gcc/halfpic.c

   1 /* OSF/rose half-pic support functions.
   2    Copyright (C) 1992, 1997, 1998 Free Software Foundation, Inc.
   3
   4 This file is part of GNU CC.
   5
   6 GNU CC is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU CC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU CC; see the file COPYING.  If not, write to
  18 the Free Software Foundation, 59 Temple Place - Suite 330,
  19 Boston, MA 02111-1307, USA.  */
  20
  21 /* The OSF/rose half-pic model assumes that the non-library code does
  22    not need to have full PIC (position independent code), but rather,
  23    that pointers to external references are put into the data section
  24    and dereferenced as normal pointers.  References to static data does
  25    not need to be PIC-ized.
  26
  27    Another optimization is to have the compiler know what symbols are
  28    in the shared libraries, and to only lay down the pointers to
  29    things which in the library proper.  */
  30
  31 #include "config.h"
  32
  33 #ifdef HALF_PIC_INIT
  34
  35 #include "system.h"
  36 #include "tree.h"
  37 #include "rtl.h"
  38 #include "obstack.h"
  39
  40 #define obstack_chunk_alloc xmalloc
  41 #define obstack_chunk_free free
  42
  43 extern rtx eliminate_constant_term ();
  44 extern void assemble_name ();
  45 extern void output_addr_const ();
  46
  47 int flag_half_pic               = 0;    /* Global half-pic flag.  */
  48 int half_pic_number_ptrs        = 0;    /* # distinct pointers found */
  49 int half_pic_number_refs        = 0;    /* # half-pic references */
  50 int (*ptr_half_pic_address_p)() = half_pic_address_p;
  51
  52 /* Obstack to hold generated pic names.  */
  53 static struct obstack half_pic_obstack;
  54
  55 /* List of pointers created to pic references.  */
  56
  57 struct all_refs {
  58   struct all_refs *hash_next;   /* next name in hash chain */
  59   struct all_refs *next;        /* next name created */
  60   int              external_p;  /* name is an external reference */
  61   int              pointer_p;   /* pointer created.  */
  62   char            *ref_name;    /* reference name to ptr to real_name */
  63   int              ref_len;     /* reference name length */
  64   char            *real_name;   /* real function/data name */
  65   int              real_len;    /* strlen (real_name) */
  66 };
  67
  68 static struct all_refs *half_pic_names;
  69
  70 static char *half_pic_prefix;
  71 static int   half_pic_prefix_len;
  72
  73 \f
  74 /* Return the hash bucket of a name or NULL.  The hash chain is
  75    organized as a self reorganizing circularly linked chain.  It is
  76    assumed that any name passed to use will never be reallocated.  For
  77    names in SYMBOL_REF's this is true, because the names are allocated
  78    on the permanent obstack.  */
  79
  80 #ifndef MAX_HASH_TABLE
  81 #define MAX_HASH_TABLE 1009
  82 #endif
  83
  84 #define HASHBITS 30
  85
  86 static struct all_refs *
  87 half_pic_hash (name, len, create_p)
  88      char *name;                /* name to hash */
  89      int len;                   /* length of the name (or 0 to call strlen) */
  90      int create_p;              /* != 0 to create new hash bucket if new */
  91 {
  92   static struct all_refs *hash_table[MAX_HASH_TABLE];
  93   static struct all_refs  zero_all_refs;
  94
  95   unsigned char *uname;
  96   int hash;
  97   int i;
  98   int ch;
  99   struct all_refs *first;
 100   struct all_refs *ptr;
 101
 102   if (len == 0)
 103     len = strlen (name);
 104
 105   /* Compute hash code */
 106   uname = (unsigned char *)name;
 107   ch = uname[0];
 108   hash = len * 613 + ch;
 109   for (i = 1; i < len; i += 2)
 110     hash = (hash * 613) + uname[i];
 111
 112   hash &= (1 << HASHBITS) - 1;
 113   hash %= MAX_HASH_TABLE;
 114
 115   /* See if the name is in the hash table.  */
 116   ptr = first = hash_table[hash];
 117   if (ptr)
 118     {
 119       do
 120         {
 121           if (len == ptr->real_len
 122               && ch == *(ptr->real_name)
 123               && !strcmp (name, ptr->real_name))
 124             {
 125               hash_table[hash] = ptr;
 126               return ptr;
 127             }
 128
 129           ptr = ptr->hash_next;
 130         }
 131       while (ptr != first);
 132     }
 133
 134   /* name not in hash table.  */
 135   if (!create_p)
 136     return (struct all_refs *) 0;
 137
 138   ptr = (struct all_refs *) obstack_alloc (&half_pic_obstack, sizeof (struct all_refs));
 139   *ptr = zero_all_refs;
 140
 141   ptr->real_name = name;
 142   ptr->real_len  = len;
 143
 144   /* Update circular links.  */
 145   if (first == (struct all_refs *) 0)
 146     ptr->hash_next = ptr;
 147
 148   else
 149     {
 150       ptr->hash_next = first->hash_next;
 151       first->hash_next = ptr;
 152     }
 153
 154   hash_table[hash] = ptr;
 155   return ptr;
 156 }
 157
 158 \f
 159 /* Do any half-pic initializations.  */
 160
 161 void
 162 half_pic_init ()
 163 {
 164   flag_half_pic = TRUE;
 165   half_pic_prefix = HALF_PIC_PREFIX;
 166   half_pic_prefix_len = strlen (half_pic_prefix);
 167   obstack_init (&half_pic_obstack);
 168 }
 169
 170 \f
 171 /* Write out all pointers to pic references.  */
 172
 173 void
 174 half_pic_finish (stream)
 175      FILE *stream;
 176 {
 177   struct all_refs *p = half_pic_names;
 178
 179   if (!p)
 180     return;
 181
 182   data_section ();
 183   for (; p != 0; p = p->next)
 184     {
 185       /* Emit the pointer if used.  */
 186       if (p->pointer_p)
 187         {
 188           ASM_OUTPUT_LABEL (stream, p->ref_name);
 189           ASM_OUTPUT_INT (stream, gen_rtx_SYMBOL_REF (Pmode, p->real_name));
 190         }
 191     }
 192 }
 193
 194 \f
 195 /* Encode in a declaration whether or not it is half-pic.  */
 196
 197 void
 198 half_pic_encode (decl)
 199      tree decl;
 200 {
 201   enum tree_code code = TREE_CODE (decl);
 202   tree asm_name;
 203   struct all_refs *ptr;
 204
 205   if (!flag_half_pic)
 206     return;
 207
 208   if (code != VAR_DECL && code != FUNCTION_DECL)
 209     return;
 210
 211   asm_name = DECL_ASSEMBLER_NAME (decl);
 212
 213   if (!asm_name)
 214     return;
 215
 216 #ifdef HALF_PIC_DEBUG
 217   if (HALF_PIC_DEBUG)
 218     {
 219       fprintf (stderr, "\n========== Half_pic_encode %.*s\n",
 220                IDENTIFIER_LENGTH (asm_name),
 221                IDENTIFIER_POINTER (asm_name));
 222       debug_tree (decl);
 223     }
 224 #endif
 225
 226   /* If this is not an external reference, it can't be half-pic.  */
 227   if (!DECL_EXTERNAL (decl) && (code != VAR_DECL || !TREE_PUBLIC (decl)))
 228     return;
 229
 230   ptr = half_pic_hash (IDENTIFIER_POINTER (asm_name),
 231                        IDENTIFIER_LENGTH (asm_name),
 232                        TRUE);
 233
 234   ptr->external_p = TRUE;
 235
 236 #ifdef HALF_PIC_DEBUG
 237   if (HALF_PIC_DEBUG)
 238     fprintf (stderr, "\n%.*s is half-pic\n",
 239              IDENTIFIER_LENGTH (asm_name),
 240              IDENTIFIER_POINTER (asm_name));
 241 #endif
 242 }
 243
 244 \f
 245 /* Mark that an object is now local, and no longer needs half-pic.  */
 246
 247 void
 248 half_pic_declare (name)
 249      char *name;
 250 {
 251   struct all_refs *ptr;
 252
 253   if (!flag_half_pic)
 254     return;
 255
 256   ptr = half_pic_hash (name, 0, FALSE);
 257   if (!ptr)
 258     return;
 259
 260   ptr->external_p = FALSE;
 261
 262 #ifdef HALF_PIC_DEBUG
 263   if (HALF_PIC_DEBUG)
 264     fprintf (stderr, "\n========== Half_pic_declare %s\n", name);
 265 #endif
 266 }
 267
 268 \f
 269 /* Mark that an object is explicitly external.  */
 270
 271 void
 272 half_pic_external (name)
 273      char *name;
 274 {
 275   struct all_refs *ptr;
 276
 277   if (!flag_half_pic)
 278     return;
 279
 280   ptr = half_pic_hash (name, 0, TRUE);
 281   if (!ptr)
 282     return;
 283
 284   ptr->external_p = TRUE;
 285
 286 #ifdef HALF_PIC_DEBUG
 287   if (HALF_PIC_DEBUG)
 288     fprintf (stderr, "\n========== Half_pic_external %s\n", name);
 289 #endif
 290 }
 291
 292 \f
 293 /* Return whether an address is half-pic.  */
 294
 295 int
 296 half_pic_address_p (addr)
 297      rtx addr;
 298 {
 299   char *name;
 300   int len;
 301   struct all_refs *ptr;
 302
 303   if (!flag_half_pic)
 304     return FALSE;
 305
 306   switch (GET_CODE (addr))
 307     {
 308     default:
 309       break;
 310
 311     case CONST:
 312       {
 313         rtx offset = const0_rtx;
 314         addr = eliminate_constant_term (XEXP (addr, 0), &offset);
 315         if (GET_CODE (addr) != SYMBOL_REF)
 316           return FALSE;
 317       }
 318       /* fall through */
 319
 320     case SYMBOL_REF:
 321       name = XSTR (addr, 0);
 322
 323 #ifdef HALF_PIC_DEBUG
 324       if (HALF_PIC_DEBUG)
 325         fprintf (stderr, "\n========== Half_pic_address_p %s\n", name);
 326 #endif
 327
 328       /* If this is a label, it will have a '*' in front of it.  */
 329       if (name[0] == '*')
 330         return FALSE;
 331
 332       /* If this is a reference to the actual half-pic pointer, it
 333          is obviously not half-pic.  */
 334
 335       len = strlen (name);
 336       if (len > half_pic_prefix_len
 337           && half_pic_prefix[0] == name[0]
 338           && !strncmp (name, half_pic_prefix, half_pic_prefix_len))
 339         return FALSE;
 340
 341       ptr = half_pic_hash (name, len, FALSE);
 342       if (ptr == (struct all_refs *) 0)
 343         return FALSE;
 344
 345       if (ptr->external_p)
 346         {
 347 #ifdef HALF_PIC_DEBUG
 348           if (HALF_PIC_DEBUG)
 349             fprintf (stderr, "%s is half-pic\n", name);
 350 #endif
 351           return TRUE;
 352         }
 353     }
 354
 355   return FALSE;
 356 }
 357
 358 \f
 359 /* Return the name of the pointer to the PIC function, allocating
 360    it if need be.  */
 361
 362 struct rtx_def *
 363 half_pic_ptr (operand)
 364      rtx operand;
 365 {
 366   char *name;
 367   struct all_refs *p;
 368   int len;
 369
 370   if (GET_CODE (operand) != SYMBOL_REF)
 371     return operand;
 372
 373   name = XSTR (operand, 0);
 374   len = strlen (name);
 375   p = half_pic_hash (name, len, FALSE);
 376   if (p == (struct all_refs *) 0 || !p->external_p)
 377     return operand;
 378
 379   if (!p->pointer_p)
 380     {                           /* first time, create pointer */
 381       obstack_grow (&half_pic_obstack, half_pic_prefix, half_pic_prefix_len);
 382       obstack_grow (&half_pic_obstack, name, len+1);
 383
 384       p->next      = half_pic_names;
 385       p->ref_name  = (char *) obstack_finish (&half_pic_obstack);
 386       p->ref_len   = len + half_pic_prefix_len;
 387       p->pointer_p = TRUE;
 388
 389       half_pic_names = p;
 390       half_pic_number_ptrs++;
 391     }
 392
 393   half_pic_number_refs++;
 394   return gen_rtx_SYMBOL_REF (Pmode, p->ref_name);
 395 }
 396
 397 #endif /* HALF_PIC_INIT */