| 1 | /* |
| 2 | * Copyright (c) 1982 Regents of the University of California |
| 3 | */ |
| 4 | #ifndef lint |
| 5 | static char sccsid[] = "@(#)asjxxx.c 4.7 %G%"; |
| 6 | #endif not lint |
| 7 | |
| 8 | #include <stdio.h> |
| 9 | #include "as.h" |
| 10 | #include "assyms.h" |
| 11 | |
| 12 | #define JBR 0x11 |
| 13 | #define BRW 0x31 |
| 14 | #define JMP 0x17 |
| 15 | |
| 16 | /* |
| 17 | * The number of bytes to add if the jxxx must be "exploded" |
| 18 | * into the long form |
| 19 | */ |
| 20 | #define JBRDELTA 1 /* brb <byte> ==> brw <byte> <byte> */ |
| 21 | #define JXXXDELTA 3 /* brb <byte> ==> brb <byte> brw <byte> <byte> */ |
| 22 | #define JBRJDELTA d124 /* brb <byte> ==> jmp L^(pc) <byte>*d124 */ |
| 23 | #define JXXXJDELTA d124+2 /* brb <byte> ==> brb <byte> jmp L^(pc) <byte>*d124 */ |
| 24 | |
| 25 | int jbrfsize = JBRDELTA; |
| 26 | int jxxxfsize = JXXXDELTA; |
| 27 | |
| 28 | /* |
| 29 | * These variables are filled by asscan.c with the |
| 30 | * last name encountered (a pointer buried in the intermediate file), |
| 31 | * and the last jxxx symbol table entry encountered. |
| 32 | */ |
| 33 | struct symtab *lastnam; |
| 34 | struct symtab *lastjxxx; |
| 35 | |
| 36 | initijxxx() |
| 37 | { |
| 38 | jbrfsize = jxxxJUMP ? JBRJDELTA : JBRDELTA; |
| 39 | jxxxfsize = jxxxJUMP ? JXXXJDELTA : JXXXDELTA; |
| 40 | /* |
| 41 | * Note: ifjxxxJUMP is set, then we do NOT do any tunnelling; |
| 42 | * this was too complicated to figure out, and in the first |
| 43 | * version of the assembler, tunnelling proved to be the hardest |
| 44 | * to get to work! |
| 45 | */ |
| 46 | } |
| 47 | /* |
| 48 | * Handle jxxx instructions |
| 49 | */ |
| 50 | ijxout(opcode, ap, nact) |
| 51 | struct Opcode opcode; |
| 52 | struct arg *ap; |
| 53 | int nact; |
| 54 | { |
| 55 | if (passno == 1){ |
| 56 | /* |
| 57 | * READ THIS BEFORE LOOKING AT jxxxfix() |
| 58 | * |
| 59 | * Record the jxxx in a special symbol table entry |
| 60 | */ |
| 61 | register struct symtab *jumpfrom; |
| 62 | |
| 63 | /* |
| 64 | * We assume the MINIMAL length |
| 65 | */ |
| 66 | putins(opcode, ap, nact); |
| 67 | jumpfrom = lastjxxx; |
| 68 | jumpfrom->s_tag = JXACTIVE; |
| 69 | jumpfrom->s_jxbump = 0; |
| 70 | if (opcode.Op_popcode == JBR) |
| 71 | jumpfrom->s_jxfear = jbrfsize; |
| 72 | else |
| 73 | jumpfrom->s_jxfear = jxxxfsize; |
| 74 | if (lastnam == 0) |
| 75 | yyerror("jxxx destination not a label"); |
| 76 | jumpfrom->s_dest = lastnam; |
| 77 | jumpfrom->s_type = dotp->e_xtype; /*only TEXT or DATA*/ |
| 78 | jumpfrom->s_index = dotp-usedot; |
| 79 | /* |
| 80 | * value ALWAYS (ALWAYS!!!) indexes the next instruction |
| 81 | * after the jump, even in the jump must be exploded |
| 82 | * (bumped) |
| 83 | */ |
| 84 | jumpfrom->s_value = dotp->e_xvalue; |
| 85 | njxxx++; |
| 86 | } else {/* pass2, resolve */ |
| 87 | /* |
| 88 | * READ THIS AFTER LOOKING AT jxxxfix() |
| 89 | */ |
| 90 | reg long oxvalue; |
| 91 | reg struct exp *xp; |
| 92 | reg struct symtab *tunnel; |
| 93 | reg struct arg *aplast; |
| 94 | struct Opcode nopcode; |
| 95 | |
| 96 | aplast = ap + nact - 1; |
| 97 | xp = aplast->a_xp; |
| 98 | if (lastjxxx->s_tag == JXTUNNEL){ |
| 99 | lastjxxx->s_tag = JXINACTIVE; |
| 100 | tunnel = lastjxxx->s_dest; |
| 101 | xp->e_xvalue = tunnel->s_value /*index of instruction following*/ |
| 102 | - 3 /* size of brw + word*/ |
| 103 | + ( ( (tunnel->s_jxfear == jbrfsize) && |
| 104 | (tunnel->s_jxbump == 0))?1:0); |
| 105 | /*non bumped branch byteis only 2 back*/ |
| 106 | } |
| 107 | if (lastjxxx->s_jxbump == 0){ /*wasn't bumped, so is short form*/ |
| 108 | putins(opcode, ap, nact); |
| 109 | } else { |
| 110 | if (opcode.Op_popcode != JBR){ |
| 111 | /* |
| 112 | * branch reverse conditional byte over |
| 113 | * branch unconditional word |
| 114 | */ |
| 115 | oxvalue = xp->e_xvalue; |
| 116 | xp->e_xvalue = lastjxxx->s_value; |
| 117 | nopcode = opcode; |
| 118 | nopcode.Op_popcode ^= 1; |
| 119 | putins(nopcode, ap, nact); |
| 120 | xp->e_xvalue = oxvalue; |
| 121 | } |
| 122 | nopcode.Op_eopcode = CORE; |
| 123 | nopcode.Op_popcode = jxxxJUMP ? JMP : BRW; |
| 124 | putins(nopcode, aplast, 1); |
| 125 | } |
| 126 | } |
| 127 | } |
| 128 | |
| 129 | jalign(xp, sp) |
| 130 | register struct exp *xp; |
| 131 | register struct symtab *sp; |
| 132 | { |
| 133 | register int mask; |
| 134 | /* |
| 135 | * Problem with .align |
| 136 | * |
| 137 | * When the loader constructs an executable file from |
| 138 | * a number of objects, it effectively concatnates |
| 139 | * together all of the text segments from all objects, |
| 140 | * and then all of the data segments. |
| 141 | * |
| 142 | * If we do an align by a large value, we can align |
| 143 | * within the a.out this assembly produces, but |
| 144 | * after the loader concatnates, the alignment can't |
| 145 | * be guaranteed if the objects preceding this one |
| 146 | * in the load are also aligned to the same size. |
| 147 | * |
| 148 | * Currently, the loader guarantees full word alignment. |
| 149 | * So, ridiculous aligns are caught here and converted |
| 150 | * to a .align 2, if possible. |
| 151 | */ |
| 152 | if ( ( (xp->e_xtype & XTYPE) != XABS) |
| 153 | || (xp->e_xvalue < 0) |
| 154 | || (xp->e_xvalue > 16) |
| 155 | ) { |
| 156 | yyerror("Illegal `align' argument"); |
| 157 | return; |
| 158 | } |
| 159 | if (xp->e_xvalue > 2){ |
| 160 | if (passno == 1){ |
| 161 | yywarning(".align %d is NOT preserved by the loader", |
| 162 | xp->e_xvalue); |
| 163 | yywarning(".align %d converted to .align 2", |
| 164 | xp->e_xvalue); |
| 165 | } |
| 166 | xp->e_xvalue = 2; |
| 167 | } |
| 168 | flushfield(NBPW/4); |
| 169 | if (passno == 1) { |
| 170 | sp->s_tag = JXALIGN; |
| 171 | sp->s_jxfear = (1 << xp->e_xvalue) - 1; |
| 172 | sp->s_type = dotp->e_xtype; |
| 173 | sp->s_index = dotp-usedot; |
| 174 | /* |
| 175 | * We guess that the align will take up at least one |
| 176 | * byte in the code output. We will correct for this |
| 177 | * initial high guess when we explode (bump) aligns |
| 178 | * when we fix the jxxxes. We must do this guess |
| 179 | * so that the symbol table is sorted correctly |
| 180 | * and labels declared to fall before the align |
| 181 | * really get their, instead of guessing zero size |
| 182 | * and have the label (incorrectly) fall after the jxxx. |
| 183 | * This is a quirk of our requirement that indices into |
| 184 | * the code stream point to the next byte following |
| 185 | * the logical entry in the symbol table |
| 186 | */ |
| 187 | dotp->e_xvalue += 1; |
| 188 | sp->s_value = dotp->e_xvalue; |
| 189 | njxxx++; |
| 190 | } else { |
| 191 | mask = (1 << xp->e_xvalue) - 1; |
| 192 | while (dotp->e_xvalue & mask) |
| 193 | Outb(0); |
| 194 | } |
| 195 | } |
| 196 | |
| 197 | /* |
| 198 | * Pass 1.5, resolve jxxx instructions and .align in .text |
| 199 | */ |
| 200 | jxxxfix() |
| 201 | { |
| 202 | register struct symtab *jumpfrom; |
| 203 | struct symtab **cojumpfrom, *ubjumpfrom; |
| 204 | register struct symtab *dest; |
| 205 | register struct symtab *intdest; /*intermediate dest*/ |
| 206 | register struct symtab **cointdest, *ubintdest; |
| 207 | |
| 208 | register struct symtab *tunnel; |
| 209 | int displ,nchange; |
| 210 | int badjxalign; /*if jump across an align*/ |
| 211 | int stillactives; /*if still active jxxxes*/ |
| 212 | int segno; /*current segment number*/ |
| 213 | int topono; /*which iteration in the topo sort*/ |
| 214 | register unsigned char tag; |
| 215 | /* |
| 216 | * consider each segment in turn... |
| 217 | */ |
| 218 | for (segno = 0; segno < NLOC + NLOC; segno++){ |
| 219 | badjxalign = 0; /*done on a per segment basis*/ |
| 220 | /* |
| 221 | * Do a lazy topological sort. |
| 222 | */ |
| 223 | for (topono = 1, nchange = 1; nchange != 0; topono++){ |
| 224 | #ifdef lint |
| 225 | topno = topno; |
| 226 | #endif lint |
| 227 | #ifdef DEBUG |
| 228 | if (debug) |
| 229 | printf("\nSegment %d, topo iteration %d\n", |
| 230 | segno, topono); |
| 231 | #endif |
| 232 | nchange = 0; |
| 233 | stillactives = 0; |
| 234 | /* |
| 235 | * We keep track of one possible tunnel location. |
| 236 | * A tunnel will eventually be an unconditional |
| 237 | * branch to the same place that another jxxx |
| 238 | * will want to branch to. We will turn a |
| 239 | * branch conditional/unconditional (word) that would |
| 240 | * have to get bumped because its destination is too |
| 241 | * far away, into a branch conditional/unconditional |
| 242 | * byte to the tunnel branch conditional/unconditional. |
| 243 | * Of course, the tunnel must branch to the same place |
| 244 | * as we want to go. |
| 245 | */ |
| 246 | tunnel = 0; /*initially, no tunnel*/ |
| 247 | SEGITERATE(segno, 0, 0, cojumpfrom, jumpfrom, ubjumpfrom, ++){ |
| 248 | tag = jumpfrom->s_tag; |
| 249 | if (tag <= IGNOREBOUND) |
| 250 | continue; /*just an ordinary symbol*/ |
| 251 | if (tag == JXALIGN){ |
| 252 | tunnel = 0; /*avoid tunneling across a flex alocation*/ |
| 253 | continue; /*we take care of these later*/ |
| 254 | } |
| 255 | if ( jumpfrom->s_jxfear == jbrfsize /*unconditional*/ |
| 256 | || ( tag == JXINACTIVE /*inactive bumped*/ |
| 257 | && (jumpfrom->s_jxbump != 0) |
| 258 | ) |
| 259 | ) tunnel = jumpfrom; |
| 260 | if (tag != JXACTIVE) |
| 261 | continue; |
| 262 | dest = jumpfrom->s_dest; |
| 263 | if (jumpfrom->s_index != dest->s_index){ |
| 264 | yyerror("Intersegment jxxx"); |
| 265 | continue; |
| 266 | } |
| 267 | displ = dest->s_value - jumpfrom->s_value; |
| 268 | if (displ < MINBYTE || displ > MAXBYTE) { |
| 269 | /* |
| 270 | * This is an immediate lose! |
| 271 | * |
| 272 | * We first attempt to tunnel |
| 273 | * by finding an intervening jump that |
| 274 | * has the same destination. |
| 275 | * The tunnel is always the first preceeding |
| 276 | * jxxx instruction, so the displacement |
| 277 | * to the tunnel is less than zero, and |
| 278 | * its relative position will be unaffected |
| 279 | * by future jxxx expansions. |
| 280 | * |
| 281 | * No tunnels if doing jumps... |
| 282 | */ |
| 283 | if ( (!jxxxJUMP) |
| 284 | && (jumpfrom->s_jxfear > jbrfsize) |
| 285 | && (tunnel) |
| 286 | && (tunnel->s_dest == jumpfrom->s_dest) |
| 287 | && (tunnel->s_index == jumpfrom->s_index) |
| 288 | && (tunnel->s_value - jumpfrom->s_value >= |
| 289 | MINBYTE + jxxxfsize) |
| 290 | ) { |
| 291 | /* |
| 292 | * tunnelling is OK |
| 293 | */ |
| 294 | jumpfrom->s_dest = tunnel; |
| 295 | /* |
| 296 | * no bumping needed, this |
| 297 | * is now effectively inactive |
| 298 | * but must be remembered |
| 299 | */ |
| 300 | jumpfrom->s_tag = JXTUNNEL; |
| 301 | #ifdef DEBUG |
| 302 | if(debug) |
| 303 | printf("Tunnel from %s from line %d\n", |
| 304 | FETCHNAME(jumpfrom), |
| 305 | lineno); |
| 306 | #endif |
| 307 | continue; |
| 308 | } else { /*tunneling not possible*/ |
| 309 | /* |
| 310 | * since this will be turned |
| 311 | * into a bumped jump, we can |
| 312 | * use the unconditional jump |
| 313 | * as a tunnel |
| 314 | */ |
| 315 | tunnel = jumpfrom; |
| 316 | jumpfrom->s_tag = JXNOTYET; |
| 317 | ++nchange; |
| 318 | continue; |
| 319 | } |
| 320 | } /*end of immediate lose*/ |
| 321 | /* |
| 322 | * Do a forward search for an intervening jxxx |
| 323 | */ |
| 324 | if (displ >= 0) { |
| 325 | SEGITERATE(segno, cojumpfrom + 1,0,cointdest, |
| 326 | intdest, ubintdest, ++){ |
| 327 | if (intdest->s_value > dest->s_value) |
| 328 | break; /* beyond destination */ |
| 329 | if (intdest->s_tag <= JXQUESTIONABLE) |
| 330 | continue; /*frozen solid*/ |
| 331 | if (intdest->s_tag == JXALIGN){ |
| 332 | jumpfrom->s_jxoveralign = 1; |
| 333 | badjxalign++; |
| 334 | } |
| 335 | /* |
| 336 | * we assume the worst case |
| 337 | * for unfrozen jxxxxes |
| 338 | */ |
| 339 | displ += intdest->s_jxfear; |
| 340 | } |
| 341 | if (displ <= MAXBYTE){ |
| 342 | /* |
| 343 | * the worst possible conditions |
| 344 | * can't hurt us, so forget about |
| 345 | * this jump |
| 346 | */ |
| 347 | jumpfrom->s_tag = JXINACTIVE; |
| 348 | } else { |
| 349 | stillactives++; |
| 350 | } |
| 351 | } else { |
| 352 | /* |
| 353 | * backward search for intervening jxxx |
| 354 | */ |
| 355 | SEGITERATE(segno, cojumpfrom - 1,1,cointdest, |
| 356 | intdest, ubintdest, --){ |
| 357 | if (intdest->s_value <= dest->s_value) |
| 358 | break; /* beyond destination */ |
| 359 | if (intdest->s_tag <= JXQUESTIONABLE) |
| 360 | continue; /*frozen solid*/ |
| 361 | if (intdest->s_tag == JXALIGN){ |
| 362 | jumpfrom->s_jxoveralign = 1; |
| 363 | badjxalign++; |
| 364 | } |
| 365 | displ -= intdest->s_jxfear; |
| 366 | } |
| 367 | if (displ >= MINBYTE) { |
| 368 | jumpfrom->s_tag = JXINACTIVE; |
| 369 | } else { |
| 370 | stillactives++; |
| 371 | } |
| 372 | } /*end of backwards search*/ |
| 373 | } /*end of iterating through all symbols in this seg*/ |
| 374 | |
| 375 | if (nchange == 0) { |
| 376 | /* |
| 377 | * Now, if there are still active jxxx entries, |
| 378 | * we are partially deadlocked. We can leave |
| 379 | * these jxxx entries in their assumed short jump |
| 380 | * form, as all initial displacement calcualtions |
| 381 | * are hanging on unresolved jxxx instructions |
| 382 | * that might explode into a long form, causing |
| 383 | * other jxxxes jumping across the first set of |
| 384 | * jxxxes to explode, etc. |
| 385 | * However, if a jxxx jumps across a .align, |
| 386 | * we assume the worst for the deadlock cycle, |
| 387 | * and resolve all of them towards the long |
| 388 | * jump. |
| 389 | * Currently, the C compiler does not produce |
| 390 | * jumps across aligns, as aligns are only used |
| 391 | * in data segments, or in text segments to align |
| 392 | * functions. |
| 393 | */ |
| 394 | if (stillactives){ |
| 395 | SEGITERATE(segno, 0, 0, cojumpfrom, jumpfrom, |
| 396 | ubjumpfrom, ++){ |
| 397 | if (jumpfrom->s_tag == JXACTIVE){ |
| 398 | jumpfrom->s_tag = |
| 399 | badjxalign?JXNOTYET:JXINACTIVE; |
| 400 | } |
| 401 | } |
| 402 | if (badjxalign){ |
| 403 | jxxxbump(segno, (struct symtab **)0); |
| 404 | } |
| 405 | } |
| 406 | /* |
| 407 | * Handle all of the .align s |
| 408 | */ |
| 409 | SEGITERATE(segno, 0, 0, cojumpfrom, jumpfrom, |
| 410 | ubjumpfrom, ++){ |
| 411 | if (jumpfrom->s_tag == JXALIGN){ |
| 412 | /* |
| 413 | * Predict the true displacement |
| 414 | * needed, irregardless of the |
| 415 | * fact that we guessed 1 |
| 416 | */ |
| 417 | displ = (jumpfrom->s_value - 1) & (unsigned)jumpfrom->s_jxfear; |
| 418 | if (displ == 0){ /*no virtual displacement*/ |
| 419 | jumpfrom->s_jxfear = -1; |
| 420 | } else { |
| 421 | jumpfrom->s_jxfear = (jumpfrom->s_jxfear + 1) - displ; |
| 422 | /* |
| 423 | * assert jumpfrom->s_jxfear > 0 |
| 424 | */ |
| 425 | if (jumpfrom->s_jxfear == 1){ |
| 426 | /*our prediction was correct*/ |
| 427 | continue; |
| 428 | } |
| 429 | /* |
| 430 | * assert jumpfrom->s_jxfear > 1 |
| 431 | */ |
| 432 | jumpfrom->s_jxfear -= 1; /*correct guess*/ |
| 433 | } |
| 434 | /* |
| 435 | * assert jumpfrom->s_jxfear = -1, +1...2**n-1 |
| 436 | */ |
| 437 | jumpfrom->s_tag = JXNOTYET; /*signal*/ |
| 438 | jxxxbump(segno, cojumpfrom); |
| 439 | jumpfrom->s_tag = JXINACTIVE; |
| 440 | /* |
| 441 | * Assert jxfrom->jxvalue indexes the first |
| 442 | * code byte after the added bytes, and |
| 443 | * has n low order zeroes. |
| 444 | */ |
| 445 | } |
| 446 | } /*end of walking through each segment*/ |
| 447 | } /*end of no changes */ |
| 448 | else { /*changes, and still have to try another pass*/ |
| 449 | jxxxbump(segno, (struct symtab **)0); |
| 450 | } |
| 451 | } /*end of doing the topologic sort*/ |
| 452 | } /*end of iterating through all segments*/ |
| 453 | } /*end of jxxxfix*/ |
| 454 | |
| 455 | /* |
| 456 | * Go through the symbols in a given segment number, |
| 457 | * and see which entries are jxxx entries that have |
| 458 | * been logically "exploded" (expanded), but for which |
| 459 | * the value of textually following symbols has not been |
| 460 | * increased |
| 461 | */ |
| 462 | |
| 463 | jxxxbump(segno, starthint) |
| 464 | int segno; |
| 465 | struct symtab **starthint; |
| 466 | { |
| 467 | register struct symtab **cosp, *sp; |
| 468 | register struct symtab *ub; |
| 469 | register int cum_bump; |
| 470 | register unsigned char tag; |
| 471 | |
| 472 | cum_bump = 0; |
| 473 | SEGITERATE(segno, starthint, 0, cosp, sp, ub, ++){ |
| 474 | tag = sp->s_tag; |
| 475 | if (tag == JXNOTYET){ |
| 476 | #ifdef DEBUG |
| 477 | if (debug){ |
| 478 | if (sp->s_dest != 0) |
| 479 | printf("Explode jump to %s on line %d\n", |
| 480 | FETCHNAME(sp->s_dest), lineno); |
| 481 | else |
| 482 | printf("Explode an align!\n"); |
| 483 | } |
| 484 | #endif |
| 485 | sp->s_tag = JXINACTIVE; |
| 486 | sp->s_jxbump = 1; |
| 487 | cum_bump += sp->s_jxfear; |
| 488 | } |
| 489 | /* |
| 490 | * Only bump labels and jxxxes. Ignored entries can |
| 491 | * be incremented, as they are thrown away later on. |
| 492 | * Stabds are given their final value in the second |
| 493 | * pass. |
| 494 | */ |
| 495 | if (tag >= OKTOBUMP) /*only bump labels and jxxxes and floating stabs*/ |
| 496 | sp->s_value += cum_bump; |
| 497 | } |
| 498 | usedot[segno].e_xvalue += cum_bump; |
| 499 | } |