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gen.go
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gen.go
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package main
//go:generate go run gen.go -out ../encodeblock_amd64.s -stubs ../encodeblock_amd64.go -pkg=s2
//go:generate gofmt -w ../encodeblock_amd64.go
//go:generate go run cleanup.go ../encodeblock_amd64.s
import (
"flag"
"fmt"
"math"
"runtime"
. "github.com/mmcloughlin/avo/build"
"github.com/mmcloughlin/avo/buildtags"
. "github.com/mmcloughlin/avo/operand"
"github.com/mmcloughlin/avo/reg"
)
// insert extra checks here and there.
const debug = false
const (
limit14B = math.MaxUint32
// Use 12 bit table when no more than...
limit12B = 16<<10 - 1
// Use 10 bit table when no more than...
limit10B = 4<<10 - 1
// Use 8 bit table when no more than...
limit8B = 512 - 1
)
func main() {
flag.Parse()
Constraint(buildtags.Not("appengine").ToConstraint())
Constraint(buildtags.Not("noasm").ToConstraint())
Constraint(buildtags.Term("gc").ToConstraint())
Constraint(buildtags.Not("noasm").ToConstraint())
// We need a function to add comments.
TEXT("_dummy_", 0, "func()")
Comment("#ifdef GOAMD64_v4")
Comment("#ifndef GOAMD64_v3")
Comment("#define GOAMD64_v3")
Comment("#endif")
Comment("#endif")
RET()
o := options{
bmi1: false,
bmi2: false,
snappy: false,
outputMargin: 9,
}
o.genEncodeBlockAsm("encodeBlockAsm", 14, 6, 6, limit14B)
o.genEncodeBlockAsm("encodeBlockAsm4MB", 14, 6, 6, 4<<20)
o.genEncodeBlockAsm("encodeBlockAsm12B", 12, 5, 5, limit12B)
o.genEncodeBlockAsm("encodeBlockAsm10B", 10, 5, 4, limit10B)
o.genEncodeBlockAsm("encodeBlockAsm8B", 8, 4, 4, limit8B)
o.outputMargin = 6
o.maxSkip = 100 // Blocks can be long, limit max skipping.
o.genEncodeBetterBlockAsm("encodeBetterBlockAsm", 17, 14, 7, 7, limit14B)
o.genEncodeBetterBlockAsm("encodeBetterBlockAsm4MB", 17, 14, 7, 7, 4<<20)
o.maxSkip = 0
o.genEncodeBetterBlockAsm("encodeBetterBlockAsm12B", 14, 12, 6, 6, limit12B)
o.genEncodeBetterBlockAsm("encodeBetterBlockAsm10B", 12, 10, 5, 6, limit10B)
o.genEncodeBetterBlockAsm("encodeBetterBlockAsm8B", 10, 8, 4, 6, limit8B)
// Snappy compatible
o.snappy = true
o.outputMargin = 9
o.genEncodeBlockAsm("encodeSnappyBlockAsm", 14, 6, 6, limit14B)
o.genEncodeBlockAsm("encodeSnappyBlockAsm64K", 14, 6, 6, 64<<10-1)
o.genEncodeBlockAsm("encodeSnappyBlockAsm12B", 12, 5, 5, limit12B)
o.genEncodeBlockAsm("encodeSnappyBlockAsm10B", 10, 5, 4, limit10B)
o.genEncodeBlockAsm("encodeSnappyBlockAsm8B", 8, 4, 4, limit8B)
o.maxSkip = 100
o.genEncodeBetterBlockAsm("encodeSnappyBetterBlockAsm", 17, 14, 7, 7, limit14B)
o.maxSkip = 0
o.genEncodeBetterBlockAsm("encodeSnappyBetterBlockAsm64K", 16, 14, 7, 7, 64<<10-1)
o.genEncodeBetterBlockAsm("encodeSnappyBetterBlockAsm12B", 14, 12, 6, 6, limit12B)
o.genEncodeBetterBlockAsm("encodeSnappyBetterBlockAsm10B", 12, 10, 5, 6, limit10B)
o.genEncodeBetterBlockAsm("encodeSnappyBetterBlockAsm8B", 10, 8, 4, 6, limit8B)
o.snappy = false
o.outputMargin = 0
o.maxLen = math.MaxUint32
o.genEmitLiteral()
o.genEmitRepeat()
o.genEmitCopy()
o.snappy = true
o.genEmitCopyNoRepeat()
o.snappy = false
o.genMatchLen()
Generate()
}
func debugval(v Op) {
value := reg.R15
MOVQ(v, value)
INT(Imm(3))
}
func debugval32(v Op) {
value := reg.R15L
MOVL(v, value)
INT(Imm(3))
}
var assertCounter int
// assert will insert code if debug is enabled.
// The code should jump to 'ok' is assertion is success.
func assert(fn func(ok LabelRef)) {
if debug {
caller := [100]uintptr{0}
runtime.Callers(2, caller[:])
frame, _ := runtime.CallersFrames(caller[:]).Next()
ok := fmt.Sprintf("assert_check_%d_ok_srcline_%d", assertCounter, frame.Line)
fn(LabelRef(ok))
// Emit several since delve is imprecise.
INT(Imm(3))
INT(Imm(3))
Label(ok)
assertCounter++
}
}
type options struct {
snappy bool
bmi1 bool
bmi2 bool
maxLen int
outputMargin int // Should be at least 5.
maxSkip int
}
func (o options) genEncodeBlockAsm(name string, tableBits, skipLog, hashBytes, maxLen int) {
TEXT(name, 0, "func(dst, src []byte) int")
Doc(name+" encodes a non-empty src to a guaranteed-large-enough dst.",
fmt.Sprintf("Maximum input %d bytes.", maxLen),
"It assumes that the varint-encoded length of the decompressed bytes has already been written.", "")
Pragma("noescape")
o.maxLen = maxLen
var literalMaxOverhead = maxLitOverheadFor(maxLen)
var tableSize = 4 * (1 << tableBits)
// Memzero needs at least 128 bytes.
if tableSize < 128 {
panic("tableSize must be at least 128 bytes")
}
lenSrcBasic, err := Param("src").Len().Resolve()
if err != nil {
panic(err)
}
lenSrcQ := lenSrcBasic.Addr
lenDstBasic, err := Param("dst").Len().Resolve()
if err != nil {
panic(err)
}
lenDstQ := lenDstBasic.Addr
// Bail if we can't compress to at least this.
dstLimitPtrQ := AllocLocal(8)
// sLimitL is when to stop looking for offset/length copies.
sLimitL := AllocLocal(4)
// nextEmitL keeps track of the point we have emitted to.
nextEmitL := AllocLocal(4)
// Repeat stores the last match offset.
repeatL := AllocLocal(4)
// nextSTempL keeps nextS while other functions are being called.
nextSTempL := AllocLocal(4)
// Alloc table last
table := AllocLocal(tableSize)
dst := GP64()
{
dstBaseBasic, err := Param("dst").Base().Resolve()
if err != nil {
panic(err)
}
dstBaseQ := dstBaseBasic.Addr
MOVQ(dstBaseQ, dst)
}
srcBaseBasic, err := Param("src").Base().Resolve()
if err != nil {
panic(err)
}
srcBaseQ := srcBaseBasic.Addr
// Zero table
{
iReg := GP64()
MOVQ(U32(tableSize/8/16), iReg)
tablePtr := GP64()
LEAQ(table, tablePtr)
zeroXmm := XMM()
PXOR(zeroXmm, zeroXmm)
Label("zero_loop_" + name)
for i := 0; i < 8; i++ {
MOVOU(zeroXmm, Mem{Base: tablePtr, Disp: i * 16})
}
ADDQ(U8(16*8), tablePtr)
DECQ(iReg)
JNZ(LabelRef("zero_loop_" + name))
}
{
// nextEmit is offset n src where the next emitLiteral should start from.
MOVL(U32(0), nextEmitL)
const inputMargin = 8
tmp, tmp2, tmp3 := GP64(), GP64(), GP64()
MOVQ(lenSrcQ, tmp)
LEAQ(Mem{Base: tmp, Disp: -o.outputMargin}, tmp2)
// sLimitL := len(src) - inputMargin
LEAQ(Mem{Base: tmp, Disp: -inputMargin}, tmp3)
assert(func(ok LabelRef) {
CMPQ(tmp3, lenSrcQ)
JL(ok)
})
MOVL(tmp3.As32(), sLimitL)
// dstLimit := (len(src) - outputMargin ) - len(src)>>5
SHRQ(U8(5), tmp)
SUBL(tmp.As32(), tmp2.As32()) // tmp2 = tmp2 - tmp
assert(func(ok LabelRef) {
// if len(src) > len(src) - len(src)>>5 - outputMargin: ok
CMPQ(lenSrcQ, tmp2)
JGE(ok)
})
LEAQ(Mem{Base: dst, Index: tmp2, Scale: 1}, tmp2)
MOVQ(tmp2, dstLimitPtrQ)
}
// s = 1
s := GP32()
MOVL(U32(1), s)
// repeatL = 1
MOVL(s, repeatL)
src := GP64()
Load(Param("src").Base(), src)
// Load cv
Label("search_loop_" + name)
candidate := GP32()
{
assert(func(ok LabelRef) {
// Check if somebody changed src
tmp := GP64()
MOVQ(srcBaseQ, tmp)
CMPQ(tmp, src)
JEQ(ok)
})
cv := GP64()
nextS := GP32()
// nextS := s + (s-nextEmit)>>6 + 4
if o.maxSkip == 0 {
tmp := GP64()
MOVL(s, tmp.As32()) // tmp = s
SUBL(nextEmitL, tmp.As32()) // tmp = s - nextEmit
SHRL(U8(skipLog), tmp.As32()) // tmp = (s - nextEmit) >> skipLog
LEAL(Mem{Base: s, Disp: 4, Index: tmp, Scale: 1}, nextS)
}
// if nextS > sLimit {goto emitRemainder}
{
CMPL(nextS.As32(), sLimitL)
JGE(LabelRef("emit_remainder_" + name))
}
MOVQ(Mem{Base: src, Index: s, Scale: 1}, cv)
assert(func(ok LabelRef) {
// Check if s is valid (we should have jumped above if not)
tmp := GP64()
MOVQ(lenSrcQ, tmp)
CMPQ(tmp, s.As64())
JG(ok)
})
// move nextS to stack.
MOVL(nextS.As32(), nextSTempL)
candidate2 := GP32()
hasher := hashN(hashBytes, tableBits)
{
hash0, hash1 := GP64(), GP64()
MOVQ(cv, hash0)
MOVQ(cv, hash1)
SHRQ(U8(8), hash1)
hasher.hash(hash0)
hasher.hash(hash1)
MOVL(table.Idx(hash0, 4), candidate)
MOVL(table.Idx(hash1, 4), candidate2)
assert(func(ok LabelRef) {
CMPQ(hash0, U32(tableSize))
JL(ok)
})
assert(func(ok LabelRef) {
CMPQ(hash1, U32(tableSize))
JL(ok)
})
MOVL(s, table.Idx(hash0, 4))
tmp := GP32()
LEAL(Mem{Base: s, Disp: 1}, tmp)
MOVL(tmp, table.Idx(hash1, 4))
}
// Can be moved up if registers are available.
hash2 := GP64()
{
// hash2 := hash6(cv>>16, tableBits)
// hasher = hash6(tableBits)
MOVQ(cv, hash2)
SHRQ(U8(16), hash2)
hasher.hash(hash2)
assert(func(ok LabelRef) {
CMPQ(hash2, U32(tableSize))
JL(ok)
})
}
// En/disable repeat matching.
if true {
// Check repeat at offset checkRep
const checkRep = 1
{
// rep = s - repeat
rep := GP32()
MOVL(s, rep)
SUBL(repeatL, rep) // rep = s - repeat
// if uint32(cv>>(checkRep*8)) == load32(src, s-repeat+checkRep) {
left, right := GP64(), GP64()
MOVL(Mem{Base: src, Index: rep, Disp: checkRep, Scale: 1}, right.As32())
MOVQ(cv, left)
SHRQ(U8(checkRep*8), left)
CMPL(left.As32(), right.As32())
// BAIL, no repeat.
JNE(LabelRef("no_repeat_found_" + name))
}
// base = s + checkRep
base := GP32()
LEAL(Mem{Base: s, Disp: checkRep}, base)
// nextEmit before repeat.
nextEmit := GP32()
MOVL(nextEmitL, nextEmit)
// Extend back
if true {
i := GP32()
MOVL(base, i)
SUBL(repeatL, i)
JZ(LabelRef("repeat_extend_back_end_" + name))
Label("repeat_extend_back_loop_" + name)
// if base <= nextemit {exit}
CMPL(base.As32(), nextEmit)
JLE(LabelRef("repeat_extend_back_end_" + name))
// if src[i-1] == src[base-1]
tmp, tmp2 := GP64(), GP64()
MOVB(Mem{Base: src, Index: i, Scale: 1, Disp: -1}, tmp.As8())
MOVB(Mem{Base: src, Index: base, Scale: 1, Disp: -1}, tmp2.As8())
CMPB(tmp.As8(), tmp2.As8())
JNE(LabelRef("repeat_extend_back_end_" + name))
LEAL(Mem{Base: base, Disp: -1}, base)
DECL(i)
JNZ(LabelRef("repeat_extend_back_loop_" + name))
}
Label("repeat_extend_back_end_" + name)
// Base is now at start. Emit until base.
// d += emitLiteral(dst[d:], src[nextEmit:base])
if true {
o.emitLiteralsDstP(nextEmitL, base, src, dst, "repeat_emit_"+name)
}
// Extend forward
{
// s += 4 + checkRep
ADDL(U8(4+checkRep), s)
if true {
// candidate := s - repeat + 4 + checkRep
MOVL(s, candidate)
SUBL(repeatL, candidate) // candidate = s - repeat
// srcLeft = len(src) - s
srcLeft := GP64()
MOVQ(lenSrcQ, srcLeft)
SUBL(s, srcLeft.As32())
assert(func(ok LabelRef) {
// if srcleft < maxint32: ok
CMPQ(srcLeft, U32(0x7fffffff))
JL(ok)
})
// Forward address
forwardStart := GP64()
LEAQ(Mem{Base: src, Index: s, Scale: 1}, forwardStart)
// End address
backStart := GP64()
LEAQ(Mem{Base: src, Index: candidate, Scale: 1}, backStart)
length := o.matchLen("repeat_extend_"+name, forwardStart, backStart, srcLeft, LabelRef("repeat_extend_forward_end_"+name))
forwardStart, backStart, srcLeft = nil, nil, nil
Label("repeat_extend_forward_end_" + name)
// s+= length
ADDL(length.As32(), s)
}
}
// Emit
if true {
// length = s-base
length := GP32()
MOVL(s, length)
SUBL(base.As32(), length) // length = s - base
offsetVal := GP32()
MOVL(repeatL, offsetVal)
if !o.snappy {
// if nextEmit == 0 {do copy instead...}
TESTL(nextEmit, nextEmit)
JZ(LabelRef("repeat_as_copy_" + name))
// Emit as repeat...
o.emitRepeat("match_repeat_"+name, length, offsetVal, nil, dst, LabelRef("repeat_end_emit_"+name), false)
// Emit as copy instead...
Label("repeat_as_copy_" + name)
}
o.emitCopy("repeat_as_copy_"+name, length, offsetVal, nil, dst, LabelRef("repeat_end_emit_"+name))
Label("repeat_end_emit_" + name)
// Store new dst and nextEmit
MOVL(s, nextEmitL)
}
// if s >= sLimit is picked up on next loop.
if false {
CMPL(s.As32(), sLimitL)
JGE(LabelRef("emit_remainder_" + name))
}
JMP(LabelRef("search_loop_" + name))
}
Label("no_repeat_found_" + name)
{
// Check candidates are ok. All must be < s and < len(src)
assert(func(ok LabelRef) {
tmp := GP64()
MOVQ(lenSrcQ, tmp)
CMPL(tmp.As32(), candidate)
JG(ok)
})
assert(func(ok LabelRef) {
CMPL(s, candidate)
JG(ok)
})
assert(func(ok LabelRef) {
tmp := GP64()
MOVQ(lenSrcQ, tmp)
CMPL(tmp.As32(), candidate2)
JG(ok)
})
assert(func(ok LabelRef) {
CMPL(s, candidate2)
JG(ok)
})
CMPL(Mem{Base: src, Index: candidate, Scale: 1}, cv.As32())
JEQ(LabelRef("candidate_match_" + name))
tmp := GP32()
// cv >>= 8
SHRQ(U8(8), cv)
// candidate = int(table[hash2]) - load early.
MOVL(table.Idx(hash2, 4), candidate)
assert(func(ok LabelRef) {
tmp := GP64()
MOVQ(lenSrcQ, tmp)
CMPL(tmp.As32(), candidate)
JG(ok)
})
assert(func(ok LabelRef) {
// We may get s and s+1
tmp := GP32()
LEAL(Mem{Base: s, Disp: 2}, tmp)
CMPL(tmp, candidate)
JG(ok)
})
LEAL(Mem{Base: s, Disp: 2}, tmp)
//if uint32(cv>>8) == load32(src, candidate2)
CMPL(Mem{Base: src, Index: candidate2, Scale: 1}, cv.As32())
JEQ(LabelRef("candidate2_match_" + name))
// table[hash2] = uint32(s + 2)
MOVL(tmp, table.Idx(hash2, 4))
// cv >>= 8 (>> 16 total)
SHRQ(U8(8), cv)
// if uint32(cv>>16) == load32(src, candidate)
CMPL(Mem{Base: src, Index: candidate, Scale: 1}, cv.As32())
JEQ(LabelRef("candidate3_match_" + name))
// No match found, next loop
// s = nextS
MOVL(nextSTempL, s)
JMP(LabelRef("search_loop_" + name))
// Matches candidate at s + 2 (3rd check)
Label("candidate3_match_" + name)
ADDL(U8(2), s)
JMP(LabelRef("candidate_match_" + name))
// Match at s + 1 (we calculated the hash, lets store it)
Label("candidate2_match_" + name)
// table[hash2] = uint32(s + 2)
MOVL(tmp, table.Idx(hash2, 4))
// s++
INCL(s)
MOVL(candidate2, candidate)
}
}
Label("candidate_match_" + name)
// We have a match at 's' with src offset in "candidate" that matches at least 4 bytes.
// Extend backwards
if true {
ne := GP32()
MOVL(nextEmitL, ne)
TESTL(candidate, candidate)
JZ(LabelRef("match_extend_back_end_" + name))
// candidate is tested when decremented, so we loop back here.
Label("match_extend_back_loop_" + name)
// if s <= nextEmit {exit}
CMPL(s, ne)
JLE(LabelRef("match_extend_back_end_" + name))
// if src[candidate-1] == src[s-1]
tmp, tmp2 := GP64(), GP64()
MOVB(Mem{Base: src, Index: candidate, Scale: 1, Disp: -1}, tmp.As8())
MOVB(Mem{Base: src, Index: s, Scale: 1, Disp: -1}, tmp2.As8())
CMPB(tmp.As8(), tmp2.As8())
JNE(LabelRef("match_extend_back_end_" + name))
LEAL(Mem{Base: s, Disp: -1}, s)
DECL(candidate)
JZ(LabelRef("match_extend_back_end_" + name))
JMP(LabelRef("match_extend_back_loop_" + name))
}
Label("match_extend_back_end_" + name)
// Bail if we exceed the maximum size.
if true {
// tmp = s-nextEmit
tmp := GP64()
MOVL(s, tmp.As32())
SUBL(nextEmitL, tmp.As32())
// tmp = &dst + s-nextEmit
LEAQ(Mem{Base: dst, Index: tmp, Scale: 1, Disp: literalMaxOverhead}, tmp)
CMPQ(tmp, dstLimitPtrQ)
JL(LabelRef("match_dst_size_check_" + name))
ri, err := ReturnIndex(0).Resolve()
if err != nil {
panic(err)
}
MOVQ(U32(0), ri.Addr)
RET()
}
Label("match_dst_size_check_" + name)
{
base := GP32()
MOVL(s, base.As32())
o.emitLiteralsDstP(nextEmitL, base, src, dst, "match_emit_"+name)
}
cv := GP64()
Label("match_nolit_loop_" + name)
{
// Update repeat
{
// repeat = base - candidate
repeatVal := GP64().As32()
MOVL(s, repeatVal)
SUBL(candidate, repeatVal)
MOVL(repeatVal, repeatL)
}
// s+=4, candidate+=4
ADDL(U8(4), s)
ADDL(U8(4), candidate)
// Extend the 4-byte match as long as possible and emit copy.
{
assert(func(ok LabelRef) {
// s must be > candidate cannot be equal.
CMPL(s, candidate)
JG(ok)
})
// srcLeft = len(src) - s
srcLeft := GP64()
MOVQ(lenSrcQ, srcLeft)
SUBL(s, srcLeft.As32())
assert(func(ok LabelRef) {
// if srcleft < maxint32: ok
CMPQ(srcLeft, U32(0x7fffffff))
JL(ok)
})
a, b := GP64(), GP64()
LEAQ(Mem{Base: src, Index: s, Scale: 1}, a)
LEAQ(Mem{Base: src, Index: candidate, Scale: 1}, b)
length := o.matchLen("match_nolit_"+name,
a, b,
srcLeft,
LabelRef("match_nolit_end_"+name),
)
Label("match_nolit_end_" + name)
assert(func(ok LabelRef) {
CMPL(length.As32(), U32(math.MaxInt32))
JL(ok)
})
a, b, srcLeft = nil, nil, nil
// s += length (length is destroyed, use it now)
ADDL(length.As32(), s)
// Load offset from repeat value.
offset := GP64()
MOVL(repeatL, offset.As32())
// length += 4
ADDL(U8(4), length.As32())
MOVL(s, nextEmitL) // nextEmit = s
o.emitCopy("match_nolit_"+name, length, offset, nil, dst, LabelRef("match_nolit_emitcopy_end_"+name))
Label("match_nolit_emitcopy_end_" + name)
// if s >= sLimit { end }
{
CMPL(s.As32(), sLimitL)
JGE(LabelRef("emit_remainder_" + name))
}
// Start load s-2 as early as possible...
MOVQ(Mem{Base: src, Index: s, Scale: 1, Disp: -2}, cv)
// Bail if we exceed the maximum size.
{
CMPQ(dst, dstLimitPtrQ)
JL(LabelRef("match_nolit_dst_ok_" + name))
ri, err := ReturnIndex(0).Resolve()
if err != nil {
panic(err)
}
MOVQ(U32(0), ri.Addr)
RET()
Label("match_nolit_dst_ok_" + name)
}
}
// cv must be set to value at s-2 before arriving here
{
// Check for an immediate match, otherwise start search at s+1
// Index s-2
hasher := hashN(hashBytes, tableBits)
hash0, hash1 := GP64(), GP64()
MOVQ(cv, hash0) // src[s-2]
SHRQ(U8(16), cv)
MOVQ(cv, hash1) // src[s]
hasher.hash(hash0)
hasher.hash(hash1)
sm2 := GP32() // s - 2
LEAL(Mem{Base: s, Disp: -2}, sm2)
assert(func(ok LabelRef) {
CMPQ(hash0, U32(tableSize))
JL(ok)
})
assert(func(ok LabelRef) {
CMPQ(hash1, U32(tableSize))
JL(ok)
})
addr := GP64()
LEAQ(table.Idx(hash1, 4), addr)
MOVL(Mem{Base: addr}, candidate)
MOVL(sm2, table.Idx(hash0, 4))
MOVL(s, Mem{Base: addr})
CMPL(Mem{Base: src, Index: candidate, Scale: 1}, cv.As32())
JEQ(LabelRef("match_nolit_loop_" + name))
INCL(s)
}
JMP(LabelRef("search_loop_" + name))
}
Label("emit_remainder_" + name)
// Bail if we exceed the maximum size.
// if d+len(src)-nextEmitL > dstLimitPtrQ { return 0
{
// remain = len(src) - nextEmit
remain := GP64()
MOVQ(lenSrcQ, remain)
SUBL(nextEmitL, remain.As32())
dstExpect := GP64()
// dst := dst + (len(src)-nextEmitL)
LEAQ(Mem{Base: dst, Index: remain, Scale: 1, Disp: literalMaxOverhead}, dstExpect)
CMPQ(dstExpect, dstLimitPtrQ)
JL(LabelRef("emit_remainder_ok_" + name))
ri, err := ReturnIndex(0).Resolve()
if err != nil {
panic(err)
}
MOVQ(U32(0), ri.Addr)
RET()
Label("emit_remainder_ok_" + name)
}
{
// emitLiteral(dst[d:], src[nextEmitL:])
emitEnd := GP64()
MOVQ(lenSrcQ, emitEnd)
// Emit final literals.
// Since we may be at the end of source,
// we cannot have output margin.
x := o.outputMargin
o.outputMargin = 0
o.emitLiteralsDstP(nextEmitL, emitEnd, src, dst, "emit_remainder_"+name)
o.outputMargin = x
// Assert size is < limit
assert(func(ok LabelRef) {
// if dstBaseQ < dstLimitPtrQ: ok
CMPQ(dst, dstLimitPtrQ)
JL(ok)
})
}
// length := start - base (ptr arithmetic)
length := GP64()
base := Load(Param("dst").Base(), GP64())
MOVQ(dst, length)
SUBQ(base, length)
// Assert size is < len(src)
assert(func(ok LabelRef) {
// if len(src) >= length: ok
CMPQ(lenSrcQ, length)
JGE(ok)
})
// Assert size is < len(dst)
assert(func(ok LabelRef) {
// if len(dst) >= length: ok
CMPQ(lenDstQ, length)
JGE(ok)
})
Store(length, ReturnIndex(0))
RET()
}
func maxLitOverheadFor(n int) int {
switch {
case n == 0:
return 0
case n < 60:
return 1
case n < 1<<8:
return 2
case n < 1<<16:
return 3
case n < 1<<24:
return 4
}
return 5
}
func (o options) genEncodeBetterBlockAsm(name string, lTableBits, sTableBits, skipLog, lHashBytes, maxLen int) {
TEXT(name, 0, "func(dst, src []byte) int")
Doc(name+" encodes a non-empty src to a guaranteed-large-enough dst.",
fmt.Sprintf("Maximum input %d bytes.", maxLen),
"It assumes that the varint-encoded length of the decompressed bytes has already been written.", "")
Pragma("noescape")
if lHashBytes > 7 || lHashBytes <= 4 {
panic("lHashBytes must be <= 7 and >4")
}
var literalMaxOverhead = maxLitOverheadFor(maxLen)
const sHashBytes = 4
o.maxLen = maxLen
var lTableSize = 4 * (1 << lTableBits)
var sTableSize = 4 * (1 << sTableBits)
// Memzero needs at least 128 bytes.
if (lTableSize + sTableSize) < 128 {
panic("tableSize must be at least 128 bytes")
}
lenSrcBasic, err := Param("src").Len().Resolve()
if err != nil {
panic(err)
}
lenSrcQ := lenSrcBasic.Addr
lenDstBasic, err := Param("dst").Len().Resolve()
if err != nil {
panic(err)
}
lenDstQ := lenDstBasic.Addr
// Bail if we can't compress to at least this.
dstLimitPtrQ := AllocLocal(8)
// sLimitL is when to stop looking for offset/length copies.
sLimitL := AllocLocal(4)
// nextEmitL keeps track of the point we have emitted to.
nextEmitL := AllocLocal(4)
// Repeat stores the last match offset.
repeatL := AllocLocal(4)
// nextSTempL keeps nextS while other functions are being called.
nextSTempL := AllocLocal(4)
// Alloc table last, lTab must be before sTab.
lTab := AllocLocal(lTableSize)
sTab := AllocLocal(sTableSize)
dst := GP64()
{
dstBaseBasic, err := Param("dst").Base().Resolve()
if err != nil {
panic(err)
}
dstBaseQ := dstBaseBasic.Addr
MOVQ(dstBaseQ, dst)
}
srcBaseBasic, err := Param("src").Base().Resolve()
if err != nil {
panic(err)
}
srcBaseQ := srcBaseBasic.Addr
// Zero table
{
iReg := GP64()
MOVQ(U32((sTableSize+lTableSize)/8/16), iReg)
tablePtr := GP64()
LEAQ(lTab, tablePtr)
zeroXmm := XMM()
PXOR(zeroXmm, zeroXmm)
Label("zero_loop_" + name)
for i := 0; i < 8; i++ {
MOVOU(zeroXmm, Mem{Base: tablePtr, Disp: i * 16})
}
ADDQ(U8(16*8), tablePtr)
DECQ(iReg)
JNZ(LabelRef("zero_loop_" + name))
}
{
// nextEmit is offset n src where the next emitLiteral should start from.
MOVL(U32(0), nextEmitL)
const inputMargin = 8
tmp, tmp2, tmp3 := GP64(), GP64(), GP64()
MOVQ(lenSrcQ, tmp)
LEAQ(Mem{Base: tmp, Disp: -o.outputMargin}, tmp2)
// sLimitL := len(src) - inputMargin
LEAQ(Mem{Base: tmp, Disp: -inputMargin}, tmp3)
assert(func(ok LabelRef) {
CMPQ(tmp3, lenSrcQ)
JL(ok)
})
MOVL(tmp3.As32(), sLimitL)
// dstLimit := (len(src) - 5 ) - len(src)>>5
SHRQ(U8(5), tmp)
SUBL(tmp.As32(), tmp2.As32()) // tmp2 = tmp2 - tmp
assert(func(ok LabelRef) {
// if len(src) > len(src) - len(src)>>5 - 5: ok
CMPQ(lenSrcQ, tmp2)
JGE(ok)
})
LEAQ(Mem{Base: dst, Index: tmp2, Scale: 1}, tmp2)
MOVQ(tmp2, dstLimitPtrQ)
}
// s = 1
s := GP32()
MOVL(U32(1), s)
// repeatL = 0
MOVL(U32(0), repeatL)
src := GP64()
Load(Param("src").Base(), src)
// Load cv
Label("search_loop_" + name)
candidate := GP32()
{
assert(func(ok LabelRef) {
// Check if somebody changed src
tmp := GP64()
MOVQ(srcBaseQ, tmp)
CMPQ(tmp, src)
JEQ(ok)
})
cv := GP64()
nextS := GP32()
// nextS := s + (s-nextEmit)>>skipLog + 1
if o.maxSkip == 0 {
tmp := GP64()
MOVL(s, tmp.As32()) // tmp = s
SUBL(nextEmitL, tmp.As32()) // tmp = s - nextEmit
SHRL(U8(skipLog), tmp.As32()) // tmp = (s - nextEmit) >> skipLog
LEAL(Mem{Base: s, Disp: 1, Index: tmp, Scale: 1}, nextS)
} else {
/*
nextS = (s-nextEmit)>>7 + 1
if nextS > maxSkip {
nextS = s + maxSkip
} else {
nextS += s
}
*/
tmp := GP64()
MOVL(s, tmp.As32()) // tmp = s
SUBL(nextEmitL, tmp.As32()) // tmp = s - nextEmit
SHRL(U8(skipLog), tmp.As32()) // tmp = (s - nextEmit) >> skipLog
CMPL(tmp.As32(), U8(o.maxSkip-1))
JLE(LabelRef("check_maxskip_ok_" + name))
LEAL(Mem{Base: s, Disp: o.maxSkip, Scale: 1}, nextS)
JMP(LabelRef("check_maxskip_cont_" + name))
Label("check_maxskip_ok_" + name)
LEAL(Mem{Base: s, Disp: 1, Index: tmp, Scale: 1}, nextS)
Label("check_maxskip_cont_" + name)
}
// if nextS > sLimit {goto emitRemainder}
{
CMPL(nextS.As32(), sLimitL)
JGE(LabelRef("emit_remainder_" + name))
}
MOVQ(Mem{Base: src, Index: s, Scale: 1}, cv)
assert(func(ok LabelRef) {
// Check if s is valid (we should have jumped above if not)
tmp := GP64()
MOVQ(lenSrcQ, tmp)
CMPQ(tmp, s.As64())
JG(ok)
})
// move nextS to stack.
MOVL(nextS.As32(), nextSTempL)
candidateS := GP32()
lHasher := hashN(lHashBytes, lTableBits)
{
sHasher := hashN(sHashBytes, sTableBits)
hash0, hash1 := GP64(), GP64()
MOVQ(cv, hash0)
MOVQ(cv, hash1)
lHasher.hash(hash0)
sHasher.hash(hash1)
MOVL(lTab.Idx(hash0, 4), candidate)
MOVL(sTab.Idx(hash1, 4), candidateS)
assert(func(ok LabelRef) {
CMPQ(hash0, U32(lTableSize))
JL(ok)
})
assert(func(ok LabelRef) {
CMPQ(hash1, U32(sTableSize))
JL(ok)
})
MOVL(s, lTab.Idx(hash0, 4))
MOVL(s, sTab.Idx(hash1, 4))
}
longVal := GP64()