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