check_spec
int check_spec(int spec, const char *valid, const char *what);
i = check_spec(spec[2], " WL", "length");
i = check_spec(spec[1], " WL", "length");
opc |= check_spec(spec[1], "01", "field") << 9;
opc |= check_spec(spec[2], "01", "field") << 9;
opc |= check_spec(spec[0], "LX", "array type") << 5;
opc |= check_spec(spec[0], "01", "algorithm") << 7;
rs = check_spec(spec[0], "LXB", "source array type");
rd = check_spec(spec[1], "LX", "destination array type");
opc |= check_spec(spec[2], "01", "field") << 9;