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>

1 files changed, 44 insertions, 77 deletions

diff --git a/lib/crc32.c b/lib/crc32.c
index 49d1c9e3ce38..02e3b31b3a79 100644
--- 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