1 //===- CorrelatedExprs.cpp - Pass to detect and eliminated c.e.'s ---------===//
3 // Correlated Expression Elimination propogates information from conditional
4 // branches to blocks dominated by destinations of the branch. It propogates
5 // information from the condition check itself into the body of the branch,
6 // allowing transformations like these for example:
9 // ... 4*i; // constant propogation
13 // X = M-N; // = M-M == 0;
15 // This is called Correlated Expression Elimination because we eliminate or
16 // simplify expressions that are correlated with the direction of a branch. In
17 // this way we use static information to give us some information about the
18 // dynamic value of a variable.
20 //===----------------------------------------------------------------------===//
22 #include "llvm/Transforms/Scalar.h"
23 #include "llvm/Pass.h"
24 #include "llvm/Function.h"
25 #include "llvm/iTerminators.h"
26 #include "llvm/iPHINode.h"
27 #include "llvm/iOperators.h"
28 #include "llvm/ConstantHandling.h"
29 #include "llvm/Assembly/Writer.h"
30 #include "llvm/Analysis/Dominators.h"
31 #include "llvm/Transforms/Utils/Local.h"
32 #include "llvm/Support/ConstantRange.h"
33 #include "llvm/Support/CFG.h"
34 #include "Support/PostOrderIterator.h"
35 #include "Support/Statistic.h"
39 Statistic<> NumSetCCRemoved("cee", "Number of setcc instruction eliminated");
40 Statistic<> NumOperandsCann("cee", "Number of operands cannonicalized");
41 Statistic<> BranchRevectors("cee", "Number of branches revectored");
45 Value *Val; // Relation to what value?
46 Instruction::BinaryOps Rel; // SetCC relation, or Add if no information
48 Relation(Value *V) : Val(V), Rel(Instruction::Add) {}
49 bool operator<(const Relation &R) const { return Val < R.Val; }
50 Value *getValue() const { return Val; }
51 Instruction::BinaryOps getRelation() const { return Rel; }
53 // contradicts - Return true if the relationship specified by the operand
54 // contradicts already known information.
56 bool contradicts(Instruction::BinaryOps Rel, const ValueInfo &VI) const;
58 // incorporate - Incorporate information in the argument into this relation
59 // entry. This assumes that the information doesn't contradict itself. If
60 // any new information is gained, true is returned, otherwise false is
61 // returned to indicate that nothing was updated.
63 bool incorporate(Instruction::BinaryOps Rel, ValueInfo &VI);
65 // KnownResult - Whether or not this condition determines the result of a
66 // setcc in the program. False & True are intentionally 0 & 1 so we can
67 // convert to bool by casting after checking for unknown.
69 enum KnownResult { KnownFalse = 0, KnownTrue = 1, Unknown = 2 };
71 // getImpliedResult - If this relationship between two values implies that
72 // the specified relationship is true or false, return that. If we cannot
73 // determine the result required, return Unknown.
75 KnownResult getImpliedResult(Instruction::BinaryOps Rel) const;
77 // print - Output this relation to the specified stream
78 void print(std::ostream &OS) const;
83 // ValueInfo - One instance of this record exists for every value with
84 // relationships between other values. It keeps track of all of the
85 // relationships to other values in the program (specified with Relation) that
86 // are known to be valid in a region.
89 // RelationShips - this value is know to have the specified relationships to
90 // other values. There can only be one entry per value, and this list is
91 // kept sorted by the Val field.
92 std::vector<Relation> Relationships;
94 // If information about this value is known or propogated from constant
95 // expressions, this range contains the possible values this value may hold.
98 // If we find that this value is equal to another value that has a lower
99 // rank, this value is used as it's replacement.
103 ValueInfo(const Type *Ty)
104 : Bounds(Ty->isIntegral() ? Ty : Type::IntTy), Replacement(0) {}
106 // getBounds() - Return the constant bounds of the value...
107 const ConstantRange &getBounds() const { return Bounds; }
108 ConstantRange &getBounds() { return Bounds; }
110 const std::vector<Relation> &getRelationships() { return Relationships; }
112 // getReplacement - Return the value this value is to be replaced with if it
113 // exists, otherwise return null.
115 Value *getReplacement() const { return Replacement; }
117 // setReplacement - Used by the replacement calculation pass to figure out
118 // what to replace this value with, if anything.
120 void setReplacement(Value *Repl) { Replacement = Repl; }
122 // getRelation - return the relationship entry for the specified value.
123 // This can invalidate references to other Relation's, so use it carefully.
125 Relation &getRelation(Value *V) {
126 // Binary search for V's entry...
127 std::vector<Relation>::iterator I =
128 std::lower_bound(Relationships.begin(), Relationships.end(), V);
130 // If we found the entry, return it...
131 if (I != Relationships.end() && I->getValue() == V)
134 // Insert and return the new relationship...
135 return *Relationships.insert(I, V);
138 const Relation *requestRelation(Value *V) const {
139 // Binary search for V's entry...
140 std::vector<Relation>::const_iterator I =
141 std::lower_bound(Relationships.begin(), Relationships.end(), V);
142 if (I != Relationships.end() && I->getValue() == V)
147 // print - Output information about this value relation...
148 void print(std::ostream &OS, Value *V) const;
152 // RegionInfo - Keeps track of all of the value relationships for a region. A
153 // region is the are dominated by a basic block. RegionInfo's keep track of
154 // the RegionInfo for their dominator, because anything known in a dominator
155 // is known to be true in a dominated block as well.
160 // ValueMap - Tracks the ValueInformation known for this region
161 typedef std::map<Value*, ValueInfo> ValueMapTy;
164 RegionInfo(BasicBlock *bb) : BB(bb) {}
166 // getEntryBlock - Return the block that dominates all of the members of
168 BasicBlock *getEntryBlock() const { return BB; }
170 const RegionInfo &operator=(const RegionInfo &RI) {
171 ValueMap = RI.ValueMap;
175 // print - Output information about this region...
176 void print(std::ostream &OS) const;
178 // Allow external access.
179 typedef ValueMapTy::iterator iterator;
180 iterator begin() { return ValueMap.begin(); }
181 iterator end() { return ValueMap.end(); }
183 ValueInfo &getValueInfo(Value *V) {
184 ValueMapTy::iterator I = ValueMap.lower_bound(V);
185 if (I != ValueMap.end() && I->first == V) return I->second;
186 return ValueMap.insert(I, std::make_pair(V, V->getType()))->second;
189 const ValueInfo *requestValueInfo(Value *V) const {
190 ValueMapTy::const_iterator I = ValueMap.find(V);
191 if (I != ValueMap.end()) return &I->second;
196 /// CEE - Correlated Expression Elimination
197 class CEE : public FunctionPass {
198 std::map<Value*, unsigned> RankMap;
199 std::map<BasicBlock*, RegionInfo> RegionInfoMap;
203 virtual bool runOnFunction(Function &F);
205 // We don't modify the program, so we preserve all analyses
206 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
207 AU.addRequired<DominatorSet>();
208 AU.addRequired<DominatorTree>();
209 AU.addRequiredID(BreakCriticalEdgesID);
212 // print - Implement the standard print form to print out analysis
214 virtual void print(std::ostream &O, const Module *M) const;
217 RegionInfo &getRegionInfo(BasicBlock *BB) {
218 std::map<BasicBlock*, RegionInfo>::iterator I
219 = RegionInfoMap.lower_bound(BB);
220 if (I != RegionInfoMap.end() && I->first == BB) return I->second;
221 return RegionInfoMap.insert(I, std::make_pair(BB, BB))->second;
224 void BuildRankMap(Function &F);
225 unsigned getRank(Value *V) const {
226 if (isa<Constant>(V) || isa<GlobalValue>(V)) return 0;
227 std::map<Value*, unsigned>::const_iterator I = RankMap.find(V);
228 if (I != RankMap.end()) return I->second;
229 return 0; // Must be some other global thing
232 bool TransformRegion(BasicBlock *BB, std::set<BasicBlock*> &VisitedBlocks);
234 BasicBlock *isCorrelatedBranchBlock(BasicBlock *BB, RegionInfo &RI);
235 void PropogateBranchInfo(BranchInst *BI);
236 void PropogateEquality(Value *Op0, Value *Op1, RegionInfo &RI);
237 void PropogateRelation(Instruction::BinaryOps Opcode, Value *Op0,
238 Value *Op1, RegionInfo &RI);
239 void UpdateUsersOfValue(Value *V, RegionInfo &RI);
240 void IncorporateInstruction(Instruction *Inst, RegionInfo &RI);
241 void ComputeReplacements(RegionInfo &RI);
244 // getSetCCResult - Given a setcc instruction, determine if the result is
245 // determined by facts we already know about the region under analysis.
246 // Return KnownTrue, KnownFalse, or Unknown based on what we can determine.
248 Relation::KnownResult getSetCCResult(SetCondInst *SC, const RegionInfo &RI);
251 bool SimplifyBasicBlock(BasicBlock &BB, const RegionInfo &RI);
252 bool SimplifyInstruction(Instruction *Inst, const RegionInfo &RI);
254 RegisterOpt<CEE> X("cee", "Correlated Expression Elimination");
257 Pass *createCorrelatedExpressionEliminationPass() { return new CEE(); }
260 bool CEE::runOnFunction(Function &F) {
261 // Build a rank map for the function...
264 // Traverse the dominator tree, computing information for each node in the
265 // tree. Note that our traversal will not even touch unreachable basic
267 DS = &getAnalysis<DominatorSet>();
268 DT = &getAnalysis<DominatorTree>();
270 std::set<BasicBlock*> VisitedBlocks;
271 bool Changed = TransformRegion(&F.getEntryNode(), VisitedBlocks);
273 RegionInfoMap.clear();
278 // TransformRegion - Transform the region starting with BB according to the
279 // calculated region information for the block. Transforming the region
280 // involves analyzing any information this block provides to successors,
281 // propogating the information to successors, and finally transforming
284 // This method processes the function in depth first order, which guarantees
285 // that we process the immediate dominator of a block before the block itself.
286 // Because we are passing information from immediate dominators down to
287 // dominatees, we obviously have to process the information source before the
288 // information consumer.
290 bool CEE::TransformRegion(BasicBlock *BB, std::set<BasicBlock*> &VisitedBlocks){
291 // Prevent infinite recursion...
292 if (VisitedBlocks.count(BB)) return false;
293 VisitedBlocks.insert(BB);
295 // Get the computed region information for this block...
296 RegionInfo &RI = getRegionInfo(BB);
298 // Compute the replacement information for this block...
299 ComputeReplacements(RI);
301 // If debugging, print computed region information...
302 DEBUG(RI.print(std::cerr));
304 // Simplify the contents of this block...
305 bool Changed = SimplifyBasicBlock(*BB, RI);
307 // Get the terminator of this basic block...
308 TerminatorInst *TI = BB->getTerminator();
310 // Loop over all of the blocks that this block is the immediate dominator for.
311 // Because all information known in this region is also known in all of the
312 // blocks that are dominated by this one, we can safely propogate the
313 // information down now.
315 DominatorTree::Node *BBN = (*DT)[BB];
316 for (unsigned i = 0, e = BBN->getChildren().size(); i != e; ++i) {
317 BasicBlock *Dominated = BBN->getChildren()[i]->getNode();
318 assert(RegionInfoMap.find(Dominated) == RegionInfoMap.end() &&
319 "RegionInfo should be calculated in dominanace order!");
320 getRegionInfo(Dominated) = RI;
323 // Now that all of our successors have information if they deserve it,
324 // propogate any information our terminator instruction finds to our
326 if (BranchInst *BI = dyn_cast<BranchInst>(TI))
327 if (BI->isConditional())
328 PropogateBranchInfo(BI);
330 // If this is a branch to a block outside our region that simply performs
331 // another conditional branch, one whose outcome is known inside of this
332 // region, then vector this outgoing edge directly to the known destination.
334 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
335 while (BasicBlock *Dest = isCorrelatedBranchBlock(TI->getSuccessor(i), RI)){
336 // If there are any PHI nodes in the Dest BB, we must duplicate the entry
337 // in the PHI node for the old successor to now include an entry from the
338 // current basic block.
340 BasicBlock *OldSucc = TI->getSuccessor(i);
342 // Loop over all of the PHI nodes...
343 for (BasicBlock::iterator I = Dest->begin();
344 PHINode *PN = dyn_cast<PHINode>(&*I); ++I) {
345 // Find the entry in the PHI node for OldSucc, create a duplicate entry
347 int BlockIndex = PN->getBasicBlockIndex(OldSucc);
348 assert(BlockIndex != -1 && "Block should have entry in PHI!");
349 PN->addIncoming(PN->getIncomingValue(BlockIndex), BB);
352 // Actually revector the branch now...
353 TI->setSuccessor(i, Dest);
358 // Now that all of our successors have information, recursively process them.
359 for (unsigned i = 0, e = BBN->getChildren().size(); i != e; ++i)
360 Changed |= TransformRegion(BBN->getChildren()[i]->getNode(), VisitedBlocks);
365 // If this block is a simple block not in the current region, which contains
366 // only a conditional branch, we determine if the outcome of the branch can be
367 // determined from information inside of the region. Instead of going to this
368 // block, we can instead go to the destination we know is the right target.
370 BasicBlock *CEE::isCorrelatedBranchBlock(BasicBlock *BB, RegionInfo &RI) {
371 // Check to see if we dominate the block. If so, this block will get the
372 // condition turned to a constant anyway.
374 //if (DS->dominates(RI.getEntryBlock(), BB))
377 // Check to see if this is a conditional branch...
378 if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator()))
379 if (BI->isConditional()) {
380 // Make sure that the block is either empty, or only contains a setcc.
381 if (BB->size() == 1 ||
382 (BB->size() == 2 && &BB->front() == BI->getCondition() &&
383 BI->getCondition()->use_size() == 1))
384 if (SetCondInst *SCI = dyn_cast<SetCondInst>(BI->getCondition())) {
385 Relation::KnownResult Result = getSetCCResult(SCI, RI);
387 if (Result == Relation::KnownTrue)
388 return BI->getSuccessor(0);
389 else if (Result == Relation::KnownFalse)
390 return BI->getSuccessor(1);
396 // BuildRankMap - This method builds the rank map data structure which gives
397 // each instruction/value in the function a value based on how early it appears
398 // in the function. We give constants and globals rank 0, arguments are
399 // numbered starting at one, and instructions are numbered in reverse post-order
400 // from where the arguments leave off. This gives instructions in loops higher
401 // values than instructions not in loops.
403 void CEE::BuildRankMap(Function &F) {
404 unsigned Rank = 1; // Skip rank zero.
406 // Number the arguments...
407 for (Function::aiterator I = F.abegin(), E = F.aend(); I != E; ++I)
410 // Number the instructions in reverse post order...
411 ReversePostOrderTraversal<Function*> RPOT(&F);
412 for (ReversePostOrderTraversal<Function*>::rpo_iterator I = RPOT.begin(),
413 E = RPOT.end(); I != E; ++I)
414 for (BasicBlock::iterator BBI = (*I)->begin(), E = (*I)->end();
416 if (BBI->getType() != Type::VoidTy)
417 RankMap[BBI] = Rank++;
421 // PropogateBranchInfo - When this method is invoked, we need to propogate
422 // information derived from the branch condition into the true and false
423 // branches of BI. Since we know that there aren't any critical edges in the
424 // flow graph, this can proceed unconditionally.
426 void CEE::PropogateBranchInfo(BranchInst *BI) {
427 assert(BI->isConditional() && "Must be a conditional branch!");
428 BasicBlock *BB = BI->getParent();
429 BasicBlock *TrueBB = BI->getSuccessor(0);
430 BasicBlock *FalseBB = BI->getSuccessor(1);
432 // Propogate information into the true block...
434 PropogateEquality(BI->getCondition(), ConstantBool::True,
435 getRegionInfo(TrueBB));
437 // Propogate information into the false block...
439 PropogateEquality(BI->getCondition(), ConstantBool::False,
440 getRegionInfo(FalseBB));
444 // PropogateEquality - If we discover that two values are equal to each other in
445 // a specified region, propogate this knowledge recursively.
447 void CEE::PropogateEquality(Value *Op0, Value *Op1, RegionInfo &RI) {
448 if (Op0 == Op1) return; // Gee whiz. Are these really equal each other?
450 if (isa<Constant>(Op0)) // Make sure the constant is always Op1
453 // Make sure we don't already know these are equal, to avoid infinite loops...
454 ValueInfo &VI = RI.getValueInfo(Op0);
456 // Get information about the known relationship between Op0 & Op1
457 Relation &KnownRelation = VI.getRelation(Op1);
459 // If we already know they're equal, don't reprocess...
460 if (KnownRelation.getRelation() == Instruction::SetEQ)
463 // If this is boolean, check to see if one of the operands is a constant. If
464 // it's a constant, then see if the other one is one of a setcc instruction,
465 // an AND, OR, or XOR instruction.
467 if (ConstantBool *CB = dyn_cast<ConstantBool>(Op1)) {
469 if (Instruction *Inst = dyn_cast<Instruction>(Op0)) {
470 // If we know that this instruction is an AND instruction, and the result
471 // is true, this means that both operands to the OR are known to be true
474 if (CB->getValue() && Inst->getOpcode() == Instruction::And) {
475 PropogateEquality(Inst->getOperand(0), CB, RI);
476 PropogateEquality(Inst->getOperand(1), CB, RI);
479 // If we know that this instruction is an OR instruction, and the result
480 // is false, this means that both operands to the OR are know to be false
483 if (!CB->getValue() && Inst->getOpcode() == Instruction::Or) {
484 PropogateEquality(Inst->getOperand(0), CB, RI);
485 PropogateEquality(Inst->getOperand(1), CB, RI);
488 // If we know that this instruction is a NOT instruction, we know that the
489 // operand is known to be the inverse of whatever the current value is.
491 if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(Inst))
492 if (BinaryOperator::isNot(BOp))
493 PropogateEquality(BinaryOperator::getNotArgument(BOp),
494 ConstantBool::get(!CB->getValue()), RI);
496 // If we know the value of a SetCC instruction, propogate the information
497 // about the relation into this region as well.
499 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Inst)) {
500 if (CB->getValue()) { // If we know the condition is true...
501 // Propogate info about the LHS to the RHS & RHS to LHS
502 PropogateRelation(SCI->getOpcode(), SCI->getOperand(0),
503 SCI->getOperand(1), RI);
504 PropogateRelation(SCI->getSwappedCondition(),
505 SCI->getOperand(1), SCI->getOperand(0), RI);
507 } else { // If we know the condition is false...
508 // We know the opposite of the condition is true...
509 Instruction::BinaryOps C = SCI->getInverseCondition();
511 PropogateRelation(C, SCI->getOperand(0), SCI->getOperand(1), RI);
512 PropogateRelation(SetCondInst::getSwappedCondition(C),
513 SCI->getOperand(1), SCI->getOperand(0), RI);
519 // Propogate information about Op0 to Op1 & visa versa
520 PropogateRelation(Instruction::SetEQ, Op0, Op1, RI);
521 PropogateRelation(Instruction::SetEQ, Op1, Op0, RI);
525 // PropogateRelation - We know that the specified relation is true in all of the
526 // blocks in the specified region. Propogate the information about Op0 and
527 // anything derived from it into this region.
529 void CEE::PropogateRelation(Instruction::BinaryOps Opcode, Value *Op0,
530 Value *Op1, RegionInfo &RI) {
531 assert(Op0->getType() == Op1->getType() && "Equal types expected!");
533 // Constants are already pretty well understood. We will apply information
534 // about the constant to Op1 in another call to PropogateRelation.
536 if (isa<Constant>(Op0)) return;
538 // Get the region information for this block to update...
539 ValueInfo &VI = RI.getValueInfo(Op0);
541 // Get information about the known relationship between Op0 & Op1
542 Relation &Op1R = VI.getRelation(Op1);
544 // Quick bailout for common case if we are reprocessing an instruction...
545 if (Op1R.getRelation() == Opcode)
548 // If we already have information that contradicts the current information we
549 // are propogating, ignore this info. Something bad must have happened!
551 if (Op1R.contradicts(Opcode, VI)) {
552 Op1R.contradicts(Opcode, VI);
553 std::cerr << "Contradiction found for opcode: "
554 << Instruction::getOpcodeName(Opcode) << "\n";
555 Op1R.print(std::cerr);
559 // If the information propogted is new, then we want process the uses of this
560 // instruction to propogate the information down to them.
562 if (Op1R.incorporate(Opcode, VI))
563 UpdateUsersOfValue(Op0, RI);
567 // UpdateUsersOfValue - The information about V in this region has been updated.
568 // Propogate this to all consumers of the value.
570 void CEE::UpdateUsersOfValue(Value *V, RegionInfo &RI) {
571 for (Value::use_iterator I = V->use_begin(), E = V->use_end();
573 if (Instruction *Inst = dyn_cast<Instruction>(*I)) {
574 // If this is an instruction using a value that we know something about,
575 // try to propogate information to the value produced by the
576 // instruction. We can only do this if it is an instruction we can
577 // propogate information for (a setcc for example), and we only WANT to
578 // do this if the instruction dominates this region.
580 // If the instruction doesn't dominate this region, then it cannot be
581 // used in this region and we don't care about it. If the instruction
582 // is IN this region, then we will simplify the instruction before we
583 // get to uses of it anyway, so there is no reason to bother with it
584 // here. This check is also effectively checking to make sure that Inst
585 // is in the same function as our region (in case V is a global f.e.).
587 if (DS->properlyDominates(Inst->getParent(), RI.getEntryBlock()))
588 IncorporateInstruction(Inst, RI);
592 // IncorporateInstruction - We just updated the information about one of the
593 // operands to the specified instruction. Update the information about the
594 // value produced by this instruction
596 void CEE::IncorporateInstruction(Instruction *Inst, RegionInfo &RI) {
597 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Inst)) {
598 // See if we can figure out a result for this instruction...
599 Relation::KnownResult Result = getSetCCResult(SCI, RI);
600 if (Result != Relation::Unknown) {
601 PropogateEquality(SCI, Result ? ConstantBool::True : ConstantBool::False,
608 // ComputeReplacements - Some values are known to be equal to other values in a
609 // region. For example if there is a comparison of equality between a variable
610 // X and a constant C, we can replace all uses of X with C in the region we are
611 // interested in. We generalize this replacement to replace variables with
612 // other variables if they are equal and there is a variable with lower rank
613 // than the current one. This offers a cannonicalizing property that exposes
614 // more redundancies for later transformations to take advantage of.
616 void CEE::ComputeReplacements(RegionInfo &RI) {
617 // Loop over all of the values in the region info map...
618 for (RegionInfo::iterator I = RI.begin(), E = RI.end(); I != E; ++I) {
619 ValueInfo &VI = I->second;
621 // If we know that this value is a particular constant, set Replacement to
623 Value *Replacement = VI.getBounds().getSingleElement();
625 // If this value is not known to be some constant, figure out the lowest
626 // rank value that it is known to be equal to (if anything).
628 if (Replacement == 0) {
629 // Find out if there are any equality relationships with values of lower
630 // rank than VI itself...
631 unsigned MinRank = getRank(I->first);
633 // Loop over the relationships known about Op0.
634 const std::vector<Relation> &Relationships = VI.getRelationships();
635 for (unsigned i = 0, e = Relationships.size(); i != e; ++i)
636 if (Relationships[i].getRelation() == Instruction::SetEQ) {
637 unsigned R = getRank(Relationships[i].getValue());
640 Replacement = Relationships[i].getValue();
645 // If we found something to replace this value with, keep track of it.
647 VI.setReplacement(Replacement);
651 // SimplifyBasicBlock - Given information about values in region RI, simplify
652 // the instructions in the specified basic block.
654 bool CEE::SimplifyBasicBlock(BasicBlock &BB, const RegionInfo &RI) {
655 bool Changed = false;
656 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ) {
657 Instruction *Inst = &*I++;
659 // Convert instruction arguments to canonical forms...
660 Changed |= SimplifyInstruction(Inst, RI);
662 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Inst)) {
663 // Try to simplify a setcc instruction based on inherited information
664 Relation::KnownResult Result = getSetCCResult(SCI, RI);
665 if (Result != Relation::Unknown) {
666 DEBUG(std::cerr << "Replacing setcc with " << Result
667 << " constant: " << SCI);
669 SCI->replaceAllUsesWith(ConstantBool::get((bool)Result));
670 // The instruction is now dead, remove it from the program.
671 SCI->getParent()->getInstList().erase(SCI);
681 // SimplifyInstruction - Inspect the operands of the instruction, converting
682 // them to their cannonical form if possible. This takes care of, for example,
683 // replacing a value 'X' with a constant 'C' if the instruction in question is
684 // dominated by a true seteq 'X', 'C'.
686 bool CEE::SimplifyInstruction(Instruction *I, const RegionInfo &RI) {
687 bool Changed = false;
689 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
690 if (const ValueInfo *VI = RI.requestValueInfo(I->getOperand(i)))
691 if (Value *Repl = VI->getReplacement()) {
692 // If we know if a replacement with lower rank than Op0, make the
694 DEBUG(std::cerr << "In Inst: " << I << " Replacing operand #" << i
695 << " with " << Repl << "\n");
696 I->setOperand(i, Repl);
705 // SimplifySetCC - Try to simplify a setcc instruction based on information
706 // inherited from a dominating setcc instruction. V is one of the operands to
707 // the setcc instruction, and VI is the set of information known about it. We
708 // take two cases into consideration here. If the comparison is against a
709 // constant value, we can use the constant range to see if the comparison is
710 // possible to succeed. If it is not a comparison against a constant, we check
711 // to see if there is a known relationship between the two values. If so, we
712 // may be able to eliminate the check.
714 Relation::KnownResult CEE::getSetCCResult(SetCondInst *SCI,
715 const RegionInfo &RI) {
716 Value *Op0 = SCI->getOperand(0), *Op1 = SCI->getOperand(1);
717 Instruction::BinaryOps Opcode = SCI->getOpcode();
719 if (isa<Constant>(Op0)) {
720 if (isa<Constant>(Op1)) {
721 if (Constant *Result = ConstantFoldInstruction(SCI)) {
722 // Wow, this is easy, directly eliminate the SetCondInst.
723 DEBUG(std::cerr << "Replacing setcc with constant fold: " << SCI);
724 return cast<ConstantBool>(Result)->getValue()
725 ? Relation::KnownTrue : Relation::KnownFalse;
728 // We want to swap this instruction so that operand #0 is the constant.
730 Opcode = SCI->getSwappedCondition();
734 // Try to figure out what the result of this comparison will be...
735 Relation::KnownResult Result = Relation::Unknown;
737 // We have to know something about the relationship to prove anything...
738 if (const ValueInfo *Op0VI = RI.requestValueInfo(Op0)) {
740 // At this point, we know that if we have a constant argument that it is in
741 // Op1. Check to see if we know anything about comparing value with a
742 // constant, and if we can use this info to fold the setcc.
744 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(Op1)) {
745 // Check to see if we already know the result of this comparison...
746 ConstantRange R = ConstantRange(Opcode, C);
747 ConstantRange Int = R.intersectWith(Op0VI->getBounds());
749 // If the intersection of the two ranges is empty, then the condition
750 // could never be true!
752 if (Int.isEmptySet()) {
753 Result = Relation::KnownFalse;
755 // Otherwise, if VI.getBounds() (the possible values) is a subset of R
756 // (the allowed values) then we know that the condition must always be
759 } else if (Int == Op0VI->getBounds()) {
760 Result = Relation::KnownTrue;
763 // If we are here, we know that the second argument is not a constant
764 // integral. See if we know anything about Op0 & Op1 that allows us to
767 // Do we have value information about Op0 and a relation to Op1?
768 if (const Relation *Op2R = Op0VI->requestRelation(Op1))
769 Result = Op2R->getImpliedResult(Opcode);
775 //===----------------------------------------------------------------------===//
776 // Relation Implementation
777 //===----------------------------------------------------------------------===//
779 // CheckCondition - Return true if the specified condition is false. Bound may
781 static bool CheckCondition(Constant *Bound, Constant *C,
782 Instruction::BinaryOps BO) {
783 assert(C != 0 && "C is not specified!");
784 if (Bound == 0) return false;
788 default: assert(0 && "Unknown Condition code!");
789 case Instruction::SetEQ: Val = *Bound == *C; break;
790 case Instruction::SetNE: Val = *Bound != *C; break;
791 case Instruction::SetLT: Val = *Bound < *C; break;
792 case Instruction::SetGT: Val = *Bound > *C; break;
793 case Instruction::SetLE: Val = *Bound <= *C; break;
794 case Instruction::SetGE: Val = *Bound >= *C; break;
797 // ConstantHandling code may not succeed in the comparison...
798 if (Val == 0) return false;
799 return !Val->getValue(); // Return true if the condition is false...
802 // contradicts - Return true if the relationship specified by the operand
803 // contradicts already known information.
805 bool Relation::contradicts(Instruction::BinaryOps Op,
806 const ValueInfo &VI) const {
807 assert (Op != Instruction::Add && "Invalid relation argument!");
809 // If this is a relationship with a constant, make sure that this relationship
810 // does not contradict properties known about the bounds of the constant.
812 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(Val))
813 if (ConstantRange(Op, C).intersectWith(VI.getBounds()).isEmptySet())
817 default: assert(0 && "Unknown Relationship code!");
818 case Instruction::Add: return false; // Nothing known, nothing contradicts
819 case Instruction::SetEQ:
820 return Op == Instruction::SetLT || Op == Instruction::SetGT ||
821 Op == Instruction::SetNE;
822 case Instruction::SetNE: return Op == Instruction::SetEQ;
823 case Instruction::SetLE: return Op == Instruction::SetGT;
824 case Instruction::SetGE: return Op == Instruction::SetLT;
825 case Instruction::SetLT:
826 return Op == Instruction::SetEQ || Op == Instruction::SetGT ||
827 Op == Instruction::SetGE;
828 case Instruction::SetGT:
829 return Op == Instruction::SetEQ || Op == Instruction::SetLT ||
830 Op == Instruction::SetLE;
834 // incorporate - Incorporate information in the argument into this relation
835 // entry. This assumes that the information doesn't contradict itself. If any
836 // new information is gained, true is returned, otherwise false is returned to
837 // indicate that nothing was updated.
839 bool Relation::incorporate(Instruction::BinaryOps Op, ValueInfo &VI) {
840 assert(!contradicts(Op, VI) &&
841 "Cannot incorporate contradictory information!");
843 // If this is a relationship with a constant, make sure that we update the
844 // range that is possible for the value to have...
846 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(Val))
847 VI.getBounds() = ConstantRange(Op, C).intersectWith(VI.getBounds());
850 default: assert(0 && "Unknown prior value!");
851 case Instruction::Add: Rel = Op; return true;
852 case Instruction::SetEQ: return false; // Nothing is more precise
853 case Instruction::SetNE: return false; // Nothing is more precise
854 case Instruction::SetLT: return false; // Nothing is more precise
855 case Instruction::SetGT: return false; // Nothing is more precise
856 case Instruction::SetLE:
857 if (Op == Instruction::SetEQ || Op == Instruction::SetLT) {
860 } else if (Op == Instruction::SetNE) {
861 Rel = Instruction::SetLT;
865 case Instruction::SetGE: return Op == Instruction::SetLT;
866 if (Op == Instruction::SetEQ || Op == Instruction::SetGT) {
869 } else if (Op == Instruction::SetNE) {
870 Rel = Instruction::SetGT;
877 // getImpliedResult - If this relationship between two values implies that
878 // the specified relationship is true or false, return that. If we cannot
879 // determine the result required, return Unknown.
881 Relation::KnownResult
882 Relation::getImpliedResult(Instruction::BinaryOps Op) const {
883 if (Rel == Op) return KnownTrue;
884 if (Rel == SetCondInst::getInverseCondition(Op)) return KnownFalse;
887 default: assert(0 && "Unknown prior value!");
888 case Instruction::SetEQ:
889 if (Op == Instruction::SetLE || Op == Instruction::SetGE) return KnownTrue;
890 if (Op == Instruction::SetLT || Op == Instruction::SetGT) return KnownFalse;
892 case Instruction::SetLT:
893 if (Op == Instruction::SetNE || Op == Instruction::SetLE) return KnownTrue;
894 if (Op == Instruction::SetEQ) return KnownFalse;
896 case Instruction::SetGT:
897 if (Op == Instruction::SetNE || Op == Instruction::SetGE) return KnownTrue;
898 if (Op == Instruction::SetEQ) return KnownFalse;
900 case Instruction::SetNE:
901 case Instruction::SetLE:
902 case Instruction::SetGE:
903 case Instruction::Add:
910 //===----------------------------------------------------------------------===//
911 // Printing Support...
912 //===----------------------------------------------------------------------===//
914 // print - Implement the standard print form to print out analysis information.
915 void CEE::print(std::ostream &O, const Module *M) const {
916 O << "\nPrinting Correlated Expression Info:\n";
917 for (std::map<BasicBlock*, RegionInfo>::const_iterator I =
918 RegionInfoMap.begin(), E = RegionInfoMap.end(); I != E; ++I)
922 // print - Output information about this region...
923 void RegionInfo::print(std::ostream &OS) const {
924 if (ValueMap.empty()) return;
926 OS << " RegionInfo for basic block: " << BB->getName() << "\n";
927 for (std::map<Value*, ValueInfo>::const_iterator
928 I = ValueMap.begin(), E = ValueMap.end(); I != E; ++I)
929 I->second.print(OS, I->first);
933 // print - Output information about this value relation...
934 void ValueInfo::print(std::ostream &OS, Value *V) const {
935 if (Relationships.empty()) return;
938 OS << " ValueInfo for: ";
939 WriteAsOperand(OS, V);
941 OS << "\n Bounds = " << Bounds << "\n";
943 OS << " Replacement = ";
944 WriteAsOperand(OS, Replacement);
947 for (unsigned i = 0, e = Relationships.size(); i != e; ++i)
948 Relationships[i].print(OS);
951 // print - Output this relation to the specified stream
952 void Relation::print(std::ostream &OS) const {
955 default: OS << "*UNKNOWN*"; break;
956 case Instruction::SetEQ: OS << "== "; break;
957 case Instruction::SetNE: OS << "!= "; break;
958 case Instruction::SetLT: OS << "< "; break;
959 case Instruction::SetGT: OS << "> "; break;
960 case Instruction::SetLE: OS << "<= "; break;
961 case Instruction::SetGE: OS << ">= "; break;
964 WriteAsOperand(OS, Val);
968 void Relation::dump() const { print(std::cerr); }
969 void ValueInfo::dump() const { print(std::cerr, 0); }