fmix Operation Font Conventions
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 (mix_l_form) {
tmp_res_hi = FR[f2].significand{63:32};
tmp_res_lo = FR[f3].significand{63:32};
} else if (mix_r_form) {
tmp_res_hi = FR[f2].significand{31:0};
tmp_res_lo = FR[f3].significand{31:0};
} else { // mix_lr_form
tmp_res_hi = FR[f2].significand{63:32};
tmp_res_lo = FR[f3].significand{31:0};
}
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);
}