_CRC(*p++);
-                       b = (u32 *)p;
-               } while ((--len) && ((long)b)&3 );
-       }
-       if(likely(len >= 4)){
-               /* load data 32 bits wide, xor data 32 bits wide. */
-               size_t save_len = len & 3;
-               len = len >> 2;
-               --b; /* use pre increment below(*++b) for speed */
-               do {
-                       crc ^= *++b;
-                       DO_CRC(0);
-                       DO_CRC(0);
-                       DO_CRC(0);
-                       DO_CRC(0);
-               } while (--len);
-               b++; /* point to next byte(s) */
-               len = save_len;
-       }
-       /* And the last few bytes */
-       if(len){
-               do {
-                       u8 *p = (u8 *)b;
-                       DO_CRC(*p++);
-                       b = (void *)p;
-               } while (--len);
-       }
+       crc = crc32_body(crc, p, len, tab);
        return __be32_to_cpu(crc);
 #undef ENDIAN_SHIFT
 #undef DO_CRC