riscv/mulhi.h

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