// SPDX-License-Identifier: GPL-2.0
/*
 * Routines to emulate some Altivec/VMX instructions, specifically
 * those that can trap when given denormalized operands in Java mode.
 */
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <asm/ptrace.h>
#include <asm/processor.h>
#include <asm/switch_to.h>
#include <linux/uaccess.h>

/* Functions in vector.S */
extern void vaddfp(vector128 *dst, vector128 *a, vector128 *b);
extern void vsubfp(vector128 *dst, vector128 *a, vector128 *b);
extern void vmaddfp(vector128 *dst, vector128 *a, vector128 *b, vector128 *c);
extern void vnmsubfp(vector128 *dst, vector128 *a, vector128 *b, vector128 *c);
extern void vrefp(vector128 *dst, vector128 *src);
extern void vrsqrtefp(vector128 *dst, vector128 *src);
extern void vexptep(vector128 *dst, vector128 *src);

static unsigned int exp2s[8] = {
        0x800000,
        0x8b95c2,
        0x9837f0,
        0xa5fed7,
        0xb504f3,
        0xc5672a,
        0xd744fd,
        0xeac0c7
};

/*
 * Computes an estimate of 2^x.  The `s' argument is the 32-bit
 * single-precision floating-point representation of x.
 */
static unsigned int eexp2(unsigned int s)
{
        int exp, pwr;
        unsigned int mant, frac;

        /* extract exponent field from input */
        exp = ((s >> 23) & 0xff) - 127;
        if (exp > 7) {
                /* check for NaN input */
                if (exp == 128 && (s & 0x7fffff) != 0)
                        return s | 0x400000;    /* return QNaN */
                /* 2^-big = 0, 2^+big = +Inf */
                return (s & 0x80000000)? 0: 0x7f800000; /* 0 or +Inf */
        }
        if (exp < -23)
                return 0x3f800000;      /* 1.0 */

        /* convert to fixed point integer in 9.23 representation */
        pwr = (s & 0x7fffff) | 0x800000;
        if (exp > 0)
                pwr <<= exp;
        else
                pwr >>= -exp;
        if (s & 0x80000000)
                pwr = -pwr;

        /* extract integer part, which becomes exponent part of result */
        exp = (pwr >> 23) + 126;
        if (exp >= 254)
                return 0x7f800000;
        if (exp < -23)
                return 0;

        /* table lookup on top 3 bits of fraction to get mantissa */
        mant = exp2s[(pwr >> 20) & 7];

        /* linear interpolation using remaining 20 bits of fraction */
        asm("mulhwu %0,%1,%2" : "=r" (frac)
            : "r" (pwr << 12), "r" (0x172b83ff));
        asm("mulhwu %0,%1,%2" : "=r" (frac) : "r" (frac), "r" (mant));
        mant += frac;

        if (exp >= 0)
                return mant + (exp << 23);

        /* denormalized result */
        exp = -exp;
        mant += 1 << (exp - 1);
        return mant >> exp;
}

/*
 * Computes an estimate of log_2(x).  The `s' argument is the 32-bit
 * single-precision floating-point representation of x.
 */
static unsigned int elog2(unsigned int s)
{
        int exp, mant, lz, frac;

        exp = s & 0x7f800000;
        mant = s & 0x7fffff;
        if (exp == 0x7f800000) {        /* Inf or NaN */
                if (mant != 0)
                        s |= 0x400000;  /* turn NaN into QNaN */
                return s;
        }
        if ((exp | mant) == 0)          /* +0 or -0 */
                return 0xff800000;      /* return -Inf */

        if (exp == 0) {
                /* denormalized */
                asm("cntlzw %0,%1" : "=r" (lz) : "r" (mant));
                mant <<= lz - 8;
                exp = (-118 - lz) << 23;
        } else {
                mant |= 0x800000;
                exp -= 127 << 23;
        }

        if (mant >= 0xb504f3) {                         /* 2^0.5 * 2^23 */
                exp |= 0x400000;                        /* 0.5 * 2^23 */
                asm("mulhwu %0,%1,%2" : "=r" (mant)
                    : "r" (mant), "r" (0xb504f334));    /* 2^-0.5 * 2^32 */
        }
        if (mant >= 0x9837f0) {                         /* 2^0.25 * 2^23 */
                exp |= 0x200000;                        /* 0.25 * 2^23 */
                asm("mulhwu %0,%1,%2" : "=r" (mant)
                    : "r" (mant), "r" (0xd744fccb));    /* 2^-0.25 * 2^32 */
        }
        if (mant >= 0x8b95c2) {                         /* 2^0.125 * 2^23 */
                exp |= 0x100000;                        /* 0.125 * 2^23 */
                asm("mulhwu %0,%1,%2" : "=r" (mant)
                    : "r" (mant), "r" (0xeac0c6e8));    /* 2^-0.125 * 2^32 */
        }
        if (mant > 0x800000) {                          /* 1.0 * 2^23 */
                /* calculate (mant - 1) * 1.381097463 */
                /* 1.381097463 == 0.125 / (2^0.125 - 1) */
                asm("mulhwu %0,%1,%2" : "=r" (frac)
                    : "r" ((mant - 0x800000) << 1), "r" (0xb0c7cd3a));
                exp += frac;
        }
        s = exp & 0x80000000;
        if (exp != 0) {
                if (s)
                        exp = -exp;
                asm("cntlzw %0,%1" : "=r" (lz) : "r" (exp));
                lz = 8 - lz;
                if (lz > 0)
                        exp >>= lz;
                else if (lz < 0)
                        exp <<= -lz;
                s += ((lz + 126) << 23) + exp;
        }
        return s;
}

#define VSCR_SAT        1

static int ctsxs(unsigned int x, int scale, unsigned int *vscrp)
{
        int exp, mant;

        exp = (x >> 23) & 0xff;
        mant = x & 0x7fffff;
        if (exp == 255 && mant != 0)
                return 0;               /* NaN -> 0 */
        exp = exp - 127 + scale;
        if (exp < 0)
                return 0;               /* round towards zero */
        if (exp >= 31) {
                /* saturate, unless the result would be -2^31 */
                if (x + (scale << 23) != 0xcf000000)
                        *vscrp |= VSCR_SAT;
                return (x & 0x80000000)? 0x80000000: 0x7fffffff;
        }
        mant |= 0x800000;
        mant = (mant << 7) >> (30 - exp);
        return (x & 0x80000000)? -mant: mant;
}

static unsigned int ctuxs(unsigned int x, int scale, unsigned int *vscrp)
{
        int exp;
        unsigned int mant;

        exp = (x >> 23) & 0xff;
        mant = x & 0x7fffff;
        if (exp == 255 && mant != 0)
                return 0;               /* NaN -> 0 */
        exp = exp - 127 + scale;
        if (exp < 0)
                return 0;               /* round towards zero */
        if (x & 0x80000000) {
                /* negative => saturate to 0 */
                *vscrp |= VSCR_SAT;
                return 0;
        }
        if (exp >= 32) {
                /* saturate */
                *vscrp |= VSCR_SAT;
                return 0xffffffff;
        }
        mant |= 0x800000;
        mant = (mant << 8) >> (31 - exp);
        return mant;
}

/* Round to floating integer, towards 0 */
static unsigned int rfiz(unsigned int x)
{
        int exp;

        exp = ((x >> 23) & 0xff) - 127;
        if (exp == 128 && (x & 0x7fffff) != 0)
                return x | 0x400000;    /* NaN -> make it a QNaN */
        if (exp >= 23)
                return x;               /* it's an integer already (or Inf) */
        if (exp < 0)
                return x & 0x80000000;  /* |x| < 1.0 rounds to 0 */
        return x & ~(0x7fffff >> exp);
}

/* Round to floating integer, towards +/- Inf */
static unsigned int rfii(unsigned int x)
{
        int exp, mask;

        exp = ((x >> 23) & 0xff) - 127;
        if (exp == 128 && (x & 0x7fffff) != 0)
                return x | 0x400000;    /* NaN -> make it a QNaN */
        if (exp >= 23)
                return x;               /* it's an integer already (or Inf) */
        if ((x & 0x7fffffff) == 0)
                return x;               /* +/-0 -> +/-0 */
        if (exp < 0)
                /* 0 < |x| < 1.0 rounds to +/- 1.0 */
                return (x & 0x80000000) | 0x3f800000;
        mask = 0x7fffff >> exp;
        /* mantissa overflows into exponent - that's OK,
           it can't overflow into the sign bit */
        return (x + mask) & ~mask;
}

/* Round to floating integer, to nearest */
static unsigned int rfin(unsigned int x)
{
        int exp, half;

        exp = ((x >> 23) & 0xff) - 127;
        if (exp == 128 && (x & 0x7fffff) != 0)
                return x | 0x400000;    /* NaN -> make it a QNaN */
        if (exp >= 23)
                return x;               /* it's an integer already (or Inf) */
        if (exp < -1)
                return x & 0x80000000;  /* |x| < 0.5 -> +/-0 */
        if (exp == -1)
                /* 0.5 <= |x| < 1.0 rounds to +/- 1.0 */
                return (x & 0x80000000) | 0x3f800000;
        half = 0x400000 >> exp;
        /* add 0.5 to the magnitude and chop off the fraction bits */
        return (x + half) & ~(0x7fffff >> exp);
}

int emulate_altivec(struct pt_regs *regs)
{
        unsigned int instr, i;
        unsigned int va, vb, vc, vd;
        vector128 *vrs;

        if (get_user(instr, (unsigned int __user *) regs->nip))
                return -EFAULT;
        if ((instr >> 26) != 4)
                return -EINVAL;         /* not an altivec instruction */
        vd = (instr >> 21) & 0x1f;
        va = (instr >> 16) & 0x1f;
        vb = (instr >> 11) & 0x1f;
        vc = (instr >> 6) & 0x1f;

        vrs = current->thread.vr_state.vr;
        switch (instr & 0x3f) {
        case 10:
                switch (vc) {
                case 0: /* vaddfp */
                        vaddfp(&vrs[vd], &vrs[va], &vrs[vb]);
                        break;
                case 1: /* vsubfp */
                        vsubfp(&vrs[vd], &vrs[va], &vrs[vb]);
                        break;
                case 4: /* vrefp */
                        vrefp(&vrs[vd], &vrs[vb]);
                        break;
                case 5: /* vrsqrtefp */
                        vrsqrtefp(&vrs[vd], &vrs[vb]);
                        break;
                case 6: /* vexptefp */
                        for (i = 0; i < 4; ++i)
                                vrs[vd].u[i] = eexp2(vrs[vb].u[i]);
                        break;
                case 7: /* vlogefp */
                        for (i = 0; i < 4; ++i)
                                vrs[vd].u[i] = elog2(vrs[vb].u[i]);
                        break;
                case 8:         /* vrfin */
                        for (i = 0; i < 4; ++i)
                                vrs[vd].u[i] = rfin(vrs[vb].u[i]);
                        break;
                case 9:         /* vrfiz */
                        for (i = 0; i < 4; ++i)
                                vrs[vd].u[i] = rfiz(vrs[vb].u[i]);
                        break;
                case 10:        /* vrfip */
                        for (i = 0; i < 4; ++i) {
                                u32 x = vrs[vb].u[i];
                                x = (x & 0x80000000)? rfiz(x): rfii(x);
                                vrs[vd].u[i] = x;
                        }
                        break;
                case 11:        /* vrfim */
                        for (i = 0; i < 4; ++i) {
                                u32 x = vrs[vb].u[i];
                                x = (x & 0x80000000)? rfii(x): rfiz(x);
                                vrs[vd].u[i] = x;
                        }
                        break;
                case 14:        /* vctuxs */
                        for (i = 0; i < 4; ++i)
                                vrs[vd].u[i] = ctuxs(vrs[vb].u[i], va,
                                        &current->thread.vr_state.vscr.u[3]);
                        break;
                case 15:        /* vctsxs */
                        for (i = 0; i < 4; ++i)
                                vrs[vd].u[i] = ctsxs(vrs[vb].u[i], va,
                                        &current->thread.vr_state.vscr.u[3]);
                        break;
                default:
                        return -EINVAL;
                }
                break;
        case 46:        /* vmaddfp */
                vmaddfp(&vrs[vd], &vrs[va], &vrs[vb], &vrs[vc]);
                break;
        case 47:        /* vnmsubfp */
                vnmsubfp(&vrs[vd], &vrs[va], &vrs[vb], &vrs[vc]);
                break;
        default:
                return -EINVAL;
        }

        return 0;
}