src/nmutil/divmod.py

   1 from copy import copy
   2 # this is a POWER ISA 3.0B compatible *signed* div function
   3 # however it is also the c, c++, rust, java *and* x86 way of doing things
   4
   5
   6 def trunc_divs(n, d):
   7     abs_n = abs(n.to_signed_int())
   8     abs_d = abs(d.to_signed_int())
   9     print("trunc_div n", abs_n, n.to_signed_int())
  10     print("trunc_div d", abs_d, d.to_signed_int())
  11     abs_q = abs_n // abs_d
  12     sign_n = n.value & (1 << (n.bits - 1)) != 0
  13     sign_d = d.value & (1 << (d.bits - 1)) != 0
  14     print("trunc_div", hex(n.value), hex(d.value),
  15           hex(abs_n), hex(abs_d), hex(abs_q),
  16           sign_n, sign_d)
  17     res = copy(n)
  18     if (sign_n == sign_d):
  19         res.value = abs_q
  20         if res.value & (1 << (res.bits - 1)) != 0:
  21             # result should be positive but is negative
  22             raise OverflowError()
  23         return res
  24     mask = (1 << res.bits) - 1
  25     res.value = (-abs_q) & mask
  26
  27     return res
  28
  29
  30 # this is a POWER ISA 3.0B compatible *signed* mod / remainder function
  31 # however it is also the c, c++, rust, java *and* x86 way of doing things
  32 def trunc_rems(n, d):
  33     m = d * trunc_divs(n, d)
  34
  35     # cheat - really shouldn't do this. mul returns full length
  36     m.bits = n.bits
  37     return n - m