// or $bitcon, REGZERO, rt. rt can't be ZR.
		mode := 64
		var as1 obj.As
		switch as {
		case AMOVW:
			as1 = AORRW
			mode = 32
		case AMOVD:
			as1 = AORR
		}
		o1 = c.opirr(p, as1)
		o1 |= bitconEncode(uint64(a.Offset), mode) | uint32(REGZERO&31)<<5 | uint32(rt&31)
		return o1
	}

	if as == AMOVW {

			}
			o1 = AOP_IRR(OP_ADDI, REGZERO, REGZERO, uint32(p.From.Offset))
		} else if p.From.Type == obj.TYPE_REG {
			o1 = LOP_RRR(OP_OR, REGZERO, uint32(p.From.Reg), uint32(p.From.Reg))
		} else {
			c.ctxt.Diag("illegal syscall: %v", p)
			o1 = 0x7fe00008 // trap always
		}

		o2 = c.oprrr(p.As)
		o3 = AOP_RRR(c.oprrr(AXOR), REGZERO, REGZERO, REGZERO) // XOR R0, R0

	case 78: /* undef */