[PATCH RESEND V8 1/2] xxHash: create arch dependent 32/64-bit xxhash()

[Timofey Titovets <nefelim4ag@gmail.com>]

xxh32() - fast on both 32/64-bit platforms
xxh64() - fast only on 64-bit platform

Create xxhash() which will pickup fastest version
on compile time.

As result depends on cpu word size,
the main proporse of that - in memory hashing.

Changes:
  v2:
    - Create that patch
  v3 -> v8:
    - Nothing, whole patchset version bump

Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com>
Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>

CC: Andrea Arcangeli <aarcange@redhat.com>
CC: linux-mm@kvack.org
CC: kvm@vger.kernel.org
CC: leesioh <solee@os.korea.ac.kr>
---
 include/linux/xxhash.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/include/linux/xxhash.h b/include/linux/xxhash.h
index 9e1f42cb57e9..52b073fea17f 100644
--- a/include/linux/xxhash.h
+++ b/include/linux/xxhash.h
@@ -107,6 +107,29 @@ uint32_t xxh32(const void *input, size_t length, uint32_t seed);
  */
 uint64_t xxh64(const void *input, size_t length, uint64_t seed);
 
+/**
+ * xxhash() - calculate wordsize hash of the input with a given seed
+ * @input:  The data to hash.
+ * @length: The length of the data to hash.
+ * @seed:   The seed can be used to alter the result predictably.
+ *
+ * If the hash does not need to be comparable between machines with
+ * different word sizes, this function will call whichever of xxh32()
+ * or xxh64() is faster.
+ *
+ * Return:  wordsize hash of the data.
+ */
+
+static inline unsigned long xxhash(const void *input, size_t length,
+				   uint64_t seed)
+{
+#if BITS_PER_LONG == 64
+       return xxh64(input, length, seed);
+#else
+       return xxh32(input, length, seed);
+#endif
+}
+
 /*-****************************
  * Streaming Hash Functions
  *****************************/
-- 
2.19.0