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// +build ignore
package main
import (
. "github.com/mmcloughlin/avo/build"
. "github.com/mmcloughlin/avo/operand"
. "github.com/mmcloughlin/avo/reg"
. "github.com/segmentio/asm/build/internal/x86"
)
func init() {
ConstraintExpr("!purego")
}
func main() {
TEXT("ContainsByte", NOSPLIT, "func(haystack []byte, needle byte) bool")
haystack := Load(Param("haystack").Base(), GP64())
length := Load(Param("haystack").Len(), GP64())
// Broadcast the needle byte to each 8 bytes in a GP64.
needle := GP64()
XORQ(needle, needle)
Load(Param("needle"), needle.As8())
tmp := GP64()
for i := 3; i <= 5; i++ {
MOVQ(needle, tmp)
SHLQ(U8(1<<i), tmp)
ORQ(tmp, needle)
}
// Prepare masks: one with LSB set in each byte, another
// with MSB set in each byte, and another zeroed YMM register.
lsb := GP64()
msb := GP64()
MOVQ(U64(0x0101010101010101), lsb)
MOVQ(U64(0x8080808080808080), msb)
ret, _ := ReturnIndex(0).Resolve()
MOVB(U8(0), ret.Addr)
JMP(LabelRef("start"))
needleVec := YMM()
zero := YMM()
Label("found")
MOVB(U8(1), ret.Addr)
JMP(LabelRef("done"))
Label("avx2_found")
MOVB(U8(1), ret.Addr)
JMP(LabelRef("avx2_done"))
VariableLengthBytes{
Unroll: 256,
SetupXMM: func() {
PXOR(zero.AsX(), zero.AsX())
PINSRQ(Imm(0), needle, needleVec.AsX())
PINSRQ(Imm(1), needle, needleVec.AsX())
},
SetupYMM: func() {
VZEROUPPER()
VPBROADCASTQ(needleVec.AsX(), needleVec)
},
Process: func(inputs []Register, memory ...Memory) {
haystack := inputs[0]
regs := make([]Op, len(memory))
for i, m := range memory {
if m.Size == 32 {
regs[i] = m.Resolve(haystack)
} else {
regs[i] = m.Load(haystack)
}
}
switch memory[0].Size {
case 1:
for i := range memory {
CMPB(regs[i], needle.As8())
JE(LabelRef("found"))
}
case 2:
results := make([]Op, len(memory))
for i := range memory {
XORW(needle.As16(), regs[i])
results[i] = GP16()
MOVW(regs[i], results[i])
}
for i := range memory {
SUBW(lsb.As16(), results[i])
NOTW(regs[i])
ANDW(regs[i], results[i])
}
result := reduce(results, binary(ORW))
ANDW(msb.As16(), result)
JNZ(LabelRef("found"))
case 4:
results := make([]Op, len(memory))
for i := range memory {
XORL(needle.As32(), regs[i])
results[i] = GP32()
MOVL(regs[i], results[i])
}
for i := range memory {
SUBL(lsb.As32(), results[i])
NOTL(regs[i])
ANDL(regs[i], results[i])
}
result := reduce(results, binary(ORL))
ANDL(msb.As32(), result)
JNZ(LabelRef("found"))
case 8:
results := make([]Op, len(memory))
for i := range memory {
XORQ(needle, regs[i])
results[i] = GP64()
MOVQ(regs[i], results[i])
}
for i := range memory {
SUBQ(lsb, results[i])
NOTQ(regs[i])
ANDQ(regs[i], results[i])
}
result := reduce(results, binary(ORQ))
ANDQ(msb, result)
JNZ(LabelRef("found"))
case 16:
for i := range memory {
PCMPEQB(needleVec.AsX(), regs[i])
}
result := reduce(regs, binary(POR))
PTEST(result, zero.AsX())
JCC(LabelRef("found"))
case 32:
results := make([]Op, len(memory))
for i := range memory {
results[i] = YMM()
VPCMPEQB(regs[i], needleVec, results[i])
}
result := reduce(results, vex(VPOR))
VPTEST(result, zero)
JCC(LabelRef("avx2_found"))
}
},
}.Generate([]Register{haystack}, length)
}
func reduce(ops []Op, op func(Op, Op) Op) Op {
for len(ops) > 1 {
ops = append(ops[2:], op(ops[0], ops[1]))
}
return ops[0]
}
func binary(ins func(Op, Op)) func(Op, Op) Op {
return func(src Op, dst Op) Op {
ins(src, dst)
return dst
}
}
func vex(ins func(Op, Op, Op)) func(Op, Op) Op {
return func(src Op, dst Op) Op {
ins(src, dst, dst)
return dst
}
}
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