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huff0: Pass a single bitReader pointer to asm
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This makes the context object smaller and frees up three registers,
which we can use to replace the limitPtr and bufferOrigin stack
variables.

Benchmark results show a tiny win (Go 1.19beta, Core i7-3770K):

	name                                           old speed      new speed      delta
	Decompress1XTable/digits-8                      347MB/s ± 0%   347MB/s ± 0%    ~     (p=0.650 n=8+10)
	Decompress1XTable/gettysburg-8                  268MB/s ± 0%   268MB/s ± 0%    ~     (p=0.400 n=9+9)
	Decompress1XTable/twain-8                       327MB/s ± 0%   327MB/s ± 1%    ~     (p=0.339 n=7+9)
	Decompress1XTable/low-ent.10k-8                 385MB/s ± 0%   385MB/s ± 1%    ~     (p=0.510 n=9+10)
	Decompress1XTable/superlow-ent-10k-8            376MB/s ± 0%   376MB/s ± 0%    ~     (p=0.712 n=8+10)
	Decompress1XTable/crash2-8                     17.3MB/s ± 1%  17.3MB/s ± 1%    ~     (p=0.926 n=10+10)
	Decompress1XTable/endzerobits-8                52.9MB/s ± 1%  52.4MB/s ± 0%  -0.94%  (p=0.000 n=10+10)
	Decompress1XTable/endnonzero-8                 11.4MB/s ± 0%  11.4MB/s ± 1%    ~     (p=0.343 n=10+10)
	Decompress1XTable/case1-8                      22.0MB/s ± 0%  22.0MB/s ± 0%    ~     (p=0.618 n=9+9)
	Decompress1XTable/case2-8                      18.1MB/s ± 0%  18.1MB/s ± 0%    ~     (p=0.348 n=9+9)
	Decompress1XTable/case3-8                      19.1MB/s ± 0%  19.1MB/s ± 0%  +0.21%  (p=0.048 n=10+10)
	Decompress1XTable/pngdata.001-8                 374MB/s ± 0%   374MB/s ± 0%    ~     (p=0.861 n=9+10)
	Decompress1XTable/normcount2-8                 54.3MB/s ± 1%  54.5MB/s ± 1%    ~     (p=0.093 n=10+10)
	Decompress1XNoTable/digits/100-8                279MB/s ± 0%   280MB/s ± 0%  +0.30%  (p=0.003 n=10+9)
	Decompress1XNoTable/digits/10000-8              366MB/s ± 0%   365MB/s ± 0%    ~     (p=0.113 n=10+9)
	Decompress1XNoTable/digits/262143-8             347MB/s ± 0%   347MB/s ± 1%    ~     (p=0.739 n=10+10)
	Decompress1XNoTable/gettysburg/100-8            278MB/s ± 1%   277MB/s ± 1%    ~     (p=0.676 n=10+9)
	Decompress1XNoTable/gettysburg/10000-8          363MB/s ± 1%   362MB/s ± 0%  -0.50%  (p=0.001 n=10+9)
	Decompress1XNoTable/gettysburg/262143-8         350MB/s ± 0%   347MB/s ± 0%  -0.90%  (p=0.000 n=10+8)
	Decompress1XNoTable/twain/100-8                 268MB/s ± 0%   267MB/s ± 0%    ~     (p=0.384 n=9+8)
	Decompress1XNoTable/twain/10000-8               363MB/s ± 0%   362MB/s ± 0%  -0.32%  (p=0.000 n=9+9)
	Decompress1XNoTable/twain/262143-8              328MB/s ± 0%   329MB/s ± 0%    ~     (p=0.063 n=9+10)
	Decompress1XNoTable/low-ent.10k/100-8           180MB/s ± 0%   181MB/s ± 0%    ~     (p=0.225 n=10+10)
	Decompress1XNoTable/low-ent.10k/10000-8         385MB/s ± 0%   385MB/s ± 0%    ~     (p=0.289 n=10+10)
	Decompress1XNoTable/low-ent.10k/262143-8        389MB/s ± 1%   389MB/s ± 1%    ~     (p=0.971 n=10+10)
	Decompress1XNoTable/superlow-ent-10k/262143-8   389MB/s ± 0%   390MB/s ± 0%  +0.27%  (p=0.017 n=9+10)
	Decompress1XNoTable/crash2/100-8                278MB/s ± 0%   279MB/s ± 1%    ~     (p=0.163 n=9+10)
	Decompress1XNoTable/crash2/10000-8              373MB/s ± 1%   373MB/s ± 0%    ~     (p=0.370 n=10+8)
	Decompress1XNoTable/crash2/262143-8             375MB/s ± 0%   375MB/s ± 0%    ~     (p=0.604 n=9+10)
	Decompress1XNoTable/endzerobits/100-8           180MB/s ± 0%   181MB/s ± 0%  +0.26%  (p=0.005 n=10+9)
	Decompress1XNoTable/endzerobits/10000-8         384MB/s ± 0%   385MB/s ± 0%    ~     (p=0.914 n=8+10)
	Decompress1XNoTable/endzerobits/262143-8        389MB/s ± 0%   390MB/s ± 0%    ~     (p=0.739 n=10+10)
	Decompress1XNoTable/endnonzero/100-8            180MB/s ± 1%   180MB/s ± 1%    ~     (p=0.926 n=10+10)
	Decompress1XNoTable/endnonzero/10000-8          384MB/s ± 0%   384MB/s ± 0%    ~     (p=0.965 n=10+8)
	Decompress1XNoTable/endnonzero/262143-8         390MB/s ± 0%   390MB/s ± 0%    ~     (p=0.633 n=8+10)
	Decompress1XNoTable/case1/100-8                 282MB/s ± 0%   283MB/s ± 0%  +0.34%  (p=0.005 n=10+10)
	Decompress1XNoTable/case1/10000-8               372MB/s ± 0%   373MB/s ± 0%    ~     (p=0.113 n=9+9)
	Decompress1XNoTable/case1/262143-8              374MB/s ± 0%   374MB/s ± 0%    ~     (p=0.448 n=10+10)
	Decompress1XNoTable/case2/100-8                 274MB/s ± 1%   274MB/s ± 0%    ~     (p=0.927 n=10+10)
	Decompress1XNoTable/case2/10000-8               376MB/s ± 0%   376MB/s ± 0%    ~     (p=0.408 n=10+8)
	Decompress1XNoTable/case2/262143-8              376MB/s ± 1%   377MB/s ± 0%    ~     (p=1.000 n=10+10)
	Decompress1XNoTable/case3/100-8                 266MB/s ± 0%   265MB/s ± 0%    ~     (p=0.113 n=9+10)
	Decompress1XNoTable/case3/10000-8               372MB/s ± 0%   372MB/s ± 0%    ~     (p=0.075 n=10+9)
	Decompress1XNoTable/case3/262143-8              374MB/s ± 0%   374MB/s ± 0%    ~     (p=0.172 n=10+10)
	Decompress1XNoTable/pngdata.001/100-8           238MB/s ± 0%   238MB/s ± 0%    ~     (p=0.438 n=9+8)
	Decompress1XNoTable/pngdata.001/10000-8         384MB/s ± 0%   384MB/s ± 0%    ~     (p=0.448 n=10+10)
	Decompress1XNoTable/pngdata.001/262143-8        378MB/s ± 0%   378MB/s ± 0%    ~     (p=0.836 n=10+10)
	Decompress1XNoTable/normcount2/100-8            281MB/s ± 0%   282MB/s ± 1%    ~     (p=0.122 n=8+10)
	Decompress1XNoTable/normcount2/10000-8          369MB/s ± 1%   369MB/s ± 0%    ~     (p=0.912 n=10+10)
	Decompress1XNoTable/normcount2/262143-8         370MB/s ± 0%   370MB/s ± 1%    ~     (p=0.342 n=10+10)
	Decompress4XNoTable/digits/100-8                197MB/s ± 0%   197MB/s ± 1%    ~     (p=0.764 n=10+9)
	Decompress4XNoTable/digits/10000-8              594MB/s ± 0%   602MB/s ± 1%  +1.35%  (p=0.000 n=10+10)
	Decompress4XNoTable/digits/262143-8             570MB/s ± 1%   578MB/s ± 0%  +1.30%  (p=0.000 n=10+8)
	Decompress4XNoTable/gettysburg/100-8            258MB/s ± 1%   260MB/s ± 0%  +0.59%  (p=0.001 n=10+10)
	Decompress4XNoTable/gettysburg/10000-8          638MB/s ± 0%   641MB/s ± 0%  +0.44%  (p=0.000 n=9+9)
	Decompress4XNoTable/gettysburg/262143-8         573MB/s ± 1%   574MB/s ± 0%    ~     (p=0.353 n=10+10)
	Decompress4XNoTable/twain/100-8                 214MB/s ± 2%   214MB/s ± 2%    ~     (p=0.853 n=10+10)
	Decompress4XNoTable/twain/10000-8               634MB/s ± 1%   638MB/s ± 0%  +0.62%  (p=0.000 n=10+10)
	Decompress4XNoTable/twain/262143-8              513MB/s ± 1%   517MB/s ± 0%  +0.85%  (p=0.000 n=10+10)
	Decompress4XNoTable/low-ent.10k/100-8           195MB/s ± 0%   194MB/s ± 0%    ~     (p=0.130 n=9+9)
	Decompress4XNoTable/low-ent.10k/10000-8         635MB/s ± 0%   642MB/s ± 0%  +1.19%  (p=0.000 n=10+10)
	Decompress4XNoTable/low-ent.10k/262143-8        675MB/s ± 0%   685MB/s ± 0%  +1.51%  (p=0.000 n=10+10)
	Decompress4XNoTable/superlow-ent-10k/262143-8   673MB/s ± 1%   684MB/s ± 0%  +1.70%  (p=0.000 n=10+10)
	Decompress4XNoTable/case1/100-8                 206MB/s ± 1%   206MB/s ± 0%    ~     (p=0.189 n=10+9)
	Decompress4XNoTable/case1/10000-8               593MB/s ± 0%   601MB/s ± 0%  +1.47%  (p=0.000 n=10+10)
	Decompress4XNoTable/case1/262143-8              603MB/s ± 0%   613MB/s ± 0%  +1.64%  (p=0.000 n=10+10)
	Decompress4XNoTable/case2/100-8                 201MB/s ± 0%   202MB/s ± 1%    ~     (p=0.053 n=9+10)
	Decompress4XNoTable/case2/10000-8               610MB/s ± 0%   618MB/s ± 0%  +1.30%  (p=0.000 n=9+10)
	Decompress4XNoTable/case2/262143-8              622MB/s ± 1%   634MB/s ± 0%  +1.90%  (p=0.000 n=9+8)
	Decompress4XNoTable/case3/100-8                 197MB/s ± 1%   198MB/s ± 0%  +0.53%  (p=0.001 n=9+10)
	Decompress4XNoTable/case3/10000-8               606MB/s ± 0%   615MB/s ± 0%  +1.49%  (p=0.000 n=8+10)
	Decompress4XNoTable/case3/262143-8              613MB/s ± 1%   622MB/s ± 0%  +1.48%  (p=0.000 n=10+10)
	Decompress4XNoTable/pngdata.001/100-8           212MB/s ± 1%   211MB/s ± 0%    ~     (p=0.136 n=9+9)
	Decompress4XNoTable/pngdata.001/10000-8         645MB/s ± 1%   649MB/s ± 1%  +0.65%  (p=0.000 n=9+10)
	Decompress4XNoTable/pngdata.001/262143-8        640MB/s ± 1%   649MB/s ± 0%  +1.44%  (p=0.000 n=10+10)
	Decompress4XNoTable/normcount2/100-8            260MB/s ± 1%   261MB/s ± 1%    ~     (p=0.211 n=10+9)
	Decompress4XNoTable/normcount2/10000-8          584MB/s ± 1%   591MB/s ± 0%  +1.33%  (p=0.000 n=9+9)
	Decompress4XNoTable/normcount2/262143-8         588MB/s ± 1%   596MB/s ± 1%  +1.39%  (p=0.000 n=10+9)
	Decompress4XNoTableTableLog8/digits-8           583MB/s ± 1%   592MB/s ± 0%  +1.48%  (p=0.000 n=10+10)
	Decompress4XTable/digits-8                      580MB/s ± 0%   588MB/s ± 0%  +1.33%  (p=0.000 n=8+10)
	Decompress4XTable/gettysburg-8                  368MB/s ± 1%   370MB/s ± 0%  +0.59%  (p=0.017 n=10+9)
	Decompress4XTable/twain-8                       510MB/s ± 0%   515MB/s ± 0%  +0.99%  (p=0.000 n=9+10)
	Decompress4XTable/low-ent.10k-8                 657MB/s ± 0%   665MB/s ± 0%  +1.24%  (p=0.000 n=10+10)
	Decompress4XTable/superlow-ent-10k-8            608MB/s ± 0%   617MB/s ± 1%  +1.48%  (p=0.000 n=8+10)
	Decompress4XTable/case1-8                      21.1MB/s ± 1%  21.0MB/s ± 2%    ~     (p=0.223 n=10+10)
	Decompress4XTable/case2-8                      17.6MB/s ± 0%  17.6MB/s ± 0%    ~     (p=0.199 n=9+10)
	Decompress4XTable/case3-8                      18.7MB/s ± 0%  18.7MB/s ± 0%    ~     (p=0.557 n=10+8)
	Decompress4XTable/pngdata.001-8                 633MB/s ± 1%   645MB/s ± 0%  +1.90%  (p=0.000 n=9+10)
	Decompress4XTable/normcount2-8                 49.9MB/s ± 1%  49.5MB/s ± 1%  -0.64%  (p=0.002 n=10+10)
	[Geo mean]                                      270MB/s        271MB/s       +0.36%
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@greatroar
greatroar committed Jul 8, 2022
1 parent 51e1025 commit 8754555
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Showing 3 changed files with 375 additions and 409 deletions.
100 changes: 43 additions & 57 deletions huff0/_generate/gen.go
View file
Expand Up @@ -49,49 +49,41 @@ func (d decompress4x) generateProcedure(name string) {
exhausted := GP64()
XORQ(exhausted.As64(), exhausted.As64()) // exhausted = false

limitPtr := AllocLocal(8)
limit := GP64()

bufferOrigin := GP64()
peekBits := GP64()
buffer := GP64()
dstEvery := GP64()
table := GP64()

br0 := GP64()
br1 := GP64()
br2 := GP64()
br3 := GP64()
br := GP64()

Comment("Preload values")
{
ctx := Dereference(Param("ctx"))
Load(ctx.Field("peekBits"), peekBits)
Load(ctx.Field("out"), buffer)
MOVQ(buffer, bufferOrigin)
limit := Load(ctx.Field("limit"), GP64())
MOVQ(limit, limitPtr)
Load(ctx.Field("out"), bufferOrigin)
Load(ctx.Field("limit"), limit)
Load(ctx.Field("dstEvery"), dstEvery)
Load(ctx.Field("tbl"), table)
Load(ctx.Field("pbr0"), br0)
Load(ctx.Field("pbr1"), br1)
Load(ctx.Field("pbr2"), br2)
Load(ctx.Field("pbr3"), br3)
Load(ctx.Field("pbr"), br)
}

Comment("Main loop")
Label("main_loop")

MOVQ(bufferOrigin, buffer)
// Check if we have space
CMPQ(buffer, limitPtr)
CMPQ(buffer, limit)
SETGE(exhausted.As8())
d.decodeTwoValues(0, br0, peekBits, table, buffer, exhausted)
d.decodeTwoValues(0, br, peekBits, table, buffer, exhausted)
ADDQ(dstEvery, buffer)
d.decodeTwoValues(1, br1, peekBits, table, buffer, exhausted)
d.decodeTwoValues(1, br, peekBits, table, buffer, exhausted)
ADDQ(dstEvery, buffer)
d.decodeTwoValues(2, br2, peekBits, table, buffer, exhausted)
d.decodeTwoValues(2, br, peekBits, table, buffer, exhausted)
ADDQ(dstEvery, buffer)
d.decodeTwoValues(3, br3, peekBits, table, buffer, exhausted)
d.decodeTwoValues(3, br, peekBits, table, buffer, exhausted)

ADDQ(U8(2), bufferOrigin) // off += 2

Expand All @@ -100,10 +92,9 @@ func (d decompress4x) generateProcedure(name string) {

{
ctx := Dereference(Param("ctx"))
tmp := Load(ctx.Field("out"), GP64())
decoded := GP64()
MOVQ(bufferOrigin, decoded)
SUBQ(tmp, decoded)
ctxout, _ := ctx.Field("out").Resolve()
decoded := bufferOrigin
SUBQ(ctxout.Addr, decoded)
SHLQ(U8(2), decoded) // decoded *= 4

Store(decoded, ctx.Field("decoded"))
Expand All @@ -118,6 +109,7 @@ 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)
Expand Down Expand Up @@ -157,9 +149,10 @@ func (d decompress4x) decodeTwoValues(id int, br, peekBits, table, buffer, exhau
Comment("out[id * dstEvery + 1] = uint8(v1.entry >> 8)")
MOVW(out.As16(), Mem{Base: buffer})

Comment("update the bitrader reader structure")
MOVQ(brValue, Mem{Base: br, Disp: bitReader_value})
MOVB(brBitsRead.As8(), Mem{Base: br, Disp: bitReader_bitsRead})
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) {
Expand All @@ -171,49 +164,41 @@ func (d decompress4x) generateProcedure4x8bit(name string) {
exhausted := GP64() // Fixed since we need 8H
XORQ(exhausted.As64(), exhausted.As64()) // exhausted = false

bufferOrigin := AllocLocal(8)
limitPtr := AllocLocal(8)
bufferOrigin := GP64()
limit := GP64()

peekBits := GP64()
buffer := GP64()
dstEvery := GP64()
table := GP64()

br0 := GP64()
br1 := GP64()
br2 := GP64()
br3 := GP64()
br := GP64()

Comment("Preload values")
{
ctx := Dereference(Param("ctx"))
Load(ctx.Field("peekBits"), peekBits)
Load(ctx.Field("out"), buffer)
MOVQ(buffer, bufferOrigin)
limit := Load(ctx.Field("limit"), GP64())
MOVQ(limit, limitPtr)
Load(ctx.Field("out"), bufferOrigin)
Load(ctx.Field("limit"), limit)
Load(ctx.Field("dstEvery"), dstEvery)
Load(ctx.Field("tbl"), table)
Load(ctx.Field("pbr0"), br0)
Load(ctx.Field("pbr1"), br1)
Load(ctx.Field("pbr2"), br2)
Load(ctx.Field("pbr3"), br3)
Load(ctx.Field("pbr"), br)
}

Comment("Main loop")
Label("main_loop")

MOVQ(bufferOrigin, buffer)
// Check if we have space
CMPQ(buffer, limitPtr)
CMPQ(buffer, limit)
SETGE(exhausted.As8())
d.decodeFourValues(0, br0, peekBits, table, buffer, exhausted)
d.decodeFourValues(0, br, peekBits, table, buffer, exhausted)
ADDQ(dstEvery, buffer)
d.decodeFourValues(1, br1, peekBits, table, buffer, exhausted)
d.decodeFourValues(1, br, peekBits, table, buffer, exhausted)
ADDQ(dstEvery, buffer)
d.decodeFourValues(2, br2, peekBits, table, buffer, exhausted)
d.decodeFourValues(2, br, peekBits, table, buffer, exhausted)
ADDQ(dstEvery, buffer)
d.decodeFourValues(3, br3, peekBits, table, buffer, exhausted)
d.decodeFourValues(3, br, peekBits, table, buffer, exhausted)

ADDQ(U8(4), bufferOrigin) // off += 4

Expand All @@ -222,10 +207,9 @@ func (d decompress4x) generateProcedure4x8bit(name string) {

{
ctx := Dereference(Param("ctx"))
tmp := Load(ctx.Field("out"), GP64())
decoded := GP64()
MOVQ(bufferOrigin, decoded)
SUBQ(tmp, decoded)
ctxout, _ := ctx.Field("out").Resolve()
decoded := bufferOrigin
SUBQ(ctxout.Addr, decoded)
SHLQ(U8(2), decoded) // decoded *= 4

Store(decoded, ctx.Field("decoded"))
Expand All @@ -234,7 +218,7 @@ func (d decompress4x) generateProcedure4x8bit(name string) {
}

func (d decompress4x) decodeFourValues(id int, br, peekBits, table, buffer, exhausted reg.GPVirtual) {
brValue, brBitsRead := d.fillFast32(id+1000, 32, br, exhausted)
brValue, brBitsRead := d.fillFast32(id, 32, br, exhausted)

decompress := func(valID int, outByte reg.Register) {
CX := reg.CL
Expand Down Expand Up @@ -269,9 +253,10 @@ func (d decompress4x) decodeFourValues(id int, br, peekBits, table, buffer, exha
Comment("out[id * dstEvery + 4] = uint8(v3.entry >> 8)")
MOVL(out.As32(), Mem{Base: buffer})

Comment("update the bitreader reader structure")
MOVQ(brValue, Mem{Base: br, Disp: bitReader_value})
MOVB(brBitsRead.As8(), Mem{Base: br, Disp: bitReader_bitsRead})
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) {
Expand All @@ -281,14 +266,15 @@ func (d decompress4x) fillFast32(id, atLeast int, br, exhausted reg.GPVirtual) (
Commentf("br%d.fillFast32()", id)
brValue = GP64()
brBitsRead = GP64()
MOVQ(Mem{Base: br, Disp: bitReader_value}, brValue)
MOVBQZX(Mem{Base: br, Disp: bitReader_bitsRead}, brBitsRead)
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: bitReader_off}, brOffset)
MOVQ(Mem{Base: br, Disp: offset + bitReader_off}, brOffset)

SUBQ(U8(32), brBitsRead) // b.bitsRead -= 32
SUBQ(U8(4), brOffset) // b.off -= 4
Expand All @@ -297,7 +283,7 @@ func (d decompress4x) fillFast32(id, atLeast int, br, exhausted reg.GPVirtual) (
// 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: bitReader_in}, tmp)
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}
Expand All @@ -306,7 +292,7 @@ func (d decompress4x) fillFast32(id, atLeast int, br, exhausted reg.GPVirtual) (
MOVQ(brBitsRead, CX.As64())
SHLQ(CX, tmp.As64())

MOVQ(brOffset, Mem{Base: br, Disp: bitReader_off})
MOVQ(brOffset, Mem{Base: br, Disp: offset + bitReader_off})
ORQ(tmp.As64(), brValue)
{
Commentf("exhausted = exhausted || (br%d.off < 4)", id)
Expand Down
10 changes: 2 additions & 8 deletions huff0/decompress_amd64.go
View file
Expand Up @@ -27,10 +27,7 @@ func decompress4x_8b_main_loop_amd64(ctx *decompress4xContext)
const fallback8BitSize = 800

type decompress4xContext struct {
pbr0 *bitReaderShifted
pbr1 *bitReaderShifted
pbr2 *bitReaderShifted
pbr3 *bitReaderShifted
pbr *[4]bitReaderShifted
peekBits uint8
out *byte
dstEvery int
Expand Down Expand Up @@ -89,10 +86,7 @@ func (d *Decoder) Decompress4X(dst, src []byte) ([]byte, error) {

if len(out) > 4*4 && !(br[0].off < 4 || br[1].off < 4 || br[2].off < 4 || br[3].off < 4) {
ctx := decompress4xContext{
pbr0: &br[0],
pbr1: &br[1],
pbr2: &br[2],
pbr3: &br[3],
pbr: &br,
peekBits: uint8((64 - d.actualTableLog) & 63), // see: bitReaderShifted.peekBitsFast()
out: &out[0],
dstEvery: dstEvery,
Expand Down

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