| 1 | /* Dummy data flow analysis for GNU compiler in nonoptimizing mode. |
| 2 | Copyright (C) 1987 Free Software Foundation, Inc. |
| 3 | |
| 4 | This file is part of GNU CC. |
| 5 | |
| 6 | GNU CC 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 1, or (at your option) |
| 9 | any later version. |
| 10 | |
| 11 | GNU CC 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. |
| 15 | |
| 16 | You should have received a copy of the GNU General Public License |
| 17 | along with GNU CC; see the file COPYING. If not, write to |
| 18 | the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */ |
| 19 | |
| 20 | |
| 21 | /* This file performs stupid register allocation, which is used |
| 22 | when cc1 gets the -noreg switch (which is when cc does not get -O). |
| 23 | |
| 24 | Stupid register allocation goes in place of the the flow_analysis, |
| 25 | local_alloc and global_alloc passes. combine_instructions cannot |
| 26 | be done with stupid allocation because the data flow info that it needs |
| 27 | is not computed here. |
| 28 | |
| 29 | In stupid allocation, the only user-defined variables that can |
| 30 | go in registers are those declared "register". They are assumed |
| 31 | to have a life span equal to their scope. Other user variables |
| 32 | are given stack slots in the rtl-generation pass and are not |
| 33 | represented as pseudo regs. A compiler-generated temporary |
| 34 | is assumed to live from its first mention to its last mention. |
| 35 | |
| 36 | Since each pseudo-reg's life span is just an interval, it can be |
| 37 | represented as a pair of numbers, each of which identifies an insn by |
| 38 | its position in the function (number of insns before it). The first |
| 39 | thing done for stupid allocation is to compute such a number for each |
| 40 | insn. It is called the suid. Then the life-interval of each |
| 41 | pseudo reg is computed. Then the pseudo regs are ordered by priority |
| 42 | and assigned hard regs in priority order. */ |
| 43 | |
| 44 | #include <stdio.h> |
| 45 | #include "config.h" |
| 46 | #include "rtl.h" |
| 47 | #include "hard-reg-set.h" |
| 48 | #include "regs.h" |
| 49 | \f |
| 50 | /* Vector mapping INSN_UIDs to suids. |
| 51 | The suids are like uids but increase monononically always. |
| 52 | We use them to see whether a subroutine call came |
| 53 | between a variable's birth and its death. */ |
| 54 | |
| 55 | static int *uid_suid; |
| 56 | |
| 57 | /* Get the suid of an insn. */ |
| 58 | |
| 59 | #define INSN_SUID(INSN) (uid_suid[INSN_UID (INSN)]) |
| 60 | |
| 61 | /* Record the suid of the last CALL_INSN |
| 62 | so we can tell whether a pseudo reg crosses any calls. */ |
| 63 | |
| 64 | static int last_call_suid; |
| 65 | |
| 66 | /* Record the suid of the last JUMP_INSN |
| 67 | so we can tell whether a pseudo reg crosses any jumps. */ |
| 68 | |
| 69 | static int last_jump_suid; |
| 70 | |
| 71 | /* Record the suid of the last CODE_LABEL |
| 72 | so we can tell whether a pseudo reg crosses any labels. */ |
| 73 | |
| 74 | static int last_label_suid; |
| 75 | |
| 76 | /* Element N is suid of insn where life span of pseudo reg N ends. |
| 77 | Element is 0 if register N has not been seen yet on backward scan. */ |
| 78 | |
| 79 | static int *reg_where_dead; |
| 80 | |
| 81 | /* Element N is suid of insn where life span of pseudo reg N begins. */ |
| 82 | |
| 83 | static int *reg_where_born; |
| 84 | |
| 85 | /* Element N is 1 if pseudo reg N lives across labels or jumps. */ |
| 86 | |
| 87 | static char *reg_crosses_blocks; |
| 88 | |
| 89 | /* Numbers of pseudo-regs to be allocated, highest priority first. */ |
| 90 | |
| 91 | static int *reg_order; |
| 92 | |
| 93 | /* Indexed by reg number (hard or pseudo), nonzero if register is live |
| 94 | at the current point in the instruction stream. */ |
| 95 | |
| 96 | static char *regs_live; |
| 97 | |
| 98 | /* Indexed by insn's suid, the set of hard regs live after that insn. */ |
| 99 | |
| 100 | static HARD_REG_SET *after_insn_hard_regs; |
| 101 | |
| 102 | /* Record that hard reg REGNO is live after insn INSN. */ |
| 103 | |
| 104 | #define MARK_LIVE_AFTER(INSN,REGNO) \ |
| 105 | SET_HARD_REG_BIT (after_insn_hard_regs[INSN_SUID (INSN)], (REGNO)) |
| 106 | |
| 107 | static void stupid_mark_refs (); |
| 108 | static int stupid_reg_compare (); |
| 109 | static int stupid_find_reg (); |
| 110 | \f |
| 111 | /* Stupid life analysis is for the case where only variables declared |
| 112 | `register' go in registers. For this case, we mark all |
| 113 | pseudo-registers that belong to register variables as |
| 114 | dying in the last instruction of the function, and all other |
| 115 | pseudo registers as dying in the last place they are referenced. |
| 116 | Hard registers are marked as dying in the last reference before |
| 117 | the end or before each store into them. */ |
| 118 | |
| 119 | void |
| 120 | stupid_life_analysis (f, nregs, file) |
| 121 | rtx f; |
| 122 | int nregs; |
| 123 | FILE *file; |
| 124 | { |
| 125 | register int i; |
| 126 | register rtx last, insn; |
| 127 | int max_uid; |
| 128 | |
| 129 | bzero (regs_ever_live, sizeof regs_ever_live); |
| 130 | |
| 131 | regs_live = (char *) alloca (nregs); |
| 132 | |
| 133 | /* First find the last real insn, and count the number of insns, |
| 134 | and assign insns their suids. */ |
| 135 | |
| 136 | for (insn = f, i = 0; insn; insn = NEXT_INSN (insn)) |
| 137 | if (INSN_UID (insn) > i) |
| 138 | i = INSN_UID (insn); |
| 139 | |
| 140 | max_uid = i + 1; |
| 141 | uid_suid = (int *) alloca ((i + 1) * sizeof (int)); |
| 142 | |
| 143 | /* Compute the mapping from uids to suids. |
| 144 | Suids are numbers assigned to insns, like uids, |
| 145 | except that suids increase monotonically through the code. */ |
| 146 | |
| 147 | last = 0; /* In case of empty function body */ |
| 148 | for (insn = f, i = 0; insn; insn = NEXT_INSN (insn)) |
| 149 | { |
| 150 | if (GET_CODE (insn) == INSN || GET_CODE (insn) == CALL_INSN |
| 151 | || GET_CODE (insn) == JUMP_INSN) |
| 152 | last = insn; |
| 153 | INSN_SUID (insn) = ++i; |
| 154 | } |
| 155 | |
| 156 | last_call_suid = i + 1; |
| 157 | last_jump_suid = i + 1; |
| 158 | last_label_suid = i + 1; |
| 159 | |
| 160 | max_regno = nregs; |
| 161 | |
| 162 | /* Allocate tables to record info about regs. */ |
| 163 | |
| 164 | reg_where_dead = (int *) alloca (nregs * sizeof (int)); |
| 165 | bzero (reg_where_dead, nregs * sizeof (int)); |
| 166 | |
| 167 | reg_where_born = (int *) alloca (nregs * sizeof (int)); |
| 168 | bzero (reg_where_born, nregs * sizeof (int)); |
| 169 | |
| 170 | reg_crosses_blocks = (char *) alloca (nregs); |
| 171 | bzero (reg_crosses_blocks, nregs); |
| 172 | |
| 173 | reg_order = (int *) alloca (nregs * sizeof (int)); |
| 174 | bzero (reg_order, nregs * sizeof (int)); |
| 175 | |
| 176 | reg_renumber = (short *) oballoc (nregs * sizeof (short)); |
| 177 | for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) |
| 178 | reg_renumber[i] = i; |
| 179 | |
| 180 | after_insn_hard_regs = (HARD_REG_SET *) alloca (max_uid * sizeof (HARD_REG_SET)); |
| 181 | bzero (after_insn_hard_regs, max_uid * sizeof (HARD_REG_SET)); |
| 182 | |
| 183 | /* Allocate and zero out many data structures |
| 184 | that will record the data from lifetime analysis. */ |
| 185 | |
| 186 | allocate_for_life_analysis (); |
| 187 | |
| 188 | for (i = 0; i < max_regno; i++) |
| 189 | { |
| 190 | reg_n_deaths[i] = 1; |
| 191 | } |
| 192 | |
| 193 | bzero (regs_live, nregs); |
| 194 | |
| 195 | /* Find where each pseudo register is born and dies, |
| 196 | by scanning all insns from the end to the start |
| 197 | and noting all mentions of the registers. |
| 198 | |
| 199 | Also find where each hard register is live |
| 200 | and record that info in after_insn_hard_regs. |
| 201 | regs_live[I] is 1 if hard reg I is live |
| 202 | at the current point in the scan. */ |
| 203 | |
| 204 | for (insn = last; insn; insn = PREV_INSN (insn)) |
| 205 | { |
| 206 | register HARD_REG_SET *p = after_insn_hard_regs + INSN_SUID (insn); |
| 207 | |
| 208 | /* Copy the info in regs_live |
| 209 | into the element of after_insn_hard_regs |
| 210 | for the current position in the rtl code. */ |
| 211 | |
| 212 | for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) |
| 213 | if (regs_live[i]) |
| 214 | SET_HARD_REG_BIT (*p, i); |
| 215 | |
| 216 | /* Mark all call-clobbered regs as live after each call insn |
| 217 | so that a pseudo whose life span includes this insn |
| 218 | will not go in one of them. |
| 219 | Then mark those regs as all dead for the continuing scan |
| 220 | of the insns before the call. */ |
| 221 | |
| 222 | if (GET_CODE (insn) == CALL_INSN) |
| 223 | { |
| 224 | last_call_suid = INSN_SUID (insn); |
| 225 | IOR_HARD_REG_SET (after_insn_hard_regs[last_call_suid], |
| 226 | call_used_reg_set); |
| 227 | for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) |
| 228 | if (call_used_regs[i]) |
| 229 | regs_live[i] = 0; |
| 230 | } |
| 231 | |
| 232 | if (GET_CODE (insn) == JUMP_INSN) |
| 233 | last_jump_suid = INSN_SUID (insn); |
| 234 | |
| 235 | if (GET_CODE (insn) == CODE_LABEL) |
| 236 | last_label_suid = INSN_SUID (insn); |
| 237 | |
| 238 | /* Update which hard regs are currently live |
| 239 | and also the birth and death suids of pseudo regs |
| 240 | based on the pattern of this insn. */ |
| 241 | |
| 242 | if (GET_CODE (insn) == INSN |
| 243 | || GET_CODE (insn) == CALL_INSN |
| 244 | || GET_CODE (insn) == JUMP_INSN) |
| 245 | { |
| 246 | stupid_mark_refs (PATTERN (insn), insn); |
| 247 | } |
| 248 | } |
| 249 | |
| 250 | /* Now decide the order in which to allocate the pseudo registers. */ |
| 251 | |
| 252 | for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++) |
| 253 | reg_order[i] = i; |
| 254 | |
| 255 | qsort (®_order[FIRST_PSEUDO_REGISTER], |
| 256 | max_regno - FIRST_PSEUDO_REGISTER, sizeof (int), |
| 257 | stupid_reg_compare); |
| 258 | |
| 259 | /* Now, in that order, try to find hard registers for those pseudo regs. */ |
| 260 | |
| 261 | for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++) |
| 262 | { |
| 263 | register int r = reg_order[i]; |
| 264 | enum reg_class class; |
| 265 | |
| 266 | /* Some regnos disappear from the rtl. Ignore them to avoid crash. */ |
| 267 | if (regno_reg_rtx[r] == 0) |
| 268 | continue; |
| 269 | |
| 270 | /* Now find the best hard-register class for this pseudo register */ |
| 271 | if (N_REG_CLASSES > 1) |
| 272 | { |
| 273 | class = reg_preferred_class (r); |
| 274 | |
| 275 | reg_renumber[r] = stupid_find_reg (reg_n_calls_crossed[r], class, |
| 276 | PSEUDO_REGNO_MODE (r), |
| 277 | reg_where_born[r], |
| 278 | reg_where_dead[r], |
| 279 | reg_crosses_blocks[r]); |
| 280 | } |
| 281 | else |
| 282 | reg_renumber[r] = -1; |
| 283 | |
| 284 | /* If no reg available in that class, |
| 285 | try any reg. */ |
| 286 | if (reg_renumber[r] == -1) |
| 287 | reg_renumber[r] = stupid_find_reg (reg_n_calls_crossed[r], |
| 288 | GENERAL_REGS, |
| 289 | PSEUDO_REGNO_MODE (r), |
| 290 | reg_where_born[r], |
| 291 | reg_where_dead[r], |
| 292 | reg_crosses_blocks[r]); |
| 293 | } |
| 294 | |
| 295 | if (file) |
| 296 | dump_flow_info (file); |
| 297 | } |
| 298 | |
| 299 | /* Comparison function for qsort. |
| 300 | Returns -1 (1) if register *R1P is higher priority than *R2P. */ |
| 301 | |
| 302 | static int |
| 303 | stupid_reg_compare (r1p, r2p) |
| 304 | int *r1p, *r2p; |
| 305 | { |
| 306 | register int r1 = *r1p, r2 = *r2p; |
| 307 | register int len1 = reg_where_dead[r1] - reg_where_born[r1]; |
| 308 | register int len2 = reg_where_dead[r2] - reg_where_born[r2]; |
| 309 | int tem; |
| 310 | |
| 311 | tem = len2 - len1; |
| 312 | if (tem != 0) return tem; |
| 313 | |
| 314 | tem = reg_n_refs[r1] - reg_n_refs[r2]; |
| 315 | if (tem != 0) return tem; |
| 316 | |
| 317 | /* If regs are equally good, sort by regno, |
| 318 | so that the results of qsort leave nothing to chance. */ |
| 319 | return r1 - r2; |
| 320 | } |
| 321 | \f |
| 322 | /* Find a block of SIZE words of hard registers in reg_class CLASS |
| 323 | that can hold a value of machine-mode MODE |
| 324 | (but actually we test only the first of the block for holding MODE) |
| 325 | currently free from after insn whose suid is BIRTH |
| 326 | through the insn whose suid is DEATH, |
| 327 | and return the number of the first of them. |
| 328 | Return -1 if such a block cannot be found. |
| 329 | |
| 330 | If CALL_PRESERVED is nonzero, insist on registers preserved |
| 331 | over subroutine calls, and return -1 if cannot find such. |
| 332 | If CROSSES_BLOCKS is nonzero, reject registers for which |
| 333 | PRESERVE_DEATH_INFO_REGNO_P is true. */ |
| 334 | |
| 335 | static int |
| 336 | stupid_find_reg (call_preserved, class, mode, |
| 337 | born_insn, dead_insn, crosses_blocks) |
| 338 | int call_preserved; |
| 339 | enum reg_class class; |
| 340 | enum machine_mode mode; |
| 341 | int born_insn, dead_insn; |
| 342 | int crosses_blocks; |
| 343 | { |
| 344 | register int i, ins; |
| 345 | #ifdef HARD_REG_SET |
| 346 | register /* Declare them register if they are scalars. */ |
| 347 | #endif |
| 348 | HARD_REG_SET used, this_reg; |
| 349 | |
| 350 | COPY_HARD_REG_SET (used, |
| 351 | call_preserved ? call_used_reg_set : fixed_reg_set); |
| 352 | |
| 353 | for (ins = born_insn; ins < dead_insn; ins++) |
| 354 | IOR_HARD_REG_SET (used, after_insn_hard_regs[ins]); |
| 355 | |
| 356 | IOR_COMPL_HARD_REG_SET (used, reg_class_contents[(int) class]); |
| 357 | |
| 358 | for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) |
| 359 | { |
| 360 | #ifdef REG_ALLOC_ORDER |
| 361 | int regno = reg_alloc_order[i]; |
| 362 | #else |
| 363 | int regno = i; |
| 364 | #endif |
| 365 | |
| 366 | /* If we need reasonable death info on this hard reg, |
| 367 | don't use it for anything whose life spans a label or a jump. */ |
| 368 | #ifdef PRESERVE_DEATH_INFO_REGNO_P |
| 369 | if (PRESERVE_DEATH_INFO_REGNO_P (regno) |
| 370 | && crosses_blocks) |
| 371 | continue; |
| 372 | #endif |
| 373 | /* If a register has screwy overlap problems, |
| 374 | don't use it at all if not optimizing. |
| 375 | Actually this is only for the 387 stack register, |
| 376 | and it's because subsequent code won't work. */ |
| 377 | #ifdef OVERLAPPING_REGNO_P |
| 378 | if (OVERLAPPING_REGNO_P (regno)) |
| 379 | continue; |
| 380 | #endif |
| 381 | |
| 382 | if (! TEST_HARD_REG_BIT (used, regno) |
| 383 | && HARD_REGNO_MODE_OK (regno, mode)) |
| 384 | { |
| 385 | register int j; |
| 386 | register int size1 = HARD_REGNO_NREGS (regno, mode); |
| 387 | for (j = 1; j < size1 && ! TEST_HARD_REG_BIT (used, regno + j); j++); |
| 388 | if (j == size1) |
| 389 | { |
| 390 | CLEAR_HARD_REG_SET (this_reg); |
| 391 | while (--j >= 0) |
| 392 | SET_HARD_REG_BIT (this_reg, regno + j); |
| 393 | for (ins = born_insn; ins < dead_insn; ins++) |
| 394 | { |
| 395 | IOR_HARD_REG_SET (after_insn_hard_regs[ins], this_reg); |
| 396 | } |
| 397 | return regno; |
| 398 | } |
| 399 | #ifndef REG_ALLOC_ORDER |
| 400 | i += j; /* Skip starting points we know will lose */ |
| 401 | #endif |
| 402 | } |
| 403 | } |
| 404 | return -1; |
| 405 | } |
| 406 | \f |
| 407 | /* Walk X, noting all assignments and references to registers |
| 408 | and recording what they imply about life spans. |
| 409 | INSN is the current insn, supplied so we can find its suid. */ |
| 410 | |
| 411 | static void |
| 412 | stupid_mark_refs (x, insn) |
| 413 | rtx x, insn; |
| 414 | { |
| 415 | register RTX_CODE code = GET_CODE (x); |
| 416 | register char *fmt; |
| 417 | register int regno, i; |
| 418 | |
| 419 | if (code == SET || code == CLOBBER) |
| 420 | { |
| 421 | if (SET_DEST (x) != 0 && GET_CODE (SET_DEST (x)) == REG) |
| 422 | { |
| 423 | /* Register is being assigned. */ |
| 424 | regno = REGNO (SET_DEST (x)); |
| 425 | |
| 426 | /* For hard regs, update the where-live info. */ |
| 427 | if (regno < FIRST_PSEUDO_REGISTER) |
| 428 | { |
| 429 | register int j |
| 430 | = HARD_REGNO_NREGS (regno, GET_MODE (SET_DEST (x))); |
| 431 | while (--j >= 0) |
| 432 | { |
| 433 | regs_ever_live[regno+j] = 1; |
| 434 | regs_live[regno+j] = 0; |
| 435 | /* The following line is for unused outputs; |
| 436 | they do get stored even though never used again. */ |
| 437 | MARK_LIVE_AFTER (insn, regno); |
| 438 | /* When a hard reg is clobbered, mark it in use |
| 439 | just before this insn, so it is live all through. */ |
| 440 | if (code == CLOBBER) |
| 441 | SET_HARD_REG_BIT (after_insn_hard_regs[INSN_SUID (insn)], |
| 442 | regno); |
| 443 | } |
| 444 | } |
| 445 | /* For pseudo regs, record where born, where dead, number of |
| 446 | times used, and whether live across a call. */ |
| 447 | else |
| 448 | { |
| 449 | /* Update the life-interval bounds of this pseudo reg. */ |
| 450 | |
| 451 | /* When a pseudo-reg is CLOBBERed, it is born just before |
| 452 | the clobbering insn. When setting, just after. */ |
| 453 | int where_born = INSN_SUID (insn) - (code == CLOBBER); |
| 454 | |
| 455 | reg_where_born[regno] = where_born; |
| 456 | /* The reg must live at least one insn even |
| 457 | in it is never again used--because it has to go |
| 458 | in SOME hard reg. */ |
| 459 | if (reg_where_dead[regno] < where_born + 1) |
| 460 | reg_where_dead[regno] = where_born + 1; |
| 461 | |
| 462 | /* Count the refs of this reg. */ |
| 463 | reg_n_refs[regno]++; |
| 464 | |
| 465 | if (last_call_suid < reg_where_dead[regno]) |
| 466 | reg_n_calls_crossed[regno] += 1; |
| 467 | if (last_jump_suid < reg_where_dead[regno] |
| 468 | || last_label_suid < reg_where_dead[regno]) |
| 469 | reg_crosses_blocks[regno] = 1; |
| 470 | } |
| 471 | } |
| 472 | /* Record references from the value being set, |
| 473 | or from addresses in the place being set if that's not a reg. |
| 474 | If setting a SUBREG, we treat the entire reg as *used*. */ |
| 475 | if (code == SET) |
| 476 | { |
| 477 | stupid_mark_refs (SET_SRC (x), insn); |
| 478 | if (GET_CODE (SET_DEST (x)) != REG) |
| 479 | stupid_mark_refs (SET_DEST (x), insn); |
| 480 | } |
| 481 | return; |
| 482 | } |
| 483 | |
| 484 | /* Register value being used, not set. */ |
| 485 | |
| 486 | if (code == REG) |
| 487 | { |
| 488 | regno = REGNO (x); |
| 489 | if (regno < FIRST_PSEUDO_REGISTER) |
| 490 | { |
| 491 | /* Hard reg: mark it live for continuing scan of previous insns. */ |
| 492 | register int j = HARD_REGNO_NREGS (regno, GET_MODE (x)); |
| 493 | while (--j >= 0) |
| 494 | { |
| 495 | regs_ever_live[regno+j] = 1; |
| 496 | regs_live[regno+j] = 1; |
| 497 | } |
| 498 | } |
| 499 | else |
| 500 | { |
| 501 | /* Pseudo reg: record first use, last use and number of uses. */ |
| 502 | |
| 503 | reg_where_born[regno] = INSN_SUID (insn); |
| 504 | reg_n_refs[regno]++; |
| 505 | if (regs_live[regno] == 0) |
| 506 | { |
| 507 | regs_live[regno] = 1; |
| 508 | reg_where_dead[regno] = INSN_SUID (insn); |
| 509 | } |
| 510 | } |
| 511 | return; |
| 512 | } |
| 513 | |
| 514 | /* Recursive scan of all other rtx's. */ |
| 515 | |
| 516 | fmt = GET_RTX_FORMAT (code); |
| 517 | for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) |
| 518 | { |
| 519 | if (fmt[i] == 'e') |
| 520 | stupid_mark_refs (XEXP (x, i), insn); |
| 521 | if (fmt[i] == 'E') |
| 522 | { |
| 523 | register int j; |
| 524 | for (j = XVECLEN (x, i) - 1; j >= 0; j--) |
| 525 | stupid_mark_refs (XVECEXP (x, i, j), insn); |
| 526 | } |
| 527 | } |
| 528 | } |