Compile cityhash code into libzfs

Make the cityhash code compile into libzfs, in preparation for the new
"zstream" command.

Reviewed-by: Paul Dagnelie <pcd@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes #10152

module/zcommon/Makefile.in

@@ -11,6 +11,7 @@ ccflags-y := $(ZFS_MODULE_CFLAGS) $(ZFS_MODULE_CPPFLAGS)
 # Suppress unused-value warnings in sparc64 architecture headers
 ccflags-$(CONFIG_SPARC64) += -Wno-unused-value
 
+$(MODULE)-objs += cityhash.o
 $(MODULE)-objs += zfeature_common.o
 $(MODULE)-objs += zfs_comutil.o
 $(MODULE)-objs += zfs_deleg.o

module/zcommon/cityhash.c

@@ -0,0 +1,67 @@
+// Copyright (c) 2011 Google, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+/*
+ * Copyright (c) 2017 by Delphix. All rights reserved.
+ */
+
+#include <cityhash.h>
+
+#define	HASH_K1 0xb492b66fbe98f273ULL
+#define	HASH_K2 0x9ae16a3b2f90404fULL
+
+/*
+ * Bitwise right rotate.  Normally this will compile to a single
+ * instruction.
+ */
+static inline uint64_t
+rotate(uint64_t val, int shift)
+{
+	// Avoid shifting by 64: doing so yields an undefined result.
+	return (shift == 0 ? val : (val >> shift) | (val << (64 - shift)));
+}
+
+static inline uint64_t
+cityhash_helper(uint64_t u, uint64_t v, uint64_t mul)
+{
+	uint64_t a = (u ^ v) * mul;
+	a ^= (a >> 47);
+	uint64_t b = (v ^ a) * mul;
+	b ^= (b >> 47);
+	b *= mul;
+	return (b);
+}
+
+uint64_t
+cityhash4(uint64_t w1, uint64_t w2, uint64_t w3, uint64_t w4)
+{
+	uint64_t mul = HASH_K2 + 64;
+	uint64_t a = w1 * HASH_K1;
+	uint64_t b = w2;
+	uint64_t c = w4 * mul;
+	uint64_t d = w3 * HASH_K2;
+	return (cityhash_helper(rotate(a + b, 43) + rotate(c, 30) + d,
+	    a + rotate(b + HASH_K2, 18) + c, mul));
+
+}
+
+#if defined(_KERNEL)
+EXPORT_SYMBOL(cityhash4);
+#endif