diff options
Diffstat (limited to 'vendor/github.com/klauspost/crc32/crc32_amd64.go')
| -rw-r--r-- | vendor/github.com/klauspost/crc32/crc32_amd64.go | 230 |
1 files changed, 0 insertions, 230 deletions
diff --git a/vendor/github.com/klauspost/crc32/crc32_amd64.go b/vendor/github.com/klauspost/crc32/crc32_amd64.go deleted file mode 100644 index af2a0b84..00000000 --- a/vendor/github.com/klauspost/crc32/crc32_amd64.go +++ /dev/null @@ -1,230 +0,0 @@ -// 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. - -// +build !appengine,!gccgo - -// AMD64-specific hardware-assisted CRC32 algorithms. See crc32.go for a -// description of the interface that each architecture-specific file -// implements. - -package crc32 - -import "unsafe" - -// 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 crc32_amd64.s and uses the SSE4.2 CRC32 -// instruction. -//go:noescape -func castagnoliSSE42(crc uint32, p []byte) uint32 - -// castagnoliSSE42Triple is defined in crc32_amd64.s and uses the SSE4.2 CRC32 -// instruction. -//go:noescape -func castagnoliSSE42Triple( - crcA, crcB, crcC uint32, - a, b, c []byte, - rounds uint32, -) (retA uint32, retB uint32, retC 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() - -const castagnoliK1 = 168 -const castagnoliK2 = 1344 - -type sse42Table [4]Table - -var castagnoliSSE42TableK1 *sse42Table -var castagnoliSSE42TableK2 *sse42Table - -func archAvailableCastagnoli() bool { - return sse42 -} - -func archInitCastagnoli() { - if !sse42 { - panic("arch-specific Castagnoli not available") - } - castagnoliSSE42TableK1 = new(sse42Table) - castagnoliSSE42TableK2 = new(sse42Table) - // See description in updateCastagnoli. - // t[0][i] = CRC(i000, O) - // t[1][i] = CRC(0i00, O) - // t[2][i] = CRC(00i0, O) - // t[3][i] = CRC(000i, O) - // where O is a sequence of K zeros. - var tmp [castagnoliK2]byte - for b := 0; b < 4; b++ { - for i := 0; i < 256; i++ { - val := uint32(i) << uint32(b*8) - castagnoliSSE42TableK1[b][i] = castagnoliSSE42(val, tmp[:castagnoliK1]) - castagnoliSSE42TableK2[b][i] = castagnoliSSE42(val, tmp[:]) - } - } -} - -// castagnoliShift computes the CRC32-C of K1 or K2 zeroes (depending on the -// table given) with the given initial crc value. This corresponds to -// CRC(crc, O) in the description in updateCastagnoli. -func castagnoliShift(table *sse42Table, crc uint32) uint32 { - return table[3][crc>>24] ^ - table[2][(crc>>16)&0xFF] ^ - table[1][(crc>>8)&0xFF] ^ - table[0][crc&0xFF] -} - -func archUpdateCastagnoli(crc uint32, p []byte) uint32 { - if !sse42 { - panic("not available") - } - - // This method is inspired from the algorithm in Intel's white paper: - // "Fast CRC Computation for iSCSI Polynomial Using CRC32 Instruction" - // The same strategy of splitting the buffer in three is used but the - // combining calculation is different; the complete derivation is explained - // below. - // - // -- The basic idea -- - // - // The CRC32 instruction (available in SSE4.2) can process 8 bytes at a - // time. In recent Intel architectures the instruction takes 3 cycles; - // however the processor can pipeline up to three instructions if they - // don't depend on each other. - // - // Roughly this means that we can process three buffers in about the same - // time we can process one buffer. - // - // The idea is then to split the buffer in three, CRC the three pieces - // separately and then combine the results. - // - // Combining the results requires precomputed tables, so we must choose a - // fixed buffer length to optimize. The longer the length, the faster; but - // only buffers longer than this length will use the optimization. We choose - // two cutoffs and compute tables for both: - // - one around 512: 168*3=504 - // - one around 4KB: 1344*3=4032 - // - // -- The nitty gritty -- - // - // Let CRC(I, X) be the non-inverted CRC32-C of the sequence X (with - // initial non-inverted CRC I). This function has the following properties: - // (a) CRC(I, AB) = CRC(CRC(I, A), B) - // (b) CRC(I, A xor B) = CRC(I, A) xor CRC(0, B) - // - // Say we want to compute CRC(I, ABC) where A, B, C are three sequences of - // K bytes each, where K is a fixed constant. Let O be the sequence of K zero - // bytes. - // - // CRC(I, ABC) = CRC(I, ABO xor C) - // = CRC(I, ABO) xor CRC(0, C) - // = CRC(CRC(I, AB), O) xor CRC(0, C) - // = CRC(CRC(I, AO xor B), O) xor CRC(0, C) - // = CRC(CRC(I, AO) xor CRC(0, B), O) xor CRC(0, C) - // = CRC(CRC(CRC(I, A), O) xor CRC(0, B), O) xor CRC(0, C) - // - // The castagnoliSSE42Triple function can compute CRC(I, A), CRC(0, B), - // and CRC(0, C) efficiently. We just need to find a way to quickly compute - // CRC(uvwx, O) given a 4-byte initial value uvwx. We can precompute these - // values; since we can't have a 32-bit table, we break it up into four - // 8-bit tables: - // - // CRC(uvwx, O) = CRC(u000, O) xor - // CRC(0v00, O) xor - // CRC(00w0, O) xor - // CRC(000x, O) - // - // We can compute tables corresponding to the four terms for all 8-bit - // values. - - crc = ^crc - - // If a buffer is long enough to use the optimization, process the first few - // bytes to align the buffer to an 8 byte boundary (if necessary). - if len(p) >= castagnoliK1*3 { - delta := int(uintptr(unsafe.Pointer(&p[0])) & 7) - if delta != 0 { - delta = 8 - delta - crc = castagnoliSSE42(crc, p[:delta]) - p = p[delta:] - } - } - - // Process 3*K2 at a time. - for len(p) >= castagnoliK2*3 { - // Compute CRC(I, A), CRC(0, B), and CRC(0, C). - crcA, crcB, crcC := castagnoliSSE42Triple( - crc, 0, 0, - p, p[castagnoliK2:], p[castagnoliK2*2:], - castagnoliK2/24) - - // CRC(I, AB) = CRC(CRC(I, A), O) xor CRC(0, B) - crcAB := castagnoliShift(castagnoliSSE42TableK2, crcA) ^ crcB - // CRC(I, ABC) = CRC(CRC(I, AB), O) xor CRC(0, C) - crc = castagnoliShift(castagnoliSSE42TableK2, crcAB) ^ crcC - p = p[castagnoliK2*3:] - } - - // Process 3*K1 at a time. - for len(p) >= castagnoliK1*3 { - // Compute CRC(I, A), CRC(0, B), and CRC(0, C). - crcA, crcB, crcC := castagnoliSSE42Triple( - crc, 0, 0, - p, p[castagnoliK1:], p[castagnoliK1*2:], - castagnoliK1/24) - - // CRC(I, AB) = CRC(CRC(I, A), O) xor CRC(0, B) - crcAB := castagnoliShift(castagnoliSSE42TableK1, crcA) ^ crcB - // CRC(I, ABC) = CRC(CRC(I, AB), O) xor CRC(0, C) - crc = castagnoliShift(castagnoliSSE42TableK1, crcAB) ^ crcC - p = p[castagnoliK1*3:] - } - - // Use the simple implementation for what's left. - crc = castagnoliSSE42(crc, p) - return ^crc -} - -func archAvailableIEEE() bool { - return useFastIEEE -} - -var archIeeeTable8 *slicing8Table - -func archInitIEEE() { - if !useFastIEEE { - panic("not available") - } - // We still use slicing-by-8 for small buffers. - archIeeeTable8 = slicingMakeTable(IEEE) -} - -func archUpdateIEEE(crc uint32, p []byte) uint32 { - if !useFastIEEE { - panic("not available") - } - - if len(p) >= 64 { - left := len(p) & 15 - do := len(p) - left - crc = ^ieeeCLMUL(^crc, p[:do]) - p = p[do:] - } - if len(p) == 0 { - return crc - } - return slicingUpdate(crc, archIeeeTable8, p) -} |