netbsd-elf.h revision 117395 
1/* Definitions of target machine for GNU compiler, NetBSD/arm ELF version.
2   Copyright (C) 2002 Free Software Foundation, Inc.
3   Contributed by Wasabi Systems, Inc.
4
5This file is part of GNU CC.
6
7GNU CC is free software; you can redistribute it and/or modify
8it under the terms of the GNU General Public License as published by
9the Free Software Foundation; either version 2, or (at your option)
10any later version.
11
12GNU CC is distributed in the hope that it will be useful,
13but WITHOUT ANY WARRANTY; without even the implied warranty of
14MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15GNU General Public License for more details.
16
17You should have received a copy of the GNU General Public License
18along with GNU CC; see the file COPYING.  If not, write to
19the Free Software Foundation, 59 Temple Place - Suite 330,
20Boston, MA 02111-1307, USA.  */
21
22/* Run-time Target Specification.  */
23#undef TARGET_VERSION
24#define TARGET_VERSION fputs (" (NetBSD/arm ELF)", stderr);
25
26/* This is used in ASM_FILE_START.  */
27#undef ARM_OS_NAME
28#define ARM_OS_NAME "NetBSD"
29
30/* arm.h defaults to ARM6 CPU.  */
31
32/* This defaults us to little-endian.  */
33#ifndef TARGET_ENDIAN_DEFAULT
34#define TARGET_ENDIAN_DEFAULT 0
35#endif
36
37#undef MULTILIB_DEFAULTS
38
39/* Default it to use ATPCS with soft-VFP.  */
40#undef TARGET_DEFAULT
41#define TARGET_DEFAULT			\
42  (ARM_FLAG_APCS_32			\
43   | ARM_FLAG_SOFT_FLOAT		\
44   | ARM_FLAG_APCS_FRAME		\
45   | ARM_FLAG_ATPCS			\
46   | ARM_FLAG_VFP			\
47   | ARM_FLAG_MMU_TRAPS			\
48   | TARGET_ENDIAN_DEFAULT)
49
50#define TARGET_OS_CPP_BUILTINS()	\
51  do					\
52    {					\
53      NETBSD_OS_CPP_BUILTINS_ELF();	\
54    }					\
55  while (0)
56
57#undef SUBTARGET_CPP_SPEC
58#define SUBTARGET_CPP_SPEC NETBSD_CPP_SPEC
59
60#undef SUBTARGET_EXTRA_ASM_SPEC
61#define SUBTARGET_EXTRA_ASM_SPEC	\
62  "-matpcs %{fpic:-k} %{fPIC:-k}"
63
64/* Default floating point model is soft-VFP.
65   FIXME: -mhard-float currently implies FPA.  */
66#undef SUBTARGET_ASM_FLOAT_SPEC
67#define SUBTARGET_ASM_FLOAT_SPEC	\
68  "%{mhard-float:-mfpu=fpa} \
69   %{msoft-float:-mfpu=softvfp} \
70   %{!mhard-float: \
71     %{!msoft-float:-mfpu=softvfp}}"
72
73#undef SUBTARGET_EXTRA_SPECS
74#define SUBTARGET_EXTRA_SPECS				\
75  { "subtarget_extra_asm_spec",	SUBTARGET_EXTRA_ASM_SPEC }, \
76  { "subtarget_asm_float_spec", SUBTARGET_ASM_FLOAT_SPEC }, \
77  { "netbsd_link_spec",		NETBSD_LINK_SPEC_ELF },	\
78  { "netbsd_entry_point",	NETBSD_ENTRY_POINT },
79
80#define NETBSD_ENTRY_POINT "__start"
81
82#undef LINK_SPEC
83#define LINK_SPEC \
84  "-X %{mbig-endian:-EB} %{mlittle-endian:-EL} \
85   %(netbsd_link_spec)"
86
87/* Make GCC agree with <machine/ansi.h>.  */
88
89#undef SIZE_TYPE
90#define SIZE_TYPE "long unsigned int"
91
92#undef PTRDIFF_TYPE
93#define PTRDIFF_TYPE "long int"
94
95/* We don't have any limit on the length as out debugger is GDB.  */
96#undef DBX_CONTIN_LENGTH
97
98/* NetBSD does its profiling differently to the Acorn compiler. We
99   don't need a word following the mcount call; and to skip it
100   requires either an assembly stub or use of fomit-frame-pointer when
101   compiling the profiling functions.  Since we break Acorn CC
102   compatibility below a little more won't hurt.  */
103
104#undef ARM_FUNCTION_PROFILER
105#define ARM_FUNCTION_PROFILER(STREAM,LABELNO)		\
106{							\
107  asm_fprintf (STREAM, "\tmov\t%Rip, %Rlr\n");		\
108  asm_fprintf (STREAM, "\tbl\t__mcount%s\n",		\
109	       NEED_PLT_RELOC ? "(PLT)" : "");		\
110}
111
112/* VERY BIG NOTE: Change of structure alignment for NetBSD/arm.
113   There are consequences you should be aware of...
114
115   Normally GCC/arm uses a structure alignment of 32 for compatibility
116   with armcc.  This means that structures are padded to a word
117   boundary.  However this causes problems with bugged NetBSD kernel
118   code (possibly userland code as well - I have not checked every
119   binary).  The nature of this bugged code is to rely on sizeof()
120   returning the correct size of various structures rounded to the
121   nearest byte (SCSI and ether code are two examples, the vm system
122   is another).  This code breaks when the structure alignment is 32
123   as sizeof() will report a word=rounded size.  By changing the
124   structure alignment to 8. GCC will conform to what is expected by
125   NetBSD.
126
127   This has several side effects that should be considered.
128   1. Structures will only be aligned to the size of the largest member.
129      i.e. structures containing only bytes will be byte aligned.
130           structures containing shorts will be half word alinged.
131           structures containing ints will be word aligned.
132
133      This means structures should be padded to a word boundary if
134      alignment of 32 is required for byte structures etc.
135
136   2. A potential performance penalty may exist if strings are no longer
137      word aligned.  GCC will not be able to use word load/stores to copy
138      short strings.
139
140   This modification is not encouraged but with the present state of the
141   NetBSD source tree it is currently the only solution that meets the
142   requirements.  */
143
144#undef DEFAULT_STRUCTURE_SIZE_BOUNDARY
145#define DEFAULT_STRUCTURE_SIZE_BOUNDARY 8
146
147/* Emit code to set up a trampoline and synchronize the caches.  */
148#undef INITIALIZE_TRAMPOLINE
149#define INITIALIZE_TRAMPOLINE(TRAMP, FNADDR, CXT)			\
150do									\
151  {									\
152    emit_move_insn (gen_rtx (MEM, SImode, plus_constant ((TRAMP), 8)),	\
153		    (CXT));						\
154    emit_move_insn (gen_rtx (MEM, SImode, plus_constant ((TRAMP), 12)),	\
155		    (FNADDR));						\
156    emit_library_call (gen_rtx_SYMBOL_REF (Pmode, "__clear_cache"),	\
157		       0, VOIDmode, 2, TRAMP, Pmode,			\
158		       plus_constant (TRAMP, TRAMPOLINE_SIZE), Pmode);	\
159  }									\
160while (0)
161
162/* Clear the instruction cache from `BEG' to `END'.  This makes a
163   call to the ARM_SYNC_ICACHE architecture specific syscall.  */
164#define CLEAR_INSN_CACHE(BEG, END)					\
165do									\
166  {									\
167    extern int sysarch(int number, void *args);				\
168    struct								\
169      {									\
170	unsigned int addr;						\
171	int          len;						\
172      } s;								\
173    s.addr = (unsigned int)(BEG);					\
174    s.len = (END) - (BEG);						\
175    (void) sysarch (0, &s);						\
176  }									\
177while (0)
178