Function emit_rex

dpdk/lib/bpf/bpf_jit_x86.c:157–191

* emit REX byte */

 * emit REX byte
 */
static void
emit_rex(struct bpf_jit_state *st, uint32_t op, uint32_t reg, uint32_t rm)
{
	uint8_t rex;

	/* mark operand registers as used*/
	USED(st->reguse, reg);
	USED(st->reguse, rm);

	rex = 0;
	if (BPF_CLASS(op) == EBPF_ALU64 ||
			op == (BPF_ST | BPF_MEM | EBPF_DW) ||
			op == (BPF_STX | BPF_MEM | EBPF_DW) ||
			op == (BPF_STX | EBPF_XADD | EBPF_DW) ||
			op == (BPF_LD | BPF_IMM | EBPF_DW) ||
			(BPF_CLASS(op) == BPF_LDX &&
			BPF_MODE(op) == BPF_MEM &&
			BPF_SIZE(op) != BPF_W))
		rex |= REX_W;

	if (IS_EXT_REG(reg))
		rex |= REX_R;

	if (IS_EXT_REG(rm))
		rex |= REX_B;

	/* store using SIL, DIL */
	if (op == (BPF_STX | BPF_MEM | BPF_B) && (reg == RDI || reg == RSI))
		rex |= REX_PREFIX;

	if (rex != 0) {
		rex |= REX_PREFIX;
		emit_bytes(st, &rex, sizeof(rex));
	}
}

/*
 * emit MODRegRM byte