contrib/gdtoa/arithchk.c

   1 /****************************************************************
   2 Copyright (C) 1997, 1998 Lucent Technologies
   3 All Rights Reserved
   4
   5 Permission to use, copy, modify, and distribute this software and
   6 its documentation for any purpose and without fee is hereby
   7 granted, provided that the above copyright notice appear in all
   8 copies and that both that the copyright notice and this
   9 permission notice and warranty disclaimer appear in supporting
  10 documentation, and that the name of Lucent or any of its entities
  11 not be used in advertising or publicity pertaining to
  12 distribution of the software without specific, written prior
  13 permission.
  14
  15 LUCENT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
  16 INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.
  17 IN NO EVENT SHALL LUCENT OR ANY OF ITS ENTITIES BE LIABLE FOR ANY
  18 SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  19 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
  20 IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
  21 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
  22 THIS SOFTWARE.
  23 ****************************************************************/
  24
  25 /* Try to deduce arith.h from arithmetic properties. */
  26
  27 #include <stdio.h>
  28
  29  static int dalign;
  30  typedef struct
  31 Akind {
  32         char *name;
  33         int   kind;
  34         } Akind;
  35
  36  static Akind
  37 IEEE_8087       = { "IEEE_8087", 1 },
  38 IEEE_MC68k      = { "IEEE_MC68k", 2 },
  39 IBM             = { "IBM", 3 },
  40 VAX             = { "VAX", 4 },
  41 CRAY            = { "CRAY", 5};
  42
  43  static Akind *
  44 Lcheck()
  45 {
  46         union {
  47                 double d;
  48                 long L[2];
  49                 } u;
  50         struct {
  51                 double d;
  52                 long L;
  53                 } x[2];
  54
  55         if (sizeof(x) > 2*(sizeof(double) + sizeof(long)))
  56                 dalign = 1;
  57         u.L[0] = u.L[1] = 0;
  58         u.d = 1e13;
  59         if (u.L[0] == 1117925532 && u.L[1] == -448790528)
  60                 return &IEEE_MC68k;
  61         if (u.L[1] == 1117925532 && u.L[0] == -448790528)
  62                 return &IEEE_8087;
  63         if (u.L[0] == -2065213935 && u.L[1] == 10752)
  64                 return &VAX;
  65         if (u.L[0] == 1267827943 && u.L[1] == 704643072)
  66                 return &IBM;
  67         return 0;
  68         }
  69
  70  static Akind *
  71 icheck()
  72 {
  73         union {
  74                 double d;
  75                 int L[2];
  76                 } u;
  77         struct {
  78                 double d;
  79                 int L;
  80                 } x[2];
  81
  82         if (sizeof(x) > 2*(sizeof(double) + sizeof(int)))
  83                 dalign = 1;
  84         u.L[0] = u.L[1] = 0;
  85         u.d = 1e13;
  86         if (u.L[0] == 1117925532 && u.L[1] == -448790528)
  87                 return &IEEE_MC68k;
  88         if (u.L[1] == 1117925532 && u.L[0] == -448790528)
  89                 return &IEEE_8087;
  90         if (u.L[0] == -2065213935 && u.L[1] == 10752)
  91                 return &VAX;
  92         if (u.L[0] == 1267827943 && u.L[1] == 704643072)
  93                 return &IBM;
  94         return 0;
  95         }
  96
  97 char *emptyfmt = "";    /* avoid possible warning message with printf("") */
  98
  99  static Akind *
 100 ccheck()
 101 {
 102         union {
 103                 double d;
 104                 long L;
 105                 } u;
 106         long Cray1;
 107
 108         /* Cray1 = 4617762693716115456 -- without overflow on non-Crays */
 109         Cray1 = printf(emptyfmt) < 0 ? 0 : 4617762;
 110         if (printf(emptyfmt, Cray1) >= 0)
 111                 Cray1 = 1000000*Cray1 + 693716;
 112         if (printf(emptyfmt, Cray1) >= 0)
 113                 Cray1 = 1000000*Cray1 + 115456;
 114         u.d = 1e13;
 115         if (u.L == Cray1)
 116                 return &CRAY;
 117         return 0;
 118         }
 119
 120  static int
 121 fzcheck()
 122 {
 123         double a, b;
 124         int i;
 125
 126         a = 1.;
 127         b = .1;
 128         for(i = 155;; b *= b, i >>= 1) {
 129                 if (i & 1) {
 130                         a *= b;
 131                         if (i == 1)
 132                                 break;
 133                         }
 134                 }
 135         b = a * a;
 136         return b == 0.;
 137         }
 138
 139  int
 140 main()
 141 {
 142         Akind *a = 0;
 143         int Ldef = 0;
 144         FILE *f;
 145
 146 #ifdef WRITE_ARITH_H    /* for Symantec's buggy "make" */
 147         f = fopen("arith.h", "w");
 148         if (!f) {
 149                 printf("Cannot open arith.h\n");
 150                 return 1;
 151                 }
 152 #else
 153         f = stdout;
 154 #endif
 155
 156         if (sizeof(double) == 2*sizeof(long))
 157                 a = Lcheck();
 158         else if (sizeof(double) == 2*sizeof(int)) {
 159                 Ldef = 1;
 160                 a = icheck();
 161                 }
 162         else if (sizeof(double) == sizeof(long))
 163                 a = ccheck();
 164         if (a) {
 165                 fprintf(f, "#define %s\n#define Arith_Kind_ASL %d\n",
 166                         a->name, a->kind);
 167                 if (Ldef)
 168                         fprintf(f, "#define Long int\n#define Intcast (int)(long)\n");
 169                 if (dalign)
 170                         fprintf(f, "#define Double_Align\n");
 171                 if (sizeof(char*) == 8)
 172                         fprintf(f, "#define X64_bit_pointers\n");
 173 #ifndef NO_LONG_LONG
 174                 if (sizeof(long long) < 8)
 175 #endif
 176                         fprintf(f, "#define NO_LONG_LONG\n");
 177                 if (a->kind <= 2 && fzcheck())
 178                         fprintf(f, "#define Sudden_Underflow\n");
 179                 return 0;
 180                 }
 181         fprintf(f, "/* Unknown arithmetic */\n");
 182         return 1;
 183         }