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_BADOP:
 117         case OP_INVOKE:
 118         case OP_UNWIND:
 119         case OP_MALLOC:
 120         case OP_FREE:
 121         case OP_ALLOCA:
 122         case OP_GET_ELEMENT_PTR:
 123         case OP_VANEXT:
 124         case OP_VAARG:
 125         case OP_SNOP:
 126         case OP_LNOP:
 127         case OP_NOP:
 128         case OP_CONTEXT:
 129                 break;
 130         }
 131 }
 132
 133 int pseudo_in_list(struct pseudo_list *list, pseudo_t pseudo)
 134 {
 135         pseudo_t old;
 136         FOR_EACH_PTR(list,old) {
 137                 if (old == pseudo)
 138                         return 1;
 139         } END_FOR_EACH_PTR(old);
 140         return 0;
 141 }
 142
 143 static int liveness_changed;
 144
 145 static void add_pseudo_exclusive(struct pseudo_list **list, pseudo_t pseudo)
 146 {
 147         if (!pseudo_in_list(*list, pseudo)) {
 148                 liveness_changed = 1;
 149                 add_pseudo(list, pseudo);
 150         }
 151 }
 152
 153 static inline int trackable_pseudo(pseudo_t pseudo)
 154 {
 155         return pseudo && (pseudo->type == PSEUDO_REG || pseudo->type == PSEUDO_PHI || pseudo->type == PSEUDO_ARG);
 156 }
 157
 158 static void insn_uses(struct basic_block *bb, struct instruction *insn, pseudo_t pseudo)
 159 {
 160         if (trackable_pseudo(pseudo))
 161                 add_pseudo_exclusive(&bb->needs, pseudo);
 162 }
 163
 164 static void insn_defines(struct basic_block *bb, struct instruction *insn, pseudo_t pseudo)
 165 {
 166         assert(trackable_pseudo(pseudo));
 167         add_pseudo(&bb->defines, pseudo);
 168 }
 169
 170 static void track_bb_liveness(struct basic_block *bb)
 171 {
 172         pseudo_t needs;
 173
 174         FOR_EACH_PTR(bb->needs, needs) {
 175                 if (!pseudo_in_list(bb->defines, needs)) {
 176                         struct basic_block *parent;
 177                         FOR_EACH_PTR(bb->parents, parent) {
 178                                 if (!pseudo_in_list(parent->defines, needs)) {
 179                                         add_pseudo_exclusive(&parent->needs, needs);
 180                                 }
 181                         } END_FOR_EACH_PTR(parent);
 182                 }
 183         } END_FOR_EACH_PTR(needs);
 184 }
 185
 186 static inline void remove_pseudo(struct pseudo_list **list, pseudo_t pseudo)
 187 {
 188         delete_ptr_list_entry((struct ptr_list **)list, pseudo, 0);
 189 }
 190
 191 /*
 192  * We need to clear the liveness information if we
 193  * are going to re-run it.
 194  */
 195 void clear_liveness(struct entrypoint *ep)
 196 {
 197         struct basic_block *bb;
 198
 199         FOR_EACH_PTR(ep->bbs, bb) {
 200                 free_ptr_list(&bb->needs);
 201                 free_ptr_list(&bb->defines);
 202         } END_FOR_EACH_PTR(bb);
 203 }
 204
 205 /*
 206  * Track inter-bb pseudo liveness. The intra-bb case
 207  * is purely local information.
 208  */
 209 void track_pseudo_liveness(struct entrypoint *ep)
 210 {
 211         struct basic_block *bb;
 212
 213         /* Add all the bb pseudo usage */
 214         FOR_EACH_PTR(ep->bbs, bb) {
 215                 struct instruction *insn;
 216                 FOR_EACH_PTR(bb->insns, insn) {
 217                         if (!insn->bb)
 218                                 continue;
 219                         assert(insn->bb == bb);
 220                         track_instruction_usage(bb, insn, insn_defines, insn_uses);
 221                 } END_FOR_EACH_PTR(insn);
 222         } END_FOR_EACH_PTR(bb);
 223
 224         /* Remove the pseudos from the "need" list that are defined internally */
 225         FOR_EACH_PTR(ep->bbs, bb) {
 226                 pseudo_t def;
 227                 FOR_EACH_PTR(bb->defines, def) {
 228                         remove_pseudo(&bb->needs, def);
 229                 } END_FOR_EACH_PTR(def);
 230         } END_FOR_EACH_PTR(bb);
 231
 232         /* Calculate liveness.. */
 233         do {
 234                 liveness_changed = 0;
 235                 FOR_EACH_PTR_REVERSE(ep->bbs, bb) {
 236                         track_bb_liveness(bb);
 237                 } END_FOR_EACH_PTR_REVERSE(bb);
 238         } while (liveness_changed);
 239
 240         /* Remove the pseudos from the "defines" list that are used internally */
 241         FOR_EACH_PTR(ep->bbs, bb) {
 242                 pseudo_t def;
 243                 FOR_EACH_PTR(bb->defines, def) {
 244                         struct basic_block *child;
 245                         FOR_EACH_PTR(bb->children, child) {
 246                                 if (pseudo_in_list(child->needs, def))
 247                                         goto is_used;
 248                         } END_FOR_EACH_PTR(child);
 249                         DELETE_CURRENT_PTR(def);
 250 is_used:
 251                 ;
 252                 } END_FOR_EACH_PTR(def);
 253                 PACK_PTR_LIST(&bb->defines);
 254         } END_FOR_EACH_PTR(bb);
 255 }
 256
 257 static void merge_pseudo_list(struct pseudo_list *src, struct pseudo_list **dest)
 258 {
 259         pseudo_t pseudo;
 260         FOR_EACH_PTR(src, pseudo) {
 261                 add_pseudo_exclusive(dest, pseudo);
 262         } END_FOR_EACH_PTR(pseudo);
 263 }
 264
 265 static struct pseudo_list **live_list;
 266 static struct pseudo_list *dead_list;
 267
 268 static void death_def(struct basic_block *bb, struct instruction *insn, pseudo_t pseudo)
 269 {
 270 }
 271
 272 static void death_use(struct basic_block *bb, struct instruction *insn, pseudo_t pseudo)
 273 {
 274         if (trackable_pseudo(pseudo) && !pseudo_in_list(*live_list, pseudo)) {
 275                 add_pseudo(&dead_list, pseudo);
 276                 add_pseudo(live_list, pseudo);
 277         }
 278 }
 279
 280 static void track_pseudo_death_bb(struct basic_block *bb)
 281 {
 282         struct pseudo_list *live = NULL;
 283         struct basic_block *child;
 284         struct instruction *insn;
 285
 286         FOR_EACH_PTR(bb->children, child) {
 287                 merge_pseudo_list(child->needs, &live);
 288         } END_FOR_EACH_PTR(child);
 289
 290         live_list = &live;
 291         FOR_EACH_PTR_REVERSE(bb->insns, insn) {
 292                 if (!insn->bb)
 293                         continue;
 294                 dead_list = NULL;
 295                 track_instruction_usage(bb, insn, death_def, death_use);
 296                 if (dead_list) {
 297                         pseudo_t dead;
 298                         FOR_EACH_PTR(dead_list, dead) {
 299                                 struct instruction *deathnote = __alloc_instruction(0);
 300                                 deathnote->bb = bb;
 301                                 deathnote->opcode = OP_DEATHNOTE;
 302                                 deathnote->target = dead;
 303                                 INSERT_CURRENT(deathnote, insn);
 304                         } END_FOR_EACH_PTR(dead);
 305                         free_ptr_list(&dead_list);
 306                 }
 307         } END_FOR_EACH_PTR_REVERSE(insn);
 308         free_ptr_list(&live);
 309 }
 310
 311 void track_pseudo_death(struct entrypoint *ep)
 312 {
 313         struct basic_block *bb;
 314
 315         FOR_EACH_PTR(ep->bbs, bb) {
 316                 track_pseudo_death_bb(bb);
 317         } END_FOR_EACH_PTR(bb);
 318 }