--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/arch/x86/lib/csum-partial_64.c	Sun Jan 11 20:20:11 2009 +0100
@@ -0,0 +1,148 @@
+/*
+ * arch/x86_64/lib/csum-partial.c
+ *
+ * This file contains network checksum routines that are better done
+ * in an architecture-specific manner due to speed.
+ */
+ 
+#include <linux/compiler.h>
+#include <linux/module.h>
+#include <asm/checksum.h>
+
+static inline unsigned short from32to16(unsigned a) 
+{
+	unsigned short b = a >> 16; 
+	asm("addw %w2,%w0\n\t"
+	    "adcw $0,%w0\n" 
+	    : "=r" (b)
+	    : "0" (b), "r" (a));
+	return b;
+}
+
+/*
+ * Do a 64-bit checksum on an arbitrary memory area.
+ * Returns a 32bit checksum.
+ *
+ * This isn't as time critical as it used to be because many NICs
+ * do hardware checksumming these days.
+ * 
+ * Things tried and found to not make it faster:
+ * Manual Prefetching
+ * Unrolling to an 128 bytes inner loop.
+ * Using interleaving with more registers to break the carry chains.
+ */
+static unsigned do_csum(const unsigned char *buff, unsigned len)
+{
+	unsigned odd, count;
+	unsigned long result = 0;
+
+	if (unlikely(len == 0))
+		return result; 
+	odd = 1 & (unsigned long) buff;
+	if (unlikely(odd)) {
+		result = *buff << 8;
+		len--;
+		buff++;
+	}
+	count = len >> 1;		/* nr of 16-bit words.. */
+	if (count) {
+		if (2 & (unsigned long) buff) {
+			result += *(unsigned short *)buff;
+			count--;
+			len -= 2;
+			buff += 2;
+		}
+		count >>= 1;		/* nr of 32-bit words.. */
+		if (count) {
+			unsigned long zero;
+			unsigned count64;
+			if (4 & (unsigned long) buff) {
+				result += *(unsigned int *) buff;
+				count--;
+				len -= 4;
+				buff += 4;
+			}
+			count >>= 1;	/* nr of 64-bit words.. */
+
+			/* main loop using 64byte blocks */
+			zero = 0;
+			count64 = count >> 3;
+			while (count64) { 
+				asm("addq 0*8(%[src]),%[res]\n\t"
+				    "adcq 1*8(%[src]),%[res]\n\t"
+				    "adcq 2*8(%[src]),%[res]\n\t"
+				    "adcq 3*8(%[src]),%[res]\n\t"
+				    "adcq 4*8(%[src]),%[res]\n\t"
+				    "adcq 5*8(%[src]),%[res]\n\t"
+				    "adcq 6*8(%[src]),%[res]\n\t"
+				    "adcq 7*8(%[src]),%[res]\n\t"
+				    "adcq %[zero],%[res]"
+				    : [res] "=r" (result)
+				    : [src] "r" (buff), [zero] "r" (zero),
+				    "[res]" (result));
+				buff += 64;
+				count64--;
+			}
+
+			/* last upto 7 8byte blocks */
+			count %= 8; 
+			while (count) { 
+				asm("addq %1,%0\n\t"
+				    "adcq %2,%0\n" 
+					    : "=r" (result)
+				    : "m" (*(unsigned long *)buff), 
+				    "r" (zero),  "0" (result));
+				--count; 
+					buff += 8;
+			}
+			result = add32_with_carry(result>>32,
+						  result&0xffffffff); 
+
+			if (len & 4) {
+				result += *(unsigned int *) buff;
+				buff += 4;
+			}
+		}
+		if (len & 2) {
+			result += *(unsigned short *) buff;
+			buff += 2;
+		}
+	}
+	if (len & 1)
+		result += *buff;
+	result = add32_with_carry(result>>32, result & 0xffffffff); 
+	if (unlikely(odd)) { 
+		result = from32to16(result);
+		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
+	}
+	return result;
+}
+
+/*
+ * computes the checksum of a memory block at buff, length len,
+ * and adds in "sum" (32-bit)
+ *
+ * returns a 32-bit number suitable for feeding into itself
+ * or csum_tcpudp_magic
+ *
+ * this function must be called with even lengths, except
+ * for the last fragment, which may be odd
+ *
+ * it's best to have buff aligned on a 64-bit boundary
+ */
+__wsum csum_partial(const void *buff, int len, __wsum sum)
+{
+	return (__force __wsum)add32_with_carry(do_csum(buff, len),
+						(__force u32)sum);
+}
+
+/*
+ * this routine is used for miscellaneous IP-like checksums, mainly
+ * in icmp.c
+ */
+__sum16 ip_compute_csum(const void *buff, int len)
+{
+	return csum_fold(csum_partial(buff,len,0));
+}
+EXPORT_SYMBOL(ip_compute_csum);
+