gcc/config/arm/netbsd-elf.h

   1 /* Definitions of target machine for GNU compiler, NetBSD/arm ELF version.
   2    Copyright (C) 2002, 2003, 2004, 2005, 2007, 2009, 2011
   3    Free Software Foundation, Inc.
   4    Contributed by Wasabi Systems, Inc.
   5
   6    This file is part of GCC.
   7
   8    GCC is free software; you can redistribute it and/or modify it
   9    under the terms of the GNU General Public License as published
  10    by the Free Software Foundation; either version 3, or (at your
  11    option) any later version.
  12
  13    GCC is distributed in the hope that it will be useful, but WITHOUT
  14    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  15    or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
  16    License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with GCC; see the file COPYING3.  If not see
  20    <http://www.gnu.org/licenses/>.  */
  21
  22 /* Run-time Target Specification.  */
  23
  24 /* arm.h defaults to ARM6 CPU.  */
  25
  26 /* This defaults us to little-endian.  */
  27 #ifndef TARGET_ENDIAN_DEFAULT
  28 #define TARGET_ENDIAN_DEFAULT 0
  29 #endif
  30
  31 #undef MULTILIB_DEFAULTS
  32
  33 /* Default it to use ATPCS with soft-VFP.  */
  34 #undef TARGET_DEFAULT
  35 #define TARGET_DEFAULT                  \
  36   (MASK_APCS_FRAME                      \
  37    | TARGET_ENDIAN_DEFAULT)
  38
  39 #undef ARM_DEFAULT_ABI
  40 #define ARM_DEFAULT_ABI ARM_ABI_ATPCS
  41
  42 #define TARGET_OS_CPP_BUILTINS()        \
  43   do                                    \
  44     {                                   \
  45       NETBSD_OS_CPP_BUILTINS_ELF();     \
  46     }                                   \
  47   while (0)
  48
  49 #undef SUBTARGET_CPP_SPEC
  50 #define SUBTARGET_CPP_SPEC NETBSD_CPP_SPEC
  51
  52 #undef SUBTARGET_EXTRA_ASM_SPEC
  53 #define SUBTARGET_EXTRA_ASM_SPEC        \
  54   "-matpcs %{fpic|fpie:-k} %{fPIC|fPIE:-k}"
  55
  56 /* Default to full VFP if -mfloat-abi=hard is specified.  */
  57 #undef SUBTARGET_ASM_FLOAT_SPEC
  58 #define SUBTARGET_ASM_FLOAT_SPEC        \
  59   "%{mfloat-abi=hard:{!mfpu=*:-mfpu=vfp}}"
  60
  61 #undef SUBTARGET_EXTRA_SPECS
  62 #define SUBTARGET_EXTRA_SPECS                           \
  63   { "subtarget_extra_asm_spec", SUBTARGET_EXTRA_ASM_SPEC }, \
  64   { "subtarget_asm_float_spec", SUBTARGET_ASM_FLOAT_SPEC }, \
  65   { "netbsd_link_spec",         NETBSD_LINK_SPEC_ELF }, \
  66   { "netbsd_entry_point",       NETBSD_ENTRY_POINT },
  67
  68 #define NETBSD_ENTRY_POINT "__start"
  69
  70 #undef LINK_SPEC
  71 #define LINK_SPEC \
  72   "-X %{mbig-endian:-EB} %{mlittle-endian:-EL} \
  73    %(netbsd_link_spec)"
  74
  75 /* Make GCC agree with <machine/ansi.h>.  */
  76
  77 #undef SIZE_TYPE
  78 #define SIZE_TYPE "long unsigned int"
  79
  80 #undef PTRDIFF_TYPE
  81 #define PTRDIFF_TYPE "long int"
  82
  83 /* We don't have any limit on the length as out debugger is GDB.  */
  84 #undef DBX_CONTIN_LENGTH
  85
  86 /* NetBSD does its profiling differently to the Acorn compiler. We
  87    don't need a word following the mcount call; and to skip it
  88    requires either an assembly stub or use of fomit-frame-pointer when
  89    compiling the profiling functions.  Since we break Acorn CC
  90    compatibility below a little more won't hurt.  */
  91
  92 #undef ARM_FUNCTION_PROFILER
  93 #define ARM_FUNCTION_PROFILER(STREAM,LABELNO)           \
  94 {                                                       \
  95   asm_fprintf (STREAM, "\tmov\t%Rip, %Rlr\n");          \
  96   asm_fprintf (STREAM, "\tbl\t__mcount%s\n",            \
  97                (TARGET_ARM && NEED_PLT_RELOC)           \
  98                ? "(PLT)" : "");                         \
  99 }
 100
 101 /* VERY BIG NOTE: Change of structure alignment for NetBSD/arm.
 102    There are consequences you should be aware of...
 103
 104    Normally GCC/arm uses a structure alignment of 32 for compatibility
 105    with armcc.  This means that structures are padded to a word
 106    boundary.  However this causes problems with bugged NetBSD kernel
 107    code (possibly userland code as well - I have not checked every
 108    binary).  The nature of this bugged code is to rely on sizeof()
 109    returning the correct size of various structures rounded to the
 110    nearest byte (SCSI and ether code are two examples, the vm system
 111    is another).  This code breaks when the structure alignment is 32
 112    as sizeof() will report a word=rounded size.  By changing the
 113    structure alignment to 8. GCC will conform to what is expected by
 114    NetBSD.
 115
 116    This has several side effects that should be considered.
 117    1. Structures will only be aligned to the size of the largest member.
 118       i.e. structures containing only bytes will be byte aligned.
 119            structures containing shorts will be half word aligned.
 120            structures containing ints will be word aligned.
 121
 122       This means structures should be padded to a word boundary if
 123       alignment of 32 is required for byte structures etc.
 124
 125    2. A potential performance penalty may exist if strings are no longer
 126       word aligned.  GCC will not be able to use word load/stores to copy
 127       short strings.
 128
 129    This modification is not encouraged but with the present state of the
 130    NetBSD source tree it is currently the only solution that meets the
 131    requirements.  */
 132
 133 #undef DEFAULT_STRUCTURE_SIZE_BOUNDARY
 134 #define DEFAULT_STRUCTURE_SIZE_BOUNDARY 8
 135
 136 /* Clear the instruction cache from `BEG' to `END'.  This makes a
 137    call to the ARM_SYNC_ICACHE architecture specific syscall.  */
 138 #define CLEAR_INSN_CACHE(BEG, END)                                      \
 139 do                                                                      \
 140   {                                                                     \
 141     extern int sysarch(int number, void *args);                         \
 142     struct                                                              \
 143       {                                                                 \
 144         unsigned int addr;                                              \
 145         int          len;                                               \
 146       } s;                                                              \
 147     s.addr = (unsigned int)(BEG);                                       \
 148     s.len = (END) - (BEG);                                              \
 149     (void) sysarch (0, &s);                                             \
 150   }                                                                     \
 151 while (0)
 152
 153 #undef FPUTYPE_DEFAULT
 154 #define FPUTYPE_DEFAULT "vfp"
 155