// SPDX-License-Identifier: GPL-2.0-only
/* IEEE754 floating point arithmetic
 * double precision: common utilities
 */
/*
 * MIPS floating point support
 * Copyright (C) 1994-2000 Algorithmics Ltd.
 */

#include "ieee754dp.h"

int ieee754dp_tint(union ieee754dp x)
{
        u64 residue;
        int round;
        int sticky;
        int odd;

        COMPXDP;

        ieee754_clearcx();

        EXPLODEXDP;
        FLUSHXDP;

        switch (xc) {
        case IEEE754_CLASS_SNAN:
        case IEEE754_CLASS_QNAN:
                ieee754_setcx(IEEE754_INVALID_OPERATION);
                return ieee754si_indef();

        case IEEE754_CLASS_INF:
                ieee754_setcx(IEEE754_INVALID_OPERATION);
                return ieee754si_overflow(xs);

        case IEEE754_CLASS_ZERO:
                return 0;

        case IEEE754_CLASS_DNORM:
        case IEEE754_CLASS_NORM:
                break;
        }
        if (xe > 31) {
                /* Set invalid. We will only use overflow for floating
                   point overflow */
                ieee754_setcx(IEEE754_INVALID_OPERATION);
                return ieee754si_overflow(xs);
        }
        /* oh gawd */
        if (xe > DP_FBITS) {
                xm <<= xe - DP_FBITS;
        } else if (xe < DP_FBITS) {
                if (xe < -1) {
                        residue = xm;
                        round = 0;
                        sticky = residue != 0;
                        xm = 0;
                } else {
                        residue = xm << (64 - DP_FBITS + xe);
                        round = (residue >> 63) != 0;
                        sticky = (residue << 1) != 0;
                        xm >>= DP_FBITS - xe;
                }
                /* Note: At this point upper 32 bits of xm are guaranteed
                   to be zero */
                odd = (xm & 0x1) != 0x0;
                switch (ieee754_csr.rm) {
                case FPU_CSR_RN:
                        if (round && (sticky || odd))
                                xm++;
                        break;
                case FPU_CSR_RZ:
                        break;
                case FPU_CSR_RU:        /* toward +Infinity */
                        if ((round || sticky) && !xs)
                                xm++;
                        break;
                case FPU_CSR_RD:        /* toward -Infinity */
                        if ((round || sticky) && xs)
                                xm++;
                        break;
                }
                /* look for valid corner case 0x80000000 */
                if ((xm >> 31) != 0 && (xs == 0 || xm != 0x80000000)) {
                        /* This can happen after rounding */
                        ieee754_setcx(IEEE754_INVALID_OPERATION);
                        return ieee754si_overflow(xs);
                }
                if (round || sticky)
                        ieee754_setcx(IEEE754_INEXACT);
        }
        if (xs)
                return -xm;
        else
                return xm;
}