1 //===- GVN.cpp - Eliminate redundant values and loads ------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // 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"
17 #include "llvm/Transforms/Scalar.h"
18 #include "llvm/BasicBlock.h"
19 #include "llvm/Constants.h"
20 #include "llvm/DerivedTypes.h"
21 #include "llvm/Function.h"
22 #include "llvm/Instructions.h"
23 #include "llvm/Value.h"
24 #include "llvm/ADT/BitVector.h"
25 #include "llvm/ADT/DenseMap.h"
26 #include "llvm/ADT/DepthFirstIterator.h"
27 #include "llvm/ADT/SmallPtrSet.h"
28 #include "llvm/ADT/SmallVector.h"
29 #include "llvm/ADT/Statistic.h"
30 #include "llvm/Analysis/Dominators.h"
31 #include "llvm/Analysis/AliasAnalysis.h"
32 #include "llvm/Analysis/MemoryDependenceAnalysis.h"
33 #include "llvm/Support/CFG.h"
34 #include "llvm/Support/Compiler.h"
37 //===----------------------------------------------------------------------===//
39 //===----------------------------------------------------------------------===//
41 /// This class holds the mapping between values and value numbers. It is used
42 /// as an efficient mechanism to determine the expression-wise equivalence of
45 struct VISIBILITY_HIDDEN Expression {
46 enum ExpressionOpcode { ADD, SUB, MUL, UDIV, SDIV, FDIV, UREM, SREM,
47 FREM, SHL, LSHR, ASHR, AND, OR, XOR, ICMPEQ,
48 ICMPNE, ICMPUGT, ICMPUGE, ICMPULT, ICMPULE,
49 ICMPSGT, ICMPSGE, ICMPSLT, ICMPSLE, FCMPOEQ,
50 FCMPOGT, FCMPOGE, FCMPOLT, FCMPOLE, FCMPONE,
51 FCMPORD, FCMPUNO, FCMPUEQ, FCMPUGT, FCMPUGE,
52 FCMPULT, FCMPULE, FCMPUNE, EXTRACT, INSERT,
53 SHUFFLE, SELECT, TRUNC, ZEXT, SEXT, FPTOUI,
54 FPTOSI, UITOFP, SITOFP, FPTRUNC, FPEXT,
55 PTRTOINT, INTTOPTR, BITCAST, GEP, CALL, EMPTY,
58 ExpressionOpcode opcode;
63 SmallVector<uint32_t, 4> varargs;
67 Expression(ExpressionOpcode o) : opcode(o) { }
69 bool operator==(const Expression &other) const {
70 if (opcode != other.opcode)
72 else if (opcode == EMPTY || opcode == TOMBSTONE)
74 else if (type != other.type)
76 else if (function != other.function)
78 else if (firstVN != other.firstVN)
80 else if (secondVN != other.secondVN)
82 else if (thirdVN != other.thirdVN)
85 if (varargs.size() != other.varargs.size())
88 for (size_t i = 0; i < varargs.size(); ++i)
89 if (varargs[i] != other.varargs[i])
96 bool operator!=(const Expression &other) const {
97 if (opcode != other.opcode)
99 else if (opcode == EMPTY || opcode == TOMBSTONE)
101 else if (type != other.type)
103 else if (function != other.function)
105 else if (firstVN != other.firstVN)
107 else if (secondVN != other.secondVN)
109 else if (thirdVN != other.thirdVN)
112 if (varargs.size() != other.varargs.size())
115 for (size_t i = 0; i < varargs.size(); ++i)
116 if (varargs[i] != other.varargs[i])
124 class VISIBILITY_HIDDEN ValueTable {
126 DenseMap<Value*, uint32_t> valueNumbering;
127 DenseMap<Expression, uint32_t> expressionNumbering;
130 uint32_t nextValueNumber;
132 Expression::ExpressionOpcode getOpcode(BinaryOperator* BO);
133 Expression::ExpressionOpcode getOpcode(CmpInst* C);
134 Expression::ExpressionOpcode getOpcode(CastInst* C);
135 Expression create_expression(BinaryOperator* BO);
136 Expression create_expression(CmpInst* C);
137 Expression create_expression(ShuffleVectorInst* V);
138 Expression create_expression(ExtractElementInst* C);
139 Expression create_expression(InsertElementInst* V);
140 Expression create_expression(SelectInst* V);
141 Expression create_expression(CastInst* C);
142 Expression create_expression(GetElementPtrInst* G);
143 Expression create_expression(CallInst* C);
145 ValueTable() : nextValueNumber(1) { }
146 uint32_t lookup_or_add(Value* V);
147 uint32_t lookup(Value* V) const;
148 void add(Value* V, uint32_t num);
150 void erase(Value* v);
152 void setAliasAnalysis(AliasAnalysis* A) { AA = A; }
153 uint32_t hash_operand(Value* v);
158 template <> struct DenseMapInfo<Expression> {
159 static inline Expression getEmptyKey() {
160 return Expression(Expression::EMPTY);
163 static inline Expression getTombstoneKey() {
164 return Expression(Expression::TOMBSTONE);
167 static unsigned getHashValue(const Expression e) {
168 unsigned hash = e.opcode;
170 hash = e.firstVN + hash * 37;
171 hash = e.secondVN + hash * 37;
172 hash = e.thirdVN + hash * 37;
174 hash = (unsigned)((uintptr_t)e.type >> 4) ^
175 (unsigned)((uintptr_t)e.type >> 9) +
178 for (SmallVector<uint32_t, 4>::const_iterator I = e.varargs.begin(),
179 E = e.varargs.end(); I != E; ++I)
180 hash = *I + hash * 37;
182 hash = (unsigned)((uintptr_t)e.function >> 4) ^
183 (unsigned)((uintptr_t)e.function >> 9) +
188 static bool isEqual(const Expression &LHS, const Expression &RHS) {
191 static bool isPod() { return true; }
195 //===----------------------------------------------------------------------===//
196 // ValueTable Internal Functions
197 //===----------------------------------------------------------------------===//
198 Expression::ExpressionOpcode
199 ValueTable::getOpcode(BinaryOperator* BO) {
200 switch(BO->getOpcode()) {
201 case Instruction::Add:
202 return Expression::ADD;
203 case Instruction::Sub:
204 return Expression::SUB;
205 case Instruction::Mul:
206 return Expression::MUL;
207 case Instruction::UDiv:
208 return Expression::UDIV;
209 case Instruction::SDiv:
210 return Expression::SDIV;
211 case Instruction::FDiv:
212 return Expression::FDIV;
213 case Instruction::URem:
214 return Expression::UREM;
215 case Instruction::SRem:
216 return Expression::SREM;
217 case Instruction::FRem:
218 return Expression::FREM;
219 case Instruction::Shl:
220 return Expression::SHL;
221 case Instruction::LShr:
222 return Expression::LSHR;
223 case Instruction::AShr:
224 return Expression::ASHR;
225 case Instruction::And:
226 return Expression::AND;
227 case Instruction::Or:
228 return Expression::OR;
229 case Instruction::Xor:
230 return Expression::XOR;
232 // THIS SHOULD NEVER HAPPEN
234 assert(0 && "Binary operator with unknown opcode?");
235 return Expression::ADD;
239 Expression::ExpressionOpcode ValueTable::getOpcode(CmpInst* C) {
240 if (C->getOpcode() == Instruction::ICmp) {
241 switch (C->getPredicate()) {
242 case ICmpInst::ICMP_EQ:
243 return Expression::ICMPEQ;
244 case ICmpInst::ICMP_NE:
245 return Expression::ICMPNE;
246 case ICmpInst::ICMP_UGT:
247 return Expression::ICMPUGT;
248 case ICmpInst::ICMP_UGE:
249 return Expression::ICMPUGE;
250 case ICmpInst::ICMP_ULT:
251 return Expression::ICMPULT;
252 case ICmpInst::ICMP_ULE:
253 return Expression::ICMPULE;
254 case ICmpInst::ICMP_SGT:
255 return Expression::ICMPSGT;
256 case ICmpInst::ICMP_SGE:
257 return Expression::ICMPSGE;
258 case ICmpInst::ICMP_SLT:
259 return Expression::ICMPSLT;
260 case ICmpInst::ICMP_SLE:
261 return Expression::ICMPSLE;
263 // THIS SHOULD NEVER HAPPEN
265 assert(0 && "Comparison with unknown predicate?");
266 return Expression::ICMPEQ;
269 switch (C->getPredicate()) {
270 case FCmpInst::FCMP_OEQ:
271 return Expression::FCMPOEQ;
272 case FCmpInst::FCMP_OGT:
273 return Expression::FCMPOGT;
274 case FCmpInst::FCMP_OGE:
275 return Expression::FCMPOGE;
276 case FCmpInst::FCMP_OLT:
277 return Expression::FCMPOLT;
278 case FCmpInst::FCMP_OLE:
279 return Expression::FCMPOLE;
280 case FCmpInst::FCMP_ONE:
281 return Expression::FCMPONE;
282 case FCmpInst::FCMP_ORD:
283 return Expression::FCMPORD;
284 case FCmpInst::FCMP_UNO:
285 return Expression::FCMPUNO;
286 case FCmpInst::FCMP_UEQ:
287 return Expression::FCMPUEQ;
288 case FCmpInst::FCMP_UGT:
289 return Expression::FCMPUGT;
290 case FCmpInst::FCMP_UGE:
291 return Expression::FCMPUGE;
292 case FCmpInst::FCMP_ULT:
293 return Expression::FCMPULT;
294 case FCmpInst::FCMP_ULE:
295 return Expression::FCMPULE;
296 case FCmpInst::FCMP_UNE:
297 return Expression::FCMPUNE;
299 // THIS SHOULD NEVER HAPPEN
301 assert(0 && "Comparison with unknown predicate?");
302 return Expression::FCMPOEQ;
307 Expression::ExpressionOpcode
308 ValueTable::getOpcode(CastInst* C) {
309 switch(C->getOpcode()) {
310 case Instruction::Trunc:
311 return Expression::TRUNC;
312 case Instruction::ZExt:
313 return Expression::ZEXT;
314 case Instruction::SExt:
315 return Expression::SEXT;
316 case Instruction::FPToUI:
317 return Expression::FPTOUI;
318 case Instruction::FPToSI:
319 return Expression::FPTOSI;
320 case Instruction::UIToFP:
321 return Expression::UITOFP;
322 case Instruction::SIToFP:
323 return Expression::SITOFP;
324 case Instruction::FPTrunc:
325 return Expression::FPTRUNC;
326 case Instruction::FPExt:
327 return Expression::FPEXT;
328 case Instruction::PtrToInt:
329 return Expression::PTRTOINT;
330 case Instruction::IntToPtr:
331 return Expression::INTTOPTR;
332 case Instruction::BitCast:
333 return Expression::BITCAST;
335 // THIS SHOULD NEVER HAPPEN
337 assert(0 && "Cast operator with unknown opcode?");
338 return Expression::BITCAST;
342 uint32_t ValueTable::hash_operand(Value* v) {
343 if (CallInst* CI = dyn_cast<CallInst>(v))
344 if (!AA->doesNotAccessMemory(CI))
345 return nextValueNumber++;
347 return lookup_or_add(v);
350 Expression ValueTable::create_expression(CallInst* C) {
353 e.type = C->getType();
357 e.function = C->getCalledFunction();
358 e.opcode = Expression::CALL;
360 for (CallInst::op_iterator I = C->op_begin()+1, E = C->op_end();
362 e.varargs.push_back(hash_operand(*I));
367 Expression ValueTable::create_expression(BinaryOperator* BO) {
370 e.firstVN = hash_operand(BO->getOperand(0));
371 e.secondVN = hash_operand(BO->getOperand(1));
374 e.type = BO->getType();
375 e.opcode = getOpcode(BO);
380 Expression ValueTable::create_expression(CmpInst* C) {
383 e.firstVN = hash_operand(C->getOperand(0));
384 e.secondVN = hash_operand(C->getOperand(1));
387 e.type = C->getType();
388 e.opcode = getOpcode(C);
393 Expression ValueTable::create_expression(CastInst* C) {
396 e.firstVN = hash_operand(C->getOperand(0));
400 e.type = C->getType();
401 e.opcode = getOpcode(C);
406 Expression ValueTable::create_expression(ShuffleVectorInst* S) {
409 e.firstVN = hash_operand(S->getOperand(0));
410 e.secondVN = hash_operand(S->getOperand(1));
411 e.thirdVN = hash_operand(S->getOperand(2));
413 e.type = S->getType();
414 e.opcode = Expression::SHUFFLE;
419 Expression ValueTable::create_expression(ExtractElementInst* E) {
422 e.firstVN = hash_operand(E->getOperand(0));
423 e.secondVN = hash_operand(E->getOperand(1));
426 e.type = E->getType();
427 e.opcode = Expression::EXTRACT;
432 Expression ValueTable::create_expression(InsertElementInst* I) {
435 e.firstVN = hash_operand(I->getOperand(0));
436 e.secondVN = hash_operand(I->getOperand(1));
437 e.thirdVN = hash_operand(I->getOperand(2));
439 e.type = I->getType();
440 e.opcode = Expression::INSERT;
445 Expression ValueTable::create_expression(SelectInst* I) {
448 e.firstVN = hash_operand(I->getCondition());
449 e.secondVN = hash_operand(I->getTrueValue());
450 e.thirdVN = hash_operand(I->getFalseValue());
452 e.type = I->getType();
453 e.opcode = Expression::SELECT;
458 Expression ValueTable::create_expression(GetElementPtrInst* G) {
461 e.firstVN = hash_operand(G->getPointerOperand());
465 e.type = G->getType();
466 e.opcode = Expression::GEP;
468 for (GetElementPtrInst::op_iterator I = G->idx_begin(), E = G->idx_end();
470 e.varargs.push_back(hash_operand(*I));
475 //===----------------------------------------------------------------------===//
476 // ValueTable External Functions
477 //===----------------------------------------------------------------------===//
479 /// lookup_or_add - Returns the value number for the specified value, assigning
480 /// it a new number if it did not have one before.
481 uint32_t ValueTable::lookup_or_add(Value* V) {
482 DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
483 if (VI != valueNumbering.end())
486 if (CallInst* C = dyn_cast<CallInst>(V)) {
487 if (AA->onlyReadsMemory(C)) { // includes doesNotAccessMemory
488 Expression e = create_expression(C);
490 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
491 if (EI != expressionNumbering.end()) {
492 valueNumbering.insert(std::make_pair(V, EI->second));
495 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
496 valueNumbering.insert(std::make_pair(V, nextValueNumber));
498 return nextValueNumber++;
501 valueNumbering.insert(std::make_pair(V, nextValueNumber));
502 return nextValueNumber++;
504 } else if (BinaryOperator* BO = dyn_cast<BinaryOperator>(V)) {
505 Expression e = create_expression(BO);
507 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
508 if (EI != expressionNumbering.end()) {
509 valueNumbering.insert(std::make_pair(V, EI->second));
512 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
513 valueNumbering.insert(std::make_pair(V, nextValueNumber));
515 return nextValueNumber++;
517 } else if (CmpInst* C = dyn_cast<CmpInst>(V)) {
518 Expression e = create_expression(C);
520 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
521 if (EI != expressionNumbering.end()) {
522 valueNumbering.insert(std::make_pair(V, EI->second));
525 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
526 valueNumbering.insert(std::make_pair(V, nextValueNumber));
528 return nextValueNumber++;
530 } else if (ShuffleVectorInst* U = dyn_cast<ShuffleVectorInst>(V)) {
531 Expression e = create_expression(U);
533 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
534 if (EI != expressionNumbering.end()) {
535 valueNumbering.insert(std::make_pair(V, EI->second));
538 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
539 valueNumbering.insert(std::make_pair(V, nextValueNumber));
541 return nextValueNumber++;
543 } else if (ExtractElementInst* U = dyn_cast<ExtractElementInst>(V)) {
544 Expression e = create_expression(U);
546 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
547 if (EI != expressionNumbering.end()) {
548 valueNumbering.insert(std::make_pair(V, EI->second));
551 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
552 valueNumbering.insert(std::make_pair(V, nextValueNumber));
554 return nextValueNumber++;
556 } else if (InsertElementInst* U = dyn_cast<InsertElementInst>(V)) {
557 Expression e = create_expression(U);
559 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
560 if (EI != expressionNumbering.end()) {
561 valueNumbering.insert(std::make_pair(V, EI->second));
564 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
565 valueNumbering.insert(std::make_pair(V, nextValueNumber));
567 return nextValueNumber++;
569 } else if (SelectInst* U = dyn_cast<SelectInst>(V)) {
570 Expression e = create_expression(U);
572 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
573 if (EI != expressionNumbering.end()) {
574 valueNumbering.insert(std::make_pair(V, EI->second));
577 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
578 valueNumbering.insert(std::make_pair(V, nextValueNumber));
580 return nextValueNumber++;
582 } else if (CastInst* U = dyn_cast<CastInst>(V)) {
583 Expression e = create_expression(U);
585 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
586 if (EI != expressionNumbering.end()) {
587 valueNumbering.insert(std::make_pair(V, EI->second));
590 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
591 valueNumbering.insert(std::make_pair(V, nextValueNumber));
593 return nextValueNumber++;
595 } else if (GetElementPtrInst* U = dyn_cast<GetElementPtrInst>(V)) {
596 Expression e = create_expression(U);
598 DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
599 if (EI != expressionNumbering.end()) {
600 valueNumbering.insert(std::make_pair(V, EI->second));
603 expressionNumbering.insert(std::make_pair(e, nextValueNumber));
604 valueNumbering.insert(std::make_pair(V, nextValueNumber));
606 return nextValueNumber++;
609 valueNumbering.insert(std::make_pair(V, nextValueNumber));
610 return nextValueNumber++;
614 /// lookup - Returns the value number of the specified value. Fails if
615 /// the value has not yet been numbered.
616 uint32_t ValueTable::lookup(Value* V) const {
617 DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
618 if (VI != valueNumbering.end())
621 assert(0 && "Value not numbered?");
626 /// clear - Remove all entries from the ValueTable
627 void ValueTable::clear() {
628 valueNumbering.clear();
629 expressionNumbering.clear();
633 /// erase - Remove a value from the value numbering
634 void ValueTable::erase(Value* V) {
635 valueNumbering.erase(V);
638 //===----------------------------------------------------------------------===//
639 // ValueNumberedSet Class
640 //===----------------------------------------------------------------------===//
642 class ValueNumberedSet {
644 SmallPtrSet<Value*, 8> contents;
647 ValueNumberedSet() { numbers.resize(1); }
648 ValueNumberedSet(const ValueNumberedSet& other) {
649 numbers = other.numbers;
650 contents = other.contents;
653 typedef SmallPtrSet<Value*, 8>::iterator iterator;
655 iterator begin() { return contents.begin(); }
656 iterator end() { return contents.end(); }
658 bool insert(Value* v) { return contents.insert(v); }
659 void insert(iterator I, iterator E) { contents.insert(I, E); }
660 void erase(Value* v) { contents.erase(v); }
661 unsigned count(Value* v) { return contents.count(v); }
662 size_t size() { return contents.size(); }
664 void set(unsigned i) {
665 if (i >= numbers.size())
671 void operator=(const ValueNumberedSet& other) {
672 contents = other.contents;
673 numbers = other.numbers;
676 void reset(unsigned i) {
677 if (i < numbers.size())
681 bool test(unsigned i) {
682 if (i >= numbers.size())
685 return numbers.test(i);
695 //===----------------------------------------------------------------------===//
697 //===----------------------------------------------------------------------===//
701 class VISIBILITY_HIDDEN GVN : public FunctionPass {
702 bool runOnFunction(Function &F);
704 static char ID; // Pass identification, replacement for typeid
705 GVN() : FunctionPass((intptr_t)&ID) { }
710 DenseMap<BasicBlock*, ValueNumberedSet> availableOut;
712 typedef DenseMap<Value*, SmallPtrSet<Instruction*, 4> > PhiMapType;
716 // This transformation requires dominator postdominator info
717 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
718 AU.setPreservesCFG();
719 AU.addRequired<DominatorTree>();
720 AU.addRequired<MemoryDependenceAnalysis>();
721 AU.addRequired<AliasAnalysis>();
722 AU.addPreserved<AliasAnalysis>();
723 AU.addPreserved<MemoryDependenceAnalysis>();
727 // FIXME: eliminate or document these better
728 Value* find_leader(ValueNumberedSet& vals, uint32_t v) ;
729 void val_insert(ValueNumberedSet& s, Value* v);
730 bool processLoad(LoadInst* L,
731 DenseMap<Value*, LoadInst*>& lastLoad,
732 SmallVector<Instruction*, 4>& toErase);
733 bool processInstruction(Instruction* I,
734 ValueNumberedSet& currAvail,
735 DenseMap<Value*, LoadInst*>& lastSeenLoad,
736 SmallVector<Instruction*, 4>& toErase);
737 bool processNonLocalLoad(LoadInst* L,
738 SmallVector<Instruction*, 4>& toErase);
739 Value *GetValueForBlock(BasicBlock *BB, LoadInst* orig,
740 DenseMap<BasicBlock*, Value*> &Phis,
741 bool top_level = false);
742 void dump(DenseMap<BasicBlock*, Value*>& d);
743 bool iterateOnFunction(Function &F);
744 Value* CollapsePhi(PHINode* p);
745 bool isSafeReplacement(PHINode* p, Instruction* inst);
752 // createGVNPass - The public interface to this file...
753 FunctionPass *llvm::createGVNPass() { return new GVN(); }
755 static RegisterPass<GVN> X("gvn",
756 "Global Value Numbering");
758 STATISTIC(NumGVNInstr, "Number of instructions deleted");
759 STATISTIC(NumGVNLoad, "Number of loads deleted");
761 /// find_leader - Given a set and a value number, return the first
762 /// element of the set with that value number, or 0 if no such element
764 Value* GVN::find_leader(ValueNumberedSet& vals, uint32_t v) {
768 for (ValueNumberedSet::iterator I = vals.begin(), E = vals.end();
770 if (v == VN.lookup(*I))
773 assert(0 && "No leader found, but present bit is set?");
777 /// val_insert - Insert a value into a set only if there is not a value
778 /// with the same value number already in the set
779 void GVN::val_insert(ValueNumberedSet& s, Value* v) {
780 uint32_t num = VN.lookup(v);
785 void GVN::dump(DenseMap<BasicBlock*, Value*>& d) {
787 for (DenseMap<BasicBlock*, Value*>::iterator I = d.begin(),
788 E = d.end(); I != E; ++I) {
789 if (I->second == MemoryDependenceAnalysis::None)
797 Value* GVN::CollapsePhi(PHINode* p) {
798 DominatorTree &DT = getAnalysis<DominatorTree>();
799 Value* constVal = p->hasConstantValue();
802 if (Instruction* inst = dyn_cast<Instruction>(constVal)) {
803 if (DT.dominates(inst, p))
804 if (isSafeReplacement(p, inst))
814 bool GVN::isSafeReplacement(PHINode* p, Instruction* inst) {
815 if (!isa<PHINode>(inst))
818 for (Instruction::use_iterator UI = p->use_begin(), E = p->use_end();
820 if (PHINode* use_phi = dyn_cast<PHINode>(UI))
821 if (use_phi->getParent() == inst->getParent())
827 /// GetValueForBlock - Get the value to use within the specified basic block.
828 /// available values are in Phis.
829 Value *GVN::GetValueForBlock(BasicBlock *BB, LoadInst* orig,
830 DenseMap<BasicBlock*, Value*> &Phis,
833 // If we have already computed this value, return the previously computed val.
834 DenseMap<BasicBlock*, Value*>::iterator V = Phis.find(BB);
835 if (V != Phis.end() && !top_level) return V->second;
837 BasicBlock* singlePred = BB->getSinglePredecessor();
839 Value *ret = GetValueForBlock(singlePred, orig, Phis);
843 // Otherwise, the idom is the loop, so we need to insert a PHI node. Do so
844 // now, then get values to fill in the incoming values for the PHI.
845 PHINode *PN = new PHINode(orig->getType(), orig->getName()+".rle",
847 PN->reserveOperandSpace(std::distance(pred_begin(BB), pred_end(BB)));
849 if (Phis.count(BB) == 0)
850 Phis.insert(std::make_pair(BB, PN));
852 // Fill in the incoming values for the block.
853 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
854 Value* val = GetValueForBlock(*PI, orig, Phis);
856 PN->addIncoming(val, *PI);
859 // Attempt to collapse PHI nodes that are trivially redundant
860 Value* v = CollapsePhi(PN);
862 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
864 MD.removeInstruction(PN);
865 PN->replaceAllUsesWith(v);
867 for (DenseMap<BasicBlock*, Value*>::iterator I = Phis.begin(),
868 E = Phis.end(); I != E; ++I)
872 PN->eraseFromParent();
879 // Cache our phi construction results
880 phiMap[orig->getPointerOperand()].insert(PN);
884 /// processNonLocalLoad - Attempt to eliminate a load whose dependencies are
885 /// non-local by performing PHI construction.
886 bool GVN::processNonLocalLoad(LoadInst* L,
887 SmallVector<Instruction*, 4>& toErase) {
888 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
890 // Find the non-local dependencies of the load
891 DenseMap<BasicBlock*, Value*> deps;
892 MD.getNonLocalDependency(L, deps);
894 DenseMap<BasicBlock*, Value*> repl;
896 // Filter out useless results (non-locals, etc)
897 for (DenseMap<BasicBlock*, Value*>::iterator I = deps.begin(), E = deps.end();
899 if (I->second == MemoryDependenceAnalysis::None) {
901 } else if (I->second == MemoryDependenceAnalysis::NonLocal) {
903 } else if (StoreInst* S = dyn_cast<StoreInst>(I->second)) {
904 if (S->getPointerOperand() == L->getPointerOperand())
905 repl[I->first] = S->getOperand(0);
908 } else if (LoadInst* LD = dyn_cast<LoadInst>(I->second)) {
909 if (LD->getPointerOperand() == L->getPointerOperand())
917 // Use cached PHI construction information from previous runs
918 SmallPtrSet<Instruction*, 4>& p = phiMap[L->getPointerOperand()];
919 for (SmallPtrSet<Instruction*, 4>::iterator I = p.begin(), E = p.end();
921 if ((*I)->getParent() == L->getParent()) {
922 MD.removeInstruction(L);
923 L->replaceAllUsesWith(*I);
924 toErase.push_back(L);
929 repl.insert(std::make_pair((*I)->getParent(), *I));
933 // Perform PHI construction
934 SmallPtrSet<BasicBlock*, 4> visited;
935 Value* v = GetValueForBlock(L->getParent(), L, repl, true);
937 MD.removeInstruction(L);
938 L->replaceAllUsesWith(v);
939 toErase.push_back(L);
945 /// processLoad - Attempt to eliminate a load, first by eliminating it
946 /// locally, and then attempting non-local elimination if that fails.
947 bool GVN::processLoad(LoadInst* L,
948 DenseMap<Value*, LoadInst*>& lastLoad,
949 SmallVector<Instruction*, 4>& toErase) {
950 if (L->isVolatile()) {
951 lastLoad[L->getPointerOperand()] = L;
955 Value* pointer = L->getPointerOperand();
956 LoadInst*& last = lastLoad[pointer];
958 // ... to a pointer that has been loaded from before...
959 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
960 bool removedNonLocal = false;
961 Instruction* dep = MD.getDependency(L);
962 if (dep == MemoryDependenceAnalysis::NonLocal &&
963 L->getParent() != &L->getParent()->getParent()->getEntryBlock()) {
964 removedNonLocal = processNonLocalLoad(L, toErase);
966 if (!removedNonLocal)
969 return removedNonLocal;
973 bool deletedLoad = false;
975 // Walk up the dependency chain until we either find
976 // a dependency we can use, or we can't walk any further
977 while (dep != MemoryDependenceAnalysis::None &&
978 dep != MemoryDependenceAnalysis::NonLocal &&
979 (isa<LoadInst>(dep) || isa<StoreInst>(dep))) {
980 // ... that depends on a store ...
981 if (StoreInst* S = dyn_cast<StoreInst>(dep)) {
982 if (S->getPointerOperand() == pointer) {
984 MD.removeInstruction(L);
986 L->replaceAllUsesWith(S->getOperand(0));
987 toErase.push_back(L);
992 // Whether we removed it or not, we can't
996 // If we don't depend on a store, and we haven't
997 // been loaded before, bail.
999 } else if (dep == last) {
1001 MD.removeInstruction(L);
1003 L->replaceAllUsesWith(last);
1004 toErase.push_back(L);
1010 dep = MD.getDependency(L, dep);
1020 /// processInstruction - When calculating availability, handle an instruction
1021 /// by inserting it into the appropriate sets
1022 bool GVN::processInstruction(Instruction* I,
1023 ValueNumberedSet& currAvail,
1024 DenseMap<Value*, LoadInst*>& lastSeenLoad,
1025 SmallVector<Instruction*, 4>& toErase) {
1026 if (LoadInst* L = dyn_cast<LoadInst>(I)) {
1027 return processLoad(L, lastSeenLoad, toErase);
1030 unsigned num = VN.lookup_or_add(I);
1032 // Collapse PHI nodes
1033 if (PHINode* p = dyn_cast<PHINode>(I)) {
1034 Value* constVal = CollapsePhi(p);
1037 for (PhiMapType::iterator PI = phiMap.begin(), PE = phiMap.end();
1039 if (PI->second.count(p))
1040 PI->second.erase(p);
1042 p->replaceAllUsesWith(constVal);
1043 toErase.push_back(p);
1045 // Perform value-number based elimination
1046 } else if (currAvail.test(num)) {
1047 Value* repl = find_leader(currAvail, num);
1049 if (CallInst* CI = dyn_cast<CallInst>(I)) {
1050 AliasAnalysis& AA = getAnalysis<AliasAnalysis>();
1051 if (!AA.doesNotAccessMemory(CI)) {
1052 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
1053 if (cast<Instruction>(repl)->getParent() != CI->getParent() ||
1054 MD.getDependency(CI) != MD.getDependency(cast<CallInst>(repl))) {
1055 // There must be an intervening may-alias store, so nothing from
1056 // this point on will be able to be replaced with the preceding call
1057 currAvail.erase(repl);
1058 currAvail.insert(I);
1066 MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
1067 MD.removeInstruction(I);
1070 I->replaceAllUsesWith(repl);
1071 toErase.push_back(I);
1073 } else if (!I->isTerminator()) {
1075 currAvail.insert(I);
1081 // GVN::runOnFunction - This is the main transformation entry point for a
1084 bool GVN::runOnFunction(Function& F) {
1085 VN.setAliasAnalysis(&getAnalysis<AliasAnalysis>());
1087 bool changed = false;
1088 bool shouldContinue = true;
1090 while (shouldContinue) {
1091 shouldContinue = iterateOnFunction(F);
1092 changed |= shouldContinue;
1099 // GVN::iterateOnFunction - Executes one iteration of GVN
1100 bool GVN::iterateOnFunction(Function &F) {
1101 // Clean out global sets from any previous functions
1103 availableOut.clear();
1106 bool changed_function = false;
1108 DominatorTree &DT = getAnalysis<DominatorTree>();
1110 SmallVector<Instruction*, 4> toErase;
1112 // Top-down walk of the dominator tree
1113 for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()),
1114 E = df_end(DT.getRootNode()); DI != E; ++DI) {
1116 // Get the set to update for this block
1117 ValueNumberedSet& currAvail = availableOut[DI->getBlock()];
1118 DenseMap<Value*, LoadInst*> lastSeenLoad;
1120 BasicBlock* BB = DI->getBlock();
1122 // A block inherits AVAIL_OUT from its dominator
1123 if (DI->getIDom() != 0)
1124 currAvail = availableOut[DI->getIDom()->getBlock()];
1126 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
1128 changed_function |= processInstruction(BI, currAvail,
1129 lastSeenLoad, toErase);
1131 NumGVNInstr += toErase.size();
1133 // Avoid iterator invalidation
1136 for (SmallVector<Instruction*, 4>::iterator I = toErase.begin(),
1137 E = toErase.end(); I != E; ++I)
1138 (*I)->eraseFromParent();
1144 return changed_function;