arch/powerpc/math-emu/udivmodti4.c

   1 /* This has so very few changes over libgcc2's __udivmoddi4 it isn't funny.  */
   2
   3 #include <math-emu/soft-fp.h>
   4
   5 #undef count_leading_zeros
   6 #define count_leading_zeros  __FP_CLZ
   7
   8 void
   9 _fp_udivmodti4(_FP_W_TYPE q[2], _FP_W_TYPE r[2],
  10                _FP_W_TYPE n1, _FP_W_TYPE n0,
  11                _FP_W_TYPE d1, _FP_W_TYPE d0)
  12 {
  13   _FP_W_TYPE q0, q1, r0, r1;
  14   _FP_I_TYPE b, bm;
  15
  16   if (d1 == 0)
  17     {
  18 #if !UDIV_NEEDS_NORMALIZATION
  19       if (d0 > n1)
  20         {
  21           /* 0q = nn / 0D */
  22
  23           udiv_qrnnd (q0, n0, n1, n0, d0);
  24           q1 = 0;
  25
  26           /* Remainder in n0.  */
  27         }
  28       else
  29         {
  30           /* qq = NN / 0d */
  31
  32           if (d0 == 0)
  33             d0 = 1 / d0;        /* Divide intentionally by zero.  */
  34
  35           udiv_qrnnd (q1, n1, 0, n1, d0);
  36           udiv_qrnnd (q0, n0, n1, n0, d0);
  37
  38           /* Remainder in n0.  */
  39         }
  40
  41       r0 = n0;
  42       r1 = 0;
  43
  44 #else /* UDIV_NEEDS_NORMALIZATION */
  45
  46       if (d0 > n1)
  47         {
  48           /* 0q = nn / 0D */
  49
  50           count_leading_zeros (bm, d0);
  51
  52           if (bm != 0)
  53             {
  54               /* Normalize, i.e. make the most significant bit of the
  55                  denominator set.  */
  56
  57               d0 = d0 << bm;
  58               n1 = (n1 << bm) | (n0 >> (_FP_W_TYPE_SIZE - bm));
  59               n0 = n0 << bm;
  60             }
  61
  62           udiv_qrnnd (q0, n0, n1, n0, d0);
  63           q1 = 0;
  64
  65           /* Remainder in n0 >> bm.  */
  66         }
  67       else
  68         {
  69           /* qq = NN / 0d */
  70
  71           if (d0 == 0)
  72             d0 = 1 / d0;        /* Divide intentionally by zero.  */
  73
  74           count_leading_zeros (bm, d0);
  75
  76           if (bm == 0)
  77             {
  78               /* From (n1 >= d0) /\ (the most significant bit of d0 is set),
  79                  conclude (the most significant bit of n1 is set) /\ (the
  80                  leading quotient digit q1 = 1).
  81
  82                  This special case is necessary, not an optimization.
  83                  (Shifts counts of SI_TYPE_SIZE are undefined.)  */
  84
  85               n1 -= d0;
  86               q1 = 1;
  87             }
  88           else
  89             {
  90               _FP_W_TYPE n2;
  91
  92               /* Normalize.  */
  93
  94               b = _FP_W_TYPE_SIZE - bm;
  95
  96               d0 = d0 << bm;
  97               n2 = n1 >> b;
  98               n1 = (n1 << bm) | (n0 >> b);
  99               n0 = n0 << bm;
 100
 101               udiv_qrnnd (q1, n1, n2, n1, d0);
 102             }
 103
 104           /* n1 != d0...  */
 105
 106           udiv_qrnnd (q0, n0, n1, n0, d0);
 107
 108           /* Remainder in n0 >> bm.  */
 109         }
 110
 111       r0 = n0 >> bm;
 112       r1 = 0;
 113 #endif /* UDIV_NEEDS_NORMALIZATION */
 114     }
 115   else
 116     {
 117       if (d1 > n1)
 118         {
 119           /* 00 = nn / DD */
 120
 121           q0 = 0;
 122           q1 = 0;
 123
 124           /* Remainder in n1n0.  */
 125           r0 = n0;
 126           r1 = n1;
 127         }
 128       else
 129         {
 130           /* 0q = NN / dd */
 131
 132           count_leading_zeros (bm, d1);
 133           if (bm == 0)
 134             {
 135               /* From (n1 >= d1) /\ (the most significant bit of d1 is set),
 136                  conclude (the most significant bit of n1 is set) /\ (the
 137                  quotient digit q0 = 0 or 1).
 138
 139                  This special case is necessary, not an optimization.  */
 140
 141               /* The condition on the next line takes advantage of that
 142                  n1 >= d1 (true due to program flow).  */
 143               if (n1 > d1 || n0 >= d0)
 144                 {
 145                   q0 = 1;
 146                   sub_ddmmss (n1, n0, n1, n0, d1, d0);
 147                 }
 148               else
 149                 q0 = 0;
 150
 151               q1 = 0;
 152
 153               r0 = n0;
 154               r1 = n1;
 155             }
 156           else
 157             {
 158               _FP_W_TYPE m1, m0, n2;
 159
 160               /* Normalize.  */
 161
 162               b = _FP_W_TYPE_SIZE - bm;
 163
 164               d1 = (d1 << bm) | (d0 >> b);
 165               d0 = d0 << bm;
 166               n2 = n1 >> b;
 167               n1 = (n1 << bm) | (n0 >> b);
 168               n0 = n0 << bm;
 169
 170               udiv_qrnnd (q0, n1, n2, n1, d1);
 171               umul_ppmm (m1, m0, q0, d0);
 172
 173               if (m1 > n1 || (m1 == n1 && m0 > n0))
 174                 {
 175                   q0--;
 176                   sub_ddmmss (m1, m0, m1, m0, d1, d0);
 177                 }
 178
 179               q1 = 0;
 180
 181               /* Remainder in (n1n0 - m1m0) >> bm.  */
 182               sub_ddmmss (n1, n0, n1, n0, m1, m0);
 183               r0 = (n1 << b) | (n0 >> bm);
 184               r1 = n1 >> bm;
 185             }
 186         }
 187     }
 188
 189   q[0] = q0; q[1] = q1;
 190   r[0] = r0, r[1] = r1;
 191 }