src/gallium/drivers/nouveau/codegen/nv50_ir_ssa.cpp

   1 /*
   2  * Copyright 2011 Christoph Bumiller
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice shall be included in
  12  * all copies or substantial portions of the Software.
  13  *
  14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  15  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  17  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  18  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  19  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  20  * OTHER DEALINGS IN THE SOFTWARE.
  21  */
  22
  23 #include "codegen/nv50_ir.h"
  24 #include "codegen/nv50_ir_target.h"
  25
  26 namespace nv50_ir {
  27
  28 // Converts nv50 IR generated from TGSI to SSA form.
  29
  30 // DominatorTree implements an algorithm for finding immediate dominators,
  31 // as described by T. Lengauer & R. Tarjan.
  32 class DominatorTree : public Graph
  33 {
  34 public:
  35    DominatorTree(Graph *cfg);
  36    ~DominatorTree() { }
  37
  38    bool dominates(BasicBlock *, BasicBlock *);
  39
  40    void findDominanceFrontiers();
  41
  42 private:
  43    void build();
  44    void buildDFS(Node *);
  45
  46    void squash(int);
  47    inline void link(int, int);
  48    inline int eval(int);
  49
  50    void debugPrint();
  51
  52    Graph *cfg;
  53
  54    Node **vert;
  55    int *data;
  56    const int count;
  57
  58    #define SEMI(i)     (data[(i) + 0 * count])
  59    #define ANCESTOR(i) (data[(i) + 1 * count])
  60    #define PARENT(i)   (data[(i) + 2 * count])
  61    #define LABEL(i)    (data[(i) + 3 * count])
  62    #define DOM(i)      (data[(i) + 4 * count])
  63 };
  64
  65 void DominatorTree::debugPrint()
  66 {
  67    for (int i = 0; i < count; ++i) {
  68       INFO("SEMI(%i) = %i\n", i, SEMI(i));
  69       INFO("ANCESTOR(%i) = %i\n", i, ANCESTOR(i));
  70       INFO("PARENT(%i) = %i\n", i, PARENT(i));
  71       INFO("LABEL(%i) = %i\n", i, LABEL(i));
  72       INFO("DOM(%i) = %i\n", i, DOM(i));
  73    }
  74 }
  75
  76 DominatorTree::DominatorTree(Graph *cfgraph) : cfg(cfgraph),
  77                                                count(cfg->getSize())
  78 {
  79    int i = 0;
  80
  81    vert = new Node * [count];
  82    data = new int[5 * count];
  83
  84    for (IteratorRef it = cfg->iteratorDFS(true); !it->end(); it->next(), ++i) {
  85       vert[i] = reinterpret_cast<Node *>(it->get());
  86       vert[i]->tag = i;
  87       LABEL(i) = i;
  88       SEMI(i) = ANCESTOR(i) = -1;
  89    }
  90
  91    build();
  92
  93    delete[] vert;
  94    delete[] data;
  95 }
  96
  97 void DominatorTree::buildDFS(Graph::Node *node)
  98 {
  99    SEMI(node->tag) = node->tag;
 100
 101    for (Graph::EdgeIterator ei = node->outgoing(); !ei.end(); ei.next()) {
 102       if (SEMI(ei.getNode()->tag) < 0) {
 103          buildDFS(ei.getNode());
 104          PARENT(ei.getNode()->tag) = node->tag;
 105       }
 106    }
 107 }
 108
 109 void DominatorTree::squash(int v)
 110 {
 111    if (ANCESTOR(ANCESTOR(v)) >= 0) {
 112       squash(ANCESTOR(v));
 113
 114       if (SEMI(LABEL(ANCESTOR(v))) < SEMI(LABEL(v)))
 115          LABEL(v) = LABEL(ANCESTOR(v));
 116       ANCESTOR(v) = ANCESTOR(ANCESTOR(v));
 117    }
 118 }
 119
 120 int DominatorTree::eval(int v)
 121 {
 122    if (ANCESTOR(v) < 0)
 123       return v;
 124    squash(v);
 125    return LABEL(v);
 126 }
 127
 128 void DominatorTree::link(int v, int w)
 129 {
 130    ANCESTOR(w) = v;
 131 }
 132
 133 void DominatorTree::build()
 134 {
 135    DLList *bucket = new DLList[count];
 136    Node *nv, *nw;
 137    int p, u, v, w;
 138
 139    buildDFS(cfg->getRoot());
 140
 141    for (w = count - 1; w >= 1; --w) {
 142       nw = vert[w];
 143       assert(nw->tag == w);
 144       for (Graph::EdgeIterator ei = nw->incident(); !ei.end(); ei.next()) {
 145          nv = ei.getNode();
 146          v = nv->tag;
 147          u = eval(v);
 148          if (SEMI(u) < SEMI(w))
 149             SEMI(w) = SEMI(u);
 150       }
 151       p = PARENT(w);
 152       bucket[SEMI(w)].insert(nw);
 153       link(p, w);
 154
 155       for (DLList::Iterator it = bucket[p].iterator(); !it.end(); it.erase()) {
 156          v = reinterpret_cast<Node *>(it.get())->tag;
 157          u = eval(v);
 158          DOM(v) = (SEMI(u) < SEMI(v)) ? u : p;
 159       }
 160    }
 161    for (w = 1; w < count; ++w) {
 162       if (DOM(w) != SEMI(w))
 163          DOM(w) = DOM(DOM(w));
 164    }
 165    DOM(0) = 0;
 166
 167    insert(&BasicBlock::get(cfg->getRoot())->dom);
 168    do {
 169       p = 0;
 170       for (v = 1; v < count; ++v) {
 171          nw = &BasicBlock::get(vert[DOM(v)])->dom;;
 172          nv = &BasicBlock::get(vert[v])->dom;
 173          if (nw->getGraph() && !nv->getGraph()) {
 174             ++p;
 175             nw->attach(nv, Graph::Edge::TREE);
 176          }
 177       }
 178    } while (p);
 179
 180    delete[] bucket;
 181 }
 182
 183 #undef SEMI
 184 #undef ANCESTOR
 185 #undef PARENT
 186 #undef LABEL
 187 #undef DOM
 188
 189 void DominatorTree::findDominanceFrontiers()
 190 {
 191    BasicBlock *bb;
 192
 193    for (IteratorRef dtIt = iteratorDFS(false); !dtIt->end(); dtIt->next()) {
 194       EdgeIterator succIt, chldIt;
 195
 196       bb = BasicBlock::get(reinterpret_cast<Node *>(dtIt->get()));
 197       bb->getDF().clear();
 198
 199       for (succIt = bb->cfg.outgoing(); !succIt.end(); succIt.next()) {
 200          BasicBlock *dfLocal = BasicBlock::get(succIt.getNode());
 201          if (dfLocal->idom() != bb)
 202             bb->getDF().insert(dfLocal);
 203       }
 204
 205       for (chldIt = bb->dom.outgoing(); !chldIt.end(); chldIt.next()) {
 206          BasicBlock *cb = BasicBlock::get(chldIt.getNode());
 207
 208          DLList::Iterator dfIt = cb->getDF().iterator();
 209          for (; !dfIt.end(); dfIt.next()) {
 210             BasicBlock *dfUp = BasicBlock::get(dfIt);
 211             if (dfUp->idom() != bb)
 212                bb->getDF().insert(dfUp);
 213          }
 214       }
 215    }
 216 }
 217
 218 // liveIn(bb) = usedBeforeAssigned(bb) U (liveOut(bb) - assigned(bb))
 219 void
 220 Function::buildLiveSetsPreSSA(BasicBlock *bb, const int seq)
 221 {
 222    Function *f = bb->getFunction();
 223    BitSet usedBeforeAssigned(allLValues.getSize(), true);
 224    BitSet assigned(allLValues.getSize(), true);
 225
 226    bb->liveSet.allocate(allLValues.getSize(), false);
 227
 228    int n = 0;
 229    for (Graph::EdgeIterator ei = bb->cfg.outgoing(); !ei.end(); ei.next()) {
 230       BasicBlock *out = BasicBlock::get(ei.getNode());
 231       if (out == bb)
 232          continue;
 233       if (out->cfg.visit(seq))
 234          buildLiveSetsPreSSA(out, seq);
 235       if (!n++)
 236          bb->liveSet = out->liveSet;
 237       else
 238          bb->liveSet |= out->liveSet;
 239    }
 240    if (!n && !bb->liveSet.marker)
 241       bb->liveSet.fill(0);
 242    bb->liveSet.marker = true;
 243
 244    for (Instruction *i = bb->getEntry(); i; i = i->next) {
 245       for (int s = 0; i->srcExists(s); ++s)
 246          if (i->getSrc(s)->asLValue() && !assigned.test(i->getSrc(s)->id))
 247             usedBeforeAssigned.set(i->getSrc(s)->id);
 248       for (int d = 0; i->defExists(d); ++d)
 249          assigned.set(i->getDef(d)->id);
 250    }
 251
 252    if (bb == BasicBlock::get(f->cfgExit)) {
 253       for (std::deque<ValueRef>::iterator it = f->outs.begin();
 254            it != f->outs.end(); ++it) {
 255          if (!assigned.test(it->get()->id))
 256             usedBeforeAssigned.set(it->get()->id);
 257       }
 258    }
 259
 260    bb->liveSet.andNot(assigned);
 261    bb->liveSet |= usedBeforeAssigned;
 262 }
 263
 264 void
 265 Function::buildDefSetsPreSSA(BasicBlock *bb, const int seq)
 266 {
 267    bb->defSet.allocate(allLValues.getSize(), !bb->liveSet.marker);
 268    bb->liveSet.marker = true;
 269
 270    for (Graph::EdgeIterator ei = bb->cfg.incident(); !ei.end(); ei.next()) {
 271       BasicBlock *in = BasicBlock::get(ei.getNode());
 272
 273       if (in->cfg.visit(seq))
 274          buildDefSetsPreSSA(in, seq);
 275
 276       bb->defSet |= in->defSet;
 277    }
 278
 279    for (Instruction *i = bb->getEntry(); i; i = i->next) {
 280       for (int d = 0; i->defExists(d); ++d)
 281          bb->defSet.set(i->getDef(d)->id);
 282    }
 283 }
 284
 285 class RenamePass
 286 {
 287 public:
 288    RenamePass(Function *);
 289    ~RenamePass();
 290
 291    bool run();
 292    void search(BasicBlock *);
 293
 294    inline LValue *getStackTop(Value *);
 295
 296    LValue *mkUndefined(Value *);
 297
 298 private:
 299    Stack *stack;
 300    Function *func;
 301    Program *prog;
 302 };
 303
 304 bool
 305 Program::convertToSSA()
 306 {
 307    for (ArrayList::Iterator fi = allFuncs.iterator(); !fi.end(); fi.next()) {
 308       Function *fn = reinterpret_cast<Function *>(fi.get());
 309       if (!fn->convertToSSA())
 310          return false;
 311    }
 312    return true;
 313 }
 314
 315 // XXX: add edge from entry to exit ?
 316
 317 // Efficiently Computing Static Single Assignment Form and
 318 //  the Control Dependence Graph,
 319 // R. Cytron, J. Ferrante, B. K. Rosen, M. N. Wegman, F. K. Zadeck
 320 bool
 321 Function::convertToSSA()
 322 {
 323    // 0. calculate live in variables (for pruned SSA)
 324    buildLiveSets();
 325
 326    // 1. create the dominator tree
 327    domTree = new DominatorTree(&cfg);
 328    reinterpret_cast<DominatorTree *>(domTree)->findDominanceFrontiers();
 329
 330    // 2. insert PHI functions
 331    DLList workList;
 332    LValue *lval;
 333    BasicBlock *bb;
 334    int var;
 335    int iterCount = 0;
 336    int *hasAlready = new int[allBBlocks.getSize() * 2];
 337    int *work = &hasAlready[allBBlocks.getSize()];
 338
 339    memset(hasAlready, 0, allBBlocks.getSize() * 2 * sizeof(int));
 340
 341    // for each variable
 342    for (var = 0; var < allLValues.getSize(); ++var) {
 343       if (!allLValues.get(var))
 344          continue;
 345       lval = reinterpret_cast<Value *>(allLValues.get(var))->asLValue();
 346       if (!lval || lval->defs.empty())
 347          continue;
 348       ++iterCount;
 349
 350       // TODO: don't add phi functions for values that aren't used outside
 351       //  the BB they're defined in
 352
 353       // gather blocks with assignments to lval in workList
 354       for (Value::DefIterator d = lval->defs.begin();
 355            d != lval->defs.end(); ++d) {
 356          bb = ((*d)->getInsn() ? (*d)->getInsn()->bb : NULL);
 357          if (!bb)
 358             continue; // instruction likely been removed but not XXX deleted
 359
 360          if (work[bb->getId()] == iterCount)
 361             continue;
 362          work[bb->getId()] = iterCount;
 363          workList.insert(bb);
 364       }
 365
 366       // for each block in workList, insert a phi for lval in the block's
 367       //  dominance frontier (if we haven't already done so)
 368       for (DLList::Iterator wI = workList.iterator(); !wI.end(); wI.erase()) {
 369          bb = BasicBlock::get(wI);
 370
 371          DLList::Iterator dfIter = bb->getDF().iterator();
 372          for (; !dfIter.end(); dfIter.next()) {
 373             Instruction *phi;
 374             BasicBlock *dfBB = BasicBlock::get(dfIter);
 375
 376             if (hasAlready[dfBB->getId()] >= iterCount)
 377                continue;
 378             hasAlready[dfBB->getId()] = iterCount;
 379
 380             // pruned SSA: don't need a phi if the value is not live-in
 381             if (!dfBB->liveSet.test(lval->id))
 382                continue;
 383
 384             phi = new_Instruction(this, OP_PHI, typeOfSize(lval->reg.size));
 385             dfBB->insertTail(phi);
 386
 387             phi->setDef(0, lval);
 388             for (int s = 0; s < dfBB->cfg.incidentCount(); ++s)
 389                phi->setSrc(s, lval);
 390
 391             if (work[dfBB->getId()] < iterCount) {
 392                work[dfBB->getId()] = iterCount;
 393                wI.insert(dfBB);
 394             }
 395          }
 396       }
 397    }
 398    delete[] hasAlready;
 399
 400    RenamePass rename(this);
 401    return rename.run();
 402 }
 403
 404 RenamePass::RenamePass(Function *fn) : func(fn), prog(fn->getProgram())
 405 {
 406    stack = new Stack[func->allLValues.getSize()];
 407 }
 408
 409 RenamePass::~RenamePass()
 410 {
 411    if (stack)
 412       delete[] stack;
 413 }
 414
 415 LValue *
 416 RenamePass::getStackTop(Value *val)
 417 {
 418    if (!stack[val->id].getSize())
 419       return 0;
 420    return reinterpret_cast<LValue *>(stack[val->id].peek().u.p);
 421 }
 422
 423 LValue *
 424 RenamePass::mkUndefined(Value *val)
 425 {
 426    LValue *lval = val->asLValue();
 427    assert(lval);
 428    LValue *ud = new_LValue(func, lval);
 429    Instruction *nop = new_Instruction(func, OP_NOP, typeOfSize(lval->reg.size));
 430    nop->setDef(0, ud);
 431    BasicBlock::get(func->cfg.getRoot())->insertHead(nop);
 432    return ud;
 433 }
 434
 435 bool RenamePass::run()
 436 {
 437    if (!stack)
 438       return false;
 439    search(BasicBlock::get(func->domTree->getRoot()));
 440
 441    return true;
 442 }
 443
 444 // Go through BBs in dominance order, create new values for each definition,
 445 // and replace all sources with their current new values.
 446 //
 447 // NOTE: The values generated for function inputs/outputs have no connection
 448 // to their corresponding outputs/inputs in other functions. Only allocation
 449 // of physical registers will establish this connection.
 450 //
 451 void RenamePass::search(BasicBlock *bb)
 452 {
 453    LValue *lval, *ssa;
 454    int d, s;
 455    const Target *targ = prog->getTarget();
 456
 457    // Put current definitions for function inputs values on the stack.
 458    // They can be used before any redefinitions are pushed.
 459    if (bb == BasicBlock::get(func->cfg.getRoot())) {
 460       for (std::deque<ValueDef>::iterator it = func->ins.begin();
 461            it != func->ins.end(); ++it) {
 462          lval = it->get()->asLValue();
 463          assert(lval);
 464
 465          ssa = new_LValue(func, targ->nativeFile(lval->reg.file));
 466          ssa->reg.size = lval->reg.size;
 467          ssa->reg.data.id = lval->reg.data.id;
 468
 469          it->setSSA(ssa);
 470          stack[lval->id].push(ssa);
 471       }
 472    }
 473
 474    for (Instruction *stmt = bb->getFirst(); stmt; stmt = stmt->next) {
 475       // PHI sources get definitions from the passes through the incident BBs,
 476       // so skip them here.
 477       if (stmt->op != OP_PHI) {
 478          for (s = 0; stmt->srcExists(s); ++s) {
 479             lval = stmt->getSrc(s)->asLValue();
 480             if (!lval)
 481                continue;
 482             // Values on the stack created in previously visited blocks, and
 483             // function inputs, will be valid because they dominate this one.
 484             lval = getStackTop(lval);
 485             if (!lval)
 486                lval = mkUndefined(stmt->getSrc(s));
 487             stmt->setSrc(s, lval);
 488          }
 489       }
 490       for (d = 0; stmt->defExists(d); ++d) {
 491          lval = stmt->def(d).get()->asLValue();
 492          assert(lval);
 493          stmt->def(d).setSSA(
 494             new_LValue(func, targ->nativeFile(lval->reg.file)));
 495          stmt->def(d).get()->reg.size = lval->reg.size;
 496          stmt->def(d).get()->reg.data.id = lval->reg.data.id;
 497          stack[lval->id].push(stmt->def(d).get());
 498       }
 499    }
 500
 501    // Update sources of PHI ops corresponding to this BB in outgoing BBs.
 502    for (Graph::EdgeIterator ei = bb->cfg.outgoing(); !ei.end(); ei.next()) {
 503       Instruction *phi;
 504       int p = 0;
 505       BasicBlock *sb = BasicBlock::get(ei.getNode());
 506
 507       // which predecessor of sb is bb ?
 508       for (Graph::EdgeIterator ei = sb->cfg.incident(); !ei.end(); ei.next()) {
 509          if (ei.getNode() == &bb->cfg)
 510             break;
 511          ++p;
 512       }
 513       assert(p < sb->cfg.incidentCount());
 514
 515       for (phi = sb->getPhi(); phi && phi->op == OP_PHI; phi = phi->next) {
 516          lval = getStackTop(phi->getSrc(p));
 517          if (!lval)
 518             lval = mkUndefined(phi->getSrc(p));
 519          phi->setSrc(p, lval);
 520       }
 521    }
 522
 523    // Visit the BBs we dominate.
 524    for (Graph::EdgeIterator ei = bb->dom.outgoing(); !ei.end(); ei.next())
 525       search(BasicBlock::get(ei.getNode()));
 526
 527    // Update function outputs to the last definitions of their pre-SSA values.
 528    // I hope they're unique, i.e. that we get PHIs for all of them ...
 529    if (bb == BasicBlock::get(func->cfgExit)) {
 530       for (std::deque<ValueRef>::iterator it = func->outs.begin();
 531            it != func->outs.end(); ++it) {
 532          lval = it->get()->asLValue();
 533          if (!lval)
 534             continue;
 535          lval = getStackTop(lval);
 536          if (!lval)
 537             lval = mkUndefined(it->get());
 538          it->set(lval);
 539       }
 540    }
 541
 542    // Pop the values we created in this block from the stack because we will
 543    // return to blocks that we do not dominate.
 544    for (Instruction *stmt = bb->getFirst(); stmt; stmt = stmt->next) {
 545       if (stmt->op == OP_NOP)
 546          continue;
 547       for (d = 0; stmt->defExists(d); ++d)
 548          stack[stmt->def(d).preSSA()->id].pop();
 549    }
 550 }
 551
 552 } // namespace nv50_ir