PrefixSS Prefix = 0x36 // SS segment override
	PrefixDS Prefix = 0x3E // DS segment override
	PrefixFS Prefix = 0x64 // FS segment override
	PrefixGS Prefix = 0x65 // GS segment override

	// Branch prediction.
	PrefixPN Prefix = 0x12E // predict not taken (conditional branch only)
	PrefixPT Prefix = 0x13E // predict taken (conditional branch only)

	// Size attributes.

					if vex == prefix {
						ok = true
					}
				} else if vex != 0 && (prefix == 0x0F || prefix == 0x0F38 || prefix == 0x0F3A ||
					prefix == 0x66 || prefix == 0xF2 || prefix == 0xF3) {
					var vexM, vexP Prefix
					if vex == 0xC5 {
						vexM = 1 // 2 byte vex always implies 0F
						vexP = inst.Prefix[vexIndex+1]
					} else {
						vexM = inst.Prefix[vexIndex+1]

			files: map[string]uint64{
				"prefix/":            0,
				"prefix/README":      0,
				"prefix/v2":          3,
				"prefix/another.txt": 8,
				"prefix/foo.txt":     13,
			},
		},
		{
			repo:   hgrepo1,
			rev:    "v2",
			subdir: "",
			files: map[string]uint64{
				"prefix/.hg_archival.txt": ^uint64(0),
				"prefix/README":           0,
				"prefix/v2":               3,

	"pclmulhqhqdq",
}

func countPrefix(inst *Inst, target Prefix) int {
	n := 0
	for _, p := range inst.Prefix {
		if p&0xFF == target&0xFF {
			n++
		}
	}
	return n
}

func markLastImplicit(inst *Inst, prefix Prefix) bool {
	for i := len(inst.Prefix) - 1; i >= 0; i-- {
		p := inst.Prefix[i]
		if p&0xFF == prefix {
			inst.Prefix[i] |= PrefixImplicit
			return true
		}
	}
	return false

func applyRewrite(path, rewrite string) (string, bool) {
	prefix, replace := rewrite, ""
	if j := strings.LastIndex(rewrite, "=>"); j >= 0 {
		prefix, replace = rewrite[:j], rewrite[j+len("=>"):]
	}

	if prefix == "" || !hasPathPrefix(path, prefix) {
		return path, false
	}
	if len(path) == len(prefix) {
		return replace, true
	}
	if replace == "" {
		return path[len(prefix)+1:], true
	}
	return replace + path[len(prefix):], true

	return fp.ToString("")
}

func (fp *FuncProps) ToString(prefix string) string {
	var sb strings.Builder
	if fp.Flags != 0 {
		fmt.Fprintf(&sb, "%sFlags %s\n", prefix, fp.Flags)
	}
	flagSliceToSB[ParamPropBits](&sb, fp.ParamFlags,
		prefix, "ParamFlags")
	flagSliceToSB[ResultPropBits](&sb, fp.ResultFlags,
		prefix, "ResultFlags")
	return sb.String()
}

func flagSliceToSB[T interface {
	~uint32

// elements in prefix.
func hasPathPrefix(s, prefix string) bool {
	switch {
	default:
		return false
	case len(s) == len(prefix):
		return s == prefix
	case len(s) > len(prefix):
		if prefix != "" && prefix[len(prefix)-1] == '/' {
			return strings.HasPrefix(s, prefix)
		}
		return s[len(prefix)] == '/' && s[:len(prefix)] == prefix
	}
}

func (p *Parser) register(name string, prefix rune) (r1, r2 int16, scale int8, ok bool) {
	// R1 or R(1) R1:R2 R1,R2 R1+R2, or R1*scale.
	r1, ok = p.registerReference(name)
	if !ok {
		return
	}
	if prefix != 0 && prefix != '*' { // *AX is OK.
		p.errorf("prefix %c not allowed for register: %c%s", prefix, prefix, name)
	}
	c := p.peek()
	if c == ':' || c == ',' || c == '+' {

	return pkg.Lookup(str)
}

// LookupNum looks up the symbol starting with prefix and ending with
// the decimal n. If prefix is too long, LookupNum panics.
func (pkg *Pkg) LookupNum(prefix string, n int) *Sym {
	var buf [20]byte // plenty long enough for all current users
	copy(buf[:], prefix)
	b := strconv.AppendInt(buf[:len(prefix)], int64(n), 10)
	return pkg.LookupBytes(b)
}

// HasPathPrefix reports whether the slash-separated path s
// begins with the elements in prefix.
func HasPathPrefix(s, prefix string) bool {
	if len(s) == len(prefix) {
		return s == prefix
	}
	if prefix == "" {
		return true
	}
	if len(s) > len(prefix) {
		if prefix[len(prefix)-1] == '/' || s[len(prefix)] == '/' {
			return s[:len(prefix)] == prefix
		}
	}
	return false
}