gcc/config/i386/sysv4.h

   1 /* Target definitions for GNU compiler for Intel 80386 running System V.4
   2    Copyright (C) 1991 Free Software Foundation, Inc.
   3
   4    Written by Ron Guilmette (rfg@ncd.com).
   5
   6 This file is part of GNU CC.
   7
   8 GNU CC is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation; either version 2, or (at your option)
  11 any later version.
  12
  13 GNU CC is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GNU CC; see the file COPYING.  If not, write to
  20 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  21
  22 #include "i386/i386.h"  /* Base i386 target machine definitions */
  23 #include "i386/att.h"   /* Use the i386 AT&T assembler syntax */
  24 #include "svr4.h"       /* Definitions common to all SVR4 targets */
  25
  26 #undef TARGET_VERSION
  27 #define TARGET_VERSION fprintf (stderr, " (i386 System V Release 4)");
  28
  29 /* The svr4 ABI for the i386 says that records and unions are returned
  30    in memory.  */
  31
  32 #undef RETURN_IN_MEMORY
  33 #define RETURN_IN_MEMORY(TYPE) \
  34   (TYPE_MODE (TYPE) == BLKmode)
  35
  36 /* Define which macros to predefine.  __svr4__ is our extension.  */
  37 /* This used to define X86, but james@bigtex.cactus.org says that
  38    is supposed to be defined optionally by user programs--not by default.  */
  39 #define CPP_PREDEFINES \
  40   "-Di386 -Dunix -D__svr4__ -Asystem(unix) -Acpu(i386) -Amachine(i386)"
  41
  42 /* If the host and target formats match, output the floats as hex.  */
  43 #if HOST_FLOAT_FORMAT == TARGET_FLOAT_FORMAT
  44 #if defined (HOST_WORDS_BIG_ENDIAN) == WORDS_BIG_ENDIAN
  45 /* This is how to output assembly code to define a `float' constant.
  46    We always have to use a .long pseudo-op to do this because the native
  47    SVR4 ELF assembler is buggy and it generates incorrect values when we
  48    try to use the .float pseudo-op instead.  */
  49
  50 #undef ASM_OUTPUT_FLOAT
  51 #define ASM_OUTPUT_FLOAT(FILE,VALUE)                                    \
  52 do { long value;                                                        \
  53      REAL_VALUE_TO_TARGET_SINGLE ((VALUE), value);                      \
  54      fprintf((FILE), "%s\t0x%x\n", ASM_LONG, value);                    \
  55    } while (0)
  56
  57 /* This is how to output assembly code to define a `double' constant.
  58    We always have to use a pair of .long pseudo-ops to do this because
  59    the native SVR4 ELF assembler is buggy and it generates incorrect
  60    values when we try to use the the .double pseudo-op instead.  */
  61
  62 #undef ASM_OUTPUT_DOUBLE
  63 #define ASM_OUTPUT_DOUBLE(FILE,VALUE)                                   \
  64 do { long value[2];                                                     \
  65      REAL_VALUE_TO_TARGET_DOUBLE ((VALUE), value);                      \
  66      fprintf((FILE), "%s\t0x%x\n", ASM_LONG, value[0]);                 \
  67      fprintf((FILE), "%s\t0x%x\n", ASM_LONG, value[1]);                 \
  68    } while (0)
  69 #endif /* word order matches */
  70 #endif /* HOST_FLOAT_FORMAT == TARGET_FLOAT_FORMAT */
  71
  72 /* Output at beginning of assembler file.  */
  73 /* The .file command should always begin the output.  */
  74
  75 #undef ASM_FILE_START
  76 #define ASM_FILE_START(FILE)                                            \
  77   do {                                                                  \
  78         output_file_directive (FILE, main_input_filename);              \
  79         fprintf (FILE, "\t.version\t\"01.01\"\n");                      \
  80   } while (0)
  81
  82 /* Define the register numbers to be used in Dwarf debugging information.
  83    The SVR4 reference port C compiler uses the following register numbers
  84    in its Dwarf output code:
  85
  86         0 for %eax (gnu regno = 0)
  87         1 for %ecx (gnu regno = 2)
  88         2 for %edx (gnu regno = 1)
  89         3 for %ebx (gnu regno = 3)
  90         4 for %esp (gnu regno = 7)
  91         5 for %ebp (gnu regno = 6)
  92         6 for %esi (gnu regno = 4)
  93         7 for %edi (gnu regno = 5)
  94
  95    The following three DWARF register numbers are never generated by
  96    the SVR4 C compiler or by the GNU compilers, but SDB on x86/svr4
  97    believes these numbers have these meanings.
  98
  99         8  for %eip    (no gnu equivalent)
 100         9  for %eflags (no gnu equivalent)
 101         10 for %trapno (no gnu equivalent)
 102
 103    It is not at all clear how we should number the FP stack registers
 104    for the x86 architecture.  If the version of SDB on x86/svr4 were
 105    a bit less brain dead with respect to floating-point then we would
 106    have a precedent to follow with respect to DWARF register numbers
 107    for x86 FP registers, but the SDB on x86/svr4 is so completely
 108    broken with respect to FP registers that it is hardly worth thinking
 109    of it as something to strive for compatibility with.
 110
 111    The verison of x86/svr4 SDB I have at the moment does (partially)
 112    seem to believe that DWARF register number 11 is associated with
 113    the x86 register %st(0), but that's about all.  Higher DWARF
 114    register numbers don't seem to be associated with anything in
 115    particular, and even for DWARF regno 11, SDB only seems to under-
 116    stand that it should say that a variable lives in %st(0) (when
 117    asked via an `=' command) if we said it was in DWARF regno 11,
 118    but SDB still prints garbage when asked for the value of the
 119    variable in question (via a `/' command).
 120
 121    (Also note that the labels SDB prints for various FP stack regs
 122    when doing an `x' command are all wrong.)
 123
 124    Note that these problems generally don't affect the native SVR4
 125    C compiler because it doesn't allow the use of -O with -g and
 126    because when it is *not* optimizing, it allocates a memory
 127    location for each floating-point variable, and the memory
 128    location is what gets described in the DWARF AT_location
 129    attribute for the variable in question.
 130
 131    Regardless of the severe mental illness of the x86/svr4 SDB, we
 132    do something sensible here and we use the following DWARF
 133    register numbers.  Note that these are all stack-top-relative
 134    numbers.
 135
 136         11 for %st(0) (gnu regno = 8)
 137         12 for %st(1) (gnu regno = 9)
 138         13 for %st(2) (gnu regno = 10)
 139         14 for %st(3) (gnu regno = 11)
 140         15 for %st(4) (gnu regno = 12)
 141         16 for %st(5) (gnu regno = 13)
 142         17 for %st(6) (gnu regno = 14)
 143         18 for %st(7) (gnu regno = 15)
 144 */
 145
 146 #undef DBX_REGISTER_NUMBER
 147 #define DBX_REGISTER_NUMBER(n) \
 148 ((n) == 0 ? 0 \
 149  : (n) == 1 ? 2 \
 150  : (n) == 2 ? 1 \
 151  : (n) == 3 ? 3 \
 152  : (n) == 4 ? 6 \
 153  : (n) == 5 ? 7 \
 154  : (n) == 6 ? 5 \
 155  : (n) == 7 ? 4 \
 156  : ((n) >= FIRST_STACK_REG && (n) <= LAST_STACK_REG) ? (n)+3 \
 157  : (-1))
 158
 159 /* The routine used to output sequences of byte values.  We use a special
 160    version of this for most svr4 targets because doing so makes the
 161    generated assembly code more compact (and thus faster to assemble)
 162    as well as more readable.  Note that if we find subparts of the
 163    character sequence which end with NUL (and which are shorter than
 164    STRING_LIMIT) we output those using ASM_OUTPUT_LIMITED_STRING.  */
 165
 166 #undef ASM_OUTPUT_ASCII
 167 #define ASM_OUTPUT_ASCII(FILE, STR, LENGTH)                             \
 168   do                                                                    \
 169     {                                                                   \
 170       register unsigned char *_ascii_bytes = (unsigned char *) (STR);   \
 171       register unsigned char *limit = _ascii_bytes + (LENGTH);          \
 172       register unsigned bytes_in_chunk = 0;                             \
 173       for (; _ascii_bytes < limit; _ascii_bytes++)                      \
 174         {                                                               \
 175           register unsigned char *p;                                    \
 176           if (bytes_in_chunk >= 64)                                     \
 177             {                                                           \
 178               fputc ('\n', (FILE));                                     \
 179               bytes_in_chunk = 0;                                       \
 180             }                                                           \
 181           for (p = _ascii_bytes; p < limit && *p != '\0'; p++)          \
 182             continue;                                                   \
 183           if (p < limit && (p - _ascii_bytes) <= STRING_LIMIT)          \
 184             {                                                           \
 185               if (bytes_in_chunk > 0)                                   \
 186                 {                                                       \
 187                   fputc ('\n', (FILE));                                 \
 188                   bytes_in_chunk = 0;                                   \
 189                 }                                                       \
 190               ASM_OUTPUT_LIMITED_STRING ((FILE), _ascii_bytes);         \
 191               _ascii_bytes = p;                                         \
 192             }                                                           \
 193           else                                                          \
 194             {                                                           \
 195               if (bytes_in_chunk == 0)                                  \
 196                 fprintf ((FILE), "\t.byte\t");                          \
 197               else                                                      \
 198                 fputc (',', (FILE));                                    \
 199               fprintf ((FILE), "0x%02x", *_ascii_bytes);                \
 200               bytes_in_chunk += 5;                                      \
 201             }                                                           \
 202         }                                                               \
 203       if (bytes_in_chunk > 0)                                           \
 204         fprintf ((FILE), "\n");                                         \
 205     }                                                                   \
 206   while (0)
 207
 208 /* This is how to output an element of a case-vector that is relative.
 209    This is only used for PIC code.  See comments by the `casesi' insn in
 210    i386.md for an explanation of the expression this outputs. */
 211
 212 #undef ASM_OUTPUT_ADDR_DIFF_ELT
 213 #define ASM_OUTPUT_ADDR_DIFF_ELT(FILE, VALUE, REL) \
 214   fprintf (FILE, "\t.long _GLOBAL_OFFSET_TABLE_+[.-%s%d]\n", LPREFIX, VALUE)
 215
 216 /* Indicate that jump tables go in the text section.  This is
 217    necessary when compiling PIC code.  */
 218
 219 #define JUMP_TABLES_IN_TEXT_SECTION
 220
 221 /* Biggest alignment that any structure field can require on this
 222    machine, in bits.  If packing is in effect, this can be smaller than
 223    normal.  */
 224
 225 #define BIGGEST_FIELD_ALIGNMENT \
 226   (maximum_field_alignment ? maximum_field_alignment : 32)
 227
 228 extern int maximum_field_alignment;
 229
 230 /* If bit field type is int, don't let it cross an int,
 231    and give entire struct the alignment of an int.  */
 232 /* Required on the 386 since it doesn't have bitfield insns.  */
 233 /* If packing is in effect, then the type doesn't matter.  */
 234
 235 #undef PCC_BITFIELD_TYPE_MATTERS
 236 #define PCC_BITFIELD_TYPE_MATTERS (maximum_field_alignment == 0)
 237
 238 /* Handle #pragma pack and sometimes #pragma weak.  */
 239 #define HANDLE_SYSV_PRAGMA