| //===- CorrelatedExprs.cpp - Pass to detect and eliminated c.e.'s ---------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file was developed by the LLVM research group and is distributed under |
| // the University of Illinois Open Source License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // Correlated Expression Elimination propagates information from conditional |
| // branches to blocks dominated by destinations of the branch. It propagates |
| // information from the condition check itself into the body of the branch, |
| // allowing transformations like these for example: |
| // |
| // if (i == 7) |
| // ... 4*i; // constant propagation |
| // |
| // M = i+1; N = j+1; |
| // if (i == j) |
| // X = M-N; // = M-M == 0; |
| // |
| // This is called Correlated Expression Elimination because we eliminate or |
| // simplify expressions that are correlated with the direction of a branch. In |
| // this way we use static information to give us some information about the |
| // dynamic value of a variable. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "cee" |
| #include "llvm/Transforms/Scalar.h" |
| #include "llvm/Constants.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Function.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/Type.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/Analysis/ConstantFolding.h" |
| #include "llvm/Analysis/Dominators.h" |
| #include "llvm/Assembly/Writer.h" |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include "llvm/Support/CFG.h" |
| #include "llvm/Support/Compiler.h" |
| #include "llvm/Support/ConstantRange.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/ADT/PostOrderIterator.h" |
| #include "llvm/ADT/Statistic.h" |
| #include <algorithm> |
| using namespace llvm; |
| |
| STATISTIC(NumCmpRemoved, "Number of cmp instruction eliminated"); |
| STATISTIC(NumOperandsCann, "Number of operands canonicalized"); |
| STATISTIC(BranchRevectors, "Number of branches revectored"); |
| |
| namespace { |
| class ValueInfo; |
| class VISIBILITY_HIDDEN Relation { |
| Value *Val; // Relation to what value? |
| unsigned Rel; // SetCC or ICmp relation, or Add if no information |
| public: |
| Relation(Value *V) : Val(V), Rel(Instruction::Add) {} |
| bool operator<(const Relation &R) const { return Val < R.Val; } |
| Value *getValue() const { return Val; } |
| unsigned getRelation() const { return Rel; } |
| |
| // contradicts - Return true if the relationship specified by the operand |
| // contradicts already known information. |
| // |
| bool contradicts(unsigned Rel, const ValueInfo &VI) const; |
| |
| // incorporate - Incorporate information in the argument into this relation |
| // entry. This assumes that the information doesn't contradict itself. If |
| // any new information is gained, true is returned, otherwise false is |
| // returned to indicate that nothing was updated. |
| // |
| bool incorporate(unsigned Rel, ValueInfo &VI); |
| |
| // KnownResult - Whether or not this condition determines the result of a |
| // setcc or icmp in the program. False & True are intentionally 0 & 1 |
| // so we can convert to bool by casting after checking for unknown. |
| // |
| enum KnownResult { KnownFalse = 0, KnownTrue = 1, Unknown = 2 }; |
| |
| // getImpliedResult - If this relationship between two values implies that |
| // the specified relationship is true or false, return that. If we cannot |
| // determine the result required, return Unknown. |
| // |
| KnownResult getImpliedResult(unsigned Rel) const; |
| |
| // print - Output this relation to the specified stream |
| void print(std::ostream &OS) const; |
| void dump() const; |
| }; |
| |
| |
| // ValueInfo - One instance of this record exists for every value with |
| // relationships between other values. It keeps track of all of the |
| // relationships to other values in the program (specified with Relation) that |
| // are known to be valid in a region. |
| // |
| class VISIBILITY_HIDDEN ValueInfo { |
| // RelationShips - this value is know to have the specified relationships to |
| // other values. There can only be one entry per value, and this list is |
| // kept sorted by the Val field. |
| std::vector<Relation> Relationships; |
| |
| // If information about this value is known or propagated from constant |
| // expressions, this range contains the possible values this value may hold. |
| ConstantRange Bounds; |
| |
| // If we find that this value is equal to another value that has a lower |
| // rank, this value is used as it's replacement. |
| // |
| Value *Replacement; |
| public: |
| ValueInfo(const Type *Ty) |
| : Bounds(Ty->isInteger() ? cast<IntegerType>(Ty)->getBitWidth() : 32), |
| Replacement(0) {} |
| |
| // getBounds() - Return the constant bounds of the value... |
| const ConstantRange &getBounds() const { return Bounds; } |
| ConstantRange &getBounds() { return Bounds; } |
| |
| const std::vector<Relation> &getRelationships() { return Relationships; } |
| |
| // getReplacement - Return the value this value is to be replaced with if it |
| // exists, otherwise return null. |
| // |
| Value *getReplacement() const { return Replacement; } |
| |
| // setReplacement - Used by the replacement calculation pass to figure out |
| // what to replace this value with, if anything. |
| // |
| void setReplacement(Value *Repl) { Replacement = Repl; } |
| |
| // getRelation - return the relationship entry for the specified value. |
| // This can invalidate references to other Relations, so use it carefully. |
| // |
| Relation &getRelation(Value *V) { |
| // Binary search for V's entry... |
| std::vector<Relation>::iterator I = |
| std::lower_bound(Relationships.begin(), Relationships.end(), |
| Relation(V)); |
| |
| // If we found the entry, return it... |
| if (I != Relationships.end() && I->getValue() == V) |
| return *I; |
| |
| // Insert and return the new relationship... |
| return *Relationships.insert(I, V); |
| } |
| |
| const Relation *requestRelation(Value *V) const { |
| // Binary search for V's entry... |
| std::vector<Relation>::const_iterator I = |
| std::lower_bound(Relationships.begin(), Relationships.end(), |
| Relation(V)); |
| if (I != Relationships.end() && I->getValue() == V) |
| return &*I; |
| return 0; |
| } |
| |
| // print - Output information about this value relation... |
| void print(std::ostream &OS, Value *V) const; |
| void dump() const; |
| }; |
| |
| // RegionInfo - Keeps track of all of the value relationships for a region. A |
| // region is the are dominated by a basic block. RegionInfo's keep track of |
| // the RegionInfo for their dominator, because anything known in a dominator |
| // is known to be true in a dominated block as well. |
| // |
| class VISIBILITY_HIDDEN RegionInfo { |
| BasicBlock *BB; |
| |
| // ValueMap - Tracks the ValueInformation known for this region |
| typedef std::map<Value*, ValueInfo> ValueMapTy; |
| ValueMapTy ValueMap; |
| public: |
| RegionInfo(BasicBlock *bb) : BB(bb) {} |
| |
| // getEntryBlock - Return the block that dominates all of the members of |
| // this region. |
| BasicBlock *getEntryBlock() const { return BB; } |
| |
| // empty - return true if this region has no information known about it. |
| bool empty() const { return ValueMap.empty(); } |
| |
| const RegionInfo &operator=(const RegionInfo &RI) { |
| ValueMap = RI.ValueMap; |
| return *this; |
| } |
| |
| // print - Output information about this region... |
| void print(std::ostream &OS) const; |
| void dump() const; |
| |
| // Allow external access. |
| typedef ValueMapTy::iterator iterator; |
| iterator begin() { return ValueMap.begin(); } |
| iterator end() { return ValueMap.end(); } |
| |
| ValueInfo &getValueInfo(Value *V) { |
| ValueMapTy::iterator I = ValueMap.lower_bound(V); |
| if (I != ValueMap.end() && I->first == V) return I->second; |
| return ValueMap.insert(I, std::make_pair(V, V->getType()))->second; |
| } |
| |
| const ValueInfo *requestValueInfo(Value *V) const { |
| ValueMapTy::const_iterator I = ValueMap.find(V); |
| if (I != ValueMap.end()) return &I->second; |
| return 0; |
| } |
| |
| /// removeValueInfo - Remove anything known about V from our records. This |
| /// works whether or not we know anything about V. |
| /// |
| void removeValueInfo(Value *V) { |
| ValueMap.erase(V); |
| } |
| }; |
| |
| /// CEE - Correlated Expression Elimination |
| class VISIBILITY_HIDDEN CEE : public FunctionPass { |
| std::map<Value*, unsigned> RankMap; |
| std::map<BasicBlock*, RegionInfo> RegionInfoMap; |
| ETForest *EF; |
| public: |
| static char ID; // Pass identification, replacement for typeid |
| CEE() : FunctionPass((intptr_t)&ID) {} |
| |
| virtual bool runOnFunction(Function &F); |
| |
| // We don't modify the program, so we preserve all analyses |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequired<ETForest>(); |
| AU.addRequiredID(BreakCriticalEdgesID); |
| }; |
| |
| // print - Implement the standard print form to print out analysis |
| // information. |
| virtual void print(std::ostream &O, const Module *M) const; |
| |
| private: |
| RegionInfo &getRegionInfo(BasicBlock *BB) { |
| std::map<BasicBlock*, RegionInfo>::iterator I |
| = RegionInfoMap.lower_bound(BB); |
| if (I != RegionInfoMap.end() && I->first == BB) return I->second; |
| return RegionInfoMap.insert(I, std::make_pair(BB, BB))->second; |
| } |
| |
| void BuildRankMap(Function &F); |
| unsigned getRank(Value *V) const { |
| if (isa<Constant>(V)) return 0; |
| std::map<Value*, unsigned>::const_iterator I = RankMap.find(V); |
| if (I != RankMap.end()) return I->second; |
| return 0; // Must be some other global thing |
| } |
| |
| bool TransformRegion(BasicBlock *BB, std::set<BasicBlock*> &VisitedBlocks); |
| |
| bool ForwardCorrelatedEdgeDestination(TerminatorInst *TI, unsigned SuccNo, |
| RegionInfo &RI); |
| |
| void ForwardSuccessorTo(TerminatorInst *TI, unsigned Succ, BasicBlock *D, |
| RegionInfo &RI); |
| void ReplaceUsesOfValueInRegion(Value *Orig, Value *New, |
| BasicBlock *RegionDominator); |
| void CalculateRegionExitBlocks(BasicBlock *BB, BasicBlock *OldSucc, |
| std::vector<BasicBlock*> &RegionExitBlocks); |
| void InsertRegionExitMerges(PHINode *NewPHI, Instruction *OldVal, |
| const std::vector<BasicBlock*> &RegionExitBlocks); |
| |
| void PropagateBranchInfo(BranchInst *BI); |
| void PropagateSwitchInfo(SwitchInst *SI); |
| void PropagateEquality(Value *Op0, Value *Op1, RegionInfo &RI); |
| void PropagateRelation(unsigned Opcode, Value *Op0, |
| Value *Op1, RegionInfo &RI); |
| void UpdateUsersOfValue(Value *V, RegionInfo &RI); |
| void IncorporateInstruction(Instruction *Inst, RegionInfo &RI); |
| void ComputeReplacements(RegionInfo &RI); |
| |
| // getCmpResult - Given a icmp instruction, determine if the result is |
| // determined by facts we already know about the region under analysis. |
| // Return KnownTrue, KnownFalse, or UnKnown based on what we can determine. |
| Relation::KnownResult getCmpResult(CmpInst *ICI, const RegionInfo &RI); |
| |
| bool SimplifyBasicBlock(BasicBlock &BB, const RegionInfo &RI); |
| bool SimplifyInstruction(Instruction *Inst, const RegionInfo &RI); |
| }; |
| |
| char CEE::ID = 0; |
| RegisterPass<CEE> X("cee", "Correlated Expression Elimination"); |
| } |
| |
| FunctionPass *llvm::createCorrelatedExpressionEliminationPass() { |
| return new CEE(); |
| } |
| |
| |
| bool CEE::runOnFunction(Function &F) { |
| // Build a rank map for the function... |
| BuildRankMap(F); |
| |
| // Traverse the dominator tree, computing information for each node in the |
| // tree. Note that our traversal will not even touch unreachable basic |
| // blocks. |
| EF = &getAnalysis<ETForest>(); |
| |
| std::set<BasicBlock*> VisitedBlocks; |
| bool Changed = TransformRegion(&F.getEntryBlock(), VisitedBlocks); |
| |
| RegionInfoMap.clear(); |
| RankMap.clear(); |
| return Changed; |
| } |
| |
| // TransformRegion - Transform the region starting with BB according to the |
| // calculated region information for the block. Transforming the region |
| // involves analyzing any information this block provides to successors, |
| // propagating the information to successors, and finally transforming |
| // successors. |
| // |
| // This method processes the function in depth first order, which guarantees |
| // that we process the immediate dominator of a block before the block itself. |
| // Because we are passing information from immediate dominators down to |
| // dominatees, we obviously have to process the information source before the |
| // information consumer. |
| // |
| bool CEE::TransformRegion(BasicBlock *BB, std::set<BasicBlock*> &VisitedBlocks){ |
| // Prevent infinite recursion... |
| if (VisitedBlocks.count(BB)) return false; |
| VisitedBlocks.insert(BB); |
| |
| // Get the computed region information for this block... |
| RegionInfo &RI = getRegionInfo(BB); |
| |
| // Compute the replacement information for this block... |
| ComputeReplacements(RI); |
| |
| // If debugging, print computed region information... |
| DEBUG(RI.print(*cerr.stream())); |
| |
| // Simplify the contents of this block... |
| bool Changed = SimplifyBasicBlock(*BB, RI); |
| |
| // Get the terminator of this basic block... |
| TerminatorInst *TI = BB->getTerminator(); |
| |
| // Loop over all of the blocks that this block is the immediate dominator for. |
| // Because all information known in this region is also known in all of the |
| // blocks that are dominated by this one, we can safely propagate the |
| // information down now. |
| // |
| std::vector<BasicBlock*> children; |
| EF->getChildren(BB, children); |
| if (!RI.empty()) { // Time opt: only propagate if we can change something |
| for (std::vector<BasicBlock*>::iterator CI = children.begin(), |
| E = children.end(); CI != E; ++CI) { |
| assert(RegionInfoMap.find(*CI) == RegionInfoMap.end() && |
| "RegionInfo should be calculated in dominanace order!"); |
| getRegionInfo(*CI) = RI; |
| } |
| } |
| |
| // Now that all of our successors have information if they deserve it, |
| // propagate any information our terminator instruction finds to our |
| // successors. |
| if (BranchInst *BI = dyn_cast<BranchInst>(TI)) { |
| if (BI->isConditional()) |
| PropagateBranchInfo(BI); |
| } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) { |
| PropagateSwitchInfo(SI); |
| } |
| |
| // If this is a branch to a block outside our region that simply performs |
| // another conditional branch, one whose outcome is known inside of this |
| // region, then vector this outgoing edge directly to the known destination. |
| // |
| for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) |
| while (ForwardCorrelatedEdgeDestination(TI, i, RI)) { |
| ++BranchRevectors; |
| Changed = true; |
| } |
| |
| // Now that all of our successors have information, recursively process them. |
| for (std::vector<BasicBlock*>::iterator CI = children.begin(), |
| E = children.end(); CI != E; ++CI) |
| Changed |= TransformRegion(*CI, VisitedBlocks); |
| |
| return Changed; |
| } |
| |
| // isBlockSimpleEnoughForCheck to see if the block is simple enough for us to |
| // revector the conditional branch in the bottom of the block, do so now. |
| // |
| static bool isBlockSimpleEnough(BasicBlock *BB) { |
| assert(isa<BranchInst>(BB->getTerminator())); |
| BranchInst *BI = cast<BranchInst>(BB->getTerminator()); |
| assert(BI->isConditional()); |
| |
| // Check the common case first: empty block, or block with just a setcc. |
| if (BB->size() == 1 || |
| (BB->size() == 2 && &BB->front() == BI->getCondition() && |
| BI->getCondition()->hasOneUse())) |
| return true; |
| |
| // Check the more complex case now... |
| BasicBlock::iterator I = BB->begin(); |
| |
| // FIXME: This should be reenabled once the regression with SIM is fixed! |
| #if 0 |
| // PHI Nodes are ok, just skip over them... |
| while (isa<PHINode>(*I)) ++I; |
| #endif |
| |
| // Accept the setcc instruction... |
| if (&*I == BI->getCondition()) |
| ++I; |
| |
| // Nothing else is acceptable here yet. We must not revector... unless we are |
| // at the terminator instruction. |
| if (&*I == BI) |
| return true; |
| |
| return false; |
| } |
| |
| |
| bool CEE::ForwardCorrelatedEdgeDestination(TerminatorInst *TI, unsigned SuccNo, |
| RegionInfo &RI) { |
| // If this successor is a simple block not in the current region, which |
| // contains only a conditional branch, we decide if the outcome of the branch |
| // can be determined from information inside of the region. Instead of going |
| // to this block, we can instead go to the destination we know is the right |
| // target. |
| // |
| |
| // Check to see if we dominate the block. If so, this block will get the |
| // condition turned to a constant anyway. |
| // |
| //if (EF->dominates(RI.getEntryBlock(), BB)) |
| // return 0; |
| |
| BasicBlock *BB = TI->getParent(); |
| |
| // Get the destination block of this edge... |
| BasicBlock *OldSucc = TI->getSuccessor(SuccNo); |
| |
| // Make sure that the block ends with a conditional branch and is simple |
| // enough for use to be able to revector over. |
| BranchInst *BI = dyn_cast<BranchInst>(OldSucc->getTerminator()); |
| if (BI == 0 || !BI->isConditional() || !isBlockSimpleEnough(OldSucc)) |
| return false; |
| |
| // We can only forward the branch over the block if the block ends with a |
| // cmp we can determine the outcome for. |
| // |
| // FIXME: we can make this more generic. Code below already handles more |
| // generic case. |
| if (!isa<CmpInst>(BI->getCondition())) |
| return false; |
| |
| // Make a new RegionInfo structure so that we can simulate the effect of the |
| // PHI nodes in the block we are skipping over... |
| // |
| RegionInfo NewRI(RI); |
| |
| // Remove value information for all of the values we are simulating... to make |
| // sure we don't have any stale information. |
| for (BasicBlock::iterator I = OldSucc->begin(), E = OldSucc->end(); I!=E; ++I) |
| if (I->getType() != Type::VoidTy) |
| NewRI.removeValueInfo(I); |
| |
| // Put the newly discovered information into the RegionInfo... |
| for (BasicBlock::iterator I = OldSucc->begin(), E = OldSucc->end(); I!=E; ++I) |
| if (PHINode *PN = dyn_cast<PHINode>(I)) { |
| int OpNum = PN->getBasicBlockIndex(BB); |
| assert(OpNum != -1 && "PHI doesn't have incoming edge for predecessor!?"); |
| PropagateEquality(PN, PN->getIncomingValue(OpNum), NewRI); |
| } else if (CmpInst *CI = dyn_cast<CmpInst>(I)) { |
| Relation::KnownResult Res = getCmpResult(CI, NewRI); |
| if (Res == Relation::Unknown) return false; |
| PropagateEquality(CI, ConstantInt::get(Type::Int1Ty, Res), NewRI); |
| } else { |
| assert(isa<BranchInst>(*I) && "Unexpected instruction type!"); |
| } |
| |
| // Compute the facts implied by what we have discovered... |
| ComputeReplacements(NewRI); |
| |
| ValueInfo &PredicateVI = NewRI.getValueInfo(BI->getCondition()); |
| if (PredicateVI.getReplacement() && |
| isa<Constant>(PredicateVI.getReplacement()) && |
| !isa<GlobalValue>(PredicateVI.getReplacement())) { |
| ConstantInt *CB = cast<ConstantInt>(PredicateVI.getReplacement()); |
| |
| // Forward to the successor that corresponds to the branch we will take. |
| ForwardSuccessorTo(TI, SuccNo, |
| BI->getSuccessor(!CB->getZExtValue()), NewRI); |
| return true; |
| } |
| |
| return false; |
| } |
| |
| static Value *getReplacementOrValue(Value *V, RegionInfo &RI) { |
| if (const ValueInfo *VI = RI.requestValueInfo(V)) |
| if (Value *Repl = VI->getReplacement()) |
| return Repl; |
| return V; |
| } |
| |
| /// ForwardSuccessorTo - We have found that we can forward successor # 'SuccNo' |
| /// of Terminator 'TI' to the 'Dest' BasicBlock. This method performs the |
| /// mechanics of updating SSA information and revectoring the branch. |
| /// |
| void CEE::ForwardSuccessorTo(TerminatorInst *TI, unsigned SuccNo, |
| BasicBlock *Dest, RegionInfo &RI) { |
| // If there are any PHI nodes in the Dest BB, we must duplicate the entry |
| // in the PHI node for the old successor to now include an entry from the |
| // current basic block. |
| // |
| BasicBlock *OldSucc = TI->getSuccessor(SuccNo); |
| BasicBlock *BB = TI->getParent(); |
| |
| DOUT << "Forwarding branch in basic block %" << BB->getName() |
| << " from block %" << OldSucc->getName() << " to block %" |
| << Dest->getName() << "\n" |
| << "Before forwarding: " << *BB->getParent(); |
| |
| // Because we know that there cannot be critical edges in the flow graph, and |
| // that OldSucc has multiple outgoing edges, this means that Dest cannot have |
| // multiple incoming edges. |
| // |
| #ifndef NDEBUG |
| pred_iterator DPI = pred_begin(Dest); ++DPI; |
| assert(DPI == pred_end(Dest) && "Critical edge found!!"); |
| #endif |
| |
| // Loop over any PHI nodes in the destination, eliminating them, because they |
| // may only have one input. |
| // |
| while (PHINode *PN = dyn_cast<PHINode>(&Dest->front())) { |
| assert(PN->getNumIncomingValues() == 1 && "Crit edge found!"); |
| // Eliminate the PHI node |
| PN->replaceAllUsesWith(PN->getIncomingValue(0)); |
| Dest->getInstList().erase(PN); |
| } |
| |
| // If there are values defined in the "OldSucc" basic block, we need to insert |
| // PHI nodes in the regions we are dealing with to emulate them. This can |
| // insert dead phi nodes, but it is more trouble to see if they are used than |
| // to just blindly insert them. |
| // |
| if (EF->dominates(OldSucc, Dest)) { |
| // RegionExitBlocks - Find all of the blocks that are not dominated by Dest, |
| // but have predecessors that are. Additionally, prune down the set to only |
| // include blocks that are dominated by OldSucc as well. |
| // |
| std::vector<BasicBlock*> RegionExitBlocks; |
| CalculateRegionExitBlocks(Dest, OldSucc, RegionExitBlocks); |
| |
| for (BasicBlock::iterator I = OldSucc->begin(), E = OldSucc->end(); |
| I != E; ++I) |
| if (I->getType() != Type::VoidTy) { |
| // Create and insert the PHI node into the top of Dest. |
| PHINode *NewPN = new PHINode(I->getType(), I->getName()+".fw_merge", |
| Dest->begin()); |
| // There is definitely an edge from OldSucc... add the edge now |
| NewPN->addIncoming(I, OldSucc); |
| |
| // There is also an edge from BB now, add the edge with the calculated |
| // value from the RI. |
| NewPN->addIncoming(getReplacementOrValue(I, RI), BB); |
| |
| // Make everything in the Dest region use the new PHI node now... |
| ReplaceUsesOfValueInRegion(I, NewPN, Dest); |
| |
| // Make sure that exits out of the region dominated by NewPN get PHI |
| // nodes that merge the values as appropriate. |
| InsertRegionExitMerges(NewPN, I, RegionExitBlocks); |
| } |
| } |
| |
| // If there were PHI nodes in OldSucc, we need to remove the entry for this |
| // edge from the PHI node, and we need to replace any references to the PHI |
| // node with a new value. |
| // |
| for (BasicBlock::iterator I = OldSucc->begin(); isa<PHINode>(I); ) { |
| PHINode *PN = cast<PHINode>(I); |
| |
| // Get the value flowing across the old edge and remove the PHI node entry |
| // for this edge: we are about to remove the edge! Don't remove the PHI |
| // node yet though if this is the last edge into it. |
| Value *EdgeValue = PN->removeIncomingValue(BB, false); |
| |
| // Make sure that anything that used to use PN now refers to EdgeValue |
| ReplaceUsesOfValueInRegion(PN, EdgeValue, Dest); |
| |
| // If there is only one value left coming into the PHI node, replace the PHI |
| // node itself with the one incoming value left. |
| // |
| if (PN->getNumIncomingValues() == 1) { |
| assert(PN->getNumIncomingValues() == 1); |
| PN->replaceAllUsesWith(PN->getIncomingValue(0)); |
| PN->getParent()->getInstList().erase(PN); |
| I = OldSucc->begin(); |
| } else if (PN->getNumIncomingValues() == 0) { // Nuke the PHI |
| // If we removed the last incoming value to this PHI, nuke the PHI node |
| // now. |
| PN->replaceAllUsesWith(Constant::getNullValue(PN->getType())); |
| PN->getParent()->getInstList().erase(PN); |
| I = OldSucc->begin(); |
| } else { |
| ++I; // Otherwise, move on to the next PHI node |
| } |
| } |
| |
| // Actually revector the branch now... |
| TI->setSuccessor(SuccNo, Dest); |
| |
| // If we just introduced a critical edge in the flow graph, make sure to break |
| // it right away... |
| SplitCriticalEdge(TI, SuccNo, this); |
| |
| // Make sure that we don't introduce critical edges from oldsucc now! |
| for (unsigned i = 0, e = OldSucc->getTerminator()->getNumSuccessors(); |
| i != e; ++i) |
| SplitCriticalEdge(OldSucc->getTerminator(), i, this); |
| |
| // Since we invalidated the CFG, recalculate the dominator set so that it is |
| // useful for later processing! |
| // FIXME: This is much worse than it really should be! |
| //EF->recalculate(); |
| |
| DOUT << "After forwarding: " << *BB->getParent(); |
| } |
| |
| /// ReplaceUsesOfValueInRegion - This method replaces all uses of Orig with uses |
| /// of New. It only affects instructions that are defined in basic blocks that |
| /// are dominated by Head. |
| /// |
| void CEE::ReplaceUsesOfValueInRegion(Value *Orig, Value *New, |
| BasicBlock *RegionDominator) { |
| assert(Orig != New && "Cannot replace value with itself"); |
| std::vector<Instruction*> InstsToChange; |
| std::vector<PHINode*> PHIsToChange; |
| InstsToChange.reserve(Orig->getNumUses()); |
| |
| // Loop over instructions adding them to InstsToChange vector, this allows us |
| // an easy way to avoid invalidating the use_iterator at a bad time. |
| for (Value::use_iterator I = Orig->use_begin(), E = Orig->use_end(); |
| I != E; ++I) |
| if (Instruction *User = dyn_cast<Instruction>(*I)) |
| if (EF->dominates(RegionDominator, User->getParent())) |
| InstsToChange.push_back(User); |
| else if (PHINode *PN = dyn_cast<PHINode>(User)) { |
| PHIsToChange.push_back(PN); |
| } |
| |
| // PHIsToChange contains PHI nodes that use Orig that do not live in blocks |
| // dominated by orig. If the block the value flows in from is dominated by |
| // RegionDominator, then we rewrite the PHI |
| for (unsigned i = 0, e = PHIsToChange.size(); i != e; ++i) { |
| PHINode *PN = PHIsToChange[i]; |
| for (unsigned j = 0, e = PN->getNumIncomingValues(); j != e; ++j) |
| if (PN->getIncomingValue(j) == Orig && |
| EF->dominates(RegionDominator, PN->getIncomingBlock(j))) |
| PN->setIncomingValue(j, New); |
| } |
| |
| // Loop over the InstsToChange list, replacing all uses of Orig with uses of |
| // New. This list contains all of the instructions in our region that use |
| // Orig. |
| for (unsigned i = 0, e = InstsToChange.size(); i != e; ++i) |
| if (PHINode *PN = dyn_cast<PHINode>(InstsToChange[i])) { |
| // PHINodes must be handled carefully. If the PHI node itself is in the |
| // region, we have to make sure to only do the replacement for incoming |
| // values that correspond to basic blocks in the region. |
| for (unsigned j = 0, e = PN->getNumIncomingValues(); j != e; ++j) |
| if (PN->getIncomingValue(j) == Orig && |
| EF->dominates(RegionDominator, PN->getIncomingBlock(j))) |
| PN->setIncomingValue(j, New); |
| |
| } else { |
| InstsToChange[i]->replaceUsesOfWith(Orig, New); |
| } |
| } |
| |
| static void CalcRegionExitBlocks(BasicBlock *Header, BasicBlock *BB, |
| std::set<BasicBlock*> &Visited, |
| ETForest &EF, |
| std::vector<BasicBlock*> &RegionExitBlocks) { |
| if (Visited.count(BB)) return; |
| Visited.insert(BB); |
| |
| if (EF.dominates(Header, BB)) { // Block in the region, recursively traverse |
| for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) |
| CalcRegionExitBlocks(Header, *I, Visited, EF, RegionExitBlocks); |
| } else { |
| // Header does not dominate this block, but we have a predecessor that does |
| // dominate us. Add ourself to the list. |
| RegionExitBlocks.push_back(BB); |
| } |
| } |
| |
| /// CalculateRegionExitBlocks - Find all of the blocks that are not dominated by |
| /// BB, but have predecessors that are. Additionally, prune down the set to |
| /// only include blocks that are dominated by OldSucc as well. |
| /// |
| void CEE::CalculateRegionExitBlocks(BasicBlock *BB, BasicBlock *OldSucc, |
| std::vector<BasicBlock*> &RegionExitBlocks){ |
| std::set<BasicBlock*> Visited; // Don't infinite loop |
| |
| // Recursively calculate blocks we are interested in... |
| CalcRegionExitBlocks(BB, BB, Visited, *EF, RegionExitBlocks); |
| |
| // Filter out blocks that are not dominated by OldSucc... |
| for (unsigned i = 0; i != RegionExitBlocks.size(); ) { |
| if (EF->dominates(OldSucc, RegionExitBlocks[i])) |
| ++i; // Block is ok, keep it. |
| else { |
| // Move to end of list... |
| std::swap(RegionExitBlocks[i], RegionExitBlocks.back()); |
| RegionExitBlocks.pop_back(); // Nuke the end |
| } |
| } |
| } |
| |
| void CEE::InsertRegionExitMerges(PHINode *BBVal, Instruction *OldVal, |
| const std::vector<BasicBlock*> &RegionExitBlocks) { |
| assert(BBVal->getType() == OldVal->getType() && "Should be derived values!"); |
| BasicBlock *BB = BBVal->getParent(); |
| |
| // Loop over all of the blocks we have to place PHIs in, doing it. |
| for (unsigned i = 0, e = RegionExitBlocks.size(); i != e; ++i) { |
| BasicBlock *FBlock = RegionExitBlocks[i]; // Block on the frontier |
| |
| // Create the new PHI node |
| PHINode *NewPN = new PHINode(BBVal->getType(), |
| OldVal->getName()+".fw_frontier", |
| FBlock->begin()); |
| |
| // Add an incoming value for every predecessor of the block... |
| for (pred_iterator PI = pred_begin(FBlock), PE = pred_end(FBlock); |
| PI != PE; ++PI) { |
| // If the incoming edge is from the region dominated by BB, use BBVal, |
| // otherwise use OldVal. |
| NewPN->addIncoming(EF->dominates(BB, *PI) ? BBVal : OldVal, *PI); |
| } |
| |
| // Now make everyone dominated by this block use this new value! |
| ReplaceUsesOfValueInRegion(OldVal, NewPN, FBlock); |
| } |
| } |
| |
| |
| |
| // BuildRankMap - This method builds the rank map data structure which gives |
| // each instruction/value in the function a value based on how early it appears |
| // in the function. We give constants and globals rank 0, arguments are |
| // numbered starting at one, and instructions are numbered in reverse post-order |
| // from where the arguments leave off. This gives instructions in loops higher |
| // values than instructions not in loops. |
| // |
| void CEE::BuildRankMap(Function &F) { |
| unsigned Rank = 1; // Skip rank zero. |
| |
| // Number the arguments... |
| for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I) |
| RankMap[I] = Rank++; |
| |
| // Number the instructions in reverse post order... |
| ReversePostOrderTraversal<Function*> RPOT(&F); |
| for (ReversePostOrderTraversal<Function*>::rpo_iterator I = RPOT.begin(), |
| E = RPOT.end(); I != E; ++I) |
| for (BasicBlock::iterator BBI = (*I)->begin(), E = (*I)->end(); |
| BBI != E; ++BBI) |
| if (BBI->getType() != Type::VoidTy) |
| RankMap[BBI] = Rank++; |
| } |
| |
| |
| // PropagateBranchInfo - When this method is invoked, we need to propagate |
| // information derived from the branch condition into the true and false |
| // branches of BI. Since we know that there aren't any critical edges in the |
| // flow graph, this can proceed unconditionally. |
| // |
| void CEE::PropagateBranchInfo(BranchInst *BI) { |
| assert(BI->isConditional() && "Must be a conditional branch!"); |
| |
| // Propagate information into the true block... |
| // |
| PropagateEquality(BI->getCondition(), ConstantInt::getTrue(), |
| getRegionInfo(BI->getSuccessor(0))); |
| |
| // Propagate information into the false block... |
| // |
| PropagateEquality(BI->getCondition(), ConstantInt::getFalse(), |
| getRegionInfo(BI->getSuccessor(1))); |
| } |
| |
| |
| // PropagateSwitchInfo - We need to propagate the value tested by the |
| // switch statement through each case block. |
| // |
| void CEE::PropagateSwitchInfo(SwitchInst *SI) { |
| // Propagate information down each of our non-default case labels. We |
| // don't yet propagate information down the default label, because a |
| // potentially large number of inequality constraints provide less |
| // benefit per unit work than a single equality constraint. |
| // |
| Value *cond = SI->getCondition(); |
| for (unsigned i = 1; i < SI->getNumSuccessors(); ++i) |
| PropagateEquality(cond, SI->getSuccessorValue(i), |
| getRegionInfo(SI->getSuccessor(i))); |
| } |
| |
| |
| // PropagateEquality - If we discover that two values are equal to each other in |
| // a specified region, propagate this knowledge recursively. |
| // |
| void CEE::PropagateEquality(Value *Op0, Value *Op1, RegionInfo &RI) { |
| if (Op0 == Op1) return; // Gee whiz. Are these really equal each other? |
| |
| if (isa<Constant>(Op0)) // Make sure the constant is always Op1 |
| std::swap(Op0, Op1); |
| |
| // Make sure we don't already know these are equal, to avoid infinite loops... |
| ValueInfo &VI = RI.getValueInfo(Op0); |
| |
| // Get information about the known relationship between Op0 & Op1 |
| Relation &KnownRelation = VI.getRelation(Op1); |
| |
| // If we already know they're equal, don't reprocess... |
| if (KnownRelation.getRelation() == FCmpInst::FCMP_OEQ || |
| KnownRelation.getRelation() == ICmpInst::ICMP_EQ) |
| return; |
| |
| // If this is boolean, check to see if one of the operands is a constant. If |
| // it's a constant, then see if the other one is one of a setcc instruction, |
| // an AND, OR, or XOR instruction. |
| // |
| ConstantInt *CB = dyn_cast<ConstantInt>(Op1); |
| if (CB && Op1->getType() == Type::Int1Ty) { |
| if (Instruction *Inst = dyn_cast<Instruction>(Op0)) { |
| // If we know that this instruction is an AND instruction, and the |
| // result is true, this means that both operands to the OR are known |
| // to be true as well. |
| // |
| if (CB->getZExtValue() && Inst->getOpcode() == Instruction::And) { |
| PropagateEquality(Inst->getOperand(0), CB, RI); |
| PropagateEquality(Inst->getOperand(1), CB, RI); |
| } |
| |
| // If we know that this instruction is an OR instruction, and the result |
| // is false, this means that both operands to the OR are know to be |
| // false as well. |
| // |
| if (!CB->getZExtValue() && Inst->getOpcode() == Instruction::Or) { |
| PropagateEquality(Inst->getOperand(0), CB, RI); |
| PropagateEquality(Inst->getOperand(1), CB, RI); |
| } |
| |
| // If we know that this instruction is a NOT instruction, we know that |
| // the operand is known to be the inverse of whatever the current |
| // value is. |
| // |
| if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(Inst)) |
| if (BinaryOperator::isNot(BOp)) |
| PropagateEquality(BinaryOperator::getNotArgument(BOp), |
| ConstantInt::get(Type::Int1Ty, |
| !CB->getZExtValue()), RI); |
| |
| // If we know the value of a FCmp instruction, propagate the information |
| // about the relation into this region as well. |
| // |
| if (FCmpInst *FCI = dyn_cast<FCmpInst>(Inst)) { |
| if (CB->getZExtValue()) { // If we know the condition is true... |
| // Propagate info about the LHS to the RHS & RHS to LHS |
| PropagateRelation(FCI->getPredicate(), FCI->getOperand(0), |
| FCI->getOperand(1), RI); |
| PropagateRelation(FCI->getSwappedPredicate(), |
| FCI->getOperand(1), FCI->getOperand(0), RI); |
| |
| } else { // If we know the condition is false... |
| // We know the opposite of the condition is true... |
| FCmpInst::Predicate C = FCI->getInversePredicate(); |
| |
| PropagateRelation(C, FCI->getOperand(0), FCI->getOperand(1), RI); |
| PropagateRelation(FCmpInst::getSwappedPredicate(C), |
| FCI->getOperand(1), FCI->getOperand(0), RI); |
| } |
| } |
| |
| // If we know the value of a ICmp instruction, propagate the information |
| // about the relation into this region as well. |
| // |
| if (ICmpInst *ICI = dyn_cast<ICmpInst>(Inst)) { |
| if (CB->getZExtValue()) { // If we know the condition is true... |
| // Propagate info about the LHS to the RHS & RHS to LHS |
| PropagateRelation(ICI->getPredicate(), ICI->getOperand(0), |
| ICI->getOperand(1), RI); |
| PropagateRelation(ICI->getSwappedPredicate(), ICI->getOperand(1), |
| ICI->getOperand(1), RI); |
| |
| } else { // If we know the condition is false ... |
| // We know the opposite of the condition is true... |
| ICmpInst::Predicate C = ICI->getInversePredicate(); |
| |
| PropagateRelation(C, ICI->getOperand(0), ICI->getOperand(1), RI); |
| PropagateRelation(ICmpInst::getSwappedPredicate(C), |
| ICI->getOperand(1), ICI->getOperand(0), RI); |
| } |
| } |
| } |
| } |
| |
| // Propagate information about Op0 to Op1 & visa versa |
| PropagateRelation(ICmpInst::ICMP_EQ, Op0, Op1, RI); |
| PropagateRelation(ICmpInst::ICMP_EQ, Op1, Op0, RI); |
| PropagateRelation(FCmpInst::FCMP_OEQ, Op0, Op1, RI); |
| PropagateRelation(FCmpInst::FCMP_OEQ, Op1, Op0, RI); |
| } |
| |
| |
| // PropagateRelation - We know that the specified relation is true in all of the |
| // blocks in the specified region. Propagate the information about Op0 and |
| // anything derived from it into this region. |
| // |
| void CEE::PropagateRelation(unsigned Opcode, Value *Op0, |
| Value *Op1, RegionInfo &RI) { |
| assert(Op0->getType() == Op1->getType() && "Equal types expected!"); |
| |
| // Constants are already pretty well understood. We will apply information |
| // about the constant to Op1 in another call to PropagateRelation. |
| // |
| if (isa<Constant>(Op0)) return; |
| |
| // Get the region information for this block to update... |
| ValueInfo &VI = RI.getValueInfo(Op0); |
| |
| // Get information about the known relationship between Op0 & Op1 |
| Relation &Op1R = VI.getRelation(Op1); |
| |
| // Quick bailout for common case if we are reprocessing an instruction... |
| if (Op1R.getRelation() == Opcode) |
| return; |
| |
| // If we already have information that contradicts the current information we |
| // are propagating, ignore this info. Something bad must have happened! |
| // |
| if (Op1R.contradicts(Opcode, VI)) { |
| Op1R.contradicts(Opcode, VI); |
| cerr << "Contradiction found for opcode: " |
| << ((isa<ICmpInst>(Op0)||isa<ICmpInst>(Op1)) ? |
| Instruction::getOpcodeName(Instruction::ICmp) : |
| Instruction::getOpcodeName(Opcode)) |
| << "\n"; |
| Op1R.print(*cerr.stream()); |
| return; |
| } |
| |
| // If the information propagated is new, then we want process the uses of this |
| // instruction to propagate the information down to them. |
| // |
| if (Op1R.incorporate(Opcode, VI)) |
| UpdateUsersOfValue(Op0, RI); |
| } |
| |
| |
| // UpdateUsersOfValue - The information about V in this region has been updated. |
| // Propagate this to all consumers of the value. |
| // |
| void CEE::UpdateUsersOfValue(Value *V, RegionInfo &RI) { |
| for (Value::use_iterator I = V->use_begin(), E = V->use_end(); |
| I != E; ++I) |
| if (Instruction *Inst = dyn_cast<Instruction>(*I)) { |
| // If this is an instruction using a value that we know something about, |
| // try to propagate information to the value produced by the |
| // instruction. We can only do this if it is an instruction we can |
| // propagate information for (a setcc for example), and we only WANT to |
| // do this if the instruction dominates this region. |
| // |
| // If the instruction doesn't dominate this region, then it cannot be |
| // used in this region and we don't care about it. If the instruction |
| // is IN this region, then we will simplify the instruction before we |
| // get to uses of it anyway, so there is no reason to bother with it |
| // here. This check is also effectively checking to make sure that Inst |
| // is in the same function as our region (in case V is a global f.e.). |
| // |
| if (EF->properlyDominates(Inst->getParent(), RI.getEntryBlock())) |
| IncorporateInstruction(Inst, RI); |
| } |
| } |
| |
| // IncorporateInstruction - We just updated the information about one of the |
| // operands to the specified instruction. Update the information about the |
| // value produced by this instruction |
| // |
| void CEE::IncorporateInstruction(Instruction *Inst, RegionInfo &RI) { |
| if (CmpInst *CI = dyn_cast<CmpInst>(Inst)) { |
| // See if we can figure out a result for this instruction... |
| Relation::KnownResult Result = getCmpResult(CI, RI); |
| if (Result != Relation::Unknown) { |
| PropagateEquality(CI, ConstantInt::get(Type::Int1Ty, Result != 0), RI); |
| } |
| } |
| } |
| |
| |
| // ComputeReplacements - Some values are known to be equal to other values in a |
| // region. For example if there is a comparison of equality between a variable |
| // X and a constant C, we can replace all uses of X with C in the region we are |
| // interested in. We generalize this replacement to replace variables with |
| // other variables if they are equal and there is a variable with lower rank |
| // than the current one. This offers a canonicalizing property that exposes |
| // more redundancies for later transformations to take advantage of. |
| // |
| void CEE::ComputeReplacements(RegionInfo &RI) { |
| // Loop over all of the values in the region info map... |
| for (RegionInfo::iterator I = RI.begin(), E = RI.end(); I != E; ++I) { |
| ValueInfo &VI = I->second; |
| |
| // If we know that this value is a particular constant, set Replacement to |
| // the constant... |
| Value *Replacement = 0; |
| const APInt * Rplcmnt = VI.getBounds().getSingleElement(); |
| if (Rplcmnt) |
| Replacement = ConstantInt::get(*Rplcmnt); |
| |
| // If this value is not known to be some constant, figure out the lowest |
| // rank value that it is known to be equal to (if anything). |
| // |
| if (Replacement == 0) { |
| // Find out if there are any equality relationships with values of lower |
| // rank than VI itself... |
| unsigned MinRank = getRank(I->first); |
| |
| // Loop over the relationships known about Op0. |
| const std::vector<Relation> &Relationships = VI.getRelationships(); |
| for (unsigned i = 0, e = Relationships.size(); i != e; ++i) |
| if (Relationships[i].getRelation() == FCmpInst::FCMP_OEQ) { |
| unsigned R = getRank(Relationships[i].getValue()); |
| if (R < MinRank) { |
| MinRank = R; |
| Replacement = Relationships[i].getValue(); |
| } |
| } |
| else if (Relationships[i].getRelation() == ICmpInst::ICMP_EQ) { |
| unsigned R = getRank(Relationships[i].getValue()); |
| if (R < MinRank) { |
| MinRank = R; |
| Replacement = Relationships[i].getValue(); |
| } |
| } |
| } |
| |
| // If we found something to replace this value with, keep track of it. |
| if (Replacement) |
| VI.setReplacement(Replacement); |
| } |
| } |
| |
| // SimplifyBasicBlock - Given information about values in region RI, simplify |
| // the instructions in the specified basic block. |
| // |
| bool CEE::SimplifyBasicBlock(BasicBlock &BB, const RegionInfo &RI) { |
| bool Changed = false; |
| for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ) { |
| Instruction *Inst = I++; |
| |
| // Convert instruction arguments to canonical forms... |
| Changed |= SimplifyInstruction(Inst, RI); |
| |
| if (CmpInst *CI = dyn_cast<CmpInst>(Inst)) { |
| // Try to simplify a setcc instruction based on inherited information |
| Relation::KnownResult Result = getCmpResult(CI, RI); |
| if (Result != Relation::Unknown) { |
| DEBUG(cerr << "Replacing icmp with " << Result |
| << " constant: " << *CI); |
| |
| CI->replaceAllUsesWith(ConstantInt::get(Type::Int1Ty, (bool)Result)); |
| // The instruction is now dead, remove it from the program. |
| CI->getParent()->getInstList().erase(CI); |
| ++NumCmpRemoved; |
| Changed = true; |
| } |
| } |
| } |
| |
| return Changed; |
| } |
| |
| // SimplifyInstruction - Inspect the operands of the instruction, converting |
| // them to their canonical form if possible. This takes care of, for example, |
| // replacing a value 'X' with a constant 'C' if the instruction in question is |
| // dominated by a true seteq 'X', 'C'. |
| // |
| bool CEE::SimplifyInstruction(Instruction *I, const RegionInfo &RI) { |
| bool Changed = false; |
| |
| for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) |
| if (const ValueInfo *VI = RI.requestValueInfo(I->getOperand(i))) |
| if (Value *Repl = VI->getReplacement()) { |
| // If we know if a replacement with lower rank than Op0, make the |
| // replacement now. |
| DOUT << "In Inst: " << *I << " Replacing operand #" << i |
| << " with " << *Repl << "\n"; |
| I->setOperand(i, Repl); |
| Changed = true; |
| ++NumOperandsCann; |
| } |
| |
| return Changed; |
| } |
| |
| // getCmpResult - Try to simplify a cmp instruction based on information |
| // inherited from a dominating icmp instruction. V is one of the operands to |
| // the icmp instruction, and VI is the set of information known about it. We |
| // take two cases into consideration here. If the comparison is against a |
| // constant value, we can use the constant range to see if the comparison is |
| // possible to succeed. If it is not a comparison against a constant, we check |
| // to see if there is a known relationship between the two values. If so, we |
| // may be able to eliminate the check. |
| // |
| Relation::KnownResult CEE::getCmpResult(CmpInst *CI, |
| const RegionInfo &RI) { |
| Value *Op0 = CI->getOperand(0), *Op1 = CI->getOperand(1); |
| unsigned short predicate = CI->getPredicate(); |
| |
| if (isa<Constant>(Op0)) { |
| if (isa<Constant>(Op1)) { |
| if (Constant *Result = ConstantFoldInstruction(CI)) { |
| // Wow, this is easy, directly eliminate the ICmpInst. |
| DEBUG(cerr << "Replacing cmp with constant fold: " << *CI); |
| return cast<ConstantInt>(Result)->getZExtValue() |
| ? Relation::KnownTrue : Relation::KnownFalse; |
| } |
| } else { |
| // We want to swap this instruction so that operand #0 is the constant. |
| std::swap(Op0, Op1); |
| if (isa<ICmpInst>(CI)) |
| predicate = cast<ICmpInst>(CI)->getSwappedPredicate(); |
| else |
| predicate = cast<FCmpInst>(CI)->getSwappedPredicate(); |
| } |
| } |
| |
| // Try to figure out what the result of this comparison will be... |
| Relation::KnownResult Result = Relation::Unknown; |
| |
| // We have to know something about the relationship to prove anything... |
| if (const ValueInfo *Op0VI = RI.requestValueInfo(Op0)) { |
| |
| // At this point, we know that if we have a constant argument that it is in |
| // Op1. Check to see if we know anything about comparing value with a |
| // constant, and if we can use this info to fold the icmp. |
| // |
| if (ConstantInt *C = dyn_cast<ConstantInt>(Op1)) { |
| // Check to see if we already know the result of this comparison... |
| ICmpInst::Predicate ipred = ICmpInst::Predicate(predicate); |
| ConstantRange R = ICmpInst::makeConstantRange(ipred, C->getValue()); |
| ConstantRange Int = R.intersectWith(Op0VI->getBounds()); |
| |
| // If the intersection of the two ranges is empty, then the condition |
| // could never be true! |
| // |
| if (Int.isEmptySet()) { |
| Result = Relation::KnownFalse; |
| |
| // Otherwise, if VI.getBounds() (the possible values) is a subset of R |
| // (the allowed values) then we know that the condition must always be |
| // true! |
| // |
| } else if (Int == Op0VI->getBounds()) { |
| Result = Relation::KnownTrue; |
| } |
| } else { |
| // If we are here, we know that the second argument is not a constant |
| // integral. See if we know anything about Op0 & Op1 that allows us to |
| // fold this anyway. |
| // |
| // Do we have value information about Op0 and a relation to Op1? |
| if (const Relation *Op2R = Op0VI->requestRelation(Op1)) |
| Result = Op2R->getImpliedResult(predicate); |
| } |
| } |
| return Result; |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // Relation Implementation |
| //===----------------------------------------------------------------------===// |
| |
| // contradicts - Return true if the relationship specified by the operand |
| // contradicts already known information. |
| // |
| bool Relation::contradicts(unsigned Op, |
| const ValueInfo &VI) const { |
| assert (Op != Instruction::Add && "Invalid relation argument!"); |
| |
| // If this is a relationship with a constant, make sure that this relationship |
| // does not contradict properties known about the bounds of the constant. |
| // |
| if (ConstantInt *C = dyn_cast<ConstantInt>(Val)) |
| if (Op >= ICmpInst::FIRST_ICMP_PREDICATE && |
| Op <= ICmpInst::LAST_ICMP_PREDICATE) { |
| ICmpInst::Predicate ipred = ICmpInst::Predicate(Op); |
| if (ICmpInst::makeConstantRange(ipred, C->getValue()) |
| .intersectWith(VI.getBounds()).isEmptySet()) |
| return true; |
| } |
| |
| switch (Rel) { |
| default: assert(0 && "Unknown Relationship code!"); |
| case Instruction::Add: return false; // Nothing known, nothing contradicts |
| case ICmpInst::ICMP_EQ: |
| return Op == ICmpInst::ICMP_ULT || Op == ICmpInst::ICMP_SLT || |
| Op == ICmpInst::ICMP_UGT || Op == ICmpInst::ICMP_SGT || |
| Op == ICmpInst::ICMP_NE; |
| case ICmpInst::ICMP_NE: return Op == ICmpInst::ICMP_EQ; |
| case ICmpInst::ICMP_ULE: |
| case ICmpInst::ICMP_SLE: return Op == ICmpInst::ICMP_UGT || |
| Op == ICmpInst::ICMP_SGT; |
| case ICmpInst::ICMP_UGE: |
| case ICmpInst::ICMP_SGE: return Op == ICmpInst::ICMP_ULT || |
| Op == ICmpInst::ICMP_SLT; |
| case ICmpInst::ICMP_ULT: |
| case ICmpInst::ICMP_SLT: |
| return Op == ICmpInst::ICMP_EQ || Op == ICmpInst::ICMP_UGT || |
| Op == ICmpInst::ICMP_SGT || Op == ICmpInst::ICMP_UGE || |
| Op == ICmpInst::ICMP_SGE; |
| case ICmpInst::ICMP_UGT: |
| case ICmpInst::ICMP_SGT: |
| return Op == ICmpInst::ICMP_EQ || Op == ICmpInst::ICMP_ULT || |
| Op == ICmpInst::ICMP_SLT || Op == ICmpInst::ICMP_ULE || |
| Op == ICmpInst::ICMP_SLE; |
| case FCmpInst::FCMP_OEQ: |
| return Op == FCmpInst::FCMP_OLT || Op == FCmpInst::FCMP_OGT || |
| Op == FCmpInst::FCMP_ONE; |
| case FCmpInst::FCMP_ONE: return Op == FCmpInst::FCMP_OEQ; |
| case FCmpInst::FCMP_OLE: return Op == FCmpInst::FCMP_OGT; |
| case FCmpInst::FCMP_OGE: return Op == FCmpInst::FCMP_OLT; |
| case FCmpInst::FCMP_OLT: |
| return Op == FCmpInst::FCMP_OEQ || Op == FCmpInst::FCMP_OGT || |
| Op == FCmpInst::FCMP_OGE; |
| case FCmpInst::FCMP_OGT: |
| return Op == FCmpInst::FCMP_OEQ || Op == FCmpInst::FCMP_OLT || |
| Op == FCmpInst::FCMP_OLE; |
| } |
| } |
| |
| // incorporate - Incorporate information in the argument into this relation |
| // entry. This assumes that the information doesn't contradict itself. If any |
| // new information is gained, true is returned, otherwise false is returned to |
| // indicate that nothing was updated. |
| // |
| bool Relation::incorporate(unsigned Op, ValueInfo &VI) { |
| assert(!contradicts(Op, VI) && |
| "Cannot incorporate contradictory information!"); |
| |
| // If this is a relationship with a constant, make sure that we update the |
| // range that is possible for the value to have... |
| // |
| if (ConstantInt *C = dyn_cast<ConstantInt>(Val)) |
| if (Op >= ICmpInst::FIRST_ICMP_PREDICATE && |
| Op <= ICmpInst::LAST_ICMP_PREDICATE) { |
| ICmpInst::Predicate ipred = ICmpInst::Predicate(Op); |
| VI.getBounds() = |
| ICmpInst::makeConstantRange(ipred, C->getValue()) |
| .intersectWith(VI.getBounds()); |
| } |
| |
| switch (Rel) { |
| default: assert(0 && "Unknown prior value!"); |
| case Instruction::Add: Rel = Op; return true; |
| case ICmpInst::ICMP_EQ: |
| case ICmpInst::ICMP_NE: |
| case ICmpInst::ICMP_ULT: |
| case ICmpInst::ICMP_SLT: |
| case ICmpInst::ICMP_UGT: |
| case ICmpInst::ICMP_SGT: return false; // Nothing is more precise |
| case ICmpInst::ICMP_ULE: |
| case ICmpInst::ICMP_SLE: |
| if (Op == ICmpInst::ICMP_EQ || Op == ICmpInst::ICMP_ULT || |
| Op == ICmpInst::ICMP_SLT) { |
| Rel = Op; |
| return true; |
| } else if (Op == ICmpInst::ICMP_NE) { |
| Rel = Rel == ICmpInst::ICMP_ULE ? ICmpInst::ICMP_ULT : |
| ICmpInst::ICMP_SLT; |
| return true; |
| } |
| return false; |
| case ICmpInst::ICMP_UGE: |
| case ICmpInst::ICMP_SGE: |
| if (Op == ICmpInst::ICMP_EQ || ICmpInst::ICMP_UGT || |
| Op == ICmpInst::ICMP_SGT) { |
| Rel = Op; |
| return true; |
| } else if (Op == ICmpInst::ICMP_NE) { |
| Rel = Rel == ICmpInst::ICMP_UGE ? ICmpInst::ICMP_UGT : |
| ICmpInst::ICMP_SGT; |
| return true; |
| } |
| return false; |
| case FCmpInst::FCMP_OEQ: return false; // Nothing is more precise |
| case FCmpInst::FCMP_ONE: return false; // Nothing is more precise |
| case FCmpInst::FCMP_OLT: return false; // Nothing is more precise |
| case FCmpInst::FCMP_OGT: return false; // Nothing is more precise |
| case FCmpInst::FCMP_OLE: |
| if (Op == FCmpInst::FCMP_OEQ || Op == FCmpInst::FCMP_OLT) { |
| Rel = Op; |
| return true; |
| } else if (Op == FCmpInst::FCMP_ONE) { |
| Rel = FCmpInst::FCMP_OLT; |
| return true; |
| } |
| return false; |
| case FCmpInst::FCMP_OGE: |
| return Op == FCmpInst::FCMP_OLT; |
| if (Op == FCmpInst::FCMP_OEQ || Op == FCmpInst::FCMP_OGT) { |
| Rel = Op; |
| return true; |
| } else if (Op == FCmpInst::FCMP_ONE) { |
| Rel = FCmpInst::FCMP_OGT; |
| return true; |
| } |
| return false; |
| } |
| } |
| |
| // getImpliedResult - If this relationship between two values implies that |
| // the specified relationship is true or false, return that. If we cannot |
| // determine the result required, return Unknown. |
| // |
| Relation::KnownResult |
| Relation::getImpliedResult(unsigned Op) const { |
| if (Rel == Op) return KnownTrue; |
| if (Op >= ICmpInst::FIRST_ICMP_PREDICATE && |
| Op <= ICmpInst::LAST_ICMP_PREDICATE) { |
| if (Rel == unsigned(ICmpInst::getInversePredicate(ICmpInst::Predicate(Op)))) |
| return KnownFalse; |
| } else if (Op <= FCmpInst::LAST_FCMP_PREDICATE) { |
| if (Rel == unsigned(FCmpInst::getInversePredicate(FCmpInst::Predicate(Op)))) |
| return KnownFalse; |
| } |
| |
| switch (Rel) { |
| default: assert(0 && "Unknown prior value!"); |
| case ICmpInst::ICMP_EQ: |
| if (Op == ICmpInst::ICMP_ULE || Op == ICmpInst::ICMP_SLE || |
| Op == ICmpInst::ICMP_UGE || Op == ICmpInst::ICMP_SGE) return KnownTrue; |
| if (Op == ICmpInst::ICMP_ULT || Op == ICmpInst::ICMP_SLT || |
| Op == ICmpInst::ICMP_UGT || Op == ICmpInst::ICMP_SGT) return KnownFalse; |
| break; |
| case ICmpInst::ICMP_ULT: |
| case ICmpInst::ICMP_SLT: |
| if (Op == ICmpInst::ICMP_ULE || Op == ICmpInst::ICMP_SLE || |
| Op == ICmpInst::ICMP_NE) return KnownTrue; |
| if (Op == ICmpInst::ICMP_EQ) return KnownFalse; |
| break; |
| case ICmpInst::ICMP_UGT: |
| case ICmpInst::ICMP_SGT: |
| if (Op == ICmpInst::ICMP_UGE || Op == ICmpInst::ICMP_SGE || |
| Op == ICmpInst::ICMP_NE) return KnownTrue; |
| if (Op == ICmpInst::ICMP_EQ) return KnownFalse; |
| break; |
| case FCmpInst::FCMP_OEQ: |
| if (Op == FCmpInst::FCMP_OLE || Op == FCmpInst::FCMP_OGE) return KnownTrue; |
| if (Op == FCmpInst::FCMP_OLT || Op == FCmpInst::FCMP_OGT) return KnownFalse; |
| break; |
| case FCmpInst::FCMP_OLT: |
| if (Op == FCmpInst::FCMP_ONE || Op == FCmpInst::FCMP_OLE) return KnownTrue; |
| if (Op == FCmpInst::FCMP_OEQ) return KnownFalse; |
| break; |
| case FCmpInst::FCMP_OGT: |
| if (Op == FCmpInst::FCMP_ONE || Op == FCmpInst::FCMP_OGE) return KnownTrue; |
| if (Op == FCmpInst::FCMP_OEQ) return KnownFalse; |
| break; |
| case ICmpInst::ICMP_NE: |
| case ICmpInst::ICMP_SLE: |
| case ICmpInst::ICMP_ULE: |
| case ICmpInst::ICMP_UGE: |
| case ICmpInst::ICMP_SGE: |
| case FCmpInst::FCMP_ONE: |
| case FCmpInst::FCMP_OLE: |
| case FCmpInst::FCMP_OGE: |
| case FCmpInst::FCMP_FALSE: |
| case FCmpInst::FCMP_ORD: |
| case FCmpInst::FCMP_UNO: |
| case FCmpInst::FCMP_UEQ: |
| case FCmpInst::FCMP_UGT: |
| case FCmpInst::FCMP_UGE: |
| case FCmpInst::FCMP_ULT: |
| case FCmpInst::FCMP_ULE: |
| case FCmpInst::FCMP_UNE: |
| case FCmpInst::FCMP_TRUE: |
| break; |
| } |
| return Unknown; |
| } |
| |
| |
| //===----------------------------------------------------------------------===// |
| // Printing Support... |
| //===----------------------------------------------------------------------===// |
| |
| // print - Implement the standard print form to print out analysis information. |
| void CEE::print(std::ostream &O, const Module *M) const { |
| O << "\nPrinting Correlated Expression Info:\n"; |
| for (std::map<BasicBlock*, RegionInfo>::const_iterator I = |
| RegionInfoMap.begin(), E = RegionInfoMap.end(); I != E; ++I) |
| I->second.print(O); |
| } |
| |
| // print - Output information about this region... |
| void RegionInfo::print(std::ostream &OS) const { |
| if (ValueMap.empty()) return; |
| |
| OS << " RegionInfo for basic block: " << BB->getName() << "\n"; |
| for (std::map<Value*, ValueInfo>::const_iterator |
| I = ValueMap.begin(), E = ValueMap.end(); I != E; ++I) |
| I->second.print(OS, I->first); |
| OS << "\n"; |
| } |
| |
| // print - Output information about this value relation... |
| void ValueInfo::print(std::ostream &OS, Value *V) const { |
| if (Relationships.empty()) return; |
| |
| if (V) { |
| OS << " ValueInfo for: "; |
| WriteAsOperand(OS, V); |
| } |
| OS << "\n Bounds = " << Bounds << "\n"; |
| if (Replacement) { |
| OS << " Replacement = "; |
| WriteAsOperand(OS, Replacement); |
| OS << "\n"; |
| } |
| for (unsigned i = 0, e = Relationships.size(); i != e; ++i) |
| Relationships[i].print(OS); |
| } |
| |
| // print - Output this relation to the specified stream |
| void Relation::print(std::ostream &OS) const { |
| OS << " is "; |
| switch (Rel) { |
| default: OS << "*UNKNOWN*"; break; |
| case ICmpInst::ICMP_EQ: |
| case FCmpInst::FCMP_ORD: |
| case FCmpInst::FCMP_UEQ: |
| case FCmpInst::FCMP_OEQ: OS << "== "; break; |
| case ICmpInst::ICMP_NE: |
| case FCmpInst::FCMP_UNO: |
| case FCmpInst::FCMP_UNE: |
| case FCmpInst::FCMP_ONE: OS << "!= "; break; |
| case ICmpInst::ICMP_ULT: |
| case ICmpInst::ICMP_SLT: |
| case FCmpInst::FCMP_ULT: |
| case FCmpInst::FCMP_OLT: OS << "< "; break; |
| case ICmpInst::ICMP_UGT: |
| case ICmpInst::ICMP_SGT: |
| case FCmpInst::FCMP_UGT: |
| case FCmpInst::FCMP_OGT: OS << "> "; break; |
| case ICmpInst::ICMP_ULE: |
| case ICmpInst::ICMP_SLE: |
| case FCmpInst::FCMP_ULE: |
| case FCmpInst::FCMP_OLE: OS << "<= "; break; |
| case ICmpInst::ICMP_UGE: |
| case ICmpInst::ICMP_SGE: |
| case FCmpInst::FCMP_UGE: |
| case FCmpInst::FCMP_OGE: OS << ">= "; break; |
| } |
| |
| WriteAsOperand(OS, Val); |
| OS << "\n"; |
| } |
| |
| // Don't inline these methods or else we won't be able to call them from GDB! |
| void Relation::dump() const { print(*cerr.stream()); } |
| void ValueInfo::dump() const { print(*cerr.stream(), 0); } |
| void RegionInfo::dump() const { print(*cerr.stream()); } |