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                 USES(symbol); DEFINES(target);
  97                 break;
  98
  99         /* Other */
 100         case OP_PHI:
 101                 /* Phi-nodes are "backwards" nodes. Their def doesn't matter */
 102                 phi_defines(insn, insn->target, def);
 103                 break;
 104
 105         case OP_PHISOURCE:
 106                 /*
 107                  * We don't care about the phi-source define, they get set
 108                  * up and expanded by the OP_PHI
 109                  */
 110                 USES(phi_src);
 111                 break;
 112
 113         case OP_CAST:
 114         case OP_PTRCAST:
 115                 USES(src); DEFINES(target);
 116                 break;
 117
 118         case OP_CALL:
 119                 USES(func);
 120                 if (insn->target != VOID)
 121                         DEFINES(target);
 122                 FOR_EACH_PTR(insn->arguments, pseudo) {
 123                         use(bb, insn, pseudo);
 124                 } END_FOR_EACH_PTR(pseudo);
 125                 break;
 126
 127         case OP_SLICE:
 128                 USES(base); DEFINES(target);
 129                 break;
 130
 131         case OP_ASM:
 132                 asm_liveness(bb, insn, def, use);
 133                 break;
 134
 135         case OP_BADOP:
 136         case OP_INVOKE:
 137         case OP_UNWIND:
 138         case OP_MALLOC:
 139         case OP_FREE:
 140         case OP_ALLOCA:
 141         case OP_GET_ELEMENT_PTR:
 142         case OP_VANEXT:
 143         case OP_VAARG:
 144         case OP_SNOP:
 145         case OP_LNOP:
 146         case OP_NOP:
 147         case OP_CONTEXT:
 148                 break;
 149         }
 150 }
 151
 152 int pseudo_in_list(struct pseudo_list *list, pseudo_t pseudo)
 153 {
 154         pseudo_t old;
 155         FOR_EACH_PTR(list,old) {
 156                 if (old == pseudo)
 157                         return 1;
 158         } END_FOR_EACH_PTR(old);
 159         return 0;
 160 }
 161
 162 static int liveness_changed;
 163
 164 static void add_pseudo_exclusive(struct pseudo_list **list, pseudo_t pseudo)
 165 {
 166         if (!pseudo_in_list(*list, pseudo)) {
 167                 liveness_changed = 1;
 168                 add_pseudo(list, pseudo);
 169         }
 170 }
 171
 172 static inline int trackable_pseudo(pseudo_t pseudo)
 173 {
 174         return pseudo && (pseudo->type == PSEUDO_REG || pseudo->type == PSEUDO_ARG);
 175 }
 176
 177 static void insn_uses(struct basic_block *bb, struct instruction *insn, pseudo_t pseudo)
 178 {
 179         if (trackable_pseudo(pseudo)) {
 180                 struct instruction *def = pseudo->def;
 181                 if (pseudo->type != PSEUDO_REG || def->bb != bb || def->opcode == OP_PHI)
 182                         add_pseudo_exclusive(&bb->needs, pseudo);
 183         }
 184 }
 185
 186 static void insn_defines(struct basic_block *bb, struct instruction *insn, pseudo_t pseudo)
 187 {
 188         assert(trackable_pseudo(pseudo));
 189         add_pseudo(&bb->defines, pseudo);
 190 }
 191
 192 static void track_bb_liveness(struct basic_block *bb)
 193 {
 194         pseudo_t needs;
 195
 196         FOR_EACH_PTR(bb->needs, needs) {
 197                 struct basic_block *parent;
 198                 FOR_EACH_PTR(bb->parents, parent) {
 199                         if (!pseudo_in_list(parent->defines, needs)) {
 200                                 add_pseudo_exclusive(&parent->needs, needs);
 201                         }
 202                 } END_FOR_EACH_PTR(parent);
 203         } END_FOR_EACH_PTR(needs);
 204 }
 205
 206 /*
 207  * We need to clear the liveness information if we
 208  * are going to re-run it.
 209  */
 210 void clear_liveness(struct entrypoint *ep)
 211 {
 212         struct basic_block *bb;
 213
 214         FOR_EACH_PTR(ep->bbs, bb) {
 215                 free_ptr_list(&bb->needs);
 216                 free_ptr_list(&bb->defines);
 217         } END_FOR_EACH_PTR(bb);
 218 }
 219
 220 /*
 221  * Track inter-bb pseudo liveness. The intra-bb case
 222  * is purely local information.
 223  */
 224 void track_pseudo_liveness(struct entrypoint *ep)
 225 {
 226         struct basic_block *bb;
 227
 228         /* Add all the bb pseudo usage */
 229         FOR_EACH_PTR(ep->bbs, bb) {
 230                 struct instruction *insn;
 231                 FOR_EACH_PTR(bb->insns, insn) {
 232                         if (!insn->bb)
 233                                 continue;
 234                         assert(insn->bb == bb);
 235                         track_instruction_usage(bb, insn, insn_defines, insn_uses);
 236                 } END_FOR_EACH_PTR(insn);
 237         } END_FOR_EACH_PTR(bb);
 238
 239         /* Calculate liveness.. */
 240         do {
 241                 liveness_changed = 0;
 242                 FOR_EACH_PTR_REVERSE(ep->bbs, bb) {
 243                         track_bb_liveness(bb);
 244                 } END_FOR_EACH_PTR_REVERSE(bb);
 245         } while (liveness_changed);
 246
 247         /* Remove the pseudos from the "defines" list that are used internally */
 248         FOR_EACH_PTR(ep->bbs, bb) {
 249                 pseudo_t def;
 250                 FOR_EACH_PTR(bb->defines, def) {
 251                         struct basic_block *child;
 252                         FOR_EACH_PTR(bb->children, child) {
 253                                 if (pseudo_in_list(child->needs, def))
 254                                         goto is_used;
 255                         } END_FOR_EACH_PTR(child);
 256                         DELETE_CURRENT_PTR(def);
 257 is_used:
 258                 ;
 259                 } END_FOR_EACH_PTR(def);
 260                 PACK_PTR_LIST(&bb->defines);
 261         } END_FOR_EACH_PTR(bb);
 262 }
 263
 264 static void merge_pseudo_list(struct pseudo_list *src, struct pseudo_list **dest)
 265 {
 266         pseudo_t pseudo;
 267         FOR_EACH_PTR(src, pseudo) {
 268                 add_pseudo_exclusive(dest, pseudo);
 269         } END_FOR_EACH_PTR(pseudo);
 270 }
 271
 272 static void track_phi_uses(struct instruction *insn)
 273 {
 274         pseudo_t phi;
 275         FOR_EACH_PTR(insn->phi_list, phi) {
 276                 struct instruction *def;
 277                 if (phi == VOID || !phi->def)
 278                         continue;
 279                 def = phi->def;
 280                 assert(def->opcode == OP_PHISOURCE);
 281                 add_ptr_list(&def->phi_users, insn);
 282         } END_FOR_EACH_PTR(phi);
 283 }
 284
 285 static void track_bb_phi_uses(struct basic_block *bb)
 286 {
 287         struct instruction *insn;
 288         FOR_EACH_PTR(bb->insns, insn) {
 289                 if (insn->bb && insn->opcode == OP_PHI)
 290                         track_phi_uses(insn);
 291         } END_FOR_EACH_PTR(insn);
 292 }
 293
 294 static struct pseudo_list **live_list;
 295 static struct pseudo_list *dead_list;
 296
 297 static void death_def(struct basic_block *bb, struct instruction *insn, pseudo_t pseudo)
 298 {
 299 }
 300
 301 static void death_use(struct basic_block *bb, struct instruction *insn, pseudo_t pseudo)
 302 {
 303         if (trackable_pseudo(pseudo) && !pseudo_in_list(*live_list, pseudo)) {
 304                 add_pseudo(&dead_list, pseudo);
 305                 add_pseudo(live_list, pseudo);
 306         }
 307 }
 308
 309 static void track_pseudo_death_bb(struct basic_block *bb)
 310 {
 311         struct pseudo_list *live = NULL;
 312         struct basic_block *child;
 313         struct instruction *insn;
 314
 315         FOR_EACH_PTR(bb->children, child) {
 316                 merge_pseudo_list(child->needs, &live);
 317         } END_FOR_EACH_PTR(child);
 318
 319         live_list = &live;
 320         FOR_EACH_PTR_REVERSE(bb->insns, insn) {
 321                 if (!insn->bb)
 322                         continue;
 323
 324                 /*
 325                  * A "def" of a pseudo removes it from the liveness
 326                  * list. However, we only bother doing that for
 327                  * phi-nodes, since no other pseudos should ever
 328                  * be even used before they are def'ed.
 329                  */
 330                 if (insn->opcode == OP_PHISOURCE) {
 331                         struct instruction *phi;
 332                         FOR_EACH_PTR(insn->phi_users, phi) {
 333                                 remove_pseudo(live_list, phi->target);
 334                         } END_FOR_EACH_PTR(phi);
 335                 }
 336
 337                 dead_list = NULL;
 338                 track_instruction_usage(bb, insn, death_def, death_use);
 339                 if (dead_list) {
 340                         pseudo_t dead;
 341                         FOR_EACH_PTR(dead_list, dead) {
 342                                 struct instruction *deathnote = __alloc_instruction(0);
 343                                 deathnote->bb = bb;
 344                                 deathnote->opcode = OP_DEATHNOTE;
 345                                 deathnote->target = dead;
 346                                 INSERT_CURRENT(deathnote, insn);
 347                         } END_FOR_EACH_PTR(dead);
 348                         free_ptr_list(&dead_list);
 349                 }
 350         } END_FOR_EACH_PTR_REVERSE(insn);
 351         free_ptr_list(&live);
 352 }
 353
 354 void track_pseudo_death(struct entrypoint *ep)
 355 {
 356         struct basic_block *bb;
 357
 358         FOR_EACH_PTR(ep->bbs, bb) {
 359                 track_bb_phi_uses(bb);
 360         } END_FOR_EACH_PTR(bb);
 361
 362         FOR_EACH_PTR(ep->bbs, bb) {
 363                 track_pseudo_death_bb(bb);
 364         } END_FOR_EACH_PTR(bb);
 365 }