--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/cpu/x86/vm/crc32c.h	Wed Sep 16 15:54:32 2015 -0700
@@ -0,0 +1,66 @@
+/*
+* Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
+* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+*
+* This code is free software; you can redistribute it and/or modify it
+* under the terms of the GNU General Public License version 2 only, as
+* published by the Free Software Foundation.
+*
+* This code is distributed in the hope that it will be useful, but WITHOUT
+* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+* version 2 for more details (a copy is included in the LICENSE file that
+* accompanied this code).
+*
+* You should have received a copy of the GNU General Public License version
+* 2 along with this work; if not, write to the Free Software Foundation,
+* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+*
+* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+* or visit www.oracle.com if you need additional information or have any
+* questions.
+*
+*/
+
+enum {
+  // S. Gueron / Information Processing Letters 112 (2012) 184
+  // shows than anything above 6K and below 32K is a good choice
+  // 32K does not deliver any further performance gains
+  // 6K=8*256 (*3 as we compute 3 blocks together)
+  //
+  // Thus selecting the smallest value so it could apply to the largest number
+  // of buffer sizes.
+  CRC32C_HIGH = 8 * 256,
+
+  // empirical
+  // based on ubench study using methodology described in
+  // V. Gopal et al. / Fast CRC Computation for iSCSI Polynomial Using CRC32 Instruction April 2011 8
+  //
+  // arbitrary value between 27 and 256
+  CRC32C_MIDDLE = 8 * 86,
+
+  // V. Gopal et al. / Fast CRC Computation for iSCSI Polynomial Using CRC32 Instruction April 2011 9
+  // shows that 240 and 1024 are equally good choices as the 216==8*27
+  //
+  // Selecting the smallest value which resulted in a significant performance improvement over
+  // sequential version
+  CRC32C_LOW = 8 * 27,
+
+  CRC32C_NUM_ChunkSizeInBytes = 3,
+
+  // We need to compute powers of 64N and 128N for each "chunk" size
+  CRC32C_NUM_PRECOMPUTED_CONSTANTS = ( 2 * CRC32C_NUM_ChunkSizeInBytes )
+};
+// Notes:
+// 1. Why we need to choose a "chunk" approach?
+// Overhead of computing a powers and powers of for an arbitrary buffer of size N is significant
+// (implementation approaches a library perf.)
+// 2. Why only 3 "chunks"?
+// Performance experiments results showed that a HIGH+LOW was not delivering a stable speedup
+// curve.
+//
+// Disclaimer:
+// If you ever decide to increase/decrease number of "chunks" be sure to modify
+// a) constants table generation (hotspot/src/cpu/x86/vm/stubRoutines_x86.cpp)
+// b) constant fetch from that table (macroAssembler_x86.cpp)
+// c) unrolled for loop (macroAssembler_x86.cpp)