[PATCH] drop xen/hash.h

[PATCH] drop xen/hash.h

[Jan Beulich]

It has no users and hasn't been touched in 10 years.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/include/xen/hash.h
+++ /dev/null
@@ -1,58 +0,0 @@
-#ifndef _XEN_HASH_H
-#define _XEN_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 /* _XEN_HASH_H */

Re: [PATCH] drop xen/hash.h

[Andrew Cooper]

On 14/10/2020 08:04, Jan Beulich wrote:
> It has no users and hasn't been touched in 10 years.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>