amd64/emit.c

   1 #include "all.h"
   2
   3
   4 #define CMP(X) \
   5         X(Ciule,      "be") \
   6         X(Ciult,      "b")  \
   7         X(Cisle,      "le") \
   8         X(Cislt,      "l")  \
   9         X(Cisgt,      "g")  \
  10         X(Cisge,      "ge") \
  11         X(Ciugt,      "a")  \
  12         X(Ciuge,      "ae") \
  13         X(Cieq,       "z")  \
  14         X(Cine,       "nz") \
  15         X(NCmpI+Cfle, "be") \
  16         X(NCmpI+Cflt, "b")  \
  17         X(NCmpI+Cfgt, "a")  \
  18         X(NCmpI+Cfge, "ae") \
  19         X(NCmpI+Cfeq, "z")  \
  20         X(NCmpI+Cfne, "nz") \
  21         X(NCmpI+Cfo,  "np") \
  22         X(NCmpI+Cfuo, "p")
  23
  24 enum {
  25         SLong = 0,
  26         SWord = 1,
  27         SShort = 2,
  28         SByte = 3,
  29
  30         Ki = -1, /* matches Kw and Kl */
  31         Ka = -2, /* matches all classes */
  32 };
  33
  34 /* Instruction format strings:
  35  *
  36  * if the format string starts with -, the instruction
  37  * is assumed to be 3-address and is put in 2-address
  38  * mode using an extra mov if necessary
  39  *
  40  * if the format string starts with +, the same as the
  41  * above applies, but commutativity is also assumed
  42  *
  43  * %k  is used to set the class of the instruction,
  44  *     it'll expand to "l", "q", "ss", "sd", depending
  45  *     on the instruction class
  46  * %0  designates the first argument
  47  * %1  designates the second argument
  48  * %=  designates the result
  49  *
  50  * if %k is not used, a prefix to 0, 1, or = must be
  51  * added, it can be:
  52  *   M - memory reference
  53  *   L - long  (64 bits)
  54  *   W - word  (32 bits)
  55  *   H - short (16 bits)
  56  *   B - byte  (8 bits)
  57  *   S - single precision float
  58  *   D - double precision float
  59  */
  60 static struct {
  61         short op;
  62         short cls;
  63         char *fmt;
  64 } omap[] = {
  65         { Oadd,    Ka, "+add%k %1, %=" },
  66         { Osub,    Ka, "-sub%k %1, %=" },
  67         { Oand,    Ki, "+and%k %1, %=" },
  68         { Oor,     Ki, "+or%k %1, %=" },
  69         { Oxor,    Ki, "+xor%k %1, %=" },
  70         { Osar,    Ki, "-sar%k %B1, %=" },
  71         { Oshr,    Ki, "-shr%k %B1, %=" },
  72         { Oshl,    Ki, "-shl%k %B1, %=" },
  73         { Omul,    Ki, "+imul%k %1, %=" },
  74         { Omul,    Ks, "+mulss %1, %=" },
  75         { Omul,    Kd, "+mulsd %1, %=" },
  76         { Odiv,    Ka, "-div%k %1, %=" },
  77         { Ostorel, Ka, "movq %L0, %M1" },
  78         { Ostorew, Ka, "movl %W0, %M1" },
  79         { Ostoreh, Ka, "movw %H0, %M1" },
  80         { Ostoreb, Ka, "movb %B0, %M1" },
  81         { Ostores, Ka, "movss %S0, %M1" },
  82         { Ostored, Ka, "movsd %D0, %M1" },
  83         { Oload,   Ka, "mov%k %M0, %=" },
  84         { Oloadsw, Kl, "movslq %M0, %L=" },
  85         { Oloadsw, Kw, "movl %M0, %W=" },
  86         { Oloaduw, Ki, "movl %M0, %W=" },
  87         { Oloadsh, Ki, "movsw%k %M0, %=" },
  88         { Oloaduh, Ki, "movzw%k %M0, %=" },
  89         { Oloadsb, Ki, "movsb%k %M0, %=" },
  90         { Oloadub, Ki, "movzb%k %M0, %=" },
  91         { Oextsw,  Kl, "movslq %W0, %L=" },
  92         { Oextuw,  Kl, "movl %W0, %W=" },
  93         { Oextsh,  Ki, "movsw%k %H0, %=" },
  94         { Oextuh,  Ki, "movzw%k %H0, %=" },
  95         { Oextsb,  Ki, "movsb%k %B0, %=" },
  96         { Oextub,  Ki, "movzb%k %B0, %=" },
  97
  98         { Oexts,   Kd, "cvtss2sd %0, %=" },
  99         { Otruncd, Ks, "cvtsd2ss %0, %=" },
 100         { Ostosi,  Ki, "cvttss2si%k %0, %=" },
 101         { Odtosi,  Ki, "cvttsd2si%k %0, %=" },
 102         { Oswtof,  Ka, "cvtsi2%k %W0, %=" },
 103         { Osltof,  Ka, "cvtsi2%k %L0, %=" },
 104         { Ocast,   Ki, "movq %D0, %L=" },
 105         { Ocast,   Ka, "movq %L0, %D=" },
 106
 107         { Oaddr,   Ki, "lea%k %M0, %=" },
 108         { Oswap,   Ki, "xchg%k %0, %1" },
 109         { Osign,   Kl, "cqto" },
 110         { Osign,   Kw, "cltd" },
 111         { Oxdiv,   Ki, "div%k %0" },
 112         { Oxidiv,  Ki, "idiv%k %0" },
 113         { Oxcmp,   Ks, "ucomiss %S0, %S1" },
 114         { Oxcmp,   Kd, "ucomisd %D0, %D1" },
 115         { Oxcmp,   Ki, "cmp%k %0, %1" },
 116         { Oxtest,  Ki, "test%k %0, %1" },
 117 #define X(c, s) \
 118         { Oflag+c, Ki, "set" s " %B=\n\tmovzb%k %B=, %=" },
 119         CMP(X)
 120 #undef X
 121         { NOp, 0, 0 }
 122 };
 123
 124 static char *rname[][4] = {
 125         [RAX] = {"rax", "eax", "ax", "al"},
 126         [RBX] = {"rbx", "ebx", "bx", "bl"},
 127         [RCX] = {"rcx", "ecx", "cx", "cl"},
 128         [RDX] = {"rdx", "edx", "dx", "dl"},
 129         [RSI] = {"rsi", "esi", "si", "sil"},
 130         [RDI] = {"rdi", "edi", "di", "dil"},
 131         [RBP] = {"rbp", "ebp", "bp", "bpl"},
 132         [RSP] = {"rsp", "esp", "sp", "spl"},
 133         [R8 ] = {"r8" , "r8d", "r8w", "r8b"},
 134         [R9 ] = {"r9" , "r9d", "r9w", "r9b"},
 135         [R10] = {"r10", "r10d", "r10w", "r10b"},
 136         [R11] = {"r11", "r11d", "r11w", "r11b"},
 137         [R12] = {"r12", "r12d", "r12w", "r12b"},
 138         [R13] = {"r13", "r13d", "r13w", "r13b"},
 139         [R14] = {"r14", "r14d", "r14w", "r14b"},
 140         [R15] = {"r15", "r15d", "r15w", "r15b"},
 141 };
 142
 143
 144 static int
 145 slot(Ref r, Fn *fn)
 146 {
 147         int s;
 148
 149         s = rsval(r);
 150         assert(s <= fn->slot);
 151         /* specific to NAlign == 3 */
 152         if (s < 0)
 153                 return -4 * s;
 154         else if (fn->vararg)
 155                 return -176 + -4 * (fn->slot - s);
 156         else
 157                 return -4 * (fn->slot - s);
 158 }
 159
 160 static void
 161 emitcon(Con *con, FILE *f)
 162 {
 163         char *p, *l;
 164
 165         switch (con->type) {
 166         case CAddr:
 167                 l = str(con->sym.id);
 168                 p = l[0] == '"' ? "" : T.assym;
 169                 if (con->sym.type == SThr) {
 170                         if (T.apple)
 171                                 fprintf(f, "%s%s@TLVP", p, l);
 172                         else
 173                                 fprintf(f, "%%fs:%s%s@tpoff", p, l);
 174                 } else
 175                         fprintf(f, "%s%s", p, l);
 176                 if (con->bits.i)
 177                         fprintf(f, "%+"PRId64, con->bits.i);
 178                 break;
 179         case CBits:
 180                 fprintf(f, "%"PRId64, con->bits.i);
 181                 break;
 182         default:
 183                 die("unreachable");
 184         }
 185 }
 186
 187 static char *
 188 regtoa(int reg, int sz)
 189 {
 190         static char buf[6];
 191
 192         assert(reg <= XMM15);
 193         if (reg >= XMM0) {
 194                 sprintf(buf, "xmm%d", reg-XMM0);
 195                 return buf;
 196         } else
 197                 return rname[reg][sz];
 198 }
 199
 200 static Ref
 201 getarg(char c, Ins *i)
 202 {
 203         switch (c) {
 204         case '0':
 205                 return i->arg[0];
 206         case '1':
 207                 return i->arg[1];
 208         case '=':
 209                 return i->to;
 210         default:
 211                 die("invalid arg letter %c", c);
 212         }
 213 }
 214
 215 static void emitins(Ins, Fn *, FILE *);
 216
 217 static void
 218 emitcopy(Ref r1, Ref r2, int k, Fn *fn, FILE *f)
 219 {
 220         Ins icp;
 221
 222         icp.op = Ocopy;
 223         icp.arg[0] = r2;
 224         icp.to = r1;
 225         icp.cls = k;
 226         emitins(icp, fn, f);
 227 }
 228
 229 static void
 230 emitf(char *s, Ins *i, Fn *fn, FILE *f)
 231 {
 232         static char clstoa[][3] = {"l", "q", "ss", "sd"};
 233         char c;
 234         int sz;
 235         Ref ref;
 236         Mem *m;
 237         Con off;
 238
 239         switch (*s) {
 240         case '+':
 241                 if (req(i->arg[1], i->to)) {
 242                         ref = i->arg[0];
 243                         i->arg[0] = i->arg[1];
 244                         i->arg[1] = ref;
 245                 }
 246                 /* fall through */
 247         case '-':
 248                 assert((!req(i->arg[1], i->to) || req(i->arg[0], i->to)) &&
 249                         "cannot convert to 2-address");
 250                 emitcopy(i->to, i->arg[0], i->cls, fn, f);
 251                 s++;
 252                 break;
 253         }
 254
 255         fputc('\t', f);
 256 Next:
 257         while ((c = *s++) != '%')
 258                 if (!c) {
 259                         fputc('\n', f);
 260                         return;
 261                 } else
 262                         fputc(c, f);
 263         switch ((c = *s++)) {
 264         case '%':
 265                 fputc('%', f);
 266                 break;
 267         case 'k':
 268                 fputs(clstoa[i->cls], f);
 269                 break;
 270         case '0':
 271         case '1':
 272         case '=':
 273                 sz = KWIDE(i->cls) ? SLong : SWord;
 274                 s--;
 275                 goto Ref;
 276         case 'D':
 277         case 'S':
 278                 sz = SLong; /* does not matter for floats */
 279         Ref:
 280                 c = *s++;
 281                 ref = getarg(c, i);
 282                 switch (rtype(ref)) {
 283                 case RTmp:
 284                         assert(isreg(ref));
 285                         fprintf(f, "%%%s", regtoa(ref.val, sz));
 286                         break;
 287                 case RSlot:
 288                         fprintf(f, "%d(%%rbp)", slot(ref, fn));
 289                         break;
 290                 case RMem:
 291                 Mem:
 292                         m = &fn->mem[ref.val];
 293                         if (rtype(m->base) == RSlot) {
 294                                 off.type = CBits;
 295                                 off.bits.i = slot(m->base, fn);
 296                                 addcon(&m->offset, &off, 1);
 297                                 m->base = TMP(RBP);
 298                         }
 299                         if (m->offset.type != CUndef)
 300                                 emitcon(&m->offset, f);
 301                         fputc('(', f);
 302                         if (!req(m->base, R))
 303                                 fprintf(f, "%%%s", regtoa(m->base.val, SLong));
 304                         else if (m->offset.type == CAddr)
 305                                 fprintf(f, "%%rip");
 306                         if (!req(m->index, R))
 307                                 fprintf(f, ", %%%s, %d",
 308                                         regtoa(m->index.val, SLong),
 309                                         m->scale
 310                                 );
 311                         fputc(')', f);
 312                         break;
 313                 case RCon:
 314                         fputc('$', f);
 315                         emitcon(&fn->con[ref.val], f);
 316                         break;
 317                 default:
 318                         die("unreachable");
 319                 }
 320                 break;
 321         case 'L':
 322                 sz = SLong;
 323                 goto Ref;
 324         case 'W':
 325                 sz = SWord;
 326                 goto Ref;
 327         case 'H':
 328                 sz = SShort;
 329                 goto Ref;
 330         case 'B':
 331                 sz = SByte;
 332                 goto Ref;
 333         case 'M':
 334                 c = *s++;
 335                 ref = getarg(c, i);
 336                 switch (rtype(ref)) {
 337                 case RMem:
 338                         goto Mem;
 339                 case RSlot:
 340                         fprintf(f, "%d(%%rbp)", slot(ref, fn));
 341                         break;
 342                 case RCon:
 343                         off = fn->con[ref.val];
 344                         emitcon(&off, f);
 345                         if (off.type == CAddr)
 346                         if (off.sym.type != SThr || T.apple)
 347                                 fprintf(f, "(%%rip)");
 348                         break;
 349                 case RTmp:
 350                         assert(isreg(ref));
 351                         fprintf(f, "(%%%s)", regtoa(ref.val, SLong));
 352                         break;
 353                 default:
 354                         die("unreachable");
 355                 }
 356                 break;
 357         default:
 358                 die("invalid format specifier %%%c", c);
 359         }
 360         goto Next;
 361 }
 362
 363 static void *negmask[4] = {
 364         [Ks] = (uint32_t[4]){ 0x80000000 },
 365         [Kd] = (uint64_t[2]){ 0x8000000000000000 },
 366 };
 367
 368 static void
 369 emitins(Ins i, Fn *fn, FILE *f)
 370 {
 371         Ref r;
 372         int64_t val;
 373         int o, t0;
 374         Ins ineg;
 375         Con *con;
 376         char *sym;
 377
 378         switch (i.op) {
 379         default:
 380         Table:
 381                 /* most instructions are just pulled out of
 382                  * the table omap[], some special cases are
 383                  * detailed below */
 384                 for (o=0;; o++) {
 385                         /* this linear search should really be a binary
 386                          * search */
 387                         if (omap[o].op == NOp)
 388                                 die("no match for %s(%c)",
 389                                         optab[i.op].name, "wlsd"[i.cls]);
 390                         if (omap[o].op == i.op)
 391                         if (omap[o].cls == i.cls
 392                         || (omap[o].cls == Ki && KBASE(i.cls) == 0)
 393                         || (omap[o].cls == Ka))
 394                                 break;
 395                 }
 396                 emitf(omap[o].fmt, &i, fn, f);
 397                 break;
 398         case Onop:
 399                 /* just do nothing for nops, they are inserted
 400                  * by some passes */
 401                 break;
 402         case Omul:
 403                 /* here, we try to use the 3-addresss form
 404                  * of multiplication when possible */
 405                 if (rtype(i.arg[1]) == RCon) {
 406                         r = i.arg[0];
 407                         i.arg[0] = i.arg[1];
 408                         i.arg[1] = r;
 409                 }
 410                 if (KBASE(i.cls) == 0 /* only available for ints */
 411                 && rtype(i.arg[0]) == RCon
 412                 && rtype(i.arg[1]) == RTmp) {
 413                         emitf("imul%k %0, %1, %=", &i, fn, f);
 414                         break;
 415                 }
 416                 goto Table;
 417         case Osub:
 418                 /* we have to use the negation trick to handle
 419                  * some 3-address subtractions */
 420                 if (req(i.to, i.arg[1]) && !req(i.arg[0], i.to)) {
 421                         ineg = (Ins){Oneg, i.cls, i.to, {i.to}};
 422                         emitins(ineg, fn, f);
 423                         emitf("add%k %0, %=", &i, fn, f);
 424                         break;
 425                 }
 426                 goto Table;
 427         case Oneg:
 428                 if (!req(i.to, i.arg[0]))
 429                         emitf("mov%k %0, %=", &i, fn, f);
 430                 if (KBASE(i.cls) == 0)
 431                         emitf("neg%k %=", &i, fn, f);
 432                 else
 433                         fprintf(f,
 434                                 "\txorp%c %sfp%d(%%rip), %%%s\n",
 435                                 "xxsd"[i.cls],
 436                                 T.asloc,
 437                                 stashbits(negmask[i.cls], 16),
 438                                 regtoa(i.to.val, SLong)
 439                         );
 440                 break;
 441         case Odiv:
 442                 /* use xmm15 to adjust the instruction when the
 443                  * conversion to 2-address in emitf() would fail */
 444                 if (req(i.to, i.arg[1])) {
 445                         i.arg[1] = TMP(XMM0+15);
 446                         emitf("mov%k %=, %1", &i, fn, f);
 447                         emitf("mov%k %0, %=", &i, fn, f);
 448                         i.arg[0] = i.to;
 449                 }
 450                 goto Table;
 451         case Ocopy:
 452                 /* copies are used for many things; see my note
 453                  * to understand how to load big constants:
 454                  * https://c9x.me/notes/2015-09-19.html */
 455                 assert(rtype(i.to) != RMem);
 456                 if (req(i.to, R) || req(i.arg[0], R))
 457                         break;
 458                 if (req(i.to, i.arg[0]))
 459                         break;
 460                 t0 = rtype(i.arg[0]);
 461                 if (i.cls == Kl
 462                 && t0 == RCon
 463                 && fn->con[i.arg[0].val].type == CBits) {
 464                         val = fn->con[i.arg[0].val].bits.i;
 465                         if (isreg(i.to))
 466                         if (val >= 0 && val <= UINT32_MAX) {
 467                                 emitf("movl %W0, %W=", &i, fn, f);
 468                                 break;
 469                         }
 470                         if (rtype(i.to) == RSlot)
 471                         if (val < INT32_MIN || val > INT32_MAX) {
 472                                 emitf("movl %0, %=", &i, fn, f);
 473                                 emitf("movl %0>>32, 4+%=", &i, fn, f);
 474                                 break;
 475                         }
 476                 }
 477                 if (isreg(i.to)
 478                 && t0 == RCon
 479                 && fn->con[i.arg[0].val].type == CAddr) {
 480                         emitf("lea%k %M0, %=", &i, fn, f);
 481                         break;
 482                 }
 483                 if (rtype(i.to) == RSlot
 484                 && (t0 == RSlot || t0 == RMem)) {
 485                         i.cls = KWIDE(i.cls) ? Kd : Ks;
 486                         i.arg[1] = TMP(XMM0+15);
 487                         emitf("mov%k %0, %1", &i, fn, f);
 488                         emitf("mov%k %1, %=", &i, fn, f);
 489                         break;
 490                 }
 491                 /* conveniently, the assembler knows if it
 492                  * should use movabsq when reading movq */
 493                 emitf("mov%k %0, %=", &i, fn, f);
 494                 break;
 495         case Oaddr:
 496                 if (!T.apple
 497                 && rtype(i.arg[0]) == RCon
 498                 && fn->con[i.arg[0].val].sym.type == SThr) {
 499                         /* derive the symbol address from the TCB
 500                          * address at offset 0 of %fs */
 501                         assert(isreg(i.to));
 502                         con = &fn->con[i.arg[0].val];
 503                         sym = str(con->sym.id);
 504                         emitf("movq %%fs:0, %L=", &i, fn, f);
 505                         fprintf(f, "\tleaq %s%s@tpoff",
 506                                 sym[0] == '"' ? "" : T.assym, sym);
 507                         if (con->bits.i)
 508                                 fprintf(f, "%+"PRId64, con->bits.i);
 509                         fprintf(f, "(%%%s), %%%s\n",
 510                                 regtoa(i.to.val, SLong),
 511                                 regtoa(i.to.val, SLong));
 512                         break;
 513                 }
 514                 goto Table;
 515         case Ocall:
 516                 /* calls simply have a weird syntax in AT&T
 517                  * assembly... */
 518                 switch (rtype(i.arg[0])) {
 519                 case RCon:
 520                         fprintf(f, "\tcallq ");
 521                         emitcon(&fn->con[i.arg[0].val], f);
 522                         fprintf(f, "\n");
 523                         break;
 524                 case RTmp:
 525                         emitf("callq *%L0", &i, fn, f);
 526                         break;
 527                 default:
 528                         die("invalid call argument");
 529                 }
 530                 break;
 531         case Osalloc:
 532                 /* there is no good reason why this is here
 533                  * maybe we should split Osalloc in 2 different
 534                  * instructions depending on the result
 535                  */
 536                 emitf("subq %L0, %%rsp", &i, fn, f);
 537                 if (!req(i.to, R))
 538                         emitcopy(i.to, TMP(RSP), Kl, fn, f);
 539                 break;
 540         case Oswap:
 541                 if (KBASE(i.cls) == 0)
 542                         goto Table;
 543                 /* for floats, there is no swap instruction
 544                  * so we use xmm15 as a temporary
 545                  */
 546                 emitcopy(TMP(XMM0+15), i.arg[0], i.cls, fn, f);
 547                 emitcopy(i.arg[0], i.arg[1], i.cls, fn, f);
 548                 emitcopy(i.arg[1], TMP(XMM0+15), i.cls, fn, f);
 549                 break;
 550         case Odbgloc:
 551                 emitdbgloc(i.arg[0].val, i.arg[1].val, f);
 552                 break;
 553         }
 554 }
 555
 556 static uint64_t
 557 framesz(Fn *fn)
 558 {
 559         uint64_t i, o, f;
 560
 561         /* specific to NAlign == 3 */
 562         for (i=0, o=0; i<NCLR; i++)
 563                 o ^= 1 & (fn->reg >> amd64_sysv_rclob[i]);
 564         f = fn->slot;
 565         f = (f + 3) & -4;
 566         return 4*f + 8*o + 176*fn->vararg;
 567 }
 568
 569 void
 570 amd64_emitfn(Fn *fn, FILE *f)
 571 {
 572         static char *ctoa[] = {
 573         #define X(c, s) [c] = s,
 574                 CMP(X)
 575         #undef X
 576         };
 577         static int id0;
 578         Blk *b, *s;
 579         Ins *i, itmp;
 580         int *r, c, o, n, lbl;
 581         uint64_t fs;
 582
 583         emitfnlnk(fn->name, &fn->lnk, f);
 584         fputs("\tendbr64\n\tpushq %rbp\n\tmovq %rsp, %rbp\n", f);
 585         fs = framesz(fn);
 586         if (fs)
 587                 fprintf(f, "\tsubq $%"PRIu64", %%rsp\n", fs);
 588         if (fn->vararg) {
 589                 o = -176;
 590                 for (r=amd64_sysv_rsave; r<&amd64_sysv_rsave[6]; r++, o+=8)
 591                         fprintf(f, "\tmovq %%%s, %d(%%rbp)\n", rname[*r][0], o);
 592                 for (n=0; n<8; ++n, o+=16)
 593                         fprintf(f, "\tmovaps %%xmm%d, %d(%%rbp)\n", n, o);
 594         }
 595         for (r=amd64_sysv_rclob; r<&amd64_sysv_rclob[NCLR]; r++)
 596                 if (fn->reg & BIT(*r)) {
 597                         itmp.arg[0] = TMP(*r);
 598                         emitf("pushq %L0", &itmp, fn, f);
 599                         fs += 8;
 600                 }
 601
 602         for (lbl=0, b=fn->start; b; b=b->link) {
 603                 if (lbl || b->npred > 1)
 604                         fprintf(f, "%sbb%d:\n", T.asloc, id0+b->id);
 605                 for (i=b->ins; i!=&b->ins[b->nins]; i++)
 606                         emitins(*i, fn, f);
 607                 lbl = 1;
 608                 switch (b->jmp.type) {
 609                 case Jhlt:
 610                         fprintf(f, "\tud2\n");
 611                         break;
 612                 case Jret0:
 613                         if (fn->dynalloc)
 614                                 fprintf(f,
 615                                         "\tmovq %%rbp, %%rsp\n"
 616                                         "\tsubq $%"PRIu64", %%rsp\n",
 617                                         fs
 618                                 );
 619                         for (r=&amd64_sysv_rclob[NCLR]; r>amd64_sysv_rclob;)
 620                                 if (fn->reg & BIT(*--r)) {
 621                                         itmp.arg[0] = TMP(*r);
 622                                         emitf("popq %L0", &itmp, fn, f);
 623                                 }
 624                         fprintf(f,
 625                                 "\tleave\n"
 626                                 "\tret\n"
 627                         );
 628                         break;
 629                 case Jjmp:
 630                 Jmp:
 631                         if (b->s1 != b->link)
 632                                 fprintf(f, "\tjmp %sbb%d\n",
 633                                         T.asloc, id0+b->s1->id);
 634                         else
 635                                 lbl = 0;
 636                         break;
 637                 default:
 638                         c = b->jmp.type - Jjf;
 639                         if (0 <= c && c <= NCmp) {
 640                                 if (b->link == b->s2) {
 641                                         s = b->s1;
 642                                         b->s1 = b->s2;
 643                                         b->s2 = s;
 644                                 } else
 645                                         c = cmpneg(c);
 646                                 fprintf(f, "\tj%s %sbb%d\n", ctoa[c],
 647                                         T.asloc, id0+b->s2->id);
 648                                 goto Jmp;
 649                         }
 650                         die("unhandled jump %d", b->jmp.type);
 651                 }
 652         }
 653         id0 += fn->nblk;
 654         if (!T.apple)
 655                 elf_emitfnfin(fn->name, f);
 656 }