muldi3.c

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#include <linux/module.h>

#include "libgcc.h"

#define DWtype long long
#define UWtype unsigned long
#define UHWtype unsigned short

#define W_TYPE_SIZE 32

#define __ll_B ((UWtype) 1 << (W_TYPE_SIZE / 2))
#define __ll_lowpart(t) ((UWtype) (t) & (__ll_B - 1))
#define __ll_highpart(t) ((UWtype) (t) >> (W_TYPE_SIZE / 2))

/* If we still don't have umul_ppmm, define it using plain C.  */
#if !defined(umul_ppmm)
#define umul_ppmm(w1, w0, u, v)                     \
    do {                                \
        UWtype __x0, __x1, __x2, __x3;              \
        UHWtype __ul, __vl, __uh, __vh;             \
                                    \
        __ul = __ll_lowpart(u);                 \
        __uh = __ll_highpart(u);                \
        __vl = __ll_lowpart(v);                 \
        __vh = __ll_highpart(v);                \
                                    \
        __x0 = (UWtype) __ul * __vl;                \
        __x1 = (UWtype) __ul * __vh;                \
        __x2 = (UWtype) __uh * __vl;                \
        __x3 = (UWtype) __uh * __vh;                \
                                    \
        __x1 += __ll_highpart(__x0); /* this can't give carry */\
        __x1 += __x2; /* but this indeed can */         \
        if (__x1 < __x2) /* did we get it? */           \
        __x3 += __ll_B; /* yes, add it in the proper pos */ \
                                    \
        (w1) = __x3 + __ll_highpart(__x1);          \
        (w0) = __ll_lowpart(__x1) * __ll_B + __ll_lowpart(__x0);\
    } while (0)
#endif

#if !defined(__umulsidi3)
#define __umulsidi3(u, v) ({                \
    DWunion __w;                    \
    umul_ppmm(__w.s.high, __w.s.low, u, v);     \
    __w.ll;                     \
    })
#endif

DWtype __muldi3(DWtype u, DWtype v)
{
    const DWunion uu = {.ll = u};
    const DWunion vv = {.ll = v};
    DWunion w = {.ll = __umulsidi3(uu.s.low, vv.s.low)};

    w.s.high += ((UWtype) uu.s.low * (UWtype) vv.s.high
        + (UWtype) uu.s.high * (UWtype) vv.s.low);

    return w.ll;
}
EXPORT_SYMBOL(__muldi3);