fpmerge 操作 字型慣例
if (PR[qp]) {
fp_check_target_register;
if (tmp_isrcode = fp_reg_disabled(f1, f2, f3, 0))
disabled_fp_register_fault(tmp_isrcode, 0);

if (fp_is_natval([f2]) || fp_is_natval(FR[f3])) {
FR[f1] = NATVAL;
} else {
if (neg_sign_form) {
tmp_res_hi = (!FR[f2].significand{63} << 31)
| (FR[f3].significand{62:32});
tmp_res_lo = (!FR[f2].significand{31} << 31)
| (FR[f3].significand{30:0});
} else if (sign_form) {
tmp_res_hi = (FR[f2].significand{63} << 31)
| (FR[f3].significand{62:32});
tmp_res_lo = (FR[f2].significand{31} << 31)
| (FR[f3].significand{30:0});
} else { // sign_exp_form
tmp_res_hi = (FR[f2].significand{63:55} << 23)
| (FR[f3].significand{54:32});
tmp_res_lo = (FR[f2].significand{31:23} << 23)
| (FR[f3].significand{22:0});
}

FR[f1].significand = fp_concatenate(tmp_res_hi, tmp_res_lo);
FR[f1].exponent = FP_INTEGER_EXP;
FR[f1].sign = FP_SIGN_POSITIVE;
}

fp_update_psr(f1);
}