# HG changeset patch
# User yamahata@xxxxxxxxxxxxx
# Node ID 3cee9325a6c60a057f0ed4a95b050e012b64ae09
# Parent  b2abc70be89e02d0d380674096c8c1fb9e552431
import linux/include/linux/hash.h.
PATCHNAME: import_linux_hash.h

Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>

diff -r b2abc70be89e -r 3cee9325a6c6 xen/include/asm-ia64/linux/README.origin
--- a/xen/include/asm-ia64/linux/README.origin	Wed Jul 19 07:17:54 2006 -0600
+++ b/xen/include/asm-ia64/linux/README.origin	Mon Jul 24 23:18:39 2006 +0900
@@ -8,6 +8,7 @@ bitmap.h		-> linux/include/linux/bitmap.
 bitmap.h		-> linux/include/linux/bitmap.h
 bitops.h		-> linux/include/linux/bitops.h
 initrd.h		-> linux/include/linux/initrd.h
+hash.h			-> linux/include/linux/hash.h
 jiffies.h		-> linux/include/linux/jiffies.h
 kmalloc_sizes.h		-> linux/include/linux/kmalloc_sizes.h
 linkage.h		-> linux/include/linux/linkage.h
diff -r b2abc70be89e -r 3cee9325a6c6 xen/include/asm-ia64/linux/hash.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xen/include/asm-ia64/linux/hash.h	Mon Jul 24 23:18:39 2006 +0900
@@ -0,0 +1,58 @@
+#ifndef _LINUX_HASH_H
+#define _LINUX_HASH_H
+/* Fast hashing routine for a long.
+   (C) 2002 William Lee Irwin III, IBM */
+
+/*
+ * Knuth recommends primes in approximately golden ratio to the maximum
+ * integer representable by a machine word for multiplicative hashing.
+ * Chuck Lever verified the effectiveness of this technique:
+ * http://www.citi.umich.edu/techreports/reports/citi-tr-00-1.pdf
+ *
+ * These primes are chosen to be bit-sparse, that is operations on
+ * them can use shifts and additions instead of multiplications for
+ * machines where multiplications are slow.
+ */
+#if BITS_PER_LONG == 32
+/* 2^31 + 2^29 - 2^25 + 2^22 - 2^19 - 2^16 + 1 */
+#define GOLDEN_RATIO_PRIME 0x9e370001UL
+#elif BITS_PER_LONG == 64
+/*  2^63 + 2^61 - 2^57 + 2^54 - 2^51 - 2^18 + 1 */
+#define GOLDEN_RATIO_PRIME 0x9e37fffffffc0001UL
+#else
+#error Define GOLDEN_RATIO_PRIME for your wordsize.
+#endif
+
+static inline unsigned long hash_long(unsigned long val, unsigned int bits)
+{
+	unsigned long hash = val;
+
+#if BITS_PER_LONG == 64
+	/*  Sigh, gcc can't optimise this alone like it does for 32 bits. */
+	unsigned long n = hash;
+	n <<= 18;
+	hash -= n;
+	n <<= 33;
+	hash -= n;
+	n <<= 3;
+	hash += n;
+	n <<= 3;
+	hash -= n;
+	n <<= 4;
+	hash += n;
+	n <<= 2;
+	hash += n;
+#else
+	/* On some cpus multiply is faster, on others gcc will do shifts */
+	hash *= GOLDEN_RATIO_PRIME;
+#endif
+
+	/* High bits are more random, so use them. */
+	return hash >> (BITS_PER_LONG - bits);
+}
+	
+static inline unsigned long hash_ptr(void *ptr, unsigned int bits)
+{
+	return hash_long((unsigned long)ptr, bits);
+}
+#endif /* _LINUX_HASH_H */