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d9a50a6531
On amd64, Ctz must include special handling of zeros.
But the prove pass has enough information to detect whether the input
is non-zero, allowing a more efficient lowering.
Introduce new CtzNonZero ops to capture and use this information.
Benchmark code:
func BenchmarkVisitBits(b *testing.B) {
b.Run("8", func(b *testing.B) {
for i := 0; i < b.N; i++ {
x := uint8(0xff)
for x != 0 {
sink = bits.TrailingZeros8(x)
x &= x - 1
}
}
})
// and similarly so for 16, 32, 64
}
name old time/op new time/op delta
VisitBits/8-8 7.27ns ± 4% 5.58ns ± 4% -23.35% (p=0.000 n=28+26)
VisitBits/16-8 14.7ns ± 7% 10.5ns ± 4% -28.43% (p=0.000 n=30+28)
VisitBits/32-8 27.6ns ± 8% 19.3ns ± 3% -30.14% (p=0.000 n=30+26)
VisitBits/64-8 44.0ns ±11% 38.0ns ± 5% -13.48% (p=0.000 n=30+30)
Fixes #25077
Change-Id: Ie6e5bd86baf39ee8a4ca7cadcf56d934e047f957
Reviewed-on: https://go-review.googlesource.com/109358
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
270 lines
5.0 KiB
Go
270 lines
5.0 KiB
Go
// asmcheck
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// Copyright 2018 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package codegen
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import "math/bits"
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// ----------------------- //
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// bits.LeadingZeros //
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// ----------------------- //
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func LeadingZeros(n uint) int {
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// amd64:"BSRQ"
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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return bits.LeadingZeros(n)
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}
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func LeadingZeros64(n uint64) int {
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// amd64:"BSRQ"
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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return bits.LeadingZeros64(n)
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}
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func LeadingZeros32(n uint32) int {
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// amd64:"BSRQ","LEAQ",-"CMOVQEQ"
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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return bits.LeadingZeros32(n)
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}
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func LeadingZeros16(n uint16) int {
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// amd64:"BSRL","LEAL",-"CMOVQEQ"
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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return bits.LeadingZeros16(n)
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}
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func LeadingZeros8(n uint8) int {
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// amd64:"BSRL","LEAL",-"CMOVQEQ"
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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return bits.LeadingZeros8(n)
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}
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// --------------- //
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// bits.Len* //
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// --------------- //
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func Len(n uint) int {
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// amd64:"BSRQ"
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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return bits.Len(n)
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}
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func Len64(n uint64) int {
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// amd64:"BSRQ"
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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return bits.Len64(n)
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}
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func Len32(n uint32) int {
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// amd64:"BSRQ","LEAQ",-"CMOVQEQ"
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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return bits.Len32(n)
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}
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func Len16(n uint16) int {
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// amd64:"BSRL","LEAL",-"CMOVQEQ"
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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return bits.Len16(n)
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}
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func Len8(n uint8) int {
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// amd64:"BSRL","LEAL",-"CMOVQEQ"
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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return bits.Len8(n)
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}
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// -------------------- //
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// bits.OnesCount //
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// -------------------- //
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func OnesCount(n uint) int {
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// amd64:"POPCNTQ",".*support_popcnt"
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// arm64:"VCNT","VUADDLV"
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return bits.OnesCount(n)
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}
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func OnesCount64(n uint64) int {
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// amd64:"POPCNTQ",".*support_popcnt"
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// arm64:"VCNT","VUADDLV"
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return bits.OnesCount64(n)
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}
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func OnesCount32(n uint32) int {
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// amd64:"POPCNTL",".*support_popcnt"
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// arm64:"VCNT","VUADDLV"
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return bits.OnesCount32(n)
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}
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func OnesCount16(n uint16) int {
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// amd64:"POPCNTL",".*support_popcnt"
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// arm64:"VCNT","VUADDLV"
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return bits.OnesCount16(n)
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}
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// ----------------------- //
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// bits.ReverseBytes //
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// ----------------------- //
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func ReverseBytes(n uint) uint {
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// amd64:"BSWAPQ"
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// s390x:"MOVDBR"
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// arm64:"REV"
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return bits.ReverseBytes(n)
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}
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func ReverseBytes64(n uint64) uint64 {
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// amd64:"BSWAPQ"
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// s390x:"MOVDBR"
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// arm64:"REV"
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return bits.ReverseBytes64(n)
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}
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func ReverseBytes32(n uint32) uint32 {
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// amd64:"BSWAPL"
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// s390x:"MOVWBR"
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// arm64:"REVW"
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return bits.ReverseBytes32(n)
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}
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func ReverseBytes16(n uint16) uint16 {
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// amd64:"ROLW"
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return bits.ReverseBytes16(n)
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}
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// --------------------- //
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// bits.RotateLeft //
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// --------------------- //
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func RotateLeft64(n uint64) uint64 {
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// amd64:"ROLQ"
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// arm64:"ROR"
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// ppc64:"ROTL"
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return bits.RotateLeft64(n, 37)
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}
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func RotateLeft32(n uint32) uint32 {
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// amd64:"ROLL" 386:"ROLL"
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// arm64:"RORW"
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// ppc64:"ROTLW"
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return bits.RotateLeft32(n, 9)
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}
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func RotateLeft16(n uint16) uint16 {
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// amd64:"ROLW" 386:"ROLW"
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return bits.RotateLeft16(n, 5)
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}
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func RotateLeft8(n uint8) uint8 {
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// amd64:"ROLB" 386:"ROLB"
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return bits.RotateLeft8(n, 5)
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}
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// ------------------------ //
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// bits.TrailingZeros //
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// ------------------------ //
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func TrailingZeros(n uint) int {
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// amd64:"BSFQ","MOVL\t\\$64","CMOVQEQ"
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// s390x:"FLOGR"
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return bits.TrailingZeros(n)
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}
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func TrailingZeros64(n uint64) int {
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// amd64:"BSFQ","MOVL\t\\$64","CMOVQEQ"
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// s390x:"FLOGR"
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return bits.TrailingZeros64(n)
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}
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func TrailingZeros32(n uint32) int {
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// amd64:"BTSQ\\t\\$32","BSFQ"
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// s390x:"FLOGR","MOVWZ"
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return bits.TrailingZeros32(n)
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}
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func TrailingZeros16(n uint16) int {
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// amd64:"BSFL","BTSL\\t\\$16"
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// s390x:"FLOGR","OR\t\\$65536"
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return bits.TrailingZeros16(n)
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}
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func TrailingZeros8(n uint8) int {
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// amd64:"BSFL","BTSL\\t\\$8"
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// s390x:"FLOGR","OR\t\\$256"
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return bits.TrailingZeros8(n)
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}
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// IterateBitsNN checks special handling of TrailingZerosNN when the input is known to be non-zero.
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func IterateBits(n uint) int {
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i := 0
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for n != 0 {
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// amd64:"BSFQ",-"CMOVEQ"
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i += bits.TrailingZeros(n)
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n &= n - 1
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}
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return i
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}
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func IterateBits64(n uint64) int {
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i := 0
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for n != 0 {
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// amd64:"BSFQ",-"CMOVEQ"
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i += bits.TrailingZeros64(n)
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n &= n - 1
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}
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return i
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}
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func IterateBits32(n uint32) int {
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i := 0
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for n != 0 {
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// amd64:"BSFL",-"BTSQ"
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i += bits.TrailingZeros32(n)
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n &= n - 1
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}
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return i
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}
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func IterateBits16(n uint16) int {
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i := 0
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for n != 0 {
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// amd64:"BSFL",-"BTSL"
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i += bits.TrailingZeros16(n)
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n &= n - 1
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}
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return i
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}
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func IterateBits8(n uint8) int {
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i := 0
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for n != 0 {
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// amd64:"BSFL",-"BTSL"
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i += bits.TrailingZeros8(n)
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n &= n - 1
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}
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return i
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}
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