VGATHERQPD 640(R15)(Z20*2), K6, Z10 // 6252fd4693546750
	VGATHERQPD 960(R15)(Z10*2), K6, Z20 // 6282fd4e93645778
	VGATHERQPD 1280(R15)(Z0*2), K6, Z10 // 6252fd4e93944700050000
	// EVEX: corner cases for High-16 registers.
	VADDPD X31, X16, X15          // 6211fd0058ff
	VADDPD X23, X15, X16          // 62a1850858c7
	VADDPD Y31, Y16, Y15          // 6211fd2058ff
	VADDPD Y23, Y15, Y16          // 62a1852858c7

		actual := LastIndexByte([]byte(test.a), test.b[0])
		if actual != test.i {
			t.Errorf("LastIndexByte(%q,%c) = %v; want %v", test.a, test.b[0], actual, test.i)
		}
	}
}

// test a larger buffer with different sizes and alignments
func TestIndexByteBig(t *testing.T) {
	var n = 1024
	if testing.Short() {
		n = 128
	}
	b := make([]byte, n)
	for i := 0; i < n; i++ {

				n.Const = fmt.Sprintf("%#x", i)
			} else if n.Define[0] == '\'' {
				if _, err := parser.ParseExpr(n.Define); err == nil {
					n.Kind = "iconst"
					n.Const = n.Define
				}
			} else if n.Define[0] == '"' {
				if _, err := parser.ParseExpr(n.Define); err == nil {
					n.Kind = "sconst"
					n.Const = n.Define
				}
			}

			if n.IsConst() {
				continue