LXR linux/arch/mips/lib/multi3.c

   1// SPDX-License-Identifier: GPL-2.0
   2#include <linux/export.h>
   3
   4#include "libgcc.h"
   5
   6/*
   7 * GCC 7 & older can suboptimally generate __multi3 calls for mips64r6, so for
   8 * that specific case only we implement that intrinsic here.
   9 *
  10 * See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82981
  11 */
  12#if defined(CONFIG_64BIT) && defined(CONFIG_CPU_MIPSR6) && (__GNUC__ < 8)
  13
  14/* multiply 64-bit values, low 64-bits returned */
  15static inline long long notrace dmulu(long long a, long long b)
  16{
  17        long long res;
  18
  19        asm ("dmulu %0,%1,%2" : "=r" (res) : "r" (a), "r" (b));
  20        return res;
  21}
  22
  23/* multiply 64-bit unsigned values, high 64-bits of 128-bit result returned */
  24static inline long long notrace dmuhu(long long a, long long b)
  25{
  26        long long res;
  27
  28        asm ("dmuhu %0,%1,%2" : "=r" (res) : "r" (a), "r" (b));
  29        return res;
  30}
  31
  32/* multiply 128-bit values, low 128-bits returned */
  33ti_type notrace __multi3(ti_type a, ti_type b)
  34{
  35        TWunion res, aa, bb;
  36
  37        aa.ti = a;
  38        bb.ti = b;
  39
  40        /*
  41         * a * b =           (a.lo * b.lo)
  42         *         + 2^64  * (a.hi * b.lo + a.lo * b.hi)
  43         *        [+ 2^128 * (a.hi * b.hi)]
  44         */
  45        res.s.low = dmulu(aa.s.low, bb.s.low);
  46        res.s.high = dmuhu(aa.s.low, bb.s.low);
  47        res.s.high += dmulu(aa.s.high, bb.s.low);
  48        res.s.high += dmulu(aa.s.low, bb.s.high);
  49
  50        return res.ti;
  51}
  52EXPORT_SYMBOL(__multi3);
  53
  54#endif /* 64BIT && CPU_MIPSR6 && GCC7 */
  55