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Commit 3427f166 authored by Keith Randall's avatar Keith Randall
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Revert "hash/crc32: improve the AMD64 implementation using SSE4.2" 

This reverts commit 54d7de7d.

It was breaking non-amd64 builds.

Change-Id: I22650e922498eeeba3d4fa08bb4ea40a210c8f97
Reviewed-on: https://go-review.googlesource.com/27925Reviewed-by: 's avatarKeith Randall <khr@golang.org>
parent 54d7de7d
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Showing with 9 additions and 287 deletions
src/hash/crc32/crc32.go
View file @ 3427f166
......@@ -52,14 +52,8 @@ var castagnoliTable8 *slicing8Table
var castagnoliOnce sync.Once
func castagnoliInit() {
// Call the arch-specific init function and let it decide if we will need
// the tables for the generic implementation.
needGenericTables := castagnoliInitArch()
if needGenericTables {
castagnoliTable = makeTable(Castagnoli)
castagnoliTable8 = makeTable8(Castagnoli)
}
}
// IEEETable is the table for the IEEE polynomial.
......
src/hash/crc32/crc32_amd64.go
View file @ 3427f166
......@@ -4,8 +4,6 @@
package crc32
import "unsafe"
// This file contains the code to call the SSE 4.2 version of the Castagnoli
// and IEEE CRC.
......@@ -15,20 +13,11 @@ func haveSSE41() bool
func haveSSE42() bool
func haveCLMUL() bool
// castagnoliSSE42 is defined in crc32_amd64.s and uses the SSE4.2 CRC32
// castagnoliSSE42 is defined in crc_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
......@@ -37,160 +26,15 @@ 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 castagnoliInitArch() (needGenericTables bool) {
if !sse42 {
return true
}
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[:])
}
}
return false
}
// 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 updateCastagnoli(crc uint32, p []byte) uint32 {
if !sse42 {
if sse42 {
return castagnoliSSE42(crc, p)
}
// Use slicing-by-8 on larger inputs.
if len(p) >= sliceBy8Cutoff {
return updateSlicingBy8(crc, castagnoliTable8, p)
}
return update(crc, castagnoliTable, p)
}
// 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 updateIEEE(crc uint32, p []byte) uint32 {
......
src/hash/crc32/crc32_amd64.s
View file @ 3427f166
......@@ -4,14 +4,14 @@
#include "textflag.h"
// castagnoliSSE42 updates the (non-inverted) crc with the given buffer.
//
// func castagnoliSSE42(crc uint32, p []byte) uint32
TEXT ·castagnoliSSE42(SB),NOSPLIT,$0
MOVL crc+0(FP), AX // CRC value
MOVQ p+8(FP), SI // data pointer
MOVQ p_len+16(FP), CX // len(p)
NOTL AX
// If there are fewer than 8 bytes to process, skip alignment.
CMPQ CX, $8
JL less_than_8
......@@ -87,53 +87,10 @@ less_than_2:
CRC32B (SI), AX
done:
NOTL AX
MOVL AX, ret+32(FP)
RET
// castagnoliSSE42Triple updates three (non-inverted) crcs with (24*rounds)
// bytes from each buffer.
//
// func castagnoliSSE42Triple(
// crc1, crc2, crc3 uint32,
// a, b, c []byte,
// rounds uint32,
// ) (retA uint32, retB uint32, retC uint32)
TEXT ·castagnoliSSE42Triple(SB),NOSPLIT,$0
MOVL crcA+0(FP), AX
MOVL crcB+4(FP), CX
MOVL crcC+8(FP), DX
MOVQ a+16(FP), R8 // data pointer
MOVQ b+40(FP), R9 // data pointer
MOVQ c+64(FP), R10 // data pointer
MOVL rounds+88(FP), R11
loop:
CRC32Q (R8), AX
CRC32Q (R9), CX
CRC32Q (R10), DX
CRC32Q 8(R8), AX
CRC32Q 8(R9), CX
CRC32Q 8(R10), DX
CRC32Q 16(R8), AX
CRC32Q 16(R9), CX
CRC32Q 16(R10), DX
ADDQ $24, R8
ADDQ $24, R9
ADDQ $24, R10
DECQ R11
JNZ loop
MOVL AX, retA+96(FP)
MOVL CX, retB+100(FP)
MOVL DX, retC+104(FP)
RET
// func haveSSE42() bool
TEXT ·haveSSE42(SB),NOSPLIT,$0
XORQ AX, AX
......
src/hash/crc32/crc32_amd64p32.go
View file @ 3427f166
......@@ -7,22 +7,17 @@ package crc32
// This file contains the code to call the SSE 4.2 version of the Castagnoli
// CRC.
// haveSSE42 is defined in crc32_amd64p32.s and uses CPUID to test for SSE 4.2
// haveSSE42 is defined in crc_amd64p32.s and uses CPUID to test for SSE 4.2
// support.
func haveSSE42() bool
// castagnoliSSE42 is defined in crc32_amd64.s and uses the SSE4.2 CRC32
// castagnoliSSE42 is defined in crc_amd64.s and uses the SSE4.2 CRC32
// instruction.
//go:noescape
func castagnoliSSE42(crc uint32, p []byte) uint32
var sse42 = haveSSE42()
func castagnoliInitArch() (needGenericTables bool) {
// We only need the generic implementation tables if we don't have SSE4.2.
return !sse42
}
func updateCastagnoli(crc uint32, p []byte) uint32 {
if sse42 {
return castagnoliSSE42(crc, p)
......
src/hash/crc32/crc32_generic.go
View file @ 3427f166
......@@ -9,10 +9,6 @@ package crc32
// This file contains the generic version of updateCastagnoli which does
// slicing-by-8, or uses the fallback for very small sizes.
func castagnoliInitArch() (needGenericTables bool) {
return true
}
func updateCastagnoli(crc uint32, p []byte) uint32 {
// Use slicing-by-8 on larger inputs.
if len(p) >= sliceBy8Cutoff {
......
src/hash/crc32/crc32_s390x.go
View file @ 3427f166
......@@ -25,10 +25,6 @@ func vectorizedCastagnoli(crc uint32, p []byte) uint32
//go:noescape
func vectorizedIEEE(crc uint32, p []byte) uint32
func castagnoliInitArch() (needGenericTables bool) {
return true
}
func genericCastagnoli(crc uint32, p []byte) uint32 {
// Use slicing-by-8 on larger inputs.
if len(p) >= sliceBy8Cutoff {
......
src/hash/crc32/crc32_test.go
View file @ 3427f166
......@@ -7,7 +7,6 @@ package crc32
import (
"hash"
"io"
"math/rand"
"testing"
)
......@@ -86,41 +85,6 @@ func TestGolden(t *testing.T) {
}
}
func TestCastagnoliSSE42(t *testing.T) {
if !sse42 {
t.Skip("SSE42 not supported")
}
// Init the SSE42 tables.
MakeTable(Castagnoli)
// Manually init the software implementation to compare against.
castagnoliTable = makeTable(Castagnoli)
castagnoliTable8 = makeTable8(Castagnoli)
// The optimized SSE4.2 implementation behaves differently for different
// lengths (especially around multiples of K*3). Crosscheck against the
// software implementation for various lengths.
for _, base := range []int{castagnoliK1, castagnoliK2, castagnoliK1 + castagnoliK2} {
for _, baseMult := range []int{2, 3, 5, 6, 9, 30} {
for _, variation := range []int{0, 1, 2, 3, 4, 7, 10, 16, 32, 50, 128} {
for _, varMult := range []int{-2, -1, +1, +2} {
length := base*baseMult + variation*varMult
p := make([]byte, length)
_, _ = rand.Read(p)
crcInit := uint32(rand.Int63())
correct := updateSlicingBy8(crcInit, castagnoliTable8, p)
result := updateCastagnoli(crcInit, p)
if result != correct {
t.Errorf("SSE42 implementation = 0x%x want 0x%x (buffer length %d)",
result, correct, len(p))
}
}
}
}
}
}
func BenchmarkIEEECrc40B(b *testing.B) {
benchmark(b, NewIEEE(), 40, 0)
}
......@@ -149,42 +113,18 @@ func BenchmarkCastagnoliCrc40B(b *testing.B) {
benchmark(b, New(MakeTable(Castagnoli)), 40, 0)
}
func BenchmarkCastagnoliCrc40BMisaligned(b *testing.B) {
benchmark(b, New(MakeTable(Castagnoli)), 40, 1)
}
func BenchmarkCastagnoliCrc512(b *testing.B) {
benchmark(b, New(MakeTable(Castagnoli)), 512, 0)
}
func BenchmarkCastagnoliCrc512Misaligned(b *testing.B) {
benchmark(b, New(MakeTable(Castagnoli)), 512, 1)
}
func BenchmarkCastagnoliCrc1KB(b *testing.B) {
benchmark(b, New(MakeTable(Castagnoli)), 1<<10, 0)
}
func BenchmarkCastagnoliCrc1KBMisaligned(b *testing.B) {
benchmark(b, New(MakeTable(Castagnoli)), 1<<10, 1)
}
func BenchmarkCastagnoliCrc4KB(b *testing.B) {
benchmark(b, New(MakeTable(Castagnoli)), 4<<10, 0)
}
func BenchmarkCastagnoliCrc4KBMisaligned(b *testing.B) {
benchmark(b, New(MakeTable(Castagnoli)), 4<<10, 1)
}
func BenchmarkCastagnoliCrc32KB(b *testing.B) {
benchmark(b, New(MakeTable(Castagnoli)), 32<<10, 0)
}
func BenchmarkCastagnoliCrc32KBMisaligned(b *testing.B) {
benchmark(b, New(MakeTable(Castagnoli)), 32<<10, 1)
}
func benchmark(b *testing.B, h hash.Hash32, n, alignment int64) {
b.SetBytes(n)
data := make([]byte, n+alignment)
......
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