// amd64/v1,amd64/v2:"BSRQ","LEAQ",-"CMOVQEQ"
	// amd64/v3: "LZCNTL",- "BSRL"
	// s390x:"FLOGR"
	// arm:"CLZ" arm64:"CLZW"
	// mips:"CLZ"
	// wasm:"I64Clz"
	// ppc64x:"CNTLZW"
	return bits.LeadingZeros32(n)
}

func LeadingZeros16(n uint16) int {
	// amd64/v1,amd64/v2:"BSRL","LEAL",-"CMOVQEQ"
	// amd64/v3: "LZCNTL",- "BSRL"
	// s390x:"FLOGR"
	// arm:"CLZ" arm64:"CLZ"
	// mips:"CLZ"

	"LODSB",
	"LODSL",
	"LODSQ",
	"LODSW",
	"LONG",
	"LOOP",
	"LOOPEQ",
	"LOOPNE",
	"LSLL",
	"LSLQ",
	"LSLW",
	"LSSL",
	"LSSQ",
	"LSSW",
	"LTR",
	"LZCNTL",
	"LZCNTQ",
	"LZCNTW",
	"MASKMOVOU",
	"MASKMOVQ",
	"MAXPD",
	"MAXPS",
	"MAXSD",
	"MAXSS",
	"MFENCE",
	"MINPD",
	"MINPS",
	"MINSD",
	"MINSS",
	"MONITOR",
	"MOVAPD",
	"MOVAPS",

		"pmovsxbw", "pmovsxbd", "pmovsxbq", "pmovsxwd", "pmovsxwq", "pmovsxdq",
		"pblendvb",
	},
	"fma":   {"vfmadd231sd"},
	"movbe": {"movbeqq", "movbeq", "movbell", "movbel", "movbe"},
	"lzcnt": {"lzcntq", "lzcntl", "lzcnt"},
}

// Test to use POPCNT instruction, if available
func TestPopCnt(t *testing.T) {
	for _, tt := range []struct {
		x    uint64
		want int
	}{
		{0b00001111, 4},

	LZCNTL (BX), DX                         // f30fbd13
	LZCNTL (R11), DX                        // f3410fbd13
	LZCNTL DX, DX                           // f30fbdd2
	LZCNTL R11, DX                          // f3410fbdd3
	LZCNTL (BX), R11                        // f3440fbd1b
	LZCNTL (R11), R11                       // f3450fbd1b
	LZCNTL DX, R11                          // f3440fbdda

// Use 64-bit version to allow const-fold remove unnecessary arithmetic.
(BitLen32 <t> x) && buildcfg.GOAMD64 >= 3 => (NEGQ (ADDQconst <t> [-32] (LZCNTL x)))
(BitLen16 <t> x) && buildcfg.GOAMD64 >= 3 => (NEGQ (ADDQconst <t> [-32] (LZCNTL (MOVWQZX <x.Type> x))))
(BitLen8 <t> x) && buildcfg.GOAMD64 >= 3 => (NEGQ (ADDQconst <t> [-32] (LZCNTL (MOVBQZX <x.Type> x))))

		// count the number of trailing zero bits, prefer TZCNTQ over BSFQ, as TZCNTQ(0)==64
		// and BSFQ(0) is undefined. Same for TZCNTL(0)==32
		{name: "TZCNTQ", argLength: 1, reg: gp11, asm: "TZCNTQ", clobberFlags: true},
		{name: "TZCNTL", argLength: 1, reg: gp11, asm: "TZCNTL", clobberFlags: true},

		// CPUID feature: LZCNT.
		// count the number of leading zero bits.

// systems by fcntl_linux_32bit.go to be SYS_FCNTL64.
var fcntl64Syscall uintptr = SYS_FCNTL

func fcntl(fd int, cmd, arg int) (int, error) {
	valptr, _, errno := Syscall(fcntl64Syscall, uintptr(fd), uintptr(cmd), uintptr(arg))
	var err error
	if errno != 0 {
		err = errno
	}
	return int(valptr), err
}

// FcntlInt performs a fcntl syscall on fd with the provided command and argument.
func FcntlInt(fd uintptr, cmd, arg int) (int, error) {

	ALLDT
	ALMSW
	ALOCK
	ALODSB
	ALODSL
	ALODSQ
	ALODSW
	ALONG
	ALOOP
	ALOOPEQ
	ALOOPNE
	ALSLL
	ALSLQ
	ALSLW
	ALSSL
	ALSSQ
	ALSSW
	ALTR
	ALZCNTL
	ALZCNTQ
	ALZCNTW
	AMASKMOVOU
	AMASKMOVQ
	AMAXPD
	AMAXPS
	AMAXSD
	AMAXSS
	AMFENCE
	AMINPD
	AMINPS
	AMINSD
	AMINSS
	AMONITOR
	AMOVAPD
	AMOVAPS
	AMOVB
	AMOVBEL

package unix

import (
	"syscall"
	_ "unsafe" // for go:linkname
)

// Implemented in the runtime package.
//
//go:linkname fcntl runtime.fcntl
func fcntl(fd int32, cmd int32, arg int32) (int32, int32)

func Fcntl(fd int, cmd int, arg int) (int, error) {
	val, errno := fcntl(int32(fd), int32(cmd), int32(arg))
	if val == -1 {
		return int(val), syscall.Errno(errno)
	}
	return int(val), nil

package unix

import "unsafe"

// FcntlInt performs a fcntl syscall on fd with the provided command and argument.
func FcntlInt(fd uintptr, cmd, arg int) (int, error) {
	return fcntl(int(fd), cmd, arg)
}

// FcntlFlock performs a fcntl syscall for the F_GETLK, F_SETLK or F_SETLKW command.
func FcntlFlock(fd uintptr, cmd int, lk *Flock_t) error {
	_, err := fcntl(int(fd), cmd, int(uintptr(unsafe.Pointer(lk))))
	return err
}