for _, growLen := range []int{0, 100, 1000, 10000, 100000} {
		for _, startLen := range []int{0, 100, 1000, 10000, 100000} {
			xBytes := Repeat(x, startLen)

			buf := NewBuffer(xBytes)
			// If we read, this affects buf.off, which is good to test.
			readBytes, _ := buf.Read(tmp)
			yBytes := Repeat(y, growLen)
			allocs := testing.AllocsPerRun(100, func() {
				buf.Grow(growLen)
				buf.Write(yBytes)
			})

	}
	buf := make([]byte, ss.Size())
	for off := int64(0); off < ss.Size(); off++ {
		for size := 1; size <= int(ss.Size()-off); size++ {
			readBuf := buf[:size]
			n, err := ss.ReadAt(readBuf, off)
			if off < ss.Size()-keep {
				if err != errDiscardedBytes {
					t.Errorf("off %d, size %d = %v, %v (%q); want errDiscardedBytes", off, size, n, err, readBuf[:n])
				}
				continue
			}

// TrimLeftFunc treats s as UTF-8-encoded bytes and returns a subslice of s by slicing off
// all leading UTF-8-encoded code points c that satisfy f(c).
func TrimLeftFunc(s []byte, f func(r rune) bool) []byte {
	i := indexFunc(s, f, false)
	if i == -1 {
		return nil
	}
	return s[i:]
}

// TrimRightFunc returns a subslice of s by slicing off all trailing
// UTF-8-encoded code points c that satisfy f(c).

			}
			count = int16((x & 31) << 7)
		}
	default:
		p.errorf("unexpected %s in register shift", tok.String())
	}
	if p.arch.Family == sys.ARM64 {
		off, err := arch.ARM64RegisterShift(r1, op, count)
		if err != nil {
			p.errorf(err.Error())
		}
		return off
	} else {
		return int64((r1 & 15) | op<<5 | count)
	}
}

// registerExtension parses a register with extension or arrangement.