libgcc/config/cris/arit.c

   1 /* Signed and unsigned multiplication and division and modulus for CRIS.
   2    Contributed by Axis Communications.
   3    Written by Hans-Peter Nilsson <hp@axis.se>, c:a 1992.
   4
   5    Copyright (C) 1998-2017 Free Software Foundation, Inc.
   6
   7 This file is part of GCC.
   8
   9 GCC is free software; you can redistribute it and/or modify it
  10 under the terms of the GNU General Public License as published by the
  11 Free Software Foundation; either version 3, or (at your option) any
  12 later version.
  13
  14 This file is distributed in the hope that it will be useful, but
  15 WITHOUT ANY WARRANTY; without even the implied warranty of
  16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17 General Public License for more details.
  18
  19 Under Section 7 of GPL version 3, you are granted additional
  20 permissions described in the GCC Runtime Library Exception, version
  21 3.1, as published by the Free Software Foundation.
  22
  23 You should have received a copy of the GNU General Public License and
  24 a copy of the GCC Runtime Library Exception along with this program;
  25 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  26 <http://www.gnu.org/licenses/>.  */
  27
  28
  29 /* Note that we provide prototypes for all "const" functions, to attach
  30    the const attribute.  This is necessary in 2.7.2 - adding the
  31    attribute to the function *definition* is a syntax error.
  32     This did not work with e.g. 2.1; back then, the return type had to
  33    be "const".  */
  34
  35 #include "config.h"
  36
  37 #if defined (__CRIS_arch_version) && __CRIS_arch_version >= 3
  38 #define LZ(v) __builtin_clz (v)
  39 #endif
  40
  41 /* In (at least) the 4.7 series, GCC doesn't automatically choose the
  42    most optimal strategy, possibly related to insufficient modelling of
  43    delay-slot costs.  */
  44 #if defined (__CRIS_arch_version) && __CRIS_arch_version >= 10
  45 #define SIGNMULT(s, a) ((s) * (a)) /* Cheap multiplication, better than branch.  */
  46 #else
  47 #define SIGNMULT(s, a) ((s) < 0 ? -(a) : (a)) /* Branches are still better.  */
  48 #endif
  49
  50 #if defined (L_udivsi3) || defined (L_divsi3) || defined (L_umodsi3) \
  51     || defined (L_modsi3)
  52 /* Result type of divmod worker function.  */
  53 struct quot_rem
  54  {
  55    long quot;
  56    long rem;
  57  };
  58
  59 /* This is the worker function for div and mod.  It is inlined into the
  60    respective library function.  Parameter A must have bit 31 == 0.  */
  61
  62 static __inline__ struct quot_rem
  63 do_31div (unsigned long a, unsigned long b)
  64      __attribute__ ((__const__, __always_inline__));
  65
  66 static __inline__ struct quot_rem
  67 do_31div (unsigned long a, unsigned long b)
  68 {
  69   /* Adjust operands and result if a is 31 bits.  */
  70   long extra = 0;
  71   int quot_digits = 0;
  72
  73   if (b == 0)
  74     {
  75       struct quot_rem ret;
  76       ret.quot = 0xffffffff;
  77       ret.rem = 0xffffffff;
  78       return ret;
  79     }
  80
  81   if (a < b)
  82     return (struct quot_rem) { 0, a };
  83
  84 #ifdef LZ
  85   if (b <= a)
  86     {
  87       quot_digits = LZ (b) - LZ (a);
  88       quot_digits += (a >= (b << quot_digits));
  89       b <<= quot_digits;
  90     }
  91 #else
  92   while (b <= a)
  93     {
  94       b <<= 1;
  95       quot_digits++;
  96     }
  97 #endif
  98
  99   /* Is a 31 bits?  Note that bit 31 is handled by the caller.  */
 100   if (a & 0x40000000)
 101     {
 102       /* Then make b:s highest bit max 0x40000000, because it must have
 103          been 0x80000000 to be 1 bit higher than a.  */
 104       b >>= 1;
 105
 106       /* Adjust a to be maximum 0x3fffffff, i.e. two upper bits zero.  */
 107       if (a >= b)
 108         {
 109           a -= b;
 110           extra = 1 << (quot_digits - 1);
 111         }
 112       else
 113         {
 114           a -= b >> 1;
 115
 116           /* Remember that we adjusted a by subtracting b * 2 ** Something.  */
 117           extra = 1 << quot_digits;
 118         }
 119
 120       /* The number of quotient digits will be one less, because
 121          we just adjusted b.  */
 122       quot_digits--;
 123     }
 124
 125   /* Now do the division part.  */
 126
 127   /* Subtract b and add ones to the right when a >= b
 128      i.e. "a - (b - 1) == (a - b) + 1".  */
 129   b--;
 130
 131 #define DS __asm__ ("dstep %2,%0" : "=r" (a) : "0" (a), "r" (b))
 132
 133   switch (quot_digits)
 134     {
 135     case 32: DS; case 31: DS; case 30: DS; case 29: DS;
 136     case 28: DS; case 27: DS; case 26: DS; case 25: DS;
 137     case 24: DS; case 23: DS; case 22: DS; case 21: DS;
 138     case 20: DS; case 19: DS; case 18: DS; case 17: DS;
 139     case 16: DS; case 15: DS; case 14: DS; case 13: DS;
 140     case 12: DS; case 11: DS; case 10: DS; case 9: DS;
 141     case 8: DS; case 7: DS; case 6: DS; case 5: DS;
 142     case 4: DS; case 3: DS; case 2: DS; case 1: DS;
 143     case 0:;
 144     }
 145
 146   {
 147     struct quot_rem ret;
 148     ret.quot = (a & ((1 << quot_digits) - 1)) + extra;
 149     ret.rem = a >> quot_digits;
 150     return ret;
 151   }
 152 }
 153
 154 #ifdef L_udivsi3
 155 unsigned long
 156 __Udiv (unsigned long a, unsigned long b) __attribute__ ((__const__));
 157
 158 unsigned long
 159 __Udiv (unsigned long a, unsigned long b)
 160 {
 161   long extra = 0;
 162
 163   /* Adjust operands and result, if a and/or b is 32 bits.  */
 164   /* Effectively: b & 0x80000000.  */
 165   if ((long) b < 0)
 166     return a >= b;
 167
 168   /* Effectively: a & 0x80000000.  */
 169   if ((long) a < 0)
 170     {
 171       int tmp = 0;
 172
 173       if (b == 0)
 174         return 0xffffffff;
 175 #ifdef LZ
 176       tmp = LZ (b);
 177 #else
 178       for (tmp = 31; (((long) b & (1 << tmp)) == 0); tmp--)
 179         ;
 180
 181       tmp = 31 - tmp;
 182 #endif
 183
 184       if ((b << tmp) > a)
 185         {
 186           extra = 1 << (tmp-1);
 187           a -= b << (tmp - 1);
 188         }
 189       else
 190         {
 191           extra = 1 << tmp;
 192           a -= b << tmp;
 193         }
 194     }
 195
 196   return do_31div (a, b).quot+extra;
 197 }
 198 #endif /* L_udivsi3 */
 199
 200 #ifdef L_divsi3
 201 long
 202 __Div (long a, long b) __attribute__ ((__const__));
 203
 204 long
 205 __Div (long a, long b)
 206 {
 207   long extra = 0;
 208   long sign = (b < 0) ? -1 : 1;
 209   long res;
 210
 211   /* We need to handle a == -2147483648 as expected and must while
 212      doing that avoid producing a sequence like "abs (a) < 0" as GCC
 213      may optimize out the test.  That sequence may not be obvious as
 214      we call inline functions.  Testing for a being negative and
 215      handling (presumably much rarer than positive) enables us to get
 216      a bit of optimization for an (accumulated) reduction of the
 217      penalty of the 0x80000000 special-case.  */
 218   if (a < 0)
 219     {
 220       sign = -sign;
 221
 222       if ((a & 0x7fffffff) == 0)
 223         {
 224           /* We're at 0x80000000.  Tread carefully.  */
 225           a -= SIGNMULT (sign, b);
 226           extra = sign;
 227         }
 228       a = -a;
 229     }
 230
 231   res = do_31div (a, __builtin_labs (b)).quot;
 232   return SIGNMULT (sign, res) + extra;
 233 }
 234 #endif /* L_divsi3 */
 235
 236
 237 #ifdef L_umodsi3
 238 unsigned long
 239 __Umod (unsigned long a, unsigned long b) __attribute__ ((__const__));
 240
 241 unsigned long
 242 __Umod (unsigned long a, unsigned long b)
 243 {
 244   /* Adjust operands and result if a and/or b is 32 bits.  */
 245   if ((long) b < 0)
 246     return a >= b ? a - b : a;
 247
 248   if ((long) a < 0)
 249     {
 250       int tmp = 0;
 251
 252       if (b == 0)
 253         return a;
 254 #ifdef LZ
 255       tmp = LZ (b);
 256 #else
 257       for (tmp = 31; (((long) b & (1 << tmp)) == 0); tmp--)
 258         ;
 259       tmp = 31 - tmp;
 260 #endif
 261
 262       if ((b << tmp) > a)
 263         {
 264           a -= b << (tmp - 1);
 265         }
 266       else
 267         {
 268           a -= b << tmp;
 269         }
 270     }
 271
 272   return do_31div (a, b).rem;
 273 }
 274 #endif /* L_umodsi3 */
 275
 276 #ifdef L_modsi3
 277 long
 278 __Mod (long a, long b) __attribute__ ((__const__));
 279
 280 long
 281 __Mod (long a, long b)
 282 {
 283   long sign = 1;
 284   long res;
 285
 286   /* We need to handle a == -2147483648 as expected and must while
 287      doing that avoid producing a sequence like "abs (a) < 0" as GCC
 288      may optimize out the test.  That sequence may not be obvious as
 289      we call inline functions.  Testing for a being negative and
 290      handling (presumably much rarer than positive) enables us to get
 291      a bit of optimization for an (accumulated) reduction of the
 292      penalty of the 0x80000000 special-case.  */
 293   if (a < 0)
 294     {
 295       sign = -1;
 296       if ((a & 0x7fffffff) == 0)
 297         /* We're at 0x80000000.  Tread carefully.  */
 298         a += __builtin_labs (b);
 299       a = -a;
 300     }
 301
 302   res = do_31div (a, __builtin_labs (b)).rem;
 303   return SIGNMULT (sign, res);
 304 }
 305 #endif /* L_modsi3 */
 306 #endif /* L_udivsi3 || L_divsi3 || L_umodsi3 || L_modsi3 */
 307
 308 /*
 309  * Local variables:
 310  * eval: (c-set-style "gnu")
 311  * indent-tabs-mode: t
 312  * End:
 313  */