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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 ../decompress_amd64.s -pkg=huff0
import (
"flag"
"fmt"
"strconv"
_ "github.com/klauspost/compress"
. "github.com/mmcloughlin/avo/build"
"github.com/mmcloughlin/avo/gotypes"
. "github.com/mmcloughlin/avo/operand"
"github.com/mmcloughlin/avo/reg"
)
func main() {
flag.Parse()
ConstraintExpr("amd64,!appengine,!noasm,gc")
{
decompress := decompress4x{}
decompress.generateProcedure("decompress4x_main_loop_amd64")
decompress.generateProcedure4x8bit("decompress4x_8b_main_loop_amd64")
}
{
decompress := decompress1x{}
decompress.generateProcedure("decompress1x_main_loop_amd64")
decompress.bmi2 = true
decompress.generateProcedure("decompress1x_main_loop_bmi2")
}
Generate()
}
type decompress4x struct {
}
func (d decompress4x) generateProcedure(name string) {
Package("github.com/klauspost/compress/huff0")
TEXT(name, 0, "func(ctx* decompress4xContext)")
Doc(name+" is an x86 assembler implementation of Decompress4X when tablelog > 8.decodes a sequence", "")
Pragma("noescape")
exhausted := GP64()
XORQ(exhausted.As64(), exhausted.As64()) // exhausted = false
limit := GP64()
bufferOrigin := GP64()
peekBits := GP64()
buffer := GP64()
dstEvery := GP64()
table := GP64()
br := GP64()
Comment("Preload values")
{
ctx := Dereference(Param("ctx"))
Load(ctx.Field("peekBits"), peekBits)
Load(ctx.Field("out"), bufferOrigin)
Load(ctx.Field("limit"), limit)
Load(ctx.Field("dstEvery"), dstEvery)
Load(ctx.Field("tbl"), table)
Load(ctx.Field("pbr"), br)
}
Comment("Main loop")
Label("main_loop")
MOVQ(bufferOrigin, buffer)
// Check if we have space
CMPQ(buffer, limit)
SETGE(exhausted.As8())
d.decodeTwoValues(0, br, peekBits, table, buffer, exhausted)
ADDQ(dstEvery, buffer)
d.decodeTwoValues(1, br, peekBits, table, buffer, exhausted)
ADDQ(dstEvery, buffer)
d.decodeTwoValues(2, br, peekBits, table, buffer, exhausted)
ADDQ(dstEvery, buffer)
d.decodeTwoValues(3, br, peekBits, table, buffer, exhausted)
ADDQ(U8(2), bufferOrigin) // off += 2
TESTB(exhausted.As8(), exhausted.As8()) // any br[i].ofs < 4?
JZ(LabelRef("main_loop"))
{
ctx := Dereference(Param("ctx"))
tmp := Load(ctx.Field("out"), GP64())
decoded := bufferOrigin
SUBQ(tmp, decoded)
SHLQ(U8(2), decoded) // decoded *= 4
Store(decoded, ctx.Field("decoded"))
}
RET()
}
// TODO [wmu]: I believe it's doable in avo, but can't figure out how to deal
// with arbitrary pointers to a given type
const bitReader_in = 0
const bitReader_off = bitReader_in + 3*8 // {ptr, len, cap}
const bitReader_value = bitReader_off + 8
const bitReader_bitsRead = bitReader_value + 8
const bitReader__size = bitReader_bitsRead + 8
func (d decompress4x) decodeTwoValues(id int, br, peekBits, table, buffer, exhausted reg.GPVirtual) {
brValue, brBitsRead := d.fillFast32(id, 32, br, exhausted)
val := GP64()
Commentf("val0 := br%d.peekTopBits(peekBits)", id)
CX := reg.CL
MOVQ(brValue, val.As64())
MOVQ(peekBits, CX.As64())
SHRQ(CX, val.As64()) // val = (value >> peek_bits) & mask
Comment("v0 := table[val0&mask]")
MOVW(Mem{Base: table, Index: val.As64(), Scale: 2}, CX.As16())
Commentf("br%d.advance(uint8(v0.entry)", id)
out := reg.RAX // Fixed since we need 8H
MOVB(CX.As8H(), out.As8()) // AL = uint8(v0.entry >> 8)
SHLQ(CX, brValue) // value <<= n
ADDB(CX.As8(), brBitsRead.As8()) // bits_read += n
Commentf("val1 := br%d.peekTopBits(peekBits)", id)
MOVQ(peekBits, CX.As64())
MOVQ(brValue, val.As64())
SHRQ(CX, val.As64()) // val = (value >> peek_bits) & mask
Comment("v1 := table[val1&mask]")
MOVW(Mem{Base: table, Index: val.As64(), Scale: 2}, CX.As16()) // tmp - v1
Commentf("br%d.advance(uint8(v1.entry))", id)
MOVB(CX.As8H(), out.As8H()) // AH = uint8(v0.entry >> 8)
SHLQ(CX, brValue) // value <<= n
ADDB(CX.As8(), brBitsRead.As8()) // bits_read += n
Comment("these two writes get coalesced")
Comment("out[id * dstEvery + 0] = uint8(v0.entry >> 8)")
Comment("out[id * dstEvery + 1] = uint8(v1.entry >> 8)")
MOVW(out.As16(), Mem{Base: buffer})
Comment("update the bitreader structure")
offset := id * bitReader__size
MOVQ(brValue, Mem{Base: br, Disp: offset + bitReader_value})
MOVB(brBitsRead.As8(), Mem{Base: br, Disp: offset + bitReader_bitsRead})
}
func (d decompress4x) generateProcedure4x8bit(name string) {
Package("github.com/klauspost/compress/huff0")
TEXT(name, 0, "func(ctx* decompress4xContext)")
Doc(name+" is an x86 assembler implementation of Decompress4X when tablelog > 8.decodes a sequence", "")
Pragma("noescape")
exhausted := GP64() // Fixed since we need 8H
XORQ(exhausted.As64(), exhausted.As64()) // exhausted = false
bufferOrigin := GP64()
limit := GP64()
peekBits := GP64()
buffer := GP64()
dstEvery := GP64()
table := GP64()
br := GP64()
Comment("Preload values")
{
ctx := Dereference(Param("ctx"))
Load(ctx.Field("peekBits"), peekBits)
Load(ctx.Field("out"), bufferOrigin)
Load(ctx.Field("limit"), limit)
Load(ctx.Field("dstEvery"), dstEvery)
Load(ctx.Field("tbl"), table)
Load(ctx.Field("pbr"), br)
}
Comment("Main loop")
Label("main_loop")
MOVQ(bufferOrigin, buffer)
// Check if we have space
CMPQ(buffer, limit)
SETGE(exhausted.As8())
d.decodeFourValues(0, br, peekBits, table, buffer, exhausted)
ADDQ(dstEvery, buffer)
d.decodeFourValues(1, br, peekBits, table, buffer, exhausted)
ADDQ(dstEvery, buffer)
d.decodeFourValues(2, br, peekBits, table, buffer, exhausted)
ADDQ(dstEvery, buffer)
d.decodeFourValues(3, br, peekBits, table, buffer, exhausted)
ADDQ(U8(4), bufferOrigin) // off += 4
TESTB(exhausted.As8(), exhausted.As8()) // any br[i].ofs < 4?
JZ(LabelRef("main_loop"))
{
ctx := Dereference(Param("ctx"))
tmp := Load(ctx.Field("out"), GP64())
decoded := bufferOrigin
SUBQ(tmp, decoded)
SHLQ(U8(2), decoded) // decoded *= 4
Store(decoded, ctx.Field("decoded"))
}
RET()
}
func (d decompress4x) decodeFourValues(id int, br, peekBits, table, buffer, exhausted reg.GPVirtual) {
brValue, brBitsRead := d.fillFast32(id, 32, br, exhausted)
decompress := func(valID int, outByte reg.Register) {
CX := reg.CL
val := GP64()
Commentf("val%d := br%d.peekTopBits(peekBits)", valID, id)
MOVQ(brValue, val.As64())
MOVQ(peekBits, CX.As64())
SHRQ(CX, val.As64()) // val = (value >> peek_bits) & mask
Commentf("v%d := table[val0&mask]", valID)
MOVW(Mem{Base: table, Index: val.As64(), Scale: 2}, CX.As16())
Commentf("br%d.advance(uint8(v%d.entry)", id, valID)
MOVB(CX.As8H(), outByte) // outByte = uint8(v0.entry >> 8)
SHLQ(CX, brValue) // value <<= n
ADDB(CX, brBitsRead.As8()) // bits_read += n
}
out := reg.RAX // Fixed since we need 8H
decompress(0, out.As8L())
decompress(1, out.As8H())
BSWAPL(out.As32())
decompress(2, out.As8H())
decompress(3, out.As8L())
BSWAPL(out.As32())
Comment("these four writes get coalesced")
Comment("out[id * dstEvery + 0] = uint8(v0.entry >> 8)")
Comment("out[id * dstEvery + 1] = uint8(v1.entry >> 8)")
Comment("out[id * dstEvery + 3] = uint8(v2.entry >> 8)")
Comment("out[id * dstEvery + 4] = uint8(v3.entry >> 8)")
MOVL(out.As32(), Mem{Base: buffer})
Comment("update the bitreader structure")
offset := id * bitReader__size
MOVQ(brValue, Mem{Base: br, Disp: offset + bitReader_value})
MOVB(brBitsRead.As8(), Mem{Base: br, Disp: offset + bitReader_bitsRead})
}
func (d decompress4x) fillFast32(id, atLeast int, br, exhausted reg.GPVirtual) (brValue, brBitsRead reg.GPVirtual) {
if atLeast > 32 {
panic(fmt.Sprintf("at least (%d) cannot be >32", atLeast))
}
Commentf("br%d.fillFast32()", id)
brValue = GP64()
brBitsRead = GP64()
offset := bitReader__size * id
MOVQ(Mem{Base: br, Disp: offset + bitReader_value}, brValue)
MOVBQZX(Mem{Base: br, Disp: offset + bitReader_bitsRead}, brBitsRead)
// We must have at least 2 * max tablelog left
CMPQ(brBitsRead, U8(64-atLeast))
JBE(LabelRef("skip_fill" + strconv.Itoa(id)))
brOffset := GP64()
MOVQ(Mem{Base: br, Disp: offset + bitReader_off}, brOffset)
SUBQ(U8(32), brBitsRead) // b.bitsRead -= 32
SUBQ(U8(4), brOffset) // b.off -= 4
// v := b.in[b.off-4 : b.off]
// v = v[:4]
// low := (uint32(v[0])) | (uint32(v[1]) << 8) | (uint32(v[2]) << 16) | (uint32(v[3]) << 24)
tmp := GP64()
MOVQ(Mem{Base: br, Disp: offset + bitReader_in}, tmp)
Comment("b.value |= uint64(low) << (b.bitsRead & 63)")
addr := Mem{Base: brOffset, Index: tmp.As64(), Scale: 1}
CX := reg.CL
MOVL(addr, tmp.As32()) // tmp = uint32(b.in[b.off:b.off+4])
MOVQ(brBitsRead, CX.As64())
SHLQ(CX, tmp.As64())
MOVQ(brOffset, Mem{Base: br, Disp: offset + bitReader_off})
ORQ(tmp.As64(), brValue)
{
Commentf("exhausted = exhausted || (br%d.off < 4)", id)
CMPQ(brOffset, U8(4))
tmp = GP64()
SETLT(tmp.As8())
ORB(tmp.As8(), exhausted.As8())
}
Label("skip_fill" + strconv.Itoa(id))
return
}
type bitReader struct {
in reg.GPVirtual
off reg.GPVirtual
value reg.GPVirtual
bitsRead reg.GPVirtual
id int
bmi2 bool
}
func (b *bitReader) uniqId() string {
b.id += 1
return strconv.Itoa(b.id)
}
func (b *bitReader) load(pointer gotypes.Component) {
b.in = GP64()
b.off = GP64()
b.value = GP64()
b.bitsRead = GP64()
Load(pointer.Field("in").Base(), b.in)
Load(pointer.Field("off"), b.off)
Load(pointer.Field("value"), b.value)
Load(pointer.Field("bitsRead"), b.bitsRead)
}
func (b *bitReader) store(pointer gotypes.Component) {
Store(b.off, pointer.Field("off"))
Store(b.value, pointer.Field("value"))
// Note: explicit As8(), without this avo reports: "could not deduce mov instruction"
Store(b.bitsRead.As8(), pointer.Field("bitsRead"))
}
func (b *bitReader) fillFast() {
label := "bitReader_fillFast_" + b.uniqId() + "_end"
CMPQ(b.bitsRead, U8(32))
JL(LabelRef(label))
SUBQ(U8(32), b.bitsRead)
SUBQ(U8(4), b.off)
tmp := GP64()
MOVL(Mem{Base: b.in, Index: b.off, Scale: 1}, tmp.As32())
if b.bmi2 {
SHLXQ(b.bitsRead, tmp, tmp)
} else {
MOVQ(b.bitsRead, reg.RCX)
SHLQ(reg.CL, tmp)
}
ORQ(tmp, b.value)
Label(label)
}
func (b *bitReader) peekTopBits(n reg.GPVirtual) reg.GPVirtual {
res := GP64()
if b.bmi2 {
SHRXQ(n, b.value, res)
} else {
MOVQ(n, reg.RCX)
MOVQ(b.value, res)
SHRQ(reg.CL, res)
}
return res
}
func (b *bitReader) advance(n reg.Register) {
ADDQ(n, b.bitsRead)
if b.bmi2 {
SHLXQ(n, b.value, b.value)
} else {
MOVQ(n, reg.RCX)
SHLQ(reg.CL, b.value)
}
}
type decompress1x struct {
bmi2 bool
}
func (d decompress1x) generateProcedure(name string) {
Package("github.com/klauspost/compress/huff0")
TEXT(name, 0, "func(ctx* decompress1xContext)")
Doc(name+" is an x86 assembler implementation of Decompress1X", "")
Pragma("noescape")
br := bitReader{}
br.bmi2 = d.bmi2
buffer := GP64()
bufferEnd := GP64() // the past-end address of buffer
dt := GP64()
peekBits := GP64()
{
ctx := Dereference(Param("ctx"))
Load(ctx.Field("out"), buffer)
outCap := GP64()
Load(ctx.Field("outCap"), outCap)
CMPQ(outCap, U8(4))
JB(LabelRef("error_max_decoded_size_exeeded"))
LEAQ(Mem{Base: buffer, Index: outCap, Scale: 1}, bufferEnd)
// load bitReader struct
pbr := Dereference(ctx.Field("pbr"))
br.load(pbr)
Load(ctx.Field("tbl"), dt)
Load(ctx.Field("peekBits"), peekBits)
}
JMP(LabelRef("loop_condition"))
Label("main_loop")
out := reg.AX // Fixed, as we need an 8H part
Comment("Check if we have room for 4 bytes in the output buffer")
{
tmp := GP64()
LEAQ(Mem{Base: buffer, Disp: 4}, tmp)
CMPQ(tmp, bufferEnd)
JGE(LabelRef("error_max_decoded_size_exeeded"))
}
decompress := func(id int, out reg.Register) {
d.decompress(id, &br, peekBits, dt, out)
}
Comment("Decode 4 values")
br.fillFast()
decompress(0, out.As8L())
decompress(1, out.As8H())
BSWAPL(out.As32())
br.fillFast()
decompress(2, out.As8H())
decompress(3, out.As8L())
BSWAPL(out.As32())
Comment("Store the decoded values")
MOVL(out.As32(), Mem{Base: buffer})
ADDQ(U8(4), buffer)
Label("loop_condition")
CMPQ(br.off, U8(8))
JGE(LabelRef("main_loop"))
Comment("Update ctx structure")
{
// calculate decoded as current `out` - initial `out`
ctx := Dereference(Param("ctx"))
decoded := GP64()
tmp := GP64()
MOVQ(buffer, decoded)
Load(ctx.Field("out"), tmp)
SUBQ(tmp, decoded)
Store(decoded, ctx.Field("decoded"))
pbr := Dereference(ctx.Field("pbr"))
br.store(pbr)
}
RET()
Comment("Report error")
Label("error_max_decoded_size_exeeded")
{
ctx := Dereference(Param("ctx"))
tmp := GP64()
MOVQ(I64(-1), tmp)
Store(tmp, ctx.Field("decoded"))
}
RET()
}
func (d decompress1x) decompress(id int, br *bitReader, peekBits, dt reg.GPVirtual, out reg.Register) {
// v := dt[br.peekBitsFast(d.actualTableLog)&tlMask]
k := br.peekTopBits(peekBits)
v := reg.RCX // Fixed, as we need 8H part
MOVW(Mem{Base: dt, Index: k, Scale: 2}, v.As16())
// buf[id] = uint8(v.entry >> 8)
MOVB(v.As8H(), out)
// br.advance(uint8(v.entry))
MOVBQZX(v.As8L(), v)
br.advance(v)
}