| // Copyright 2011 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| package crc32 |
| |
| // This file contains the code to call the SSE 4.2 version of the Castagnoli |
| // and IEEE CRC. |
| |
| // haveSSE41/haveSSE42/haveCLMUL are defined in crc_amd64.s and use |
| // CPUID to test for SSE 4.1, 4.2 and CLMUL support. |
| func haveSSE41() bool |
| func haveSSE42() bool |
| func haveCLMUL() bool |
| |
| // castagnoliSSE42 is defined in crc_amd64.s and uses the SSE4.2 CRC32 |
| // instruction. |
| //go:noescape |
| func castagnoliSSE42(crc uint32, p []byte) uint32 |
| |
| // ieeeCLMUL is defined in crc_amd64.s and uses the PCLMULQDQ |
| // instruction as well as SSE 4.1. |
| //go:noescape |
| func ieeeCLMUL(crc uint32, p []byte) uint32 |
| |
| var sse42 = haveSSE42() |
| var useFastIEEE = haveCLMUL() && haveSSE41() |
| |
| func updateCastagnoli(crc uint32, p []byte) uint32 { |
| if sse42 { |
| return castagnoliSSE42(crc, p) |
| } |
| return update(crc, castagnoliTable, p) |
| } |
| |
| func updateIEEE(crc uint32, p []byte) uint32 { |
| if useFastIEEE && len(p) >= 64 { |
| left := len(p) & 15 |
| do := len(p) - left |
| crc = ^ieeeCLMUL(^crc, p[:do]) |
| if left > 0 { |
| crc = update(crc, IEEETable, p[do:]) |
| } |
| return crc |
| } |
| |
| // only use slicing-by-8 when input is >= 4KB |
| if len(p) >= 4096 { |
| ieeeTable8Once.Do(func() { |
| ieeeTable8 = makeTable8(IEEE) |
| }) |
| return updateSlicingBy8(crc, ieeeTable8, p) |
| } |
| |
| return update(crc, IEEETable, p) |
| } |