gcc/halfpic.c

   1 /* OSF/rose half-pic support functions.
   2    Copyright (C) 1992, 1997 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 char *xmalloc ();
  44 extern rtx eliminate_constant_term ();
  45 extern void assemble_name ();
  46 extern void output_addr_const ();
  47
  48 int flag_half_pic               = 0;    /* Global half-pic flag.  */
  49 int half_pic_number_ptrs        = 0;    /* # distinct pointers found */
  50 int half_pic_number_refs        = 0;    /* # half-pic references */
  51 int (*ptr_half_pic_address_p)() = half_pic_address_p;
  52
  53 /* Obstack to hold generated pic names.  */
  54 static struct obstack half_pic_obstack;
  55
  56 /* List of pointers created to pic references.  */
  57
  58 struct all_refs {
  59   struct all_refs *hash_next;   /* next name in hash chain */
  60   struct all_refs *next;        /* next name created */
  61   int              external_p;  /* name is an external reference */
  62   int              pointer_p;   /* pointer created.  */
  63   char            *ref_name;    /* reference name to ptr to real_name */
  64   int              ref_len;     /* reference name length */
  65   char            *real_name;   /* real function/data name */
  66   int              real_len;    /* strlen (real_name) */
  67 };
  68
  69 static struct all_refs *half_pic_names;
  70
  71 static char *half_pic_prefix;
  72 static int   half_pic_prefix_len;
  73
  74 \f
  75 /* Return the hash bucket of a name or NULL.  The hash chain is
  76    organized as a self reorganizing circularly linked chain.  It is
  77    assumed that any name passed to use will never be reallocated.  For
  78    names in SYMBOL_REF's this is true, because the names are allocated
  79    on the permanent obstack.  */
  80
  81 #ifndef MAX_HASH_TABLE
  82 #define MAX_HASH_TABLE 1009
  83 #endif
  84
  85 #define HASHBITS 30
  86
  87 static struct all_refs *
  88 half_pic_hash (name, len, create_p)
  89      char *name;                /* name to hash */
  90      int len;                   /* length of the name (or 0 to call strlen) */
  91      int create_p;              /* != 0 to create new hash bucket if new */
  92 {
  93   static struct all_refs *hash_table[MAX_HASH_TABLE];
  94   static struct all_refs  zero_all_refs;
  95
  96   unsigned char *uname;
  97   int hash;
  98   int i;
  99   int ch;
 100   struct all_refs *first;
 101   struct all_refs *ptr;
 102
 103   if (len == 0)
 104     len = strlen (name);
 105
 106   /* Compute hash code */
 107   uname = (unsigned char *)name;
 108   ch = uname[0];
 109   hash = len * 613 + ch;
 110   for (i = 1; i < len; i += 2)
 111     hash = (hash * 613) + uname[i];
 112
 113   hash &= (1 << HASHBITS) - 1;
 114   hash %= MAX_HASH_TABLE;
 115
 116   /* See if the name is in the hash table.  */
 117   ptr = first = hash_table[hash];
 118   if (ptr)
 119     {
 120       do
 121         {
 122           if (len == ptr->real_len
 123               && ch == *(ptr->real_name)
 124               && !strcmp (name, ptr->real_name))
 125             {
 126               hash_table[hash] = ptr;
 127               return ptr;
 128             }
 129
 130           ptr = ptr->hash_next;
 131         }
 132       while (ptr != first);
 133     }
 134
 135   /* name not in hash table.  */
 136   if (!create_p)
 137     return (struct all_refs *) 0;
 138
 139   ptr = (struct all_refs *) obstack_alloc (&half_pic_obstack, sizeof (struct all_refs));
 140   *ptr = zero_all_refs;
 141
 142   ptr->real_name = name;
 143   ptr->real_len  = len;
 144
 145   /* Update circular links.  */
 146   if (first == (struct all_refs *) 0)
 147     ptr->hash_next = ptr;
 148
 149   else
 150     {
 151       ptr->hash_next = first->hash_next;
 152       first->hash_next = ptr;
 153     }
 154
 155   hash_table[hash] = ptr;
 156   return ptr;
 157 }
 158
 159 \f
 160 /* Do any half-pic initializations.  */
 161
 162 void
 163 half_pic_init ()
 164 {
 165   flag_half_pic = TRUE;
 166   half_pic_prefix = HALF_PIC_PREFIX;
 167   half_pic_prefix_len = strlen (half_pic_prefix);
 168   obstack_init (&half_pic_obstack);
 169 }
 170
 171 \f
 172 /* Write out all pointers to pic references.  */
 173
 174 void
 175 half_pic_finish (stream)
 176      FILE *stream;
 177 {
 178   struct all_refs *p = half_pic_names;
 179
 180   if (!p)
 181     return;
 182
 183   data_section ();
 184   for (; p != 0; p = p->next)
 185     {
 186       /* Emit the pointer if used.  */
 187       if (p->pointer_p)
 188         {
 189           ASM_OUTPUT_LABEL (stream, p->ref_name);
 190           ASM_OUTPUT_INT (stream, gen_rtx_SYMBOL_REF (Pmode, p->real_name));
 191         }
 192     }
 193 }
 194
 195 \f
 196 /* Encode in a declaration whether or not it is half-pic.  */
 197
 198 void
 199 half_pic_encode (decl)
 200      tree decl;
 201 {
 202   enum tree_code code = TREE_CODE (decl);
 203   tree asm_name;
 204   struct all_refs *ptr;
 205
 206   if (!flag_half_pic)
 207     return;
 208
 209   if (code != VAR_DECL && code != FUNCTION_DECL)
 210     return;
 211
 212   asm_name = DECL_ASSEMBLER_NAME (decl);
 213
 214   if (!asm_name)
 215     return;
 216
 217 #ifdef HALF_PIC_DEBUG
 218   if (HALF_PIC_DEBUG)
 219     {
 220       if (HALF_PIC_DEBUG)
 221         fprintf (stderr, "\n========== Half_pic_encode %.*s\n",
 222                  IDENTIFIER_LENGTH (asm_name),
 223                  IDENTIFIER_POINTER (asm_name));
 224       debug_tree (decl);
 225     }
 226 #endif
 227
 228   /* If this is not an external reference, it can't be half-pic.  */
 229   if (!DECL_EXTERNAL (decl) && (code != VAR_DECL || !TREE_PUBLIC (decl)))
 230     return;
 231
 232   ptr = half_pic_hash (IDENTIFIER_POINTER (asm_name),
 233                        IDENTIFIER_LENGTH (asm_name),
 234                        TRUE);
 235
 236   ptr->external_p = TRUE;
 237
 238 #ifdef HALF_PIC_DEBUG
 239   if (HALF_PIC_DEBUG)
 240     fprintf (stderr, "\n%.*s is half-pic\n",
 241              IDENTIFIER_LENGTH (asm_name),
 242              IDENTIFIER_POINTER (asm_name));
 243 #endif
 244 }
 245
 246 \f
 247 /* Mark that an object is now local, and no longer needs half-pic.  */
 248
 249 void
 250 half_pic_declare (name)
 251      char *name;
 252 {
 253   struct all_refs *ptr;
 254
 255   if (!flag_half_pic)
 256     return;
 257
 258   ptr = half_pic_hash (name, 0, FALSE);
 259   if (!ptr)
 260     return;
 261
 262   ptr->external_p = FALSE;
 263
 264 #ifdef HALF_PIC_DEBUG
 265   if (HALF_PIC_DEBUG)
 266     fprintf (stderr, "\n========== Half_pic_declare %s\n", name);
 267 #endif
 268 }
 269
 270 \f
 271 /* Mark that an object is explicitly external.  */
 272
 273 void
 274 half_pic_external (name)
 275      char *name;
 276 {
 277   struct all_refs *ptr;
 278
 279   if (!flag_half_pic)
 280     return;
 281
 282   ptr = half_pic_hash (name, 0, TRUE);
 283   if (!ptr)
 284     return;
 285
 286   ptr->external_p = TRUE;
 287
 288 #ifdef HALF_PIC_DEBUG
 289   if (HALF_PIC_DEBUG)
 290     fprintf (stderr, "\n========== Half_pic_external %s\n", name);
 291 #endif
 292 }
 293
 294 \f
 295 /* Return whether an address is half-pic.  */
 296
 297 int
 298 half_pic_address_p (addr)
 299      rtx addr;
 300 {
 301   char *name;
 302   int len;
 303   struct all_refs *ptr;
 304
 305   if (!flag_half_pic)
 306     return FALSE;
 307
 308   switch (GET_CODE (addr))
 309     {
 310     default:
 311       break;
 312
 313     case CONST:
 314       {
 315         rtx offset = const0_rtx;
 316         addr = eliminate_constant_term (XEXP (addr, 0), &offset);
 317         if (GET_CODE (addr) != SYMBOL_REF)
 318           return FALSE;
 319       }
 320       /* fall through */
 321
 322     case SYMBOL_REF:
 323       name = XSTR (addr, 0);
 324
 325 #ifdef HALF_PIC_DEBUG
 326       if (HALF_PIC_DEBUG)
 327         fprintf (stderr, "\n========== Half_pic_address_p %s\n", name);
 328 #endif
 329
 330       /* If this is a label, it will have a '*' in front of it.  */
 331       if (name[0] == '*')
 332         return FALSE;
 333
 334       /* If this is a reference to the actual half-pic pointer, it
 335          is obviously not half-pic.  */
 336
 337       len = strlen (name);
 338       if (len > half_pic_prefix_len
 339           && half_pic_prefix[0] == name[0]
 340           && !strncmp (name, half_pic_prefix, half_pic_prefix_len))
 341         return FALSE;
 342
 343       ptr = half_pic_hash (name, len, FALSE);
 344       if (ptr == (struct all_refs *) 0)
 345         return FALSE;
 346
 347       if (ptr->external_p)
 348         {
 349 #ifdef HALF_PIC_DEBUG
 350           if (HALF_PIC_DEBUG)
 351             fprintf (stderr, "%s is half-pic\n", name);
 352 #endif
 353           return TRUE;
 354         }
 355     }
 356
 357   return FALSE;
 358 }
 359
 360 \f
 361 /* Return the name of the pointer to the PIC function, allocating
 362    it if need be.  */
 363
 364 struct rtx_def *
 365 half_pic_ptr (operand)
 366      rtx operand;
 367 {
 368   char *name;
 369   struct all_refs *p;
 370   int len;
 371
 372   if (GET_CODE (operand) != SYMBOL_REF)
 373     return operand;
 374
 375   name = XSTR (operand, 0);
 376   len = strlen (name);
 377   p = half_pic_hash (name, len, FALSE);
 378   if (p == (struct all_refs *) 0 || !p->external_p)
 379     return operand;
 380
 381   if (!p->pointer_p)
 382     {                           /* first time, create pointer */
 383       obstack_grow (&half_pic_obstack, half_pic_prefix, half_pic_prefix_len);
 384       obstack_grow (&half_pic_obstack, name, len+1);
 385
 386       p->next      = half_pic_names;
 387       p->ref_name  = (char *) obstack_finish (&half_pic_obstack);
 388       p->ref_len   = len + half_pic_prefix_len;
 389       p->pointer_p = TRUE;
 390
 391       half_pic_names = p;
 392       half_pic_number_ptrs++;
 393     }
 394
 395   half_pic_number_refs++;
 396   return gen_rtx_SYMBOL_REF (Pmode, p->ref_name);
 397 }
 398
 399 #endif /* HALF_PIC_INIT */