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1.1 root 1: /* Dummy data flow analysis for GNU compiler in nonoptimizing mode. 1.1.1.4 ! root 2: Copyright (C) 1987, 1991, 1994 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 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: #include "flags.h" 50: 51: /* Vector mapping INSN_UIDs to suids. 1.1.1.2 root 52: The suids are like uids but increase monotonically always. 1.1 root 53: We use them to see whether a subroutine call came 54: between a variable's birth and its death. */ 55: 56: static int *uid_suid; 57: 58: /* Get the suid of an insn. */ 59: 60: #define INSN_SUID(INSN) (uid_suid[INSN_UID (INSN)]) 61: 62: /* Record the suid of the last CALL_INSN 63: so we can tell whether a pseudo reg crosses any calls. */ 64: 65: static int last_call_suid; 66: 67: /* Element N is suid of insn where life span of pseudo reg N ends. 68: Element is 0 if register N has not been seen yet on backward scan. */ 69: 70: static int *reg_where_dead; 71: 72: /* Element N is suid of insn where life span of pseudo reg N begins. */ 73: 74: static int *reg_where_born; 75: 76: /* Numbers of pseudo-regs to be allocated, highest priority first. */ 77: 78: static int *reg_order; 79: 80: /* Indexed by reg number (hard or pseudo), nonzero if register is live 81: at the current point in the instruction stream. */ 82: 83: static char *regs_live; 84: 1.1.1.4 ! root 85: /* Indexed by reg number, nonzero if reg was used in a SUBREG that changes ! 86: its size. */ ! 87: ! 88: static char *regs_change_size; ! 89: 1.1 root 90: /* Indexed by insn's suid, the set of hard regs live after that insn. */ 91: 92: static HARD_REG_SET *after_insn_hard_regs; 93: 94: /* Record that hard reg REGNO is live after insn INSN. */ 95: 96: #define MARK_LIVE_AFTER(INSN,REGNO) \ 97: SET_HARD_REG_BIT (after_insn_hard_regs[INSN_SUID (INSN)], (REGNO)) 98: 1.1.1.4 ! root 99: static int stupid_reg_compare PROTO((int *, int *)); ! 100: static int stupid_find_reg PROTO((int, enum reg_class, enum machine_mode, ! 101: int, int, int)); ! 102: static void stupid_mark_refs PROTO((rtx, rtx)); 1.1 root 103: 104: /* Stupid life analysis is for the case where only variables declared 105: `register' go in registers. For this case, we mark all 106: pseudo-registers that belong to register variables as 107: dying in the last instruction of the function, and all other 108: pseudo registers as dying in the last place they are referenced. 109: Hard registers are marked as dying in the last reference before 110: the end or before each store into them. */ 111: 112: void 113: stupid_life_analysis (f, nregs, file) 114: rtx f; 115: int nregs; 116: FILE *file; 117: { 118: register int i; 119: register rtx last, insn; 1.1.1.4 ! root 120: int max_uid, max_suid; 1.1 root 121: 122: bzero (regs_ever_live, sizeof regs_ever_live); 123: 124: regs_live = (char *) alloca (nregs); 125: 126: /* First find the last real insn, and count the number of insns, 127: and assign insns their suids. */ 128: 129: for (insn = f, i = 0; insn; insn = NEXT_INSN (insn)) 130: if (INSN_UID (insn) > i) 131: i = INSN_UID (insn); 132: 133: max_uid = i + 1; 134: uid_suid = (int *) alloca ((i + 1) * sizeof (int)); 135: 136: /* Compute the mapping from uids to suids. 137: Suids are numbers assigned to insns, like uids, 138: except that suids increase monotonically through the code. */ 139: 140: last = 0; /* In case of empty function body */ 141: for (insn = f, i = 0; insn; insn = NEXT_INSN (insn)) 142: { 1.1.1.4 ! root 143: if (GET_RTX_CLASS (GET_CODE (insn)) == 'i') 1.1 root 144: last = insn; 1.1.1.4 ! root 145: 1.1 root 146: INSN_SUID (insn) = ++i; 147: } 148: 149: last_call_suid = i + 1; 1.1.1.4 ! root 150: max_suid = i + 1; 1.1 root 151: 152: max_regno = nregs; 153: 154: /* Allocate tables to record info about regs. */ 155: 156: reg_where_dead = (int *) alloca (nregs * sizeof (int)); 1.1.1.4 ! root 157: bzero ((char *) reg_where_dead, nregs * sizeof (int)); 1.1 root 158: 159: reg_where_born = (int *) alloca (nregs * sizeof (int)); 1.1.1.4 ! root 160: bzero ((char *) reg_where_born, nregs * sizeof (int)); 1.1 root 161: 162: reg_order = (int *) alloca (nregs * sizeof (int)); 1.1.1.4 ! root 163: bzero ((char *) reg_order, nregs * sizeof (int)); ! 164: ! 165: regs_change_size = (char *) alloca (nregs * sizeof (char)); ! 166: bzero ((char *) regs_change_size, nregs * sizeof (char)); 1.1 root 167: 168: reg_renumber = (short *) oballoc (nregs * sizeof (short)); 169: for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) 170: reg_renumber[i] = i; 171: 1.1.1.4 ! root 172: for (i = FIRST_VIRTUAL_REGISTER; i < max_regno; i++) 1.1 root 173: reg_renumber[i] = -1; 174: 1.1.1.4 ! root 175: after_insn_hard_regs ! 176: = (HARD_REG_SET *) alloca (max_suid * sizeof (HARD_REG_SET)); ! 177: ! 178: bzero ((char *) after_insn_hard_regs, max_suid * sizeof (HARD_REG_SET)); 1.1 root 179: 180: /* Allocate and zero out many data structures 181: that will record the data from lifetime analysis. */ 182: 183: allocate_for_life_analysis (); 184: 185: for (i = 0; i < max_regno; i++) 1.1.1.4 ! root 186: reg_n_deaths[i] = 1; 1.1 root 187: 188: bzero (regs_live, nregs); 189: 190: /* Find where each pseudo register is born and dies, 191: by scanning all insns from the end to the start 192: and noting all mentions of the registers. 193: 194: Also find where each hard register is live 195: and record that info in after_insn_hard_regs. 196: regs_live[I] is 1 if hard reg I is live 197: at the current point in the scan. */ 198: 199: for (insn = last; insn; insn = PREV_INSN (insn)) 200: { 201: register HARD_REG_SET *p = after_insn_hard_regs + INSN_SUID (insn); 202: 1.1.1.4 ! root 203: /* Copy the info in regs_live into the element of after_insn_hard_regs 1.1 root 204: for the current position in the rtl code. */ 205: 206: for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) 207: if (regs_live[i]) 208: SET_HARD_REG_BIT (*p, i); 209: 1.1.1.4 ! root 210: /* Update which hard regs are currently live ! 211: and also the birth and death suids of pseudo regs ! 212: based on the pattern of this insn. */ ! 213: ! 214: if (GET_RTX_CLASS (GET_CODE (insn)) == 'i') ! 215: stupid_mark_refs (PATTERN (insn), insn); ! 216: 1.1 root 217: /* Mark all call-clobbered regs as live after each call insn 218: so that a pseudo whose life span includes this insn 219: will not go in one of them. 220: Then mark those regs as all dead for the continuing scan 221: of the insns before the call. */ 222: 223: if (GET_CODE (insn) == CALL_INSN) 224: { 225: last_call_suid = INSN_SUID (insn); 226: IOR_HARD_REG_SET (after_insn_hard_regs[last_call_suid], 227: call_used_reg_set); 1.1.1.4 ! root 228: 1.1 root 229: for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) 230: if (call_used_regs[i]) 231: regs_live[i] = 0; 232: 1.1.1.4 ! root 233: /* It is important that this be done after processing the insn's ! 234: pattern because we want the function result register to still ! 235: be live if it's also used to pass arguments. */ ! 236: stupid_mark_refs (CALL_INSN_FUNCTION_USAGE (insn), insn); 1.1 root 237: } 238: } 239: 240: /* Now decide the order in which to allocate the pseudo registers. */ 241: 242: for (i = LAST_VIRTUAL_REGISTER + 1; i < max_regno; i++) 243: reg_order[i] = i; 244: 245: qsort (®_order[LAST_VIRTUAL_REGISTER + 1], 246: max_regno - LAST_VIRTUAL_REGISTER - 1, sizeof (int), 247: stupid_reg_compare); 248: 249: /* Now, in that order, try to find hard registers for those pseudo regs. */ 250: 251: for (i = LAST_VIRTUAL_REGISTER + 1; i < max_regno; i++) 252: { 253: register int r = reg_order[i]; 254: 255: /* Some regnos disappear from the rtl. Ignore them to avoid crash. */ 256: if (regno_reg_rtx[r] == 0) 257: continue; 258: 259: /* Now find the best hard-register class for this pseudo register */ 260: if (N_REG_CLASSES > 1) 1.1.1.4 ! root 261: reg_renumber[r] = stupid_find_reg (reg_n_calls_crossed[r], ! 262: reg_preferred_class (r), ! 263: PSEUDO_REGNO_MODE (r), ! 264: reg_where_born[r], ! 265: reg_where_dead[r], ! 266: regs_change_size[r]); 1.1 root 267: 1.1.1.4 ! root 268: /* If no reg available in that class, try alternate class. */ ! 269: if (reg_renumber[r] == -1 && reg_alternate_class (r) != NO_REGS) 1.1 root 270: reg_renumber[r] = stupid_find_reg (reg_n_calls_crossed[r], 1.1.1.4 ! root 271: reg_alternate_class (r), 1.1 root 272: PSEUDO_REGNO_MODE (r), 273: reg_where_born[r], 274: reg_where_dead[r], 1.1.1.4 ! root 275: regs_change_size[r]); 1.1 root 276: } 277: 278: if (file) 279: dump_flow_info (file); 280: } 281: 282: /* Comparison function for qsort. 283: Returns -1 (1) if register *R1P is higher priority than *R2P. */ 284: 285: static int 286: stupid_reg_compare (r1p, r2p) 287: int *r1p, *r2p; 288: { 289: register int r1 = *r1p, r2 = *r2p; 290: register int len1 = reg_where_dead[r1] - reg_where_born[r1]; 291: register int len2 = reg_where_dead[r2] - reg_where_born[r2]; 292: int tem; 293: 294: tem = len2 - len1; 1.1.1.4 ! root 295: if (tem != 0) ! 296: return tem; 1.1 root 297: 298: tem = reg_n_refs[r1] - reg_n_refs[r2]; 1.1.1.4 ! root 299: if (tem != 0) ! 300: return tem; 1.1 root 301: 302: /* If regs are equally good, sort by regno, 303: so that the results of qsort leave nothing to chance. */ 304: return r1 - r2; 305: } 306: 307: /* Find a block of SIZE words of hard registers in reg_class CLASS 308: that can hold a value of machine-mode MODE 309: (but actually we test only the first of the block for holding MODE) 310: currently free from after insn whose suid is BIRTH 311: through the insn whose suid is DEATH, 312: and return the number of the first of them. 313: Return -1 if such a block cannot be found. 314: 315: If CALL_PRESERVED is nonzero, insist on registers preserved 316: over subroutine calls, and return -1 if cannot find such. 1.1.1.4 ! root 317: ! 318: If CHANGES_SIZE is nonzero, it means this register was used as the ! 319: operand of a SUBREG that changes its size. */ 1.1 root 320: 321: static int 322: stupid_find_reg (call_preserved, class, mode, 1.1.1.4 ! root 323: born_insn, dead_insn, changes_size) 1.1 root 324: int call_preserved; 325: enum reg_class class; 326: enum machine_mode mode; 327: int born_insn, dead_insn; 1.1.1.4 ! root 328: int changes_size; 1.1 root 329: { 330: register int i, ins; 331: #ifdef HARD_REG_SET 332: register /* Declare them register if they are scalars. */ 333: #endif 334: HARD_REG_SET used, this_reg; 335: #ifdef ELIMINABLE_REGS 336: static struct {int from, to; } eliminables[] = ELIMINABLE_REGS; 337: #endif 338: 339: COPY_HARD_REG_SET (used, 340: call_preserved ? call_used_reg_set : fixed_reg_set); 341: 342: #ifdef ELIMINABLE_REGS 343: for (i = 0; i < sizeof eliminables / sizeof eliminables[0]; i++) 344: SET_HARD_REG_BIT (used, eliminables[i].from); 1.1.1.3 root 345: #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM 346: SET_HARD_REG_BIT (used, HARD_FRAME_POINTER_REGNUM); 347: #endif 1.1 root 348: #else 349: SET_HARD_REG_BIT (used, FRAME_POINTER_REGNUM); 350: #endif 351: 352: for (ins = born_insn; ins < dead_insn; ins++) 353: IOR_HARD_REG_SET (used, after_insn_hard_regs[ins]); 354: 355: IOR_COMPL_HARD_REG_SET (used, reg_class_contents[(int) class]); 356: 1.1.1.4 ! root 357: #ifdef CLASS_CANNOT_CHANGE_SIZE ! 358: if (changes_size) ! 359: IOR_HARD_REG_SET (used, ! 360: reg_class_contents[(int) CLASS_CANNOT_CHANGE_SIZE]); ! 361: #endif ! 362: 1.1 root 363: for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) 364: { 365: #ifdef REG_ALLOC_ORDER 366: int regno = reg_alloc_order[i]; 367: #else 368: int regno = i; 369: #endif 370: 371: /* If a register has screwy overlap problems, 372: don't use it at all if not optimizing. 373: Actually this is only for the 387 stack register, 374: and it's because subsequent code won't work. */ 375: #ifdef OVERLAPPING_REGNO_P 376: if (OVERLAPPING_REGNO_P (regno)) 377: continue; 378: #endif 379: 380: if (! TEST_HARD_REG_BIT (used, regno) 381: && HARD_REGNO_MODE_OK (regno, mode)) 382: { 383: register int j; 384: register int size1 = HARD_REGNO_NREGS (regno, mode); 385: for (j = 1; j < size1 && ! TEST_HARD_REG_BIT (used, regno + j); j++); 386: if (j == size1) 387: { 388: CLEAR_HARD_REG_SET (this_reg); 389: while (--j >= 0) 390: SET_HARD_REG_BIT (this_reg, regno + j); 391: for (ins = born_insn; ins < dead_insn; ins++) 392: { 393: IOR_HARD_REG_SET (after_insn_hard_regs[ins], this_reg); 394: } 395: return regno; 396: } 397: #ifndef REG_ALLOC_ORDER 1.1.1.4 ! root 398: i += j; /* Skip starting points we know will lose */ 1.1 root 399: #endif 400: } 401: } 1.1.1.4 ! root 402: 1.1 root 403: return -1; 404: } 405: 406: /* Walk X, noting all assignments and references to registers 407: and recording what they imply about life spans. 408: INSN is the current insn, supplied so we can find its suid. */ 409: 410: static void 411: stupid_mark_refs (x, insn) 412: rtx x, insn; 413: { 1.1.1.4 ! root 414: register RTX_CODE code; 1.1 root 415: register char *fmt; 416: register int regno, i; 417: 1.1.1.4 ! root 418: if (x == 0) ! 419: return; ! 420: ! 421: code = GET_CODE (x); ! 422: 1.1 root 423: if (code == SET || code == CLOBBER) 424: { 425: if (SET_DEST (x) != 0 && GET_CODE (SET_DEST (x)) == REG) 426: { 427: /* Register is being assigned. */ 428: regno = REGNO (SET_DEST (x)); 429: 430: /* For hard regs, update the where-live info. */ 431: if (regno < FIRST_PSEUDO_REGISTER) 432: { 433: register int j 434: = HARD_REGNO_NREGS (regno, GET_MODE (SET_DEST (x))); 1.1.1.4 ! root 435: 1.1 root 436: while (--j >= 0) 437: { 438: regs_ever_live[regno+j] = 1; 439: regs_live[regno+j] = 0; 1.1.1.4 ! root 440: 1.1 root 441: /* The following line is for unused outputs; 442: they do get stored even though never used again. */ 443: MARK_LIVE_AFTER (insn, regno); 1.1.1.4 ! root 444: 1.1 root 445: /* When a hard reg is clobbered, mark it in use 446: just before this insn, so it is live all through. */ 447: if (code == CLOBBER && INSN_SUID (insn) > 0) 448: SET_HARD_REG_BIT (after_insn_hard_regs[INSN_SUID (insn) - 1], 449: regno); 450: } 451: } 452: /* For pseudo regs, record where born, where dead, number of 453: times used, and whether live across a call. */ 454: else 455: { 456: /* Update the life-interval bounds of this pseudo reg. */ 457: 458: /* When a pseudo-reg is CLOBBERed, it is born just before 459: the clobbering insn. When setting, just after. */ 460: int where_born = INSN_SUID (insn) - (code == CLOBBER); 461: 462: reg_where_born[regno] = where_born; 1.1.1.4 ! root 463: 1.1 root 464: /* The reg must live at least one insn even 465: in it is never again used--because it has to go 466: in SOME hard reg. Mark it as dying after the current 467: insn so that it will conflict with any other outputs of 468: this insn. */ 469: if (reg_where_dead[regno] < where_born + 2) 1.1.1.4 ! root 470: { ! 471: reg_where_dead[regno] = where_born + 2; ! 472: regs_live[regno] = 1; ! 473: } 1.1 root 474: 475: /* Count the refs of this reg. */ 476: reg_n_refs[regno]++; 477: 478: if (last_call_suid < reg_where_dead[regno]) 479: reg_n_calls_crossed[regno] += 1; 480: } 481: } 1.1.1.4 ! root 482: 1.1 root 483: /* Record references from the value being set, 484: or from addresses in the place being set if that's not a reg. 485: If setting a SUBREG, we treat the entire reg as *used*. */ 486: if (code == SET) 487: { 488: stupid_mark_refs (SET_SRC (x), insn); 489: if (GET_CODE (SET_DEST (x)) != REG) 490: stupid_mark_refs (SET_DEST (x), insn); 491: } 492: return; 493: } 494: 1.1.1.4 ! root 495: else if (code == SUBREG ! 496: && GET_CODE (SUBREG_REG (x)) == REG ! 497: && REGNO (SUBREG_REG (x)) >= FIRST_PSEUDO_REGISTER ! 498: && (GET_MODE_SIZE (GET_MODE (x)) ! 499: != GET_MODE_SIZE (GET_MODE (SUBREG_REG (x)))) ! 500: && (INTEGRAL_MODE_P (GET_MODE (x)) ! 501: || INTEGRAL_MODE_P (GET_MODE (SUBREG_REG (x))))) ! 502: regs_change_size[REGNO (SUBREG_REG (x))] = 1; ! 503: 1.1 root 504: /* Register value being used, not set. */ 505: 1.1.1.4 ! root 506: else if (code == REG) 1.1 root 507: { 508: regno = REGNO (x); 509: if (regno < FIRST_PSEUDO_REGISTER) 510: { 511: /* Hard reg: mark it live for continuing scan of previous insns. */ 512: register int j = HARD_REGNO_NREGS (regno, GET_MODE (x)); 513: while (--j >= 0) 514: { 515: regs_ever_live[regno+j] = 1; 516: regs_live[regno+j] = 1; 517: } 518: } 519: else 520: { 521: /* Pseudo reg: record first use, last use and number of uses. */ 522: 523: reg_where_born[regno] = INSN_SUID (insn); 524: reg_n_refs[regno]++; 525: if (regs_live[regno] == 0) 526: { 527: regs_live[regno] = 1; 528: reg_where_dead[regno] = INSN_SUID (insn); 529: } 530: } 531: return; 532: } 533: 534: /* Recursive scan of all other rtx's. */ 535: 536: fmt = GET_RTX_FORMAT (code); 537: for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) 538: { 539: if (fmt[i] == 'e') 540: stupid_mark_refs (XEXP (x, i), insn); 541: if (fmt[i] == 'E') 542: { 543: register int j; 544: for (j = XVECLEN (x, i) - 1; j >= 0; j--) 545: stupid_mark_refs (XVECEXP (x, i, j), insn); 546: } 547: } 548: }
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