MOVL (AX)(X0*1), AX             // ERROR "invalid instruction"
	MOVL (AX)(Y0*1), AX             // ERROR "invalid instruction"
	// VSIB/VM is invalid without vector index.
	// TODO(quasilyte): improve error message (#21860).
	// "invalid VSIB address (missing vector index)"
	VPGATHERQQ Y2, (BP), Y1         // ERROR "invalid instruction"
	// AVX2GATHER mask/index/dest #UD cases.

	// difference that for some j, a[j]>b[j] and a[j+1]<b[j+1]. If the implementation
	// compares large chunks with wrong endianness, it gets wrong result.
	// no vector register is larger than 512 bytes for now
	const maxLength = 512
	a := make([]byte, maxLength)
	b := make([]byte, maxLength)
	// randomish but deterministic data. No 0 or 255.
	for i := 0; i < maxLength; i++ {