gcc/halfpic.c

   1 /* OSF/rose half-pic support functions.
   2    Copyright (C) 1992 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, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  19
  20 /* The OSF/rose half-pic model assumes that the non-library code does
  21    not need to have full PIC (position independent code), but rather,
  22    that pointers to external references are put into the data section
  23    and dereferenced as normal pointers.  References to static data does
  24    not need to be PIC-ized.
  25
  26    Another optimization is to have the compiler know what symbols are
  27    in the shared libraries, and to only lay down the pointers to
  28    things which in the library proper.  */
  29
  30 #include "config.h"
  31
  32 #ifdef HALF_PIC_INIT
  33
  34 #include "tree.h"
  35 #include "rtl.h"
  36 #include <stdio.h>
  37 #include "obstack.h"
  38
  39 #define obstack_chunk_alloc xmalloc
  40 #define obstack_chunk_free free
  41
  42 extern char *xmalloc ();
  43 extern void  free ();
  44 extern rtx eliminate_constant_term ();
  45 extern void assemble_name ();
  46 extern void output_addr_const ();
  47
  48 int flag_half_pic;              /* Global half-pic flag.  */
  49 int half_pic_number_ptrs;       /* # distinct pointers found */
  50 int half_pic_number_refs;       /* # half-pic references */
  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       if (HALF_PIC_DEBUG)
 220         fprintf (stderr, "\n========== Half_pic_encode %.*s\n",
 221                  IDENTIFIER_LENGTH (asm_name),
 222                  IDENTIFIER_POINTER (asm_name));
 223       debug_tree (decl);
 224     }
 225 #endif
 226
 227   /* If this is not an external reference, it can't be half-pic.  */
 228   if (!TREE_EXTERNAL (decl) && (code != VAR_DECL || !TREE_PUBLIC (decl)))
 229     return;
 230
 231   ptr = half_pic_hash (IDENTIFIER_POINTER (asm_name),
 232                        IDENTIFIER_LENGTH (asm_name),
 233                        TRUE);
 234
 235   ptr->external_p = TRUE;
 236
 237 #ifdef HALF_PIC_DEBUG
 238   if (HALF_PIC_DEBUG)
 239     fprintf (stderr, "\n%.*s is half-pic\n",
 240              IDENTIFIER_LENGTH (asm_name),
 241              IDENTIFIER_POINTER (asm_name));
 242 #endif
 243 }
 244
 245 \f
 246 /* Mark that an object is now local, and no longer needs half-pic.  */
 247
 248 void
 249 half_pic_declare (name)
 250      char *name;
 251 {
 252   struct all_refs *ptr;
 253
 254   if (!flag_half_pic)
 255     return;
 256
 257   ptr = half_pic_hash (name, 0, FALSE);
 258   if (!ptr)
 259     return;
 260
 261   ptr->external_p = FALSE;
 262
 263 #ifdef HALF_PIC_DEBUG
 264   if (HALF_PIC_DEBUG)
 265     fprintf (stderr, "\n========== Half_pic_declare %s\n", name);
 266 #endif
 267 }
 268
 269 \f
 270 /* Return whether an address is half-pic.  */
 271
 272 int
 273 half_pic_address_p (addr)
 274      rtx addr;
 275 {
 276   char *name;
 277   int len;
 278   struct all_refs *ptr;
 279
 280   if (!flag_half_pic)
 281     return FALSE;
 282
 283   switch (GET_CODE (addr))
 284     {
 285     default:
 286       break;
 287
 288     case CONST:
 289       {
 290         rtx offset = const0_rtx;
 291         addr = eliminate_constant_term (XEXP (addr, 0), &offset);
 292         if (GET_CODE (addr) != SYMBOL_REF)
 293           return FALSE;
 294       }
 295       /* fall through */
 296
 297     case SYMBOL_REF:
 298       name = XSTR (addr, 0);
 299
 300 #ifdef HALF_PIC_DEBUG
 301       if (HALF_PIC_DEBUG)
 302         fprintf (stderr, "\n========== Half_pic_address_p %s\n", name);
 303 #endif
 304
 305       /* If this is a label, it will have a '*' in front of it.  */
 306       if (name[0] == '*')
 307         return FALSE;
 308
 309       /* If this is a reference to the actual half-pic pointer, it
 310          is obviously not half-pic.  */
 311
 312       len = strlen (name);
 313       if (len > half_pic_prefix_len
 314           && half_pic_prefix[0] == name[0]
 315           && !strncmp (name, half_pic_prefix, half_pic_prefix_len))
 316         return FALSE;
 317
 318       ptr = half_pic_hash (name, len, FALSE);
 319       if (ptr == (struct all_refs *)0)
 320         return FALSE;
 321
 322       if (ptr->external_p)
 323         {
 324 #ifdef HALF_PIC_DEBUG
 325           if (HALF_PIC_DEBUG)
 326             fprintf (stderr, "%s is half-pic\n", name);
 327 #endif
 328           return TRUE;
 329         }
 330     }
 331
 332   return FALSE;
 333 }
 334
 335 \f
 336 /* Return the name of the pointer to the PIC function, allocating
 337    it if need be.  */
 338
 339 struct rtx_def *
 340 half_pic_ptr (operand)
 341      rtx operand;
 342 {
 343   char *name;
 344   struct all_refs *p;
 345   int len;
 346
 347   if (GET_CODE (operand) != SYMBOL_REF)
 348     return operand;
 349
 350   name = XSTR (operand, 0);
 351   len = strlen (name);
 352   p = half_pic_hash (name, len, FALSE);
 353   if (p == (struct all_refs *)0 || !p->external_p)
 354     return operand;
 355
 356   if (!p->pointer_p)
 357     {                           /* first time, create pointer */
 358       obstack_grow (&half_pic_obstack, half_pic_prefix, half_pic_prefix_len);
 359       obstack_grow (&half_pic_obstack, name, len+1);
 360
 361       p->next      = half_pic_names;
 362       p->ref_name  = (char *) obstack_finish (&half_pic_obstack);
 363       p->ref_len   = len + half_pic_prefix_len;
 364       p->pointer_p = TRUE;
 365
 366       half_pic_names = p;
 367       half_pic_number_ptrs++;
 368     }
 369
 370   half_pic_number_refs++;
 371   return gen_rtx (SYMBOL_REF, Pmode, p->ref_name);
 372 }
 373
 374 #endif /* HALF_PIC_INIT */