if shift >= 0 && shift < 64 {
		// arm64:"LSL",-"CSEL"
		r1 = val64 << shift
	}
	if shift >= 0 && shift < 32 {
		// arm64:"LSL",-"CSEL"
		r2 = val32 << shift
	}
	if shift >= 0 && shift < 16 {
		// arm64:"LSL",-"CSEL"
		r3 = val16 << shift
	}
	if shift >= 0 && shift < 8 {
		// arm64:"LSL",-"CSEL"
		r4 = val8 << shift
	}
	return r1, r2, r3, r4

if($ARGV[0] eq "-b32") {
	$_32bit = "big-endian";
	shift;
} elsif($ARGV[0] eq "-l32") {
	$_32bit = "little-endian";
	shift;
}
if($ARGV[0] eq "-plan9") {
	$plan9 = 1;
	shift;
}
if($ARGV[0] eq "-darwin") {
	$darwin = 1;
	$libc = 1;
	shift;
}
if($ARGV[0] eq "-openbsd") {
	$openbsd = 1;
	shift;
}
if($ARGV[0] eq "-netbsd") {
	$netbsd = 1;
	shift;
}
if($ARGV[0] eq "-dragonfly") {
	$dragonfly = 1;

	case isPowerOfTwo(et.Size_):
		var shift uintptr
		if goarch.PtrSize == 8 {
			// Mask shift for better code generation.
			shift = uintptr(sys.TrailingZeros64(uint64(et.Size_))) & 63
		} else {
			shift = uintptr(sys.TrailingZeros32(uint32(et.Size_))) & 31
		}
		lenmem = uintptr(oldLen) << shift
		newlenmem = uintptr(newLen) << shift
		capmem = roundupsize(uintptr(newcap)<<shift, noscan)

	}

	// Bits 0:51 (bytes 0:8, bits 0:64, shift 0, mask 51).
	v.l0 = byteorder.LeUint64(x[0:8])
	v.l0 &= maskLow51Bits
	// Bits 51:102 (bytes 6:14, bits 48:112, shift 3, mask 51).
	v.l1 = byteorder.LeUint64(x[6:14]) >> 3
	v.l1 &= maskLow51Bits
	// Bits 102:153 (bytes 12:20, bits 96:160, shift 6, mask 51).
	v.l2 = byteorder.LeUint64(x[12:20]) >> 6
	v.l2 &= maskLow51Bits

	for p > 0 {
		if p <= k {
			// Shift p 0s down into the top of each run of 1s.
			c &= c >> (p & 63)
			break
		}
		// Shift k 0s down into the top of each run of 1s.
		c &= c >> (k & 63)
		if c == 0 {
			return 64
		}
		p -= k
		// We've just doubled the minimum length of 0-runs.
		// This allows us to shift farther in the next iteration.
		k *= 2
	}

			//    floating-point numbers if possible,
			// 2) if one of them is not constant (possible because
			//    it contains a shift that is yet untyped), convert
			//    both of them to float64 since they must have the
			//    same type to succeed (this will result in an error
			//    because shifts of floats are not permitted)
			if x.mode == constant_ && y.mode == constant_ {
				toFloat := func(x *operand) {

	var a []complex64
	_ = imag(a... /* ERROR "invalid use of ..." */ )

	// if argument is untyped, result is untyped
	const _ byte = imag(1.2 + 3i)
	const _ complex128 = imag(1.2 + 3i)

	// lhs constant shift operands are typed as complex128
	var s uint
	_ = imag(1 /* ERROR "must be integer" */ << s)
}

func imag2() {
	f1 := func() (x complex128) { return }
	f2 := func() (x, y complex128) { return }

			//    floating-point numbers if possible,
			// 2) if one of them is not constant (possible because
			//    it contains a shift that is yet untyped), convert
			//    both of them to float64 since they must have the
			//    same type to succeed (this will result in an error
			//    because shifts of floats are not permitted)
			if x.mode == constant_ && y.mode == constant_ {
				toFloat := func(x *operand) {

// uses unsafe.Pointer for speed.
func readvarintUnsafe(fd unsafe.Pointer) (uint32, unsafe.Pointer) {
	var r uint32
	var shift int
	for {
		b := *(*uint8)(fd)
		fd = add(fd, unsafe.Sizeof(b))
		if b < 128 {
			return r + uint32(b)<<shift, fd
		}
		r += uint32(b&0x7F) << (shift & 31)
		shift += 7
		if shift > 28 {
			panic("Bad varint")
		}
	}
}

// A PanicNilError happens when code calls panic(nil).
//

	// TODO(gri) having a combined add-and-shift primitive
	//           could make this code significantly faster
	switch {
	case ex < ey:
		if al {
			t := nat(nil).shl(y.mant, uint(ey-ex))
			z.mant = z.mant.add(x.mant, t)
		} else {
			z.mant = z.mant.shl(y.mant, uint(ey-ex))
			z.mant = z.mant.add(x.mant, z.mant)
		}
	default:
		// ex == ey, no shift needed
		z.mant = z.mant.add(x.mant, y.mant)