riscv/mulhi.h

   1 // See LICENSE for license details.
   2
   3 #ifndef _RISCV_MULHI_H
   4 #define _RISCV_MULHI_H
   5
   6 #include <cstdint>
   7
   8 inline uint64_t mulhu(uint64_t a, uint64_t b)
   9 {
  10   uint64_t t;
  11   uint32_t y1, y2, y3;
  12   uint64_t a0 = (uint32_t)a, a1 = a >> 32;
  13   uint64_t b0 = (uint32_t)b, b1 = b >> 32;
  14
  15   t = a1*b0 + ((a0*b0) >> 32);
  16   y1 = t;
  17   y2 = t >> 32;
  18
  19   t = a0*b1 + y1;
  20   y1 = t;
  21
  22   t = a1*b1 + y2 + (t >> 32);
  23   y2 = t;
  24   y3 = t >> 32;
  25
  26   return ((uint64_t)y3 << 32) | y2;
  27 }
  28
  29 inline int64_t mulh(int64_t a, int64_t b)
  30 {
  31   int negate = (a < 0) != (b < 0);
  32   uint64_t res = mulhu(a < 0 ? -a : a, b < 0 ? -b : b);
  33   return negate ? ~res + (a * b == 0) : res;
  34 }
  35
  36 inline int64_t mulhsu(int64_t a, uint64_t b)
  37 {
  38   int negate = a < 0;
  39   uint64_t res = mulhu(a < 0 ? -a : a, b);
  40   return negate ? ~res + (a * b == 0) : res;
  41 }
  42
  43 #endif