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 track_instruction_usage(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         pseudo_t pseudo;
  39
  40         #define USES(x)         use(bb, insn, insn->x)
  41         #define DEFINES(x)      def(bb, insn, insn->x)
  42
  43         switch (insn->opcode) {
  44         case OP_RET:
  45                 USES(src);
  46                 break;
  47
  48         case OP_BR: case OP_SWITCH:
  49                 USES(cond);
  50                 break;
  51
  52         case OP_COMPUTEDGOTO:
  53                 USES(target);
  54                 break;
  55
  56         /* Binary */
  57         case OP_BINARY ... OP_BINARY_END:
  58         case OP_BINCMP ... OP_BINCMP_END:
  59                 USES(src1); USES(src2); DEFINES(target);
  60                 break;
  61
  62         /* Uni */
  63         case OP_NOT: case OP_NEG:
  64                 USES(src1); DEFINES(target);
  65                 break;
  66
  67         case OP_SEL:
  68                 USES(src1); USES(src2); USES(src3); DEFINES(target);
  69                 break;
  70
  71         /* Memory */
  72         case OP_LOAD:
  73                 USES(src); DEFINES(target);
  74                 break;
  75
  76         case OP_STORE:
  77                 USES(src); USES(target);
  78                 break;
  79
  80         case OP_SETVAL:
  81                 USES(symbol); DEFINES(target);
  82                 break;
  83
  84         /* Other */
  85         case OP_PHI:
  86                 /* Phi-nodes are "backwards" nodes. Their def doesn't matter */
  87                 phi_defines(insn, insn->target, def);
  88                 break;
  89
  90         case OP_PHISOURCE:
  91                 /*
  92                  * We don't care about the phi-source define, they get set
  93                  * up and expanded by the OP_PHI
  94                  */
  95                 USES(src1);
  96                 break;
  97
  98         case OP_CAST:
  99         case OP_PTRCAST:
 100                 USES(src); DEFINES(target);
 101                 break;
 102
 103         case OP_CALL:
 104                 USES(func);
 105                 if (insn->target != VOID)
 106                         DEFINES(target);
 107                 FOR_EACH_PTR(insn->arguments, pseudo) {
 108                         use(bb, insn, pseudo);
 109                 } END_FOR_EACH_PTR(pseudo);
 110                 break;
 111
 112         case OP_SLICE:
 113                 USES(base); DEFINES(target);
 114                 break;
 115
 116         case OP_ASM:
 117                 FOR_EACH_PTR(insn->inputs, pseudo) {
 118                         use(bb, insn, pseudo);
 119                 } END_FOR_EACH_PTR(pseudo);
 120
 121                 FOR_EACH_PTR(insn->outputs, pseudo) {
 122                         def(bb, insn, pseudo);
 123                 } END_FOR_EACH_PTR(pseudo);
 124                 break;
 125
 126         case OP_BADOP:
 127         case OP_INVOKE:
 128         case OP_UNWIND:
 129         case OP_MALLOC:
 130         case OP_FREE:
 131         case OP_ALLOCA:
 132         case OP_GET_ELEMENT_PTR:
 133         case OP_VANEXT:
 134         case OP_VAARG:
 135         case OP_SNOP:
 136         case OP_LNOP:
 137         case OP_NOP:
 138         case OP_CONTEXT:
 139                 break;
 140         }
 141 }
 142
 143 int pseudo_in_list(struct pseudo_list *list, pseudo_t pseudo)
 144 {
 145         pseudo_t old;
 146         FOR_EACH_PTR(list,old) {
 147                 if (old == pseudo)
 148                         return 1;
 149         } END_FOR_EACH_PTR(old);
 150         return 0;
 151 }
 152
 153 static int liveness_changed;
 154
 155 static void add_pseudo_exclusive(struct pseudo_list **list, pseudo_t pseudo)
 156 {
 157         if (!pseudo_in_list(*list, pseudo)) {
 158                 liveness_changed = 1;
 159                 add_pseudo(list, pseudo);
 160         }
 161 }
 162
 163 static inline int trackable_pseudo(pseudo_t pseudo)
 164 {
 165         return pseudo && (pseudo->type == PSEUDO_REG || pseudo->type == PSEUDO_PHI || pseudo->type == PSEUDO_ARG);
 166 }
 167
 168 static void insn_uses(struct basic_block *bb, struct instruction *insn, pseudo_t pseudo)
 169 {
 170         if (trackable_pseudo(pseudo))
 171                 add_pseudo_exclusive(&bb->needs, pseudo);
 172 }
 173
 174 static void insn_defines(struct basic_block *bb, struct instruction *insn, pseudo_t pseudo)
 175 {
 176         assert(trackable_pseudo(pseudo));
 177         add_pseudo(&bb->defines, pseudo);
 178 }
 179
 180 static void track_bb_liveness(struct basic_block *bb)
 181 {
 182         pseudo_t needs;
 183
 184         FOR_EACH_PTR(bb->needs, needs) {
 185                 if (!pseudo_in_list(bb->defines, needs)) {
 186                         struct basic_block *parent;
 187                         FOR_EACH_PTR(bb->parents, parent) {
 188                                 if (!pseudo_in_list(parent->defines, needs)) {
 189                                         add_pseudo_exclusive(&parent->needs, needs);
 190                                 }
 191                         } END_FOR_EACH_PTR(parent);
 192                 }
 193         } END_FOR_EACH_PTR(needs);
 194 }
 195
 196 static inline void remove_pseudo(struct pseudo_list **list, pseudo_t pseudo)
 197 {
 198         delete_ptr_list_entry((struct ptr_list **)list, pseudo, 0);
 199 }
 200
 201 /*
 202  * We need to clear the liveness information if we
 203  * are going to re-run it.
 204  */
 205 void clear_liveness(struct entrypoint *ep)
 206 {
 207         struct basic_block *bb;
 208
 209         FOR_EACH_PTR(ep->bbs, bb) {
 210                 free_ptr_list(&bb->needs);
 211                 free_ptr_list(&bb->defines);
 212         } END_FOR_EACH_PTR(bb);
 213 }
 214
 215 /*
 216  * Track inter-bb pseudo liveness. The intra-bb case
 217  * is purely local information.
 218  */
 219 void track_pseudo_liveness(struct entrypoint *ep)
 220 {
 221         struct basic_block *bb;
 222
 223         /* Add all the bb pseudo usage */
 224         FOR_EACH_PTR(ep->bbs, bb) {
 225                 struct instruction *insn;
 226                 FOR_EACH_PTR(bb->insns, insn) {
 227                         if (!insn->bb)
 228                                 continue;
 229                         assert(insn->bb == bb);
 230                         track_instruction_usage(bb, insn, insn_defines, insn_uses);
 231                 } END_FOR_EACH_PTR(insn);
 232         } END_FOR_EACH_PTR(bb);
 233
 234         /* Remove the pseudos from the "need" list that are defined internally */
 235         FOR_EACH_PTR(ep->bbs, bb) {
 236                 pseudo_t def;
 237                 FOR_EACH_PTR(bb->defines, def) {
 238                         remove_pseudo(&bb->needs, def);
 239                 } END_FOR_EACH_PTR(def);
 240         } END_FOR_EACH_PTR(bb);
 241
 242         /* Calculate liveness.. */
 243         do {
 244                 liveness_changed = 0;
 245                 FOR_EACH_PTR_REVERSE(ep->bbs, bb) {
 246                         track_bb_liveness(bb);
 247                 } END_FOR_EACH_PTR_REVERSE(bb);
 248         } while (liveness_changed);
 249
 250         /* Remove the pseudos from the "defines" list that are used internally */
 251         FOR_EACH_PTR(ep->bbs, bb) {
 252                 pseudo_t def;
 253                 FOR_EACH_PTR(bb->defines, def) {
 254                         struct basic_block *child;
 255                         FOR_EACH_PTR(bb->children, child) {
 256                                 if (pseudo_in_list(child->needs, def))
 257                                         goto is_used;
 258                         } END_FOR_EACH_PTR(child);
 259                         DELETE_CURRENT_PTR(def);
 260 is_used:
 261                 ;
 262                 } END_FOR_EACH_PTR(def);
 263                 PACK_PTR_LIST(&bb->defines);
 264         } END_FOR_EACH_PTR(bb);
 265 }
 266
 267 static void merge_pseudo_list(struct pseudo_list *src, struct pseudo_list **dest)
 268 {
 269         pseudo_t pseudo;
 270         FOR_EACH_PTR(src, pseudo) {
 271                 add_pseudo_exclusive(dest, pseudo);
 272         } END_FOR_EACH_PTR(pseudo);
 273 }
 274
 275 static struct pseudo_list **live_list;
 276 static struct pseudo_list *dead_list;
 277
 278 static void death_def(struct basic_block *bb, struct instruction *insn, pseudo_t pseudo)
 279 {
 280 }
 281
 282 static void death_use(struct basic_block *bb, struct instruction *insn, pseudo_t pseudo)
 283 {
 284         if (trackable_pseudo(pseudo) && !pseudo_in_list(*live_list, pseudo)) {
 285                 add_pseudo(&dead_list, pseudo);
 286                 add_pseudo(live_list, pseudo);
 287         }
 288 }
 289
 290 static void track_pseudo_death_bb(struct basic_block *bb)
 291 {
 292         struct pseudo_list *live = NULL;
 293         struct basic_block *child;
 294         struct instruction *insn;
 295
 296         FOR_EACH_PTR(bb->children, child) {
 297                 merge_pseudo_list(child->needs, &live);
 298         } END_FOR_EACH_PTR(child);
 299
 300         live_list = &live;
 301         FOR_EACH_PTR_REVERSE(bb->insns, insn) {
 302                 if (!insn->bb)
 303                         continue;
 304                 dead_list = NULL;
 305                 track_instruction_usage(bb, insn, death_def, death_use);
 306                 if (dead_list) {
 307                         pseudo_t dead;
 308                         FOR_EACH_PTR(dead_list, dead) {
 309                                 struct instruction *deathnote = __alloc_instruction(0);
 310                                 deathnote->bb = bb;
 311                                 deathnote->opcode = OP_DEATHNOTE;
 312                                 deathnote->target = dead;
 313                                 INSERT_CURRENT(deathnote, insn);
 314                         } END_FOR_EACH_PTR(dead);
 315                         free_ptr_list(&dead_list);
 316                 }
 317         } END_FOR_EACH_PTR_REVERSE(insn);
 318         free_ptr_list(&live);
 319 }
 320
 321 void track_pseudo_death(struct entrypoint *ep)
 322 {
 323         struct basic_block *bb;
 324
 325         FOR_EACH_PTR(ep->bbs, bb) {
 326                 track_pseudo_death_bb(bb);
 327         } END_FOR_EACH_PTR(bb);
 328 }