1 /* frags.c - manage frags -
2 Copyright (C) 1987-2019 Free Software Foundation, Inc.
4 This file is part of GAS, the GNU Assembler.
6 GAS 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 3, or (at your option)
11 GAS 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.
16 You should have received a copy of the GNU General Public License
17 along with GAS; see the file COPYING. If not, write to the Free
18 Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
25 extern fragS zero_address_frag;
26 extern fragS predefined_address_frag;
28 static int totalfrags;
37 clear_frag_count (void)
42 /* Initialization for frag routines. */
47 zero_address_frag.fr_type = rs_fill;
48 predefined_address_frag.fr_type = rs_fill;
51 /* Check that we're not trying to assemble into a section that can't
52 allocate frags (currently, this is only possible in the absolute
53 section), or into an mri common. */
56 frag_alloc_check (const struct obstack *ob)
58 if (ob->chunk_size == 0)
60 as_bad (_("attempt to allocate data in absolute section"));
61 subseg_set (text_section, 0);
64 if (mri_common_symbol != NULL)
66 as_bad (_("attempt to allocate data in common section"));
67 mri_common_symbol = NULL;
71 /* Allocate a frag on the specified obstack.
72 Call this routine from everywhere else, so that all the weird alignment
73 hackery can be done in just one place. */
76 frag_alloc (struct obstack *ob)
81 (void) obstack_alloc (ob, 0);
82 oalign = obstack_alignment_mask (ob);
83 obstack_alignment_mask (ob) = 0;
84 ptr = (fragS *) obstack_alloc (ob, SIZEOF_STRUCT_FRAG);
85 obstack_alignment_mask (ob) = oalign;
86 memset (ptr, 0, SIZEOF_STRUCT_FRAG);
91 /* Try to augment current frag by nchars chars.
92 If there is no room, close of the current frag with a ".fill 0"
93 and begin a new frag. Unless the new frag has nchars chars available
94 do not return. Do not set up any fields of *now_frag. */
97 frag_grow (size_t nchars)
99 if (obstack_room (&frchain_now->frch_obstack) < nchars)
104 /* Try to allocate a bit more than needed right now. But don't do
105 this if we would waste too much memory. Especially necessary
106 for extremely big (like 2GB initialized) frags. */
107 if (nchars < 0x10000)
110 newc = nchars + 0x10000;
111 newc += SIZEOF_STRUCT_FRAG;
113 /* Check for possible overflow. */
115 as_fatal (ngettext ("can't extend frag %lu char",
116 "can't extend frag %lu chars",
117 (unsigned long) nchars),
118 (unsigned long) nchars);
120 /* Force to allocate at least NEWC bytes, but not less than the
122 oldc = obstack_chunk_size (&frchain_now->frch_obstack);
124 obstack_chunk_size (&frchain_now->frch_obstack) = newc;
126 while (obstack_room (&frchain_now->frch_obstack) < nchars)
128 /* Not enough room in this frag. Close it and start a new one.
129 This must be done in a loop because the created frag may not
130 be big enough if the current obstack chunk is used. */
131 frag_wane (frag_now);
135 /* Restore the old chunk size. */
136 obstack_chunk_size (&frchain_now->frch_obstack) = oldc;
140 /* Call this to close off a completed frag, and start up a new (empty)
141 frag, in the same subsegment as the old frag.
142 [frchain_now remains the same but frag_now is updated.]
143 Because this calculates the correct value of fr_fix by
144 looking at the obstack 'frags', it needs to know how many
145 characters at the end of the old frag belong to the maximal
146 variable part; The rest must belong to fr_fix.
147 It doesn't actually set up the old frag's fr_var. You may have
148 set fr_var == 1, but allocated 10 chars to the end of the frag;
149 In this case you pass old_frags_var_max_size == 10.
150 In fact, you may use fr_var for something totally unrelated to the
151 size of the variable part of the frag; None of the generic frag
152 handling code makes use of fr_var.
154 Make a new frag, initialising some components. Link new frag at end
158 frag_new (size_t old_frags_var_max_size
159 /* Number of chars (already allocated on obstack frags) in
160 variable_length part of frag. */)
162 fragS *former_last_fragP;
165 gas_assert (frchain_now->frch_last == frag_now);
167 /* Fix up old frag's fr_fix. */
168 frag_now->fr_fix = frag_now_fix_octets ();
169 gas_assert (frag_now->fr_fix >= old_frags_var_max_size);
170 frag_now->fr_fix -= old_frags_var_max_size;
171 /* Make sure its type is valid. */
172 gas_assert (frag_now->fr_type != 0);
174 /* This will align the obstack so the next struct we allocate on it
175 will begin at a correct boundary. */
176 obstack_finish (&frchain_now->frch_obstack);
179 former_last_fragP = frchP->frch_last;
180 gas_assert (former_last_fragP != 0);
181 gas_assert (former_last_fragP == frag_now);
182 frag_now = frag_alloc (&frchP->frch_obstack);
184 frag_now->fr_file = as_where (&frag_now->fr_line);
186 /* Generally, frag_now->points to an address rounded up to next
187 alignment. However, characters will add to obstack frags
188 IMMEDIATELY after the struct frag, even if they are not starting
189 at an alignment address. */
190 former_last_fragP->fr_next = frag_now;
191 frchP->frch_last = frag_now;
195 extern struct list_info_struct *listing_tail;
196 frag_now->line = listing_tail;
200 gas_assert (frchain_now->frch_last == frag_now);
202 frag_now->fr_next = NULL;
205 /* Start a new frag unless we have n more chars of room in the current frag.
206 Close off the old frag with a .fill 0.
208 Return the address of the 1st char to write into. Advance
209 frag_now_growth past the new chars. */
212 frag_more (size_t nchars)
216 frag_alloc_check (&frchain_now->frch_obstack);
218 retval = obstack_next_free (&frchain_now->frch_obstack);
219 obstack_blank_fast (&frchain_now->frch_obstack, nchars);
223 /* Close the current frag, setting its fields for a relaxable frag. Start a
227 frag_var_init (relax_stateT type, size_t max_chars, size_t var,
228 relax_substateT subtype, symbolS *symbol, offsetT offset,
231 frag_now->fr_var = var;
232 frag_now->fr_type = type;
233 frag_now->fr_subtype = subtype;
234 frag_now->fr_symbol = symbol;
235 frag_now->fr_offset = offset;
236 frag_now->fr_opcode = opcode;
238 frag_now->fr_cgen.insn = 0;
239 frag_now->fr_cgen.opindex = 0;
240 frag_now->fr_cgen.opinfo = 0;
243 TC_FRAG_INIT (frag_now, max_chars);
245 frag_now->fr_file = as_where (&frag_now->fr_line);
247 frag_new (max_chars);
250 /* Start a new frag unless we have max_chars more chars of room in the
251 current frag. Close off the old frag with a .fill 0.
253 Set up a machine_dependent relaxable frag, then start a new frag.
254 Return the address of the 1st char of the var part of the old frag
258 frag_var (relax_stateT type, size_t max_chars, size_t var,
259 relax_substateT subtype, symbolS *symbol, offsetT offset,
264 frag_grow (max_chars);
265 retval = obstack_next_free (&frchain_now->frch_obstack);
266 obstack_blank_fast (&frchain_now->frch_obstack, max_chars);
267 frag_var_init (type, max_chars, var, subtype, symbol, offset, opcode);
271 /* OVE: This variant of frag_var assumes that space for the tail has been
273 No call to frag_grow is done. */
276 frag_variant (relax_stateT type, size_t max_chars, size_t var,
277 relax_substateT subtype, symbolS *symbol, offsetT offset,
282 retval = obstack_next_free (&frchain_now->frch_obstack);
283 frag_var_init (type, max_chars, var, subtype, symbol, offset, opcode);
288 /* Reduce the variable end of a frag to a harmless state. */
291 frag_wane (fragS *fragP)
293 fragP->fr_type = rs_fill;
294 fragP->fr_offset = 0;
298 /* Return the number of bytes by which the current frag can be grown. */
303 return obstack_room (&frchain_now->frch_obstack);
306 /* Make an alignment frag. The size of this frag will be adjusted to
307 force the next frag to have the appropriate alignment. ALIGNMENT
308 is the power of two to which to align. FILL_CHARACTER is the
309 character to use to fill in any bytes which are skipped. MAX is
310 the maximum number of characters to skip when doing the alignment,
311 or 0 if there is no maximum. */
314 frag_align (int alignment, int fill_character, int max)
316 if (now_seg == absolute_section)
321 mask = (~(addressT) 0) << alignment;
322 new_off = (abs_section_offset + ~mask) & mask;
323 if (max == 0 || new_off - abs_section_offset <= (addressT) max)
324 abs_section_offset = new_off;
330 p = frag_var (rs_align, 1, 1, (relax_substateT) max,
331 (symbolS *) 0, (offsetT) alignment, (char *) 0);
336 /* Make an alignment frag like frag_align, but fill with a repeating
337 pattern rather than a single byte. ALIGNMENT is the power of two
338 to which to align. FILL_PATTERN is the fill pattern to repeat in
339 the bytes which are skipped. N_FILL is the number of bytes in
340 FILL_PATTERN. MAX is the maximum number of characters to skip when
341 doing the alignment, or 0 if there is no maximum. */
344 frag_align_pattern (int alignment, const char *fill_pattern,
345 size_t n_fill, int max)
349 p = frag_var (rs_align, n_fill, n_fill, (relax_substateT) max,
350 (symbolS *) 0, (offsetT) alignment, (char *) 0);
351 memcpy (p, fill_pattern, n_fill);
354 /* The NOP_OPCODE is for the alignment fill value. Fill it with a nop
355 instruction so that the disassembler does not choke on it. */
357 #define NOP_OPCODE 0x00
360 /* Use this to restrict the amount of memory allocated for representing
361 the alignment code. Needs to be large enough to hold any fixed sized
362 prologue plus the replicating portion. */
363 #ifndef MAX_MEM_FOR_RS_ALIGN_CODE
364 /* Assume that if HANDLE_ALIGN is not defined then no special action
365 is required to code fill, which means that we get just repeat the
366 one NOP_OPCODE byte. */
367 # ifndef HANDLE_ALIGN
368 # define MAX_MEM_FOR_RS_ALIGN_CODE 1
370 # define MAX_MEM_FOR_RS_ALIGN_CODE ((1 << alignment) - 1)
375 frag_align_code (int alignment, int max)
379 p = frag_var (rs_align_code, MAX_MEM_FOR_RS_ALIGN_CODE, 1,
380 (relax_substateT) max, (symbolS *) 0,
381 (offsetT) alignment, (char *) 0);
386 frag_now_fix_octets (void)
388 if (now_seg == absolute_section)
389 return abs_section_offset;
391 return ((char *) obstack_next_free (&frchain_now->frch_obstack)
392 - frag_now->fr_literal);
398 return frag_now_fix_octets () / OCTETS_PER_BYTE;
402 frag_append_1_char (int datum)
404 frag_alloc_check (&frchain_now->frch_obstack);
405 if (obstack_room (&frchain_now->frch_obstack) <= 1)
407 frag_wane (frag_now);
410 obstack_1grow (&frchain_now->frch_obstack, datum);
413 /* Return TRUE if FRAG1 and FRAG2 have a fixed relationship between
414 their start addresses. Set OFFSET to the difference in address
415 not already accounted for in the frag FR_ADDRESS. */
418 frag_offset_fixed_p (const fragS *frag1, const fragS *frag2, offsetT *offset)
423 /* Start with offset initialised to difference between the two frags.
424 Prior to assigning frag addresses this will be zero. */
425 off = frag1->fr_address - frag2->fr_address;
432 /* Maybe frag2 is after frag1. */
434 while (frag->fr_type == rs_fill)
436 off += frag->fr_fix + frag->fr_offset * frag->fr_var;
437 frag = frag->fr_next;
447 /* Maybe frag1 is after frag2. */
448 off = frag1->fr_address - frag2->fr_address;
450 while (frag->fr_type == rs_fill)
452 off -= frag->fr_fix + frag->fr_offset * frag->fr_var;
453 frag = frag->fr_next;