popcount_amd64.s

// func popcnt64ASM(x uint64) uint64
TEXT ·popcnt64ASM(SB),4,$0-8
XORQ AX, AX
MOVQ x+0(FP), SI
BYTE $0xf3; BYTE $0x48; BYTE $0x0f; BYTE $0xb8; BYTE $0xc6;//POPCNT (SI), AX
MOVQ AX, ret+8(FP)
RET

// func havePOPCNT() bool
TEXT ·havePOPCNT(SB),4,$0
XORQ AX, AX
INCL AX
CPUID
SHRQ $23, CX
ANDQ $1, CX
MOVB CX, ret+0(FP)
RET