Py   = 0x80 // defaults to 64-bit mode
	Py1  = 0x81 // symbolic; exact value doesn't matter
	Py3  = 0x83 // symbolic; exact value doesn't matter
	Pavx = 0x84 // symbolic; exact value doesn't matter

	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
)