[patches v5 resending 7/8] crc32: add-slicing-by-8.diff
From: Bob Pearson
Date: Thu Aug 11 2011 - 13:44:26 EST
extend add slicing-by-8 algorithm to the existing
slicing-by-4 algorithm. This consists of:
- extend largest BITS size from 32 to 64
- extend table from tab[4][256] to tab[8][256]
- change algorithm to align on 8 byte boundary
(it was noted that all that is really required
is that the inner loop must comsume 8 bytes.
As written it can start on even or odd 4 byte
boundary.)
- Add code for inner loop.
Signed-off-by: Bob Pearson <rpearson@xxxxxxxxxxxxxxxxxxxxx>
---
lib/crc32.c | 60 ++++++++++++++++++++++++++++++++++++++++++---------
lib/crc32defs.h | 14 +++++------
lib/gen_crc32table.c | 42 ++++++++++++++++++++++-------------
3 files changed, 83 insertions(+), 33 deletions(-)
Index: infiniband/lib/crc32.c
===================================================================
--- infiniband.orig/lib/crc32.c
+++ infiniband/lib/crc32.c
@@ -45,6 +45,7 @@ MODULE_LICENSE("GPL");
#if CRC_LE_BITS > 8 || CRC_BE_BITS > 8
+/* implements slicing-by-4 or slicing-by-8 algorithm */
static inline u32
crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])
{
@@ -54,42 +55,81 @@ crc32_body(u32 crc, unsigned char const
t2[(crc >> 8) & 255] ^ \
t1[(crc >> 16) & 255] ^ \
t0[(crc >> 24) & 255]
+# define DO_CRC8a (t7[(q) & 255] ^ \
+ t6[(q >> 8) & 255] ^ \
+ t5[(q >> 16) & 255] ^ \
+ t4[(q >> 24) & 255])
+# define DO_CRC8b (t3[(q) & 255] ^ \
+ t2[(q >> 8) & 255] ^ \
+ t1[(q >> 16) & 255] ^ \
+ t0[(q >> 24) & 255])
# else
# define DO_CRC(x) (crc = t0[((crc >> 24) ^ (x)) & 255] ^ (crc << 8))
# define DO_CRC4 crc = t0[(crc) & 255] ^ \
t1[(crc >> 8) & 255] ^ \
t2[(crc >> 16) & 255] ^ \
t3[(crc >> 24) & 255]
+# define DO_CRC8a (t4[(q) & 255] ^ \
+ t5[(q >> 8) & 255] ^ \
+ t6[(q >> 16) & 255] ^ \
+ t7[(q >> 24) & 255])
+# define DO_CRC8b (t0[(q) & 255] ^ \
+ t1[(q >> 8) & 255] ^ \
+ t2[(q >> 16) & 255] ^ \
+ t3[(q >> 24) & 255])
# endif
const u32 *b;
- size_t rem_len;
const u32 *t0 = tab[0], *t1 = tab[1], *t2 = tab[2], *t3 = tab[3];
+ const u32 *t4 = tab[4], *t5 = tab[5], *t6 = tab[6], *t7 = tab[7];
+ size_t init_len;
+ size_t middle_len;
+ size_t rem_len;
+
+ /* break buf into init_len bytes before and
+ * rem_len bytes after a middle section with
+ * middle_len properly aligned words
+ * note 8 byte loop need only be aligned on
+ * a 4 byte boundary */
+ init_len = min((-((uintptr_t)buf)) & 3, len);
+# if CRC_LE_BITS == 32
+ middle_len = (len - init_len) >> 2;
+ rem_len = (len - init_len) & 3;
+# else
+ middle_len = (len - init_len) >> 3;
+ rem_len = (len - init_len) & 7;
+# endif
/* Align it */
- if (unlikely((long)buf & 3 && len)) {
+ if (unlikely(init_len)) {
do {
DO_CRC(*buf++);
- } while ((--len) && ((long)buf)&3);
+ } while (--init_len);
}
- rem_len = len & 3;
- /* load data 32 bits wide, xor data 32 bits wide. */
- len = len >> 2;
b = (const u32 *)buf;
- for (--b; len; --len) {
+ for (--b; middle_len; --middle_len) {
+# if CRC_LE_BITS == 32
crc ^= *++b; /* use pre increment for speed */
DO_CRC4;
+# else
+ u32 q;
+ q = crc ^ *++b;
+ crc = DO_CRC8a;
+ q = *++b;
+ crc ^= DO_CRC8b;
+# endif
}
- len = rem_len;
/* And the last few bytes */
- if (len) {
+ if (rem_len) {
u8 *p = (u8 *)(b + 1) - 1;
do {
DO_CRC(*++p); /* use pre increment for speed */
- } while (--len);
+ } while (--rem_len);
}
return crc;
#undef DO_CRC
#undef DO_CRC4
+#undef DO_CRC8a
+#undef DO_CRC8b
}
#endif
Index: infiniband/lib/crc32defs.h
===================================================================
--- infiniband.orig/lib/crc32defs.h
+++ infiniband/lib/crc32defs.h
@@ -6,29 +6,29 @@
#define CRCPOLY_LE 0xedb88320
#define CRCPOLY_BE 0x04c11db7
-/* How many bits at a time to use. Valid values are 1, 2, 4, 8, and 32. */
+/* How many bits at a time to use. Valid values are 1, 2, 4, 8, 32 and 64. */
/* For less performance-sensitive, use 4 or 8 */
#ifndef CRC_LE_BITS
-# define CRC_LE_BITS 32
+# define CRC_LE_BITS 64
#endif
#ifndef CRC_BE_BITS
-# define CRC_BE_BITS 32
+# define CRC_BE_BITS 64
#endif
/*
* Little-endian CRC computation. Used with serial bit streams sent
* lsbit-first. Be sure to use cpu_to_le32() to append the computed CRC.
*/
-#if CRC_LE_BITS > 32 || CRC_LE_BITS < 1 || CRC_LE_BITS == 16 || \
+#if CRC_LE_BITS > 64 || CRC_LE_BITS < 1 || CRC_LE_BITS == 16 || \
CRC_LE_BITS & CRC_LE_BITS-1
-# error "CRC_LE_BITS must be one of {1, 2, 4, 8, 32}"
+# error "CRC_LE_BITS must be one of {1, 2, 4, 8, 64}"
#endif
/*
* Big-endian CRC computation. Used with serial bit streams sent
* msbit-first. Be sure to use cpu_to_be32() to append the computed CRC.
*/
-#if CRC_BE_BITS > 32 || CRC_BE_BITS < 1 || CRC_BE_BITS == 16 || \
+#if CRC_BE_BITS > 64 || CRC_BE_BITS < 1 || CRC_BE_BITS == 16 || \
CRC_BE_BITS & CRC_BE_BITS-1
-# error "CRC_BE_BITS must be one of {1, 2, 4, 8, 32}"
+# error "CRC_BE_BITS must be one of {1, 2, 4, 8, 64}"
#endif
Index: infiniband/lib/gen_crc32table.c
===================================================================
--- infiniband.orig/lib/gen_crc32table.c
+++ infiniband/lib/gen_crc32table.c
@@ -4,20 +4,24 @@
#define ENTRIES_PER_LINE 4
-#if CRC_LE_BITS <= 8
-#define LE_TABLE_SIZE (1 << CRC_LE_BITS)
+#if CRC_LE_BITS > 8
+# define LE_TABLE_ROWS (CRC_LE_BITS/8)
+# define LE_TABLE_SIZE 256
#else
-#define LE_TABLE_SIZE 256
+# define LE_TABLE_ROWS 1
+# define LE_TABLE_SIZE (1 << CRC_LE_BITS)
#endif
-#if CRC_BE_BITS <= 8
-#define BE_TABLE_SIZE (1 << CRC_BE_BITS)
+#if CRC_BE_BITS > 8
+# define BE_TABLE_ROWS (CRC_BE_BITS/8)
+# define BE_TABLE_SIZE 256
#else
-#define BE_TABLE_SIZE 256
+# define BE_TABLE_ROWS 1
+# define BE_TABLE_SIZE (1 << CRC_BE_BITS)
#endif
-static uint32_t crc32table_le[4][256];
-static uint32_t crc32table_be[4][256];
+static uint32_t crc32table_le[LE_TABLE_ROWS][256];
+static uint32_t crc32table_be[BE_TABLE_ROWS][256];
/**
* crc32init_le() - allocate and initialize LE table data
@@ -40,7 +44,7 @@ static void crc32init_le(void)
}
for (i = 0; i < LE_TABLE_SIZE; i++) {
crc = crc32table_le[0][i];
- for (j = 1; j < 4; j++) {
+ for (j = 1; j < LE_TABLE_ROWS; j++) {
crc = crc32table_le[0][crc & 0xff] ^ (crc >> 8);
crc32table_le[j][i] = crc;
}
@@ -64,18 +68,18 @@ static void crc32init_be(void)
}
for (i = 0; i < BE_TABLE_SIZE; i++) {
crc = crc32table_be[0][i];
- for (j = 1; j < 4; j++) {
+ for (j = 1; j < BE_TABLE_ROWS; j++) {
crc = crc32table_be[0][(crc >> 24) & 0xff] ^ (crc << 8);
crc32table_be[j][i] = crc;
}
}
}
-static void output_table(uint32_t table[4][256], int len, char *trans)
+static void output_table(uint32_t (*table)[256], int rows, int len, char *trans)
{
int i, j;
- for (j = 0 ; j < 4; j++) {
+ for (j = 0 ; j < rows; j++) {
printf("{");
for (i = 0; i < len - 1; i++) {
if (i % ENTRIES_PER_LINE == 0)
@@ -92,15 +96,21 @@ int main(int argc, char** argv)
if (CRC_LE_BITS > 1) {
crc32init_le();
- printf("static const u32 crc32table_le[4][256] = {");
- output_table(crc32table_le, LE_TABLE_SIZE, "tole");
+ printf("static const u32 __cacheline_aligned "
+ "crc32table_le[%d][%d] = {",
+ LE_TABLE_ROWS, LE_TABLE_SIZE);
+ output_table(crc32table_le, LE_TABLE_ROWS,
+ LE_TABLE_SIZE, "tole");
printf("};\n");
}
if (CRC_BE_BITS > 1) {
crc32init_be();
- printf("static const u32 crc32table_be[4][256] = {");
- output_table(crc32table_be, BE_TABLE_SIZE, "tobe");
+ printf("static const u32 __cacheline_aligned "
+ "crc32table_be[%d][%d] = {",
+ BE_TABLE_ROWS, BE_TABLE_SIZE);
+ output_table(crc32table_be, LE_TABLE_ROWS,
+ BE_TABLE_SIZE, "tobe");
printf("};\n");
}
--
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