1 //===- GVN.cpp - Eliminate redundant values and loads ------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the Owen Anderson and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass performs global value numbering to eliminate fully redundant
11 // instructions. It also performs simple dead load elimination.
13 //===----------------------------------------------------------------------===//
15 #define DEBUG_TYPE "gvn"
16 #include "llvm/Value.h"
17 #include "llvm/Transforms/Scalar.h"
18 #include "llvm/BasicBlock.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/Function.h"
21 #include "llvm/DerivedTypes.h"
22 #include "llvm/Analysis/Dominators.h"
23 #include "llvm/ADT/BitVector.h"
24 #include "llvm/ADT/DenseMap.h"
25 #include "llvm/ADT/DepthFirstIterator.h"
26 #include "llvm/ADT/SmallPtrSet.h"
27 #include "llvm/ADT/SmallVector.h"
28 #include "llvm/ADT/Statistic.h"
29 #include "llvm/Analysis/MemoryDependenceAnalysis.h"
30 #include "llvm/Support/CFG.h"
31 #include "llvm/Support/Compiler.h"
34 //===----------------------------------------------------------------------===//
36 //===----------------------------------------------------------------------===//
38 /// This class holds the mapping between values and value numbers. It is used
39 /// as an efficient mechanism to determine the expression-wise equivalence of
42 struct VISIBILITY_HIDDEN Expression {
43 enum ExpressionOpcode { ADD, SUB, MUL, UDIV, SDIV, FDIV, UREM, SREM,
44 FREM, SHL, LSHR, ASHR, AND, OR, XOR, ICMPEQ,
45 ICMPNE, ICMPUGT, ICMPUGE, ICMPULT, ICMPULE,
46 ICMPSGT, ICMPSGE, ICMPSLT, ICMPSLE, FCMPOEQ,
47 FCMPOGT, FCMPOGE, FCMPOLT, FCMPOLE, FCMPONE,
48 FCMPORD, FCMPUNO, FCMPUEQ, FCMPUGT, FCMPUGE,
49 FCMPULT, FCMPULE, FCMPUNE, EXTRACT, INSERT,
50 SHUFFLE, SELECT, TRUNC, ZEXT, SEXT, FPTOUI,
51 FPTOSI, UITOFP, SITOFP, FPTRUNC, FPEXT,
52 PTRTOINT, INTTOPTR, BITCAST, GEP, EMPTY,
55 ExpressionOpcode opcode;
60 SmallVector<uint32_t, 4> varargs;
63 Expression(ExpressionOpcode o) : opcode(o) { }
65 bool operator==(const Expression &other) const {
66 if (opcode != other.opcode)
68 else if (opcode == EMPTY || opcode == TOMBSTONE)
70 else if (type != other.type)
72 else if (firstVN != other.firstVN)
74 else if (secondVN != other.secondVN)
76 else if (thirdVN != other.thirdVN)
79 if (varargs.size() != other.varargs.size())
82 for (size_t i = 0; i < varargs.size(); ++i)
83 if (varargs[i] != other.varargs[i])
90 bool operator!=(const Expression &other) const {
91 if (opcode != other.opcode)
93 else if (opcode == EMPTY || opcode == TOMBSTONE)
95 else if (type != other.type)
97 else if (firstVN != other.firstVN)
99 else if (secondVN != other.secondVN)
101 else if (thirdVN != other.thirdVN)
104 if (varargs.size() != other.varargs.size())
107 for (size_t i = 0; i < varargs.size(); ++i)
108 if (varargs[i] != other.varargs[i])
116 class VISIBILITY_HIDDEN ValueTable {
118 DenseMap<Value*, uint32_t> valueNumbering;
119 DenseMap<Expression, uint32_t> expressionNumbering;
121 uint32_t nextValueNumber;
123 Expression::ExpressionOpcode getOpcode(BinaryOperator* BO);
124 Expression::ExpressionOpcode getOpcode(CmpInst* C);
125 Expression::ExpressionOpcode getOpcode(CastInst* C);
126 Expression create_expression(BinaryOperator* BO);
127 Expression create_expression(CmpInst* C);
128 Expression create_expression(ShuffleVectorInst* V);
129 Expression create_expression(ExtractElementInst* C);
130 Expression create_expression(InsertElementInst* V);
131 Expression create_expression(SelectInst* V);
132 Expression create_expression(CastInst* C);
133 Expression create_expression(GetElementPtrInst* G);
135 ValueTable() { nextValueNumber = 1; }
136 uint32_t lookup_or_add(Value* V);
137 uint32_t lookup(Value* V) const;
138 void add(Value* V, uint32_t num);
140 void erase(Value* v);
146 template <> struct DenseMapKeyInfo<Expression> {
147 static inline Expression getEmptyKey() { return Expression(Expression::EMPTY); }
148 static inline Expression getTombstoneKey() { return Expression(Expression::TOMBSTONE); }
150 static unsigned getHashValue(const Expression e) {
151 unsigned hash = e.opcode;
153 hash = e.firstVN + hash * 37;
154 hash = e.secondVN + hash * 37;
155 hash = e.thirdVN + hash * 37;
157 hash = (unsigned)((uintptr_t)e.type >> 4) ^
158 (unsigned)((uintptr_t)e.type >> 9) +
161 for (SmallVector<uint32_t, 4>::const_iterator I = e.varargs.begin(), E = e.varargs.end();
163 hash = *I + hash * 37;
167 static bool isPod() { return true; }
171 //===----------------------------------------------------------------------===//
172 // ValueTable Internal Functions
173 //===----------------------------------------------------------------------===//
174 Expression::ExpressionOpcode
175 ValueTable::getOpcode(BinaryOperator* BO) {
176 switch(BO->getOpcode()) {
177 case Instruction::Add:
178 return Expression::ADD;
179 case Instruction::Sub:
180 return Expression::SUB;
181 case Instruction::Mul:
182 return Expression::MUL;
183 case Instruction::UDiv:
184 return Expression::UDIV;
185 case Instruction::SDiv:
186 return Expression::SDIV;
187 case Instruction::FDiv:
188 return Expression::FDIV;
189 case Instruction::URem:
190 return Expression::UREM;
191 case Instruction::SRem:
192 return Expression::SREM;
193 case Instruction::FRem:
194 return Expression::FREM;
195 case Instruction::Shl:
196 return Expression::SHL;
197 case Instruction::LShr:
198 return Expression::LSHR;
199 case Instruction::AShr:
200 return Expression::ASHR;
201 case Instruction::And:
202 return Expression::AND;
203 case Instruction::Or:
204 return Expression::OR;
205 case Instruction::Xor:
206 return Expression::XOR;
208 // THIS SHOULD NEVER HAPPEN
210 assert(0 && "Binary operator with unknown opcode?");
211 return Expression::ADD;
215 Expression::ExpressionOpcode ValueTable::getOpcode(CmpInst* C) {
216 if (C->getOpcode() == Instruction::ICmp) {
217 switch (C->getPredicate()) {
218 case ICmpInst::ICMP_EQ:
219 return Expression::ICMPEQ;
220 case ICmpInst::ICMP_NE:
221 return Expression::ICMPNE;
222 case ICmpInst::ICMP_UGT:
223 return Expression::ICMPUGT;
224 case ICmpInst::ICMP_UGE:
225 return Expression::ICMPUGE;
226 case ICmpInst::ICMP_ULT:
227 return Expression::ICMPULT;
228 case ICmpInst::ICMP_ULE:
229 return Expression::ICMPULE;
230 case ICmpInst::ICMP_SGT:
231 return Expression::ICMPSGT;
232 case ICmpInst::ICMP_SGE:
233 return Expression::ICMPSGE;
234 case ICmpInst::ICMP_SLT:
235 return Expression::ICMPSLT;
236 case ICmpInst::ICMP_SLE:
237 return Expression::ICMPSLE;
239 // THIS SHOULD NEVER HAPPEN
241 assert(0 && "Comparison with unknown predicate?");
242 return Expression::ICMPEQ;
245 switch (C->getPredicate()) {
246 case FCmpInst::FCMP_OEQ:
247 return Expression::FCMPOEQ;
248 case FCmpInst::FCMP_OGT:
249 return Expression::FCMPOGT;
250 case FCmpInst::FCMP_OGE:
251 return Expression::FCMPOGE;
252 case FCmpInst::FCMP_OLT:
253 return Expression::FCMPOLT;
254 case FCmpInst::FCMP_OLE:
255 return Expression::FCMPOLE;
256 case FCmpInst::FCMP_ONE:
257 return Expression::FCMPONE;
258 case FCmpInst::FCMP_ORD:
259 return Expression::FCMPORD;
260 case FCmpInst::FCMP_UNO:
261 return Expression::FCMPUNO;
262 case FCmpInst::FCMP_UEQ:
263 return Expression::FCMPUEQ;
264 case FCmpInst::FCMP_UGT:
265 return Expression::FCMPUGT;
266 case FCmpInst::FCMP_UGE:
267 return Expression::FCMPUGE;
268 case FCmpInst::FCMP_ULT:
269 return Expression::FCMPULT;
270 case FCmpInst::FCMP_ULE:
271 return Expression::FCMPULE;
272 case FCmpInst::FCMP_UNE:
273 return Expression::FCMPUNE;
275 // THIS SHOULD NEVER HAPPEN
277 assert(0 && "Comparison with unknown predicate?");
278 return Expression::FCMPOEQ;
283 Expression::ExpressionOpcode
284 ValueTable::getOpcode(CastInst* C) {
285 switch(C->getOpcode()) {
286 case Instruction::Trunc:
287 return Expression::TRUNC;
288 case Instruction::ZExt:
289 return Expression::ZEXT;
290 case Instruction::SExt:
291 return Expression::SEXT;
292 case Instruction::FPToUI:
293 return Expression::FPTOUI;
294 case Instruction::FPToSI:
295 return Expression::FPTOSI;
296 case Instruction::UIToFP:
297 return Expression::UITOFP;
298 case Instruction::SIToFP:
299 return Expression::SITOFP;
300 case Instruction::FPTrunc:
301 return Expression::FPTRUNC;
302 case Instruction::FPExt:
303 return Expression::FPEXT;
304 case Instruction::PtrToInt:
305 return Expression::PTRTOINT;
306 case Instruction::IntToPtr:
307 return Expression::INTTOPTR;
308 case Instruction::BitCast:
309 return Expression::BITCAST;
311 // THIS SHOULD NEVER HAPPEN
313 assert(0 && "Cast operator with unknown opcode?");
314 return Expression::BITCAST;
318 Expression ValueTable::create_expression(BinaryOperator* BO) {
321 e.firstVN = lookup_or_add(BO->getOperand(0));
322 e.secondVN = lookup_or_add(BO->getOperand(1));
324 e.type = BO->getType();
325 e.opcode = getOpcode(BO);
330 Expression ValueTable::create_expression(CmpInst* C) {
333 e.firstVN = lookup_or_add(C->getOperand(0));
334 e.secondVN = lookup_or_add(C->getOperand(1));
336 e.type = C->getType();
337 e.opcode = getOpcode(C);
342 Expression ValueTable::create_expression(CastInst* C) {
345 e.firstVN = lookup_or_add(C->getOperand(0));
348 e.type = C->getType();
349 e.opcode = getOpcode(C);
354 Expression ValueTable::create_expression(ShuffleVectorInst* S) {
357 e.firstVN = lookup_or_add(S->getOperand(0));
358 e.secondVN = lookup_or_add(S->getOperand(1));
359 e.thirdVN = lookup_or_add(S->getOperand(2));
360 e.type = S->getType();
361 e.opcode = Expression::SHUFFLE;
366 Expression ValueTable::create_expression(ExtractElementInst* E) {
369 e.firstVN = lookup_or_add(E->getOperand(0));
370 e.secondVN = lookup_or_add(E->getOperand(1));
372 e.type = E->getType();
373 e.opcode = Expression::EXTRACT;
378 Expression ValueTable::create_expression(InsertElementInst* I) {
381 e.firstVN = lookup_or_add(I->getOperand(0));
382 e.secondVN = lookup_or_add(I->getOperand(1));
383 e.thirdVN = lookup_or_add(I->getOperand(2));
384 e.type = I->getType();
385 e.opcode = Expression::INSERT;
390 Expression ValueTable::create_expression(SelectInst* I) {
393 e.firstVN = lookup_or_add(I->getCondition());
394 e.secondVN = lookup_or_add(I->getTrueValue());
395 e.thirdVN = lookup_or_add(I->getFalseValue());
396 e.type = I->getType();
397 e.opcode = Expression::SELECT;
402 Expression ValueTable::create_expression(GetElementPtrInst* G) {
405 e.firstVN = lookup_or_add(G->getPointerOperand());
408 e.type = G->getType();
409 e.opcode = Expression::GEP;
411 for (GetElementPtrInst::op_iterator I = G->idx_begin(), E = G->idx_end();
413 e.varargs.push_back(lookup_or_add(*I));
418 //===----------------------------------------------------------------------===//
419 // ValueTable External Functions
420 //===----------------------------------------------------------------------===//
422 /// lookup_or_add - Returns the value number for the specified value, assigning
423 /// it a new number if it did not have one before.
424 uint32_t ValueTable::lookup_or_add(Value* V) {
425 DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
426 if (VI != valueNumbering.end())
430 if (BinaryOperator* BO = dyn_cast<BinaryOperator>(V)) {
431 Expression e = create_expression(BO);
433 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
434 if (EI != expressionNumbering.end()) {
435 valueNumbering.insert(std::make_pair(V, EI->second));
438 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
439 valueNumbering.insert(std::make_pair(V, nextValueNumber));
441 return nextValueNumber++;
443 } else if (CmpInst* C = dyn_cast<CmpInst>(V)) {
444 Expression e = create_expression(C);
446 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
447 if (EI != expressionNumbering.end()) {
448 valueNumbering.insert(std::make_pair(V, EI->second));
451 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
452 valueNumbering.insert(std::make_pair(V, nextValueNumber));
454 return nextValueNumber++;
456 } else if (ShuffleVectorInst* U = dyn_cast<ShuffleVectorInst>(V)) {
457 Expression e = create_expression(U);
459 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
460 if (EI != expressionNumbering.end()) {
461 valueNumbering.insert(std::make_pair(V, EI->second));
464 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
465 valueNumbering.insert(std::make_pair(V, nextValueNumber));
467 return nextValueNumber++;
469 } else if (ExtractElementInst* U = dyn_cast<ExtractElementInst>(V)) {
470 Expression e = create_expression(U);
472 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
473 if (EI != expressionNumbering.end()) {
474 valueNumbering.insert(std::make_pair(V, EI->second));
477 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
478 valueNumbering.insert(std::make_pair(V, nextValueNumber));
480 return nextValueNumber++;
482 } else if (InsertElementInst* U = dyn_cast<InsertElementInst>(V)) {
483 Expression e = create_expression(U);
485 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
486 if (EI != expressionNumbering.end()) {
487 valueNumbering.insert(std::make_pair(V, EI->second));
490 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
491 valueNumbering.insert(std::make_pair(V, nextValueNumber));
493 return nextValueNumber++;
495 } else if (SelectInst* U = dyn_cast<SelectInst>(V)) {
496 Expression e = create_expression(U);
498 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
499 if (EI != expressionNumbering.end()) {
500 valueNumbering.insert(std::make_pair(V, EI->second));
503 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
504 valueNumbering.insert(std::make_pair(V, nextValueNumber));
506 return nextValueNumber++;
508 } else if (CastInst* U = dyn_cast<CastInst>(V)) {
509 Expression e = create_expression(U);
511 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
512 if (EI != expressionNumbering.end()) {
513 valueNumbering.insert(std::make_pair(V, EI->second));
516 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
517 valueNumbering.insert(std::make_pair(V, nextValueNumber));
519 return nextValueNumber++;
521 } else if (GetElementPtrInst* U = dyn_cast<GetElementPtrInst>(V)) {
522 Expression e = create_expression(U);
524 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
525 if (EI != expressionNumbering.end()) {
526 valueNumbering.insert(std::make_pair(V, EI->second));
529 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
530 valueNumbering.insert(std::make_pair(V, nextValueNumber));
532 return nextValueNumber++;
535 valueNumbering.insert(std::make_pair(V, nextValueNumber));
536 return nextValueNumber++;
540 /// lookup - Returns the value number of the specified value. Fails if
541 /// the value has not yet been numbered.
542 uint32_t ValueTable::lookup(Value* V) const {
543 DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
544 if (VI != valueNumbering.end())
547 assert(0 && "Value not numbered?");
552 /// clear - Remove all entries from the ValueTable
553 void ValueTable::clear() {
554 valueNumbering.clear();
555 expressionNumbering.clear();
559 //===----------------------------------------------------------------------===//
560 // ValueNumberedSet Class
561 //===----------------------------------------------------------------------===//
563 class ValueNumberedSet {
565 SmallPtrSet<Value*, 8> contents;
568 ValueNumberedSet() { numbers.resize(1); }
569 ValueNumberedSet(const ValueNumberedSet& other) {
570 numbers = other.numbers;
571 contents = other.contents;
574 typedef SmallPtrSet<Value*, 8>::iterator iterator;
576 iterator begin() { return contents.begin(); }
577 iterator end() { return contents.end(); }
579 bool insert(Value* v) { return contents.insert(v); }
580 void insert(iterator I, iterator E) { contents.insert(I, E); }
581 void erase(Value* v) { contents.erase(v); }
582 unsigned count(Value* v) { return contents.count(v); }
583 size_t size() { return contents.size(); }
585 void set(unsigned i) {
586 if (i >= numbers.size())
592 void operator=(const ValueNumberedSet& other) {
593 contents = other.contents;
594 numbers = other.numbers;
597 void reset(unsigned i) {
598 if (i < numbers.size())
602 bool test(unsigned i) {
603 if (i >= numbers.size())
606 return numbers.test(i);
616 //===----------------------------------------------------------------------===//
618 //===----------------------------------------------------------------------===//
622 class VISIBILITY_HIDDEN GVN : public FunctionPass {
623 bool runOnFunction(Function &F);
625 static char ID; // Pass identification, replacement for typeid
626 GVN() : FunctionPass((intptr_t)&ID) { }
631 DenseMap<BasicBlock*, ValueNumberedSet> availableOut;
633 // This transformation requires dominator postdominator info
634 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
635 AU.setPreservesCFG();
636 AU.addRequired<DominatorTree>();
637 AU.addRequired<MemoryDependenceAnalysis>();
638 AU.addPreserved<MemoryDependenceAnalysis>();
642 // FIXME: eliminate or document these better
643 Value* find_leader(ValueNumberedSet& vals, uint32_t v) ;
644 void val_insert(ValueNumberedSet& s, Value* v);
645 bool processLoad(LoadInst* L,
646 DenseMap<Value*, LoadInst*>& lastLoad,
647 SmallVector<Instruction*, 4>& toErase);
648 bool processInstruction(Instruction* I,
649 ValueNumberedSet& currAvail,
650 DenseMap<Value*, LoadInst*>& lastSeenLoad,
651 SmallVector<Instruction*, 4>& toErase);
652 bool processNonLocalLoad(LoadInst* L, SmallVector<Instruction*, 4>& toErase);
653 Value *performPHIConstruction(BasicBlock *BB, LoadInst* orig,
654 DenseMap<BasicBlock*, Value*> &Phis,
655 SmallPtrSet<BasicBlock*, 4>& visited);
656 void dump(DenseMap<BasicBlock*, Value*>& d);
663 // createGVNPass - The public interface to this file...
664 FunctionPass *llvm::createGVNPass() { return new GVN(); }
666 static RegisterPass<GVN> X("gvn",
667 "Global Value Numbering");
669 STATISTIC(NumGVNInstr, "Number of instructions deleted");
670 STATISTIC(NumGVNLoad, "Number of loads deleted");
672 /// find_leader - Given a set and a value number, return the first
673 /// element of the set with that value number, or 0 if no such element
675 Value* GVN::find_leader(ValueNumberedSet& vals, uint32_t v) {
679 for (ValueNumberedSet::iterator I = vals.begin(), E = vals.end();
681 if (v == VN.lookup(*I))
684 assert(0 && "No leader found, but present bit is set?");
688 /// val_insert - Insert a value into a set only if there is not a value
689 /// with the same value number already in the set
690 void GVN::val_insert(ValueNumberedSet& s, Value* v) {
691 uint32_t num = VN.lookup(v);
696 void GVN::dump(DenseMap<BasicBlock*, Value*>& d) {
698 for (DenseMap<BasicBlock*, Value*>::iterator I = d.begin(),
699 E = d.end(); I != E; ++I) {
700 if (I->second == MemoryDependenceAnalysis::None)
709 Value *GVN::performPHIConstruction(BasicBlock *BB, LoadInst* orig,
710 DenseMap<BasicBlock*, Value*> &Phis,
711 SmallPtrSet<BasicBlock*, 4>& visited) {
712 DenseMap<BasicBlock*, Value*>::iterator DI = Phis.find(BB);
713 if (DI != Phis.end())
716 unsigned numPreds = std::distance(pred_begin(BB), pred_end(BB));
719 DenseMap<BasicBlock*, Value*>::iterator DI = Phis.find(BB);
720 if (DI != Phis.end()) {
721 Phis.insert(std::make_pair(BB, DI->second));
725 Value* domV = performPHIConstruction(*pred_begin(BB), orig, Phis, visited);
728 Phis.insert(std::make_pair(BB, domV));
732 PHINode *PN = new PHINode(orig->getType(), orig->getName()+".rle", BB->begin());
733 PN->reserveOperandSpace(numPreds);
737 // Fill in the incoming values for the block.
738 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
739 if (!visited.count(*PI))
740 PN->addIncoming(performPHIConstruction(*PI, orig, Phis, visited), *PI);
743 PN->addIncoming(Phis[*PI], *PI);
745 PN->addIncoming(PN, *PI);
749 bool all_same = PN->getNumIncomingValues() != 1;
750 Value* first = PN->getIncomingValue(0);
751 for (unsigned i = 1; i < PN->getNumIncomingValues(); ++i)
752 all_same &= (PN->getIncomingValue(i) == first);
755 PN->eraseFromParent();
764 bool GVN::processNonLocalLoad(LoadInst* L, SmallVector<Instruction*, 4>& toErase) {
765 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
767 DenseMap<BasicBlock*, Value*> deps;
768 bool ret = MD.getNonLocalDependency(L, deps);
772 DenseMap<BasicBlock*, Value*> repl;
773 for (DenseMap<BasicBlock*, Value*>::iterator I = deps.begin(), E = deps.end();
775 if (I->second == MemoryDependenceAnalysis::None) {
777 } else if (StoreInst* S = dyn_cast<StoreInst>(I->second)) {
778 if (S->getPointerOperand() == L->getPointerOperand())
779 repl.insert(std::make_pair(I->first, S->getOperand(0)));
782 } else if (LoadInst* LD = dyn_cast<LoadInst>(I->second)) {
783 if (LD->getPointerOperand() == L->getPointerOperand())
784 repl.insert(std::make_pair(I->first, LD));
791 SmallPtrSet<BasicBlock*, 4> visited;
792 Value* v = performPHIConstruction(L->getParent(), L, repl, visited);
794 MD.removeInstruction(L);
795 L->replaceAllUsesWith(v);
796 toErase.push_back(L);
801 bool GVN::processLoad(LoadInst* L,
802 DenseMap<Value*, LoadInst*>& lastLoad,
803 SmallVector<Instruction*, 4>& toErase) {
804 if (L->isVolatile()) {
805 lastLoad[L->getPointerOperand()] = L;
809 Value* pointer = L->getPointerOperand();
810 LoadInst*& last = lastLoad[pointer];
812 // ... to a pointer that has been loaded from before...
813 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
814 Instruction* dep = MD.getDependency(L);
815 if (dep == MemoryDependenceAnalysis::NonLocal &&
816 L->getParent() != &L->getParent()->getParent()->getEntryBlock())
817 processNonLocalLoad(L, toErase);
818 bool deletedLoad = false;
820 while (dep != MemoryDependenceAnalysis::None &&
821 dep != MemoryDependenceAnalysis::NonLocal &&
822 (isa<LoadInst>(dep) || isa<StoreInst>(dep))) {
823 // ... that depends on a store ...
824 if (StoreInst* S = dyn_cast<StoreInst>(dep)) {
825 if (S->getPointerOperand() == pointer) {
827 MD.removeInstruction(L);
829 L->replaceAllUsesWith(S->getOperand(0));
830 toErase.push_back(L);
835 // Whether we removed it or not, we can't
839 // If we don't depend on a store, and we haven't
840 // been loaded before, bail.
842 } else if (dep == last) {
844 MD.removeInstruction(L);
846 L->replaceAllUsesWith(last);
847 toErase.push_back(L);
853 dep = MD.getDependency(L, dep);
863 /// buildsets_availout - When calculating availability, handle an instruction
864 /// by inserting it into the appropriate sets
865 bool GVN::processInstruction(Instruction* I,
866 ValueNumberedSet& currAvail,
867 DenseMap<Value*, LoadInst*>& lastSeenLoad,
868 SmallVector<Instruction*, 4>& toErase) {
869 if (LoadInst* L = dyn_cast<LoadInst>(I)) {
870 return processLoad(L, lastSeenLoad, toErase);
873 unsigned num = VN.lookup_or_add(I);
875 if (currAvail.test(num)) {
876 Value* repl = find_leader(currAvail, num);
878 I->replaceAllUsesWith(repl);
879 toErase.push_back(I);
881 } else if (!I->isTerminator()) {
889 // GVN::runOnFunction - This is the main transformation entry point for a
892 bool GVN::runOnFunction(Function &F) {
893 // Clean out global sets from any previous functions
895 availableOut.clear();
897 bool changed_function = false;
899 DominatorTree &DT = getAnalysis<DominatorTree>();
901 SmallVector<Instruction*, 4> toErase;
903 // Top-down walk of the dominator tree
904 for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()),
905 E = df_end(DT.getRootNode()); DI != E; ++DI) {
907 // Get the set to update for this block
908 ValueNumberedSet& currAvail = availableOut[DI->getBlock()];
909 DenseMap<Value*, LoadInst*> lastSeenLoad;
911 BasicBlock* BB = DI->getBlock();
913 // A block inherits AVAIL_OUT from its dominator
914 if (DI->getIDom() != 0)
915 currAvail = availableOut[DI->getIDom()->getBlock()];
917 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
919 changed_function |= processInstruction(BI, currAvail, lastSeenLoad, toErase);
921 NumGVNInstr += toErase.size();
923 for (SmallVector<Instruction*, 4>::iterator I = toErase.begin(),
924 E = toErase.end(); I != E; ++I)
925 (*I)->eraseFromParent();
931 return changed_function;