RxrEvex = 1 << 4 // AVX512 extension to REX.R/VEX.R
	Rxw     = 1 << 3 // =1, 64-bit operand size
	Rxr     = 1 << 2 // extend modrm reg
	Rxx     = 1 << 1 // extend sib index
	Rxb     = 1 << 0 // extend modrm r/m, sib base, or opcode reg
)

const (
	// Encoding for VEX prefix in tables.
	// The P, L, and W fields are chosen to match
	// their eventual locations in the VEX prefix bytes.