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1.1 root 1: /* Dummy data flow analysis for GNU compiler in nonoptimizing mode. 1.1.1.5 ! root 2: Copyright (C) 1987, 1991, 1994, 1995 Free Software Foundation, Inc. 1.1 root 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 2, 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 1.1.1.5 ! root 18: the Free Software Foundation, 59 Temple Place - Suite 330, ! 19: Boston, MA 02111-1307, USA. */ 1.1 root 20: 21: 22: /* This file performs stupid register allocation, which is used 23: when cc1 gets the -noreg switch (which is when cc does not get -O). 24: 25: Stupid register allocation goes in place of the the flow_analysis, 26: local_alloc and global_alloc passes. combine_instructions cannot 27: be done with stupid allocation because the data flow info that it needs 28: is not computed here. 29: 30: In stupid allocation, the only user-defined variables that can 31: go in registers are those declared "register". They are assumed 32: to have a life span equal to their scope. Other user variables 33: are given stack slots in the rtl-generation pass and are not 34: represented as pseudo regs. A compiler-generated temporary 35: is assumed to live from its first mention to its last mention. 36: 37: Since each pseudo-reg's life span is just an interval, it can be 38: represented as a pair of numbers, each of which identifies an insn by 39: its position in the function (number of insns before it). The first 40: thing done for stupid allocation is to compute such a number for each 41: insn. It is called the suid. Then the life-interval of each 42: pseudo reg is computed. Then the pseudo regs are ordered by priority 43: and assigned hard regs in priority order. */ 44: 45: #include <stdio.h> 46: #include "config.h" 47: #include "rtl.h" 48: #include "hard-reg-set.h" 49: #include "regs.h" 50: #include "flags.h" 51: 52: /* Vector mapping INSN_UIDs to suids. 1.1.1.2 root 53: The suids are like uids but increase monotonically always. 1.1 root 54: We use them to see whether a subroutine call came 55: between a variable's birth and its death. */ 56: 57: static int *uid_suid; 58: 59: /* Get the suid of an insn. */ 60: 61: #define INSN_SUID(INSN) (uid_suid[INSN_UID (INSN)]) 62: 63: /* Record the suid of the last CALL_INSN 64: so we can tell whether a pseudo reg crosses any calls. */ 65: 66: static int last_call_suid; 67: 68: /* Element N is suid of insn where life span of pseudo reg N ends. 69: Element is 0 if register N has not been seen yet on backward scan. */ 70: 71: static int *reg_where_dead; 72: 73: /* Element N is suid of insn where life span of pseudo reg N begins. */ 74: 75: static int *reg_where_born; 76: 77: /* Numbers of pseudo-regs to be allocated, highest priority first. */ 78: 79: static int *reg_order; 80: 81: /* Indexed by reg number (hard or pseudo), nonzero if register is live 82: at the current point in the instruction stream. */ 83: 84: static char *regs_live; 85: 1.1.1.4 root 86: /* Indexed by reg number, nonzero if reg was used in a SUBREG that changes 87: its size. */ 88: 89: static char *regs_change_size; 90: 1.1 root 91: /* Indexed by insn's suid, the set of hard regs live after that insn. */ 92: 93: static HARD_REG_SET *after_insn_hard_regs; 94: 95: /* Record that hard reg REGNO is live after insn INSN. */ 96: 97: #define MARK_LIVE_AFTER(INSN,REGNO) \ 98: SET_HARD_REG_BIT (after_insn_hard_regs[INSN_SUID (INSN)], (REGNO)) 99: 1.1.1.4 root 100: static int stupid_reg_compare PROTO((int *, int *)); 101: static int stupid_find_reg PROTO((int, enum reg_class, enum machine_mode, 102: int, int, int)); 103: static void stupid_mark_refs PROTO((rtx, rtx)); 1.1 root 104: 105: /* Stupid life analysis is for the case where only variables declared 106: `register' go in registers. For this case, we mark all 107: pseudo-registers that belong to register variables as 108: dying in the last instruction of the function, and all other 109: pseudo registers as dying in the last place they are referenced. 110: Hard registers are marked as dying in the last reference before 111: the end or before each store into them. */ 112: 113: void 114: stupid_life_analysis (f, nregs, file) 115: rtx f; 116: int nregs; 117: FILE *file; 118: { 119: register int i; 120: register rtx last, insn; 1.1.1.4 root 121: int max_uid, max_suid; 1.1 root 122: 123: bzero (regs_ever_live, sizeof regs_ever_live); 124: 125: regs_live = (char *) alloca (nregs); 126: 127: /* First find the last real insn, and count the number of insns, 128: and assign insns their suids. */ 129: 130: for (insn = f, i = 0; insn; insn = NEXT_INSN (insn)) 131: if (INSN_UID (insn) > i) 132: i = INSN_UID (insn); 133: 134: max_uid = i + 1; 135: uid_suid = (int *) alloca ((i + 1) * sizeof (int)); 136: 137: /* Compute the mapping from uids to suids. 138: Suids are numbers assigned to insns, like uids, 139: except that suids increase monotonically through the code. */ 140: 141: last = 0; /* In case of empty function body */ 142: for (insn = f, i = 0; insn; insn = NEXT_INSN (insn)) 143: { 1.1.1.4 root 144: if (GET_RTX_CLASS (GET_CODE (insn)) == 'i') 1.1 root 145: last = insn; 1.1.1.4 root 146: 1.1 root 147: INSN_SUID (insn) = ++i; 148: } 149: 150: last_call_suid = i + 1; 1.1.1.4 root 151: max_suid = i + 1; 1.1 root 152: 153: max_regno = nregs; 154: 155: /* Allocate tables to record info about regs. */ 156: 157: reg_where_dead = (int *) alloca (nregs * sizeof (int)); 1.1.1.4 root 158: bzero ((char *) reg_where_dead, nregs * sizeof (int)); 1.1 root 159: 160: reg_where_born = (int *) alloca (nregs * sizeof (int)); 1.1.1.4 root 161: bzero ((char *) reg_where_born, nregs * sizeof (int)); 1.1 root 162: 163: reg_order = (int *) alloca (nregs * sizeof (int)); 1.1.1.4 root 164: bzero ((char *) reg_order, nregs * sizeof (int)); 165: 166: regs_change_size = (char *) alloca (nregs * sizeof (char)); 167: bzero ((char *) regs_change_size, nregs * sizeof (char)); 1.1 root 168: 169: reg_renumber = (short *) oballoc (nregs * sizeof (short)); 170: for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) 171: reg_renumber[i] = i; 172: 1.1.1.4 root 173: for (i = FIRST_VIRTUAL_REGISTER; i < max_regno; i++) 1.1 root 174: reg_renumber[i] = -1; 175: 1.1.1.4 root 176: after_insn_hard_regs 177: = (HARD_REG_SET *) alloca (max_suid * sizeof (HARD_REG_SET)); 178: 179: bzero ((char *) after_insn_hard_regs, max_suid * sizeof (HARD_REG_SET)); 1.1 root 180: 181: /* Allocate and zero out many data structures 182: that will record the data from lifetime analysis. */ 183: 184: allocate_for_life_analysis (); 185: 186: for (i = 0; i < max_regno; i++) 1.1.1.4 root 187: reg_n_deaths[i] = 1; 1.1 root 188: 189: bzero (regs_live, nregs); 190: 191: /* Find where each pseudo register is born and dies, 192: by scanning all insns from the end to the start 193: and noting all mentions of the registers. 194: 195: Also find where each hard register is live 196: and record that info in after_insn_hard_regs. 197: regs_live[I] is 1 if hard reg I is live 198: at the current point in the scan. */ 199: 200: for (insn = last; insn; insn = PREV_INSN (insn)) 201: { 202: register HARD_REG_SET *p = after_insn_hard_regs + INSN_SUID (insn); 203: 1.1.1.4 root 204: /* Copy the info in regs_live into the element of after_insn_hard_regs 1.1 root 205: for the current position in the rtl code. */ 206: 207: for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) 208: if (regs_live[i]) 209: SET_HARD_REG_BIT (*p, i); 210: 1.1.1.4 root 211: /* Update which hard regs are currently live 212: and also the birth and death suids of pseudo regs 213: based on the pattern of this insn. */ 214: 215: if (GET_RTX_CLASS (GET_CODE (insn)) == 'i') 216: stupid_mark_refs (PATTERN (insn), insn); 217: 1.1 root 218: /* Mark all call-clobbered regs as live after each call insn 219: so that a pseudo whose life span includes this insn 220: will not go in one of them. 221: Then mark those regs as all dead for the continuing scan 222: of the insns before the call. */ 223: 224: if (GET_CODE (insn) == CALL_INSN) 225: { 226: last_call_suid = INSN_SUID (insn); 227: IOR_HARD_REG_SET (after_insn_hard_regs[last_call_suid], 228: call_used_reg_set); 1.1.1.4 root 229: 1.1 root 230: for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) 231: if (call_used_regs[i]) 232: regs_live[i] = 0; 233: 1.1.1.4 root 234: /* It is important that this be done after processing the insn's 235: pattern because we want the function result register to still 236: be live if it's also used to pass arguments. */ 237: stupid_mark_refs (CALL_INSN_FUNCTION_USAGE (insn), insn); 1.1 root 238: } 239: } 240: 241: /* Now decide the order in which to allocate the pseudo registers. */ 242: 243: for (i = LAST_VIRTUAL_REGISTER + 1; i < max_regno; i++) 244: reg_order[i] = i; 245: 246: qsort (®_order[LAST_VIRTUAL_REGISTER + 1], 247: max_regno - LAST_VIRTUAL_REGISTER - 1, sizeof (int), 248: stupid_reg_compare); 249: 250: /* Now, in that order, try to find hard registers for those pseudo regs. */ 251: 252: for (i = LAST_VIRTUAL_REGISTER + 1; i < max_regno; i++) 253: { 254: register int r = reg_order[i]; 255: 256: /* Some regnos disappear from the rtl. Ignore them to avoid crash. */ 257: if (regno_reg_rtx[r] == 0) 258: continue; 259: 260: /* Now find the best hard-register class for this pseudo register */ 261: if (N_REG_CLASSES > 1) 1.1.1.4 root 262: reg_renumber[r] = stupid_find_reg (reg_n_calls_crossed[r], 263: reg_preferred_class (r), 264: PSEUDO_REGNO_MODE (r), 265: reg_where_born[r], 266: reg_where_dead[r], 267: regs_change_size[r]); 1.1 root 268: 1.1.1.4 root 269: /* If no reg available in that class, try alternate class. */ 270: if (reg_renumber[r] == -1 && reg_alternate_class (r) != NO_REGS) 1.1 root 271: reg_renumber[r] = stupid_find_reg (reg_n_calls_crossed[r], 1.1.1.4 root 272: reg_alternate_class (r), 1.1 root 273: PSEUDO_REGNO_MODE (r), 274: reg_where_born[r], 275: reg_where_dead[r], 1.1.1.4 root 276: regs_change_size[r]); 1.1 root 277: } 278: 279: if (file) 280: dump_flow_info (file); 281: } 282: 283: /* Comparison function for qsort. 284: Returns -1 (1) if register *R1P is higher priority than *R2P. */ 285: 286: static int 287: stupid_reg_compare (r1p, r2p) 288: int *r1p, *r2p; 289: { 290: register int r1 = *r1p, r2 = *r2p; 291: register int len1 = reg_where_dead[r1] - reg_where_born[r1]; 292: register int len2 = reg_where_dead[r2] - reg_where_born[r2]; 293: int tem; 294: 295: tem = len2 - len1; 1.1.1.4 root 296: if (tem != 0) 297: return tem; 1.1 root 298: 299: tem = reg_n_refs[r1] - reg_n_refs[r2]; 1.1.1.4 root 300: if (tem != 0) 301: return tem; 1.1 root 302: 303: /* If regs are equally good, sort by regno, 304: so that the results of qsort leave nothing to chance. */ 305: return r1 - r2; 306: } 307: 308: /* Find a block of SIZE words of hard registers in reg_class CLASS 309: that can hold a value of machine-mode MODE 310: (but actually we test only the first of the block for holding MODE) 311: currently free from after insn whose suid is BIRTH 312: through the insn whose suid is DEATH, 313: and return the number of the first of them. 314: Return -1 if such a block cannot be found. 315: 316: If CALL_PRESERVED is nonzero, insist on registers preserved 317: over subroutine calls, and return -1 if cannot find such. 1.1.1.4 root 318: 319: If CHANGES_SIZE is nonzero, it means this register was used as the 320: operand of a SUBREG that changes its size. */ 1.1 root 321: 322: static int 323: stupid_find_reg (call_preserved, class, mode, 1.1.1.4 root 324: born_insn, dead_insn, changes_size) 1.1 root 325: int call_preserved; 326: enum reg_class class; 327: enum machine_mode mode; 328: int born_insn, dead_insn; 1.1.1.4 root 329: int changes_size; 1.1 root 330: { 331: register int i, ins; 332: #ifdef HARD_REG_SET 333: register /* Declare them register if they are scalars. */ 334: #endif 335: HARD_REG_SET used, this_reg; 336: #ifdef ELIMINABLE_REGS 337: static struct {int from, to; } eliminables[] = ELIMINABLE_REGS; 338: #endif 339: 340: COPY_HARD_REG_SET (used, 341: call_preserved ? call_used_reg_set : fixed_reg_set); 342: 343: #ifdef ELIMINABLE_REGS 344: for (i = 0; i < sizeof eliminables / sizeof eliminables[0]; i++) 345: SET_HARD_REG_BIT (used, eliminables[i].from); 1.1.1.3 root 346: #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM 347: SET_HARD_REG_BIT (used, HARD_FRAME_POINTER_REGNUM); 348: #endif 1.1 root 349: #else 350: SET_HARD_REG_BIT (used, FRAME_POINTER_REGNUM); 351: #endif 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: 1.1.1.4 root 358: #ifdef CLASS_CANNOT_CHANGE_SIZE 359: if (changes_size) 360: IOR_HARD_REG_SET (used, 361: reg_class_contents[(int) CLASS_CANNOT_CHANGE_SIZE]); 362: #endif 363: 1.1 root 364: for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) 365: { 366: #ifdef REG_ALLOC_ORDER 367: int regno = reg_alloc_order[i]; 368: #else 369: int regno = i; 370: #endif 371: 372: /* If a register has screwy overlap problems, 373: don't use it at all if not optimizing. 374: Actually this is only for the 387 stack register, 375: and it's because subsequent code won't work. */ 376: #ifdef OVERLAPPING_REGNO_P 377: if (OVERLAPPING_REGNO_P (regno)) 378: continue; 379: #endif 380: 381: if (! TEST_HARD_REG_BIT (used, regno) 382: && HARD_REGNO_MODE_OK (regno, mode)) 383: { 384: register int j; 385: register int size1 = HARD_REGNO_NREGS (regno, mode); 386: for (j = 1; j < size1 && ! TEST_HARD_REG_BIT (used, regno + j); j++); 387: if (j == size1) 388: { 389: CLEAR_HARD_REG_SET (this_reg); 390: while (--j >= 0) 391: SET_HARD_REG_BIT (this_reg, regno + j); 392: for (ins = born_insn; ins < dead_insn; ins++) 393: { 394: IOR_HARD_REG_SET (after_insn_hard_regs[ins], this_reg); 395: } 396: return regno; 397: } 398: #ifndef REG_ALLOC_ORDER 1.1.1.4 root 399: i += j; /* Skip starting points we know will lose */ 1.1 root 400: #endif 401: } 402: } 1.1.1.4 root 403: 1.1 root 404: return -1; 405: } 406: 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: { 1.1.1.4 root 415: register RTX_CODE code; 1.1 root 416: register char *fmt; 417: register int regno, i; 418: 1.1.1.4 root 419: if (x == 0) 420: return; 421: 422: code = GET_CODE (x); 423: 1.1 root 424: if (code == SET || code == CLOBBER) 425: { 1.1.1.5 ! root 426: if (SET_DEST (x) != 0 ! 427: && (GET_CODE (SET_DEST (x)) == REG ! 428: || (GET_CODE (SET_DEST (x)) == SUBREG ! 429: && GET_CODE (SUBREG_REG (SET_DEST (x))) == REG ! 430: && (REGNO (SUBREG_REG (SET_DEST (x))) ! 431: >= FIRST_PSEUDO_REGISTER)))) 1.1 root 432: { 433: /* Register is being assigned. */ 1.1.1.5 ! root 434: /* If setting a SUBREG, we treat the entire reg as being set. */ ! 435: if (GET_CODE (SET_DEST (x)) == SUBREG) ! 436: regno = REGNO (SUBREG_REG (SET_DEST (x))); ! 437: else ! 438: regno = REGNO (SET_DEST (x)); 1.1 root 439: 440: /* For hard regs, update the where-live info. */ 441: if (regno < FIRST_PSEUDO_REGISTER) 442: { 443: register int j 444: = HARD_REGNO_NREGS (regno, GET_MODE (SET_DEST (x))); 1.1.1.4 root 445: 1.1 root 446: while (--j >= 0) 447: { 448: regs_ever_live[regno+j] = 1; 449: regs_live[regno+j] = 0; 1.1.1.4 root 450: 1.1 root 451: /* The following line is for unused outputs; 452: they do get stored even though never used again. */ 453: MARK_LIVE_AFTER (insn, regno); 1.1.1.4 root 454: 1.1 root 455: /* When a hard reg is clobbered, mark it in use 456: just before this insn, so it is live all through. */ 457: if (code == CLOBBER && INSN_SUID (insn) > 0) 458: SET_HARD_REG_BIT (after_insn_hard_regs[INSN_SUID (insn) - 1], 459: regno); 460: } 461: } 462: /* For pseudo regs, record where born, where dead, number of 463: times used, and whether live across a call. */ 464: else 465: { 466: /* Update the life-interval bounds of this pseudo reg. */ 467: 468: /* When a pseudo-reg is CLOBBERed, it is born just before 469: the clobbering insn. When setting, just after. */ 470: int where_born = INSN_SUID (insn) - (code == CLOBBER); 471: 472: reg_where_born[regno] = where_born; 1.1.1.4 root 473: 1.1 root 474: /* The reg must live at least one insn even 475: in it is never again used--because it has to go 476: in SOME hard reg. Mark it as dying after the current 477: insn so that it will conflict with any other outputs of 478: this insn. */ 479: if (reg_where_dead[regno] < where_born + 2) 1.1.1.4 root 480: { 481: reg_where_dead[regno] = where_born + 2; 482: regs_live[regno] = 1; 483: } 1.1 root 484: 485: /* Count the refs of this reg. */ 486: reg_n_refs[regno]++; 487: 488: if (last_call_suid < reg_where_dead[regno]) 489: reg_n_calls_crossed[regno] += 1; 490: } 491: } 1.1.1.4 root 492: 1.1 root 493: /* Record references from the value being set, 494: or from addresses in the place being set if that's not a reg. 495: If setting a SUBREG, we treat the entire reg as *used*. */ 496: if (code == SET) 497: { 498: stupid_mark_refs (SET_SRC (x), insn); 499: if (GET_CODE (SET_DEST (x)) != REG) 500: stupid_mark_refs (SET_DEST (x), insn); 501: } 502: return; 503: } 504: 1.1.1.4 root 505: else if (code == SUBREG 506: && GET_CODE (SUBREG_REG (x)) == REG 507: && REGNO (SUBREG_REG (x)) >= FIRST_PSEUDO_REGISTER 508: && (GET_MODE_SIZE (GET_MODE (x)) 509: != GET_MODE_SIZE (GET_MODE (SUBREG_REG (x)))) 510: && (INTEGRAL_MODE_P (GET_MODE (x)) 511: || INTEGRAL_MODE_P (GET_MODE (SUBREG_REG (x))))) 512: regs_change_size[REGNO (SUBREG_REG (x))] = 1; 513: 1.1 root 514: /* Register value being used, not set. */ 515: 1.1.1.4 root 516: else if (code == REG) 1.1 root 517: { 518: regno = REGNO (x); 519: if (regno < FIRST_PSEUDO_REGISTER) 520: { 521: /* Hard reg: mark it live for continuing scan of previous insns. */ 522: register int j = HARD_REGNO_NREGS (regno, GET_MODE (x)); 523: while (--j >= 0) 524: { 525: regs_ever_live[regno+j] = 1; 526: regs_live[regno+j] = 1; 527: } 528: } 529: else 530: { 531: /* Pseudo reg: record first use, last use and number of uses. */ 532: 533: reg_where_born[regno] = INSN_SUID (insn); 534: reg_n_refs[regno]++; 535: if (regs_live[regno] == 0) 536: { 537: regs_live[regno] = 1; 538: reg_where_dead[regno] = INSN_SUID (insn); 539: } 540: } 541: return; 542: } 543: 544: /* Recursive scan of all other rtx's. */ 545: 546: fmt = GET_RTX_FORMAT (code); 547: for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) 548: { 549: if (fmt[i] == 'e') 550: stupid_mark_refs (XEXP (x, i), insn); 551: if (fmt[i] == 'E') 552: { 553: register int j; 554: for (j = XVECLEN (x, i) - 1; j >= 0; j--) 555: stupid_mark_refs (XVECEXP (x, i, j), insn); 556: } 557: } 558: }
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