liveness.c

   1 /*
   2  * Register - track pseudo usage, maybe eventually try to do register
   3  * allocation.
   4  *
   5  * Copyright (C) 2004 Linus Torvalds
   6  */
   7
   8 #include <assert.h>
   9
  10 #include "parse.h"
  11 #include "expression.h"
  12 #include "linearize.h"
  13 #include "flow.h"
  14
  15 static void phi_defines(struct instruction * phi_node, pseudo_t target,
  16         void (*defines)(struct basic_block *, struct instruction *, pseudo_t))
  17 {
  18         pseudo_t phi;
  19         FOR_EACH_PTR(phi_node->phi_list, phi) {
  20                 struct instruction *def;
  21                 if (phi == VOID)
  22                         continue;
  23                 def = phi->def;
  24                 if (!def || !def->bb)
  25                         continue;
  26                 if (def->opcode == OP_PHI) {
  27                         phi_defines(def, target, defines);
  28                         continue;
  29                 }
  30                 defines(def->bb, phi->def, target);
  31         } END_FOR_EACH_PTR(phi);
  32 }
  33
  34 static void asm_liveness(struct basic_block *bb, struct instruction *insn,
  35         void (*def)(struct basic_block *, struct instruction *, pseudo_t),
  36         void (*use)(struct basic_block *, struct instruction *, pseudo_t))
  37 {
  38         struct asm_constraint *entry;
  39
  40         FOR_EACH_PTR(insn->asm_rules->inputs, entry) {
  41                 use(bb, insn, entry->pseudo);
  42         } END_FOR_EACH_PTR(entry);
  43
  44         FOR_EACH_PTR(insn->asm_rules->outputs, entry) {
  45                 def(bb, insn, entry->pseudo);
  46         } END_FOR_EACH_PTR(entry);
  47 }
  48
  49 static void track_instruction_usage(struct basic_block *bb, struct instruction *insn,
  50         void (*def)(struct basic_block *, struct instruction *, pseudo_t),
  51         void (*use)(struct basic_block *, struct instruction *, pseudo_t))
  52 {
  53         pseudo_t pseudo;
  54
  55         #define USES(x)         use(bb, insn, insn->x)
  56         #define DEFINES(x)      def(bb, insn, insn->x)
  57
  58         switch (insn->opcode) {
  59         case OP_RET:
  60                 USES(src);
  61                 break;
  62
  63         case OP_BR: case OP_SWITCH:
  64                 USES(cond);
  65                 break;
  66
  67         case OP_COMPUTEDGOTO:
  68                 USES(target);
  69                 break;
  70
  71         /* Binary */
  72         case OP_BINARY ... OP_BINARY_END:
  73         case OP_BINCMP ... OP_BINCMP_END:
  74                 USES(src1); USES(src2); DEFINES(target);
  75                 break;
  76
  77         /* Uni */
  78         case OP_NOT: case OP_NEG:
  79                 USES(src1); DEFINES(target);
  80                 break;
  81
  82         case OP_SEL:
  83                 USES(src1); USES(src2); USES(src3); DEFINES(target);
  84                 break;
  85
  86         /* Memory */
  87         case OP_LOAD:
  88                 USES(src); DEFINES(target);
  89                 break;
  90
  91         case OP_STORE:
  92                 USES(src); USES(target);
  93                 break;
  94
  95         case OP_SETVAL:
  96                 DEFINES(target);
  97                 break;
  98
  99         case OP_SYMADDR:
 100                 USES(symbol); DEFINES(target);
 101                 break;
 102
 103         /* Other */
 104         case OP_PHI:
 105                 /* Phi-nodes are "backwards" nodes. Their def doesn't matter */
 106                 phi_defines(insn, insn->target, def);
 107                 break;
 108
 109         case OP_PHISOURCE:
 110                 /*
 111                  * We don't care about the phi-source define, they get set
 112                  * up and expanded by the OP_PHI
 113                  */
 114                 USES(phi_src);
 115                 break;
 116
 117         case OP_CAST:
 118         case OP_PTRCAST:
 119                 USES(src); DEFINES(target);
 120                 break;
 121
 122         case OP_CALL:
 123                 USES(func);
 124                 if (insn->target != VOID)
 125                         DEFINES(target);
 126                 FOR_EACH_PTR(insn->arguments, pseudo) {
 127                         use(bb, insn, pseudo);
 128                 } END_FOR_EACH_PTR(pseudo);
 129                 break;
 130
 131         case OP_SLICE:
 132                 USES(base); DEFINES(target);
 133                 break;
 134
 135         case OP_ASM:
 136                 asm_liveness(bb, insn, def, use);
 137                 break;
 138
 139         case OP_BADOP:
 140         case OP_INVOKE:
 141         case OP_UNWIND:
 142         case OP_MALLOC:
 143         case OP_FREE:
 144         case OP_ALLOCA:
 145         case OP_GET_ELEMENT_PTR:
 146         case OP_VANEXT:
 147         case OP_VAARG:
 148         case OP_SNOP:
 149         case OP_LNOP:
 150         case OP_NOP:
 151         case OP_CONTEXT:
 152                 break;
 153         }
 154 }
 155
 156 int pseudo_in_list(struct pseudo_list *list, pseudo_t pseudo)
 157 {
 158         pseudo_t old;
 159         FOR_EACH_PTR(list,old) {
 160                 if (old == pseudo)
 161                         return 1;
 162         } END_FOR_EACH_PTR(old);
 163         return 0;
 164 }
 165
 166 static int liveness_changed;
 167
 168 static void add_pseudo_exclusive(struct pseudo_list **list, pseudo_t pseudo)
 169 {
 170         if (!pseudo_in_list(*list, pseudo)) {
 171                 liveness_changed = 1;
 172                 add_pseudo(list, pseudo);
 173         }
 174 }
 175
 176 static inline int trackable_pseudo(pseudo_t pseudo)
 177 {
 178         return pseudo && (pseudo->type == PSEUDO_REG || pseudo->type == PSEUDO_ARG);
 179 }
 180
 181 static void insn_uses(struct basic_block *bb, struct instruction *insn, pseudo_t pseudo)
 182 {
 183         if (trackable_pseudo(pseudo)) {
 184                 struct instruction *def = pseudo->def;
 185                 if (pseudo->type != PSEUDO_REG || def->bb != bb || def->opcode == OP_PHI)
 186                         add_pseudo_exclusive(&bb->needs, pseudo);
 187         }
 188 }
 189
 190 static void insn_defines(struct basic_block *bb, struct instruction *insn, pseudo_t pseudo)
 191 {
 192         assert(trackable_pseudo(pseudo));
 193         add_pseudo(&bb->defines, pseudo);
 194 }
 195
 196 static void track_bb_liveness(struct basic_block *bb)
 197 {
 198         pseudo_t needs;
 199
 200         FOR_EACH_PTR(bb->needs, needs) {
 201                 struct basic_block *parent;
 202                 FOR_EACH_PTR(bb->parents, parent) {
 203                         if (!pseudo_in_list(parent->defines, needs)) {
 204                                 add_pseudo_exclusive(&parent->needs, needs);
 205                         }
 206                 } END_FOR_EACH_PTR(parent);
 207         } END_FOR_EACH_PTR(needs);
 208 }
 209
 210 /*
 211  * We need to clear the liveness information if we
 212  * are going to re-run it.
 213  */
 214 void clear_liveness(struct entrypoint *ep)
 215 {
 216         struct basic_block *bb;
 217
 218         FOR_EACH_PTR(ep->bbs, bb) {
 219                 free_ptr_list(&bb->needs);
 220                 free_ptr_list(&bb->defines);
 221         } END_FOR_EACH_PTR(bb);
 222 }
 223
 224 /*
 225  * Track inter-bb pseudo liveness. The intra-bb case
 226  * is purely local information.
 227  */
 228 void track_pseudo_liveness(struct entrypoint *ep)
 229 {
 230         struct basic_block *bb;
 231
 232         /* Add all the bb pseudo usage */
 233         FOR_EACH_PTR(ep->bbs, bb) {
 234                 struct instruction *insn;
 235                 FOR_EACH_PTR(bb->insns, insn) {
 236                         if (!insn->bb)
 237                                 continue;
 238                         assert(insn->bb == bb);
 239                         track_instruction_usage(bb, insn, insn_defines, insn_uses);
 240                 } END_FOR_EACH_PTR(insn);
 241         } END_FOR_EACH_PTR(bb);
 242
 243         /* Calculate liveness.. */
 244         do {
 245                 liveness_changed = 0;
 246                 FOR_EACH_PTR_REVERSE(ep->bbs, bb) {
 247                         track_bb_liveness(bb);
 248                 } END_FOR_EACH_PTR_REVERSE(bb);
 249         } while (liveness_changed);
 250
 251         /* Remove the pseudos from the "defines" list that are used internally */
 252         FOR_EACH_PTR(ep->bbs, bb) {
 253                 pseudo_t def;
 254                 FOR_EACH_PTR(bb->defines, def) {
 255                         struct basic_block *child;
 256                         FOR_EACH_PTR(bb->children, child) {
 257                                 if (pseudo_in_list(child->needs, def))
 258                                         goto is_used;
 259                         } END_FOR_EACH_PTR(child);
 260                         DELETE_CURRENT_PTR(def);
 261 is_used:
 262                 ;
 263                 } END_FOR_EACH_PTR(def);
 264                 PACK_PTR_LIST(&bb->defines);
 265         } END_FOR_EACH_PTR(bb);
 266 }
 267
 268 static void merge_pseudo_list(struct pseudo_list *src, struct pseudo_list **dest)
 269 {
 270         pseudo_t pseudo;
 271         FOR_EACH_PTR(src, pseudo) {
 272                 add_pseudo_exclusive(dest, pseudo);
 273         } END_FOR_EACH_PTR(pseudo);
 274 }
 275
 276 static void track_phi_uses(struct instruction *insn)
 277 {
 278         pseudo_t phi;
 279         FOR_EACH_PTR(insn->phi_list, phi) {
 280                 struct instruction *def;
 281                 if (phi == VOID || !phi->def)
 282                         continue;
 283                 def = phi->def;
 284                 assert(def->opcode == OP_PHISOURCE);
 285                 add_ptr_list(&def->phi_users, insn);
 286         } END_FOR_EACH_PTR(phi);
 287 }
 288
 289 static void track_bb_phi_uses(struct basic_block *bb)
 290 {
 291         struct instruction *insn;
 292         FOR_EACH_PTR(bb->insns, insn) {
 293                 if (insn->bb && insn->opcode == OP_PHI)
 294                         track_phi_uses(insn);
 295         } END_FOR_EACH_PTR(insn);
 296 }
 297
 298 static struct pseudo_list **live_list;
 299 static struct pseudo_list *dead_list;
 300
 301 static void death_def(struct basic_block *bb, struct instruction *insn, pseudo_t pseudo)
 302 {
 303 }
 304
 305 static void death_use(struct basic_block *bb, struct instruction *insn, pseudo_t pseudo)
 306 {
 307         if (trackable_pseudo(pseudo) && !pseudo_in_list(*live_list, pseudo)) {
 308                 add_pseudo(&dead_list, pseudo);
 309                 add_pseudo(live_list, pseudo);
 310         }
 311 }
 312
 313 static void track_pseudo_death_bb(struct basic_block *bb)
 314 {
 315         struct pseudo_list *live = NULL;
 316         struct basic_block *child;
 317         struct instruction *insn;
 318
 319         FOR_EACH_PTR(bb->children, child) {
 320                 merge_pseudo_list(child->needs, &live);
 321         } END_FOR_EACH_PTR(child);
 322
 323         live_list = &live;
 324         FOR_EACH_PTR_REVERSE(bb->insns, insn) {
 325                 if (!insn->bb)
 326                         continue;
 327
 328                 /*
 329                  * A "def" of a pseudo removes it from the liveness
 330                  * list. However, we only bother doing that for
 331                  * phi-nodes, since no other pseudos should ever
 332                  * be even used before they are def'ed.
 333                  */
 334                 if (insn->opcode == OP_PHISOURCE) {
 335                         struct instruction *phi;
 336                         FOR_EACH_PTR(insn->phi_users, phi) {
 337                                 remove_pseudo(live_list, phi->target);
 338                         } END_FOR_EACH_PTR(phi);
 339                 }
 340
 341                 dead_list = NULL;
 342                 track_instruction_usage(bb, insn, death_def, death_use);
 343                 if (dead_list) {
 344                         pseudo_t dead;
 345                         FOR_EACH_PTR(dead_list, dead) {
 346                                 struct instruction *deathnote = __alloc_instruction(0);
 347                                 deathnote->bb = bb;
 348                                 deathnote->opcode = OP_DEATHNOTE;
 349                                 deathnote->target = dead;
 350                                 INSERT_CURRENT(deathnote, insn);
 351                         } END_FOR_EACH_PTR(dead);
 352                         free_ptr_list(&dead_list);
 353                 }
 354         } END_FOR_EACH_PTR_REVERSE(insn);
 355         free_ptr_list(&live);
 356 }
 357
 358 void track_pseudo_death(struct entrypoint *ep)
 359 {
 360         struct basic_block *bb;
 361
 362         FOR_EACH_PTR(ep->bbs, bb) {
 363                 track_bb_phi_uses(bb);
 364         } END_FOR_EACH_PTR(bb);
 365
 366         FOR_EACH_PTR(ep->bbs, bb) {
 367                 track_pseudo_death_bb(bb);
 368         } END_FOR_EACH_PTR(bb);
 369 }