1 /* frags.c - manage frags -
2 Copyright (C) 1987-2014 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 (unsigned int 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 (_("can't extend frag %u chars"), nchars);
117 /* Force to allocate at least NEWC bytes, but not less than the
119 oldc = obstack_chunk_size (&frchain_now->frch_obstack);
121 obstack_chunk_size (&frchain_now->frch_obstack) = newc;
123 while (obstack_room (&frchain_now->frch_obstack) < nchars)
125 /* Not enough room in this frag. Close it and start a new one.
126 This must be done in a loop because the created frag may not
127 be big enough if the current obstack chunk is used. */
128 frag_wane (frag_now);
132 /* Restore the old chunk size. */
133 obstack_chunk_size (&frchain_now->frch_obstack) = oldc;
137 /* Call this to close off a completed frag, and start up a new (empty)
138 frag, in the same subsegment as the old frag.
139 [frchain_now remains the same but frag_now is updated.]
140 Because this calculates the correct value of fr_fix by
141 looking at the obstack 'frags', it needs to know how many
142 characters at the end of the old frag belong to the maximal
143 variable part; The rest must belong to fr_fix.
144 It doesn't actually set up the old frag's fr_var. You may have
145 set fr_var == 1, but allocated 10 chars to the end of the frag;
146 In this case you pass old_frags_var_max_size == 10.
147 In fact, you may use fr_var for something totally unrelated to the
148 size of the variable part of the frag; None of the generic frag
149 handling code makes use of fr_var.
151 Make a new frag, initialising some components. Link new frag at end
155 frag_new (int old_frags_var_max_size
156 /* Number of chars (already allocated on obstack frags) in
157 variable_length part of frag. */)
159 fragS *former_last_fragP;
162 gas_assert (frchain_now->frch_last == frag_now);
164 /* Fix up old frag's fr_fix. */
165 frag_now->fr_fix = frag_now_fix_octets () - old_frags_var_max_size;
166 /* Make sure its type is valid. */
167 gas_assert (frag_now->fr_type != 0);
169 /* This will align the obstack so the next struct we allocate on it
170 will begin at a correct boundary. */
171 obstack_finish (&frchain_now->frch_obstack);
174 former_last_fragP = frchP->frch_last;
175 gas_assert (former_last_fragP != 0);
176 gas_assert (former_last_fragP == frag_now);
177 frag_now = frag_alloc (&frchP->frch_obstack);
179 as_where (&frag_now->fr_file, &frag_now->fr_line);
181 /* Generally, frag_now->points to an address rounded up to next
182 alignment. However, characters will add to obstack frags
183 IMMEDIATELY after the struct frag, even if they are not starting
184 at an alignment address. */
185 former_last_fragP->fr_next = frag_now;
186 frchP->frch_last = frag_now;
190 extern struct list_info_struct *listing_tail;
191 frag_now->line = listing_tail;
195 gas_assert (frchain_now->frch_last == frag_now);
197 frag_now->fr_next = NULL;
200 /* Start a new frag unless we have n more chars of room in the current frag.
201 Close off the old frag with a .fill 0.
203 Return the address of the 1st char to write into. Advance
204 frag_now_growth past the new chars. */
207 frag_more (int nchars)
209 register char *retval;
211 frag_alloc_check (&frchain_now->frch_obstack);
213 retval = obstack_next_free (&frchain_now->frch_obstack);
214 obstack_blank_fast (&frchain_now->frch_obstack, nchars);
218 /* Close the current frag, setting its fields for a relaxable frag. Start a
222 frag_var_init (relax_stateT type, int max_chars, int var,
223 relax_substateT subtype, symbolS *symbol, offsetT offset,
226 frag_now->fr_var = var;
227 frag_now->fr_type = type;
228 frag_now->fr_subtype = subtype;
229 frag_now->fr_symbol = symbol;
230 frag_now->fr_offset = offset;
231 frag_now->fr_opcode = opcode;
233 frag_now->fr_cgen.insn = 0;
234 frag_now->fr_cgen.opindex = 0;
235 frag_now->fr_cgen.opinfo = 0;
238 TC_FRAG_INIT (frag_now);
240 as_where (&frag_now->fr_file, &frag_now->fr_line);
242 frag_new (max_chars);
245 /* Start a new frag unless we have max_chars more chars of room in the
246 current frag. Close off the old frag with a .fill 0.
248 Set up a machine_dependent relaxable frag, then start a new frag.
249 Return the address of the 1st char of the var part of the old frag
253 frag_var (relax_stateT type, int max_chars, int var, relax_substateT subtype,
254 symbolS *symbol, offsetT offset, char *opcode)
256 register char *retval;
258 frag_grow (max_chars);
259 retval = obstack_next_free (&frchain_now->frch_obstack);
260 obstack_blank_fast (&frchain_now->frch_obstack, max_chars);
261 frag_var_init (type, max_chars, var, subtype, symbol, offset, opcode);
265 /* OVE: This variant of frag_var assumes that space for the tail has been
267 No call to frag_grow is done. */
270 frag_variant (relax_stateT type, int max_chars, int var,
271 relax_substateT subtype, symbolS *symbol, offsetT offset,
274 register char *retval;
276 retval = obstack_next_free (&frchain_now->frch_obstack);
277 frag_var_init (type, max_chars, var, subtype, symbol, offset, opcode);
282 /* Reduce the variable end of a frag to a harmless state. */
285 frag_wane (register fragS *fragP)
287 fragP->fr_type = rs_fill;
288 fragP->fr_offset = 0;
292 /* Return the number of bytes by which the current frag can be grown. */
297 return obstack_room (&frchain_now->frch_obstack);
300 /* Make an alignment frag. The size of this frag will be adjusted to
301 force the next frag to have the appropriate alignment. ALIGNMENT
302 is the power of two to which to align. FILL_CHARACTER is the
303 character to use to fill in any bytes which are skipped. MAX is
304 the maximum number of characters to skip when doing the alignment,
305 or 0 if there is no maximum. */
308 frag_align (int alignment, int fill_character, int max)
310 if (now_seg == absolute_section)
315 mask = (~(addressT) 0) << alignment;
316 new_off = (abs_section_offset + ~mask) & mask;
317 if (max == 0 || new_off - abs_section_offset <= (addressT) max)
318 abs_section_offset = new_off;
324 p = frag_var (rs_align, 1, 1, (relax_substateT) max,
325 (symbolS *) 0, (offsetT) alignment, (char *) 0);
330 /* Make an alignment frag like frag_align, but fill with a repeating
331 pattern rather than a single byte. ALIGNMENT is the power of two
332 to which to align. FILL_PATTERN is the fill pattern to repeat in
333 the bytes which are skipped. N_FILL is the number of bytes in
334 FILL_PATTERN. MAX is the maximum number of characters to skip when
335 doing the alignment, or 0 if there is no maximum. */
338 frag_align_pattern (int alignment, const char *fill_pattern,
343 p = frag_var (rs_align, n_fill, n_fill, (relax_substateT) max,
344 (symbolS *) 0, (offsetT) alignment, (char *) 0);
345 memcpy (p, fill_pattern, n_fill);
348 /* The NOP_OPCODE is for the alignment fill value. Fill it with a nop
349 instruction so that the disassembler does not choke on it. */
351 #define NOP_OPCODE 0x00
354 /* Use this to restrict the amount of memory allocated for representing
355 the alignment code. Needs to be large enough to hold any fixed sized
356 prologue plus the replicating portion. */
357 #ifndef MAX_MEM_FOR_RS_ALIGN_CODE
358 /* Assume that if HANDLE_ALIGN is not defined then no special action
359 is required to code fill, which means that we get just repeat the
360 one NOP_OPCODE byte. */
361 # ifndef HANDLE_ALIGN
362 # define MAX_MEM_FOR_RS_ALIGN_CODE 1
364 # define MAX_MEM_FOR_RS_ALIGN_CODE ((1 << alignment) - 1)
369 frag_align_code (int alignment, int max)
373 p = frag_var (rs_align_code, MAX_MEM_FOR_RS_ALIGN_CODE, 1,
374 (relax_substateT) max, (symbolS *) 0,
375 (offsetT) alignment, (char *) 0);
380 frag_now_fix_octets (void)
382 if (now_seg == absolute_section)
383 return abs_section_offset;
385 return ((char *) obstack_next_free (&frchain_now->frch_obstack)
386 - frag_now->fr_literal);
392 return frag_now_fix_octets () / OCTETS_PER_BYTE;
396 frag_append_1_char (int datum)
398 frag_alloc_check (&frchain_now->frch_obstack);
399 if (obstack_room (&frchain_now->frch_obstack) <= 1)
401 frag_wane (frag_now);
404 obstack_1grow (&frchain_now->frch_obstack, datum);
407 /* Return TRUE if FRAG1 and FRAG2 have a fixed relationship between
408 their start addresses. Set OFFSET to the difference in address
409 not already accounted for in the frag FR_ADDRESS. */
412 frag_offset_fixed_p (const fragS *frag1, const fragS *frag2, offsetT *offset)
417 /* Start with offset initialised to difference between the two frags.
418 Prior to assigning frag addresses this will be zero. */
419 off = frag1->fr_address - frag2->fr_address;
426 /* Maybe frag2 is after frag1. */
428 while (frag->fr_type == rs_fill)
430 off += frag->fr_fix + frag->fr_offset * frag->fr_var;
431 frag = frag->fr_next;
441 /* Maybe frag1 is after frag2. */
442 off = frag1->fr_address - frag2->fr_address;
444 while (frag->fr_type == rs_fill)
446 off -= frag->fr_fix + frag->fr_offset * frag->fr_var;
447 frag = frag->fr_next;