require_rv64; require_extension(EXT_XZBT); int shamt = RS2 & 63; reg_t a = RS1, b = RS3; if (shamt >= 32) { a = RS3, b = RS1; shamt -= 32; } int rshamt = -shamt & 31; WRITE_RD(sext32(shamt ? (a << shamt) | (zext32(b) >> rshamt) : a));