// A backup implementation to use by assembly.
func countGeneric(b []byte, c byte) int {
	n := 0
	for _, x := range b {
		if x == c {
			n++
		}
	}
	return n
}
func countGenericString(s string, c byte) int {
	n := 0
	for i := 0; i < len(s); i++ {
		if s[i] == c {
			n++
		}
	}
	return n

	MOVB	c+24(FP), AL
	LEAQ	ret+32(FP), R8
	JMP	countbody<>(SB)

TEXT ·CountString(SB),NOSPLIT,$0-32
#ifndef hasPOPCNT
	CMPB	internal∕cpu·X86+const_offsetX86HasPOPCNT(SB), $1
	JEQ	2(PC)
	JMP	·countGenericString(SB)
#endif
	MOVQ	s_base+0(FP), SI
	MOVQ	s_len+8(FP), BX
	MOVB	c+16(FP), AL
	LEAQ	ret+24(FP), R8
	JMP	countbody<>(SB)

// input:
//   SI: data
//   BX: data len
//   AL: byte sought