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s2: Clean up matchlen assembly #825

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Jun 13, 2023
Merged

s2: Clean up matchlen assembly #825

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14c3442
s2: Clean up matchlen assembly
klauspost Jun 12, 2023
a5ddb5a
Test for final zero after SUB
klauspost Jun 12, 2023
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169 changes: 77 additions & 92 deletions s2/_generate/gen.go
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,7 @@ func main() {
bmi1: false,
bmi2: false,
snappy: false,
avx2: false,
outputMargin: 9,
}
o.genEncodeBlockAsm("encodeBlockAsm", 14, 6, 6, limit14B)
Expand Down Expand Up @@ -150,6 +151,7 @@ type options struct {
bmi1 bool
bmi2 bool
skipOutput bool
avx2 bool
maxLen int
maxOffset int
outputMargin int // Should be at least 5.
Expand Down Expand Up @@ -614,6 +616,9 @@ func (o options) genEncodeBlockAsm(name string, tableBits, skipLog, hashBytes, m
panic(err)
}
MOVQ(U32(0), ri.Addr)
if o.avx2 {
VZEROUPPER()
}
RET()
}
Label("match_dst_size_check_" + name)
Expand Down Expand Up @@ -697,6 +702,9 @@ func (o options) genEncodeBlockAsm(name string, tableBits, skipLog, hashBytes, m
panic(err)
}
MOVQ(U32(0), ri.Addr)
if o.avx2 {
VZEROUPPER()
}
RET()
Label("match_nolit_dst_ok_" + name)
}
Expand Down Expand Up @@ -753,6 +761,9 @@ func (o options) genEncodeBlockAsm(name string, tableBits, skipLog, hashBytes, m
if err != nil {
panic(err)
}
if o.avx2 {
VZEROUPPER()
}
MOVQ(U32(0), ri.Addr)
RET()
Label("emit_remainder_ok_" + name)
Expand Down Expand Up @@ -801,6 +812,9 @@ func (o options) genEncodeBlockAsm(name string, tableBits, skipLog, hashBytes, m
JAE(ok)
})
}
if o.avx2 {
VZEROUPPER()
}
Store(length, ReturnIndex(0))
RET()
}
Expand Down Expand Up @@ -1273,6 +1287,9 @@ func (o options) genEncodeBetterBlockAsm(name string, lTableBits, sTableBits, sk
panic(err)
}
MOVQ(U32(0), ri.Addr)
if o.avx2 {
VZEROUPPER()
}
RET()
}
Label("match_dst_size_check_" + name)
Expand Down Expand Up @@ -1385,6 +1402,9 @@ func (o options) genEncodeBetterBlockAsm(name string, lTableBits, sTableBits, sk
panic(err)
}
MOVQ(U32(0), ri.Addr)
if o.avx2 {
VZEROUPPER()
}
RET()
}
}
Expand Down Expand Up @@ -1538,6 +1558,9 @@ func (o options) genEncodeBetterBlockAsm(name string, lTableBits, sTableBits, sk
panic(err)
}
MOVQ(U32(0), ri.Addr)
if o.avx2 {
VZEROUPPER()
}
RET()
Label("emit_remainder_ok_" + name)
}
Expand Down Expand Up @@ -1579,6 +1602,9 @@ func (o options) genEncodeBetterBlockAsm(name string, lTableBits, sTableBits, sk
JAE(ok)
})
Store(length, ReturnIndex(0))
if o.avx2 {
VZEROUPPER()
}
RET()
}

Expand Down Expand Up @@ -2696,6 +2722,9 @@ func (o options) genMatchLen() {
Load(Param("a").Len(), length)
l := o.matchLen("standalone", aBase, bBase, length, LabelRef("gen_match_len_end"))
Label("gen_match_len_end")
if o.avx2 {
VZEROUPPER()
}
Store(l.As64(), ReturnIndex(0))
RET()
}
Expand All @@ -2706,11 +2735,13 @@ func (o options) genMatchLen() {
// Uses 2 GP registers.
func (o options) matchLen(name string, a, b, len reg.GPVirtual, end LabelRef) reg.GPVirtual {
Comment("matchLen")
if false {
return o.matchLenAlt(name, a, b, len, end)
}
tmp, matched := GP64(), GP32()
XORL(matched, matched)
if o.avx2 {
// Not faster...
o.matchLenAVX2(name+"Avx2", a, b, len, LabelRef("avx2_continue_"+name), end, matched)
}
Label("avx2_continue_" + name)

CMPL(len.As32(), U8(8))
JB(LabelRef("matchlen_match4_" + name))
Expand Down Expand Up @@ -2740,7 +2771,6 @@ func (o options) matchLen(name string, a, b, len reg.GPVirtual, end LabelRef) re
LEAL(Mem{Base: matched, Disp: 8}, matched)
CMPL(len.As32(), U8(8))
JAE(LabelRef("matchlen_loopback_" + name))
JZ(end)

// Less than 8 bytes left.
// Test 4 bytes...
Expand All @@ -2750,23 +2780,25 @@ func (o options) matchLen(name string, a, b, len reg.GPVirtual, end LabelRef) re
MOVL(Mem{Base: a, Index: matched, Scale: 1}, tmp.As32())
CMPL(Mem{Base: b, Index: matched, Scale: 1}, tmp.As32())
JNE(LabelRef("matchlen_match2_" + name))
SUBL(U8(4), len.As32())
LEAL(Mem{Base: len.As32(), Disp: -4}, len.As32())
LEAL(Mem{Base: matched, Disp: 4}, matched)

// Test 2 bytes...
Label("matchlen_match2_" + name)
CMPL(len.As32(), U8(2))
JB(LabelRef("matchlen_match1_" + name))
CMPL(len.As32(), U8(1))
// If we don't have 1, branch appropriately
JE(LabelRef("matchlen_match1_" + name))
JB(end)
// 2 or 3
MOVW(Mem{Base: a, Index: matched, Scale: 1}, tmp.As16())
CMPW(Mem{Base: b, Index: matched, Scale: 1}, tmp.As16())
JNE(LabelRef("matchlen_match1_" + name))
SUBL(U8(2), len.As32())
LEAL(Mem{Base: matched, Disp: 2}, matched)
SUBL(U8(2), len.As32())
JZ(end)

// Test 1 byte...
Label("matchlen_match1_" + name)
CMPL(len.As32(), U8(1))
JB(end)
MOVB(Mem{Base: a, Index: matched, Scale: 1}, tmp.As8())
CMPB(Mem{Base: b, Index: matched, Scale: 1}, tmp.As8())
JNE(end)
Expand All @@ -2780,94 +2812,47 @@ func (o options) matchLen(name string, a, b, len reg.GPVirtual, end LabelRef) re
// Will jump to end when done and returns the length.
// Uses 3 GP registers.
// It is better on longer matches.
func (o options) matchLenAlt(name string, a, b, len reg.GPVirtual, end LabelRef) reg.GPVirtual {
Comment("matchLenAlt")
tmp, tmp2, matched := GP64(), GP64(), GP32()
XORL(matched, matched)

CMPL(len.As32(), U8(16))
JB(LabelRef("matchlen_short_" + name))
func (o options) matchLenAVX2(name string, a, b, len reg.GPVirtual, cont, end LabelRef, dst reg.GPVirtual) {
Comment("matchLenAVX2")

Label("matchlen_loopback_" + name)
MOVQ(Mem{Base: a}, tmp)
MOVQ(Mem{Base: a, Disp: 8}, tmp2)
XORQ(Mem{Base: b, Disp: 0}, tmp)
XORQ(Mem{Base: b, Disp: 8}, tmp2)
endTest := func(xored reg.GPVirtual, disp int, ok LabelRef) {
TESTQ(xored, xored)
JZ(ok)
// Not all match.
BSFQ(xored, xored)
SARQ(U8(3), xored)
LEAL(Mem{Base: matched, Index: xored, Scale: 1, Disp: disp}, matched)
JMP(end)
}
endTest(tmp, 0, LabelRef("matchlen_loop_tmp2_"+name))
Label("matchlen_loop_tmp2_" + name)
endTest(tmp2, 8, LabelRef("matchlen_loop_"+name))

// All 16 byte matched, update and loop.
Label("matchlen_loop_" + name)
SUBL(U8(16), len.As32())
ADDL(U8(16), matched)
ADDQ(U8(16), a)
ADDQ(U8(16), b)
CMPL(len.As32(), U8(16))
JAE(LabelRef("matchlen_loopback_" + name))

// Test 4 bytes at the time...
Label("matchlen_short_" + name)
lenoff := 0
if true {
lenoff = 4
SUBL(U8(4), len.As32())
JC(LabelRef("matchlen_single_resume_" + name))

Label("matchlen_four_loopback_" + name)
assert(func(ok LabelRef) {
CMPL(len.As32(), U32(math.MaxInt32))
JB(ok)
})

MOVL(Mem{Base: a}, tmp.As32())
XORL(Mem{Base: b}, tmp.As32())
{
JZ(LabelRef("matchlen_four_loopback_next" + name))
BSFL(tmp.As32(), tmp.As32())
SARQ(U8(3), tmp)
LEAL(Mem{Base: matched, Index: tmp, Scale: 1}, matched)
JMP(end)
}
Label("matchlen_four_loopback_next" + name)
ADDL(U8(4), matched)
ADDQ(U8(4), a)
ADDQ(U8(4), b)
SUBL(U8(4), len.As32())
JNC(LabelRef("matchlen_four_loopback_" + name))
equalMaskBits := GP64()
Label(name + "loop")
{
CMPQ(len, U8(32))
JB(cont)
Comment("load 32 bytes into YMM registers")
adata := YMM()
bdata := YMM()
equalMaskBytes := YMM()
VMOVDQU(Mem{Base: a}, adata)
VMOVDQU(Mem{Base: b}, bdata)
Comment("compare bytes in adata and bdata, like 'bytewise XNOR'",
"if the byte is the same in adata and bdata, VPCMPEQB will store 0xFF in the same position in equalMaskBytes")
VPCMPEQB(adata, bdata, equalMaskBytes)
Comment("like convert byte to bit, store equalMaskBytes into general reg")
VPMOVMSKB(equalMaskBytes, equalMaskBits.As32())
CMPL(equalMaskBits.As32(), U32(0xffffffff))
JNE(LabelRef(name + "cal_prefix"))
ADDQ(U8(32), a)
ADDQ(U8(32), b)
ADDL(U8(32), dst)
SUBQ(U8(32), len)
JZ(end)
JMP(LabelRef(name + "loop"))
}

// Test one at the time
Label("matchlen_single_resume_" + name)
if true {
// Less than 16 bytes left.
if lenoff > 0 {
ADDL(U8(lenoff), len.As32())
Label(name + "cal_prefix")
{
NOTQ(equalMaskBits)
if o.bmi1 {
TZCNTQ(equalMaskBits, equalMaskBits)
} else {
BSFQ(equalMaskBits, equalMaskBits)
}
TESTL(len.As32(), len.As32())
JZ(end)

Label("matchlen_single_loopback_" + name)
MOVB(Mem{Base: a}, tmp.As8())
CMPB(Mem{Base: b}, tmp.As8())
JNE(end)
INCL(matched)
INCQ(a)
INCQ(b)
DECL(len.As32())
JNZ(LabelRef("matchlen_single_loopback_" + name))
ADDL(equalMaskBits.As32(), dst)
}
JMP(end)
return matched
return
}

func (o options) cvtLZ4BlockAsm(lz4s bool) {
Expand Down