diff --git a/lib/Transforms/Scalar/CorrelatedExprs.cpp b/lib/Transforms/Scalar/CorrelatedExprs.cpp new file mode 100644 index 00000000000..9ac8a4a8939 --- /dev/null +++ b/lib/Transforms/Scalar/CorrelatedExprs.cpp @@ -0,0 +1,974 @@ +//===- CorrelatedExprs.cpp - Pass to detect and eliminated c.e.'s ---------===// +// +// Correlated Expression Elimination propogates information from conditional +// branches to blocks dominated by destinations of the branch. It propogates +// information from the condition check itself into the body of the branch, +// allowing transformations like these for example: +// +// if (i == 7) +// ... 4*i; // constant propogation +// +// 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. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Transforms/Scalar.h" +#include "llvm/Pass.h" +#include "llvm/Function.h" +#include "llvm/iTerminators.h" +#include "llvm/iOperators.h" +#include "llvm/ConstantHandling.h" +#include "llvm/Assembly/Writer.h" +#include "llvm/Analysis/Dominators.h" +#include "llvm/Transforms/Utils/Local.h" +#include "llvm/Support/ConstantRange.h" +#include "llvm/Support/CFG.h" +#include "Support/PostOrderIterator.h" +#include "Support/StatisticReporter.h" +#include + +namespace { + Statistic<>NumSetCCRemoved("cee\t\t- Number of setcc instruction eliminated"); + Statistic<>NumOperandsCann("cee\t\t- Number of operands cannonicalized"); + Statistic<>BranchRevectors("cee\t\t- Number of branches revectored"); + + class ValueInfo; + class Relation { + Value *Val; // Relation to what value? + Instruction::BinaryOps Rel; // SetCC 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; } + Instruction::BinaryOps getRelation() const { return Rel; } + + // contradicts - Return true if the relationship specified by the operand + // contradicts already known information. + // + bool contradicts(Instruction::BinaryOps 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(Instruction::BinaryOps Rel, ValueInfo &VI); + + // KnownResult - Whether or not this condition determines the result of a + // setcc 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(Instruction::BinaryOps 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 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 Relationships; + + // If information about this value is known or propogated 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->isIntegral() ? Ty : Type::IntTy), Replacement(0) {} + + // getBounds() - Return the constant bounds of the value... + const ConstantRange &getBounds() const { return Bounds; } + ConstantRange &getBounds() { return Bounds; } + + const std::vector &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 Relation's, so use it carefully. + // + Relation &getRelation(Value *V) { + // Binary search for V's entry... + std::vector::iterator I = + std::lower_bound(Relationships.begin(), Relationships.end(), 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::const_iterator I = + std::lower_bound(Relationships.begin(), Relationships.end(), 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 RegionInfo { + BasicBlock *BB; + + // ValueMap - Tracks the ValueInformation known for this region + typedef std::map 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; } + + const RegionInfo &operator=(const RegionInfo &RI) { + ValueMap = RI.ValueMap; + return *this; + } + + // print - Output information about this region... + void print(std::ostream &OS) 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; + } + }; + + /// CEE - Correlated Expression Elimination + class CEE : public FunctionPass { + std::map RankMap; + std::map RegionInfoMap; + DominatorSet *DS; + DominatorTree *DT; + public: + virtual bool runOnFunction(Function &F); + + // We don't modify the program, so we preserve all analyses + virtual void getAnalysisUsage(AnalysisUsage &AU) const { + //AU.preservesCFG(); + AU.addRequired(); + AU.addRequired(); + }; + + // print - Implement the standard print form to print out analysis + // information. + virtual void print(std::ostream &O, const Module *M) const; + + virtual void releaseMemory() { + RegionInfoMap.clear(); + RankMap.clear(); + } + + private: + RegionInfo &getRegionInfo(BasicBlock *BB) { + std::map::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(V) || isa(V)) return 0; + std::map::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 &VisitedBlocks); + + BasicBlock *isCorrelatedBranchBlock(BasicBlock *BB, RegionInfo &RI); + void PropogateBranchInfo(BranchInst *BI); + void PropogateEquality(Value *Op0, Value *Op1, RegionInfo &RI); + void PropogateRelation(Instruction::BinaryOps Opcode, Value *Op0, + Value *Op1, RegionInfo &RI); + void UpdateUsersOfValue(Value *V, RegionInfo &RI); + void IncorporateInstruction(Instruction *Inst, RegionInfo &RI); + void ComputeReplacements(RegionInfo &RI); + + + // getSetCCResult - Given a setcc 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 getSetCCResult(SetCondInst *SC, const RegionInfo &RI); + + + bool SimplifyBasicBlock(BasicBlock &BB, const RegionInfo &RI); + bool SimplifyInstruction(Instruction *Inst, const RegionInfo &RI); + }; + RegisterOpt X("cee", "Correlated Expression Elimination"); +} + +Pass *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. + DS = &getAnalysis(); + DT = &getAnalysis(); + + std::set VisitedBlocks; + return TransformRegion(&F.getEntryNode(), VisitedBlocks); +} + +// 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, +// propogating 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 &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(std::cerr)); + + // Simplify the contents of this block... + bool Changed = SimplifyBasicBlock(*BB, RI); + + // Get the terminator of this basic block... + TerminatorInst *TI = BB->getTerminator(); + + // If this is a conditional branch, make sure that there is a branch target + // for each successor that can hold any information gleaned from the branch, + // by breaking any critical edges that may be laying about. + // + if (TI->getNumSuccessors() > 1) { + // If any of the successors has multiple incoming branches, add a new dummy + // destination branch that only contains an unconditional branch to the real + // target. + for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) { + BasicBlock *Succ = TI->getSuccessor(i); + // If there is more than one predecessor of the destination block, break + // this critical edge by inserting a new block. This updates dominatorset + // and dominatortree information. + // + if (isCriticalEdge(TI, i)) + SplitCriticalEdge(TI, i, this); + } + } + + // 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 propogate the + // information down now. + // + DominatorTree::Node *BBN = (*DT)[BB]; + for (unsigned i = 0, e = BBN->getChildren().size(); i != e; ++i) { + BasicBlock *Dominated = BBN->getChildren()[i]->getNode(); + assert(RegionInfoMap.find(Dominated) == RegionInfoMap.end() && + "RegionInfo should be calculated in dominanace order!"); + getRegionInfo(Dominated) = RI; + } + + // Now that all of our successors have information if they deserve it, + // propogate any information our terminator instruction finds to our + // successors. + if (BranchInst *BI = dyn_cast(TI)) + if (BI->isConditional()) + PropogateBranchInfo(BI); + + // 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 (BasicBlock *Dest = isCorrelatedBranchBlock(TI->getSuccessor(i), RI)){ + TI->setSuccessor(i, Dest); + ++BranchRevectors; + } + } + + // Now that all of our successors have information, recursively process them. + for (unsigned i = 0, e = BBN->getChildren().size(); i != e; ++i) + Changed |= TransformRegion(BBN->getChildren()[i]->getNode(), VisitedBlocks); + + // for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) + //Changed |= TransformRegion(TI->getSuccessor(i), VisitedBlocks); + + return Changed; +} + +// If this block is a simple block not in the current region, which contains +// only a conditional branch, we determine 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. +// +BasicBlock *CEE::isCorrelatedBranchBlock(BasicBlock *BB, RegionInfo &RI) { + // Check to see if we dominate the block. If so, this block will get the + // condition turned to a constant anyway. + // + //if (DS->dominates(RI.getEntryBlock(), BB)) + // return 0; + + // Check to see if this is a conditional branch... + if (BranchInst *BI = dyn_cast(BB->getTerminator())) + if (BI->isConditional()) { + // Make sure that the block is either empty, or only contains a setcc. + if (BB->size() == 1 || + (BB->size() == 2 && &BB->front() == BI->getCondition() && + BI->getCondition()->use_size() == 1)) + if (SetCondInst *SCI = dyn_cast(BI->getCondition())) { + Relation::KnownResult Result = getSetCCResult(SCI, RI); + + if (Result == Relation::KnownTrue) + return BI->getSuccessor(0); + else if (Result == Relation::KnownFalse) + return BI->getSuccessor(1); + } + } + return 0; +} + +// 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::aiterator I = F.abegin(), E = F.aend(); I != E; ++I) + RankMap[I] = Rank++; + + // Number the instructions in reverse post order... + ReversePostOrderTraversal RPOT(&F); + for (ReversePostOrderTraversal::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++; +} + + +// PropogateBranchInfo - When this method is invoked, we need to propogate +// 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::PropogateBranchInfo(BranchInst *BI) { + assert(BI->isConditional() && "Must be a conditional branch!"); + BasicBlock *BB = BI->getParent(); + BasicBlock *TrueBB = BI->getSuccessor(0); + BasicBlock *FalseBB = BI->getSuccessor(1); + + // Propogate information into the true block... + // + PropogateEquality(BI->getCondition(), ConstantBool::True, + getRegionInfo(TrueBB)); + + // Propogate information into the false block... + // + PropogateEquality(BI->getCondition(), ConstantBool::False, + getRegionInfo(FalseBB)); +} + + +// PropogateEquality - If we discover that two values are equal to each other in +// a specified region, propogate this knowledge recursively. +// +void CEE::PropogateEquality(Value *Op0, Value *Op1, RegionInfo &RI) { + if (Op0 == Op1) return; // Gee whiz. Are these really equal each other? + + if (isa(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() == Instruction::SetEQ) + 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. + // + if (ConstantBool *CB = dyn_cast(Op1)) { + + if (Instruction *Inst = dyn_cast(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->getValue() && Inst->getOpcode() == Instruction::And) { + PropogateEquality(Inst->getOperand(0), CB, RI); + PropogateEquality(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->getValue() && Inst->getOpcode() == Instruction::Or) { + PropogateEquality(Inst->getOperand(0), CB, RI); + PropogateEquality(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(Inst)) + if (BinaryOperator::isNot(BOp)) + PropogateEquality(BinaryOperator::getNotArgument(BOp), + ConstantBool::get(!CB->getValue()), RI); + + // If we know the value of a SetCC instruction, propogate the information + // about the relation into this region as well. + // + if (SetCondInst *SCI = dyn_cast(Inst)) { + if (CB->getValue()) { // If we know the condition is true... + // Propogate info about the LHS to the RHS & RHS to LHS + PropogateRelation(SCI->getOpcode(), SCI->getOperand(0), + SCI->getOperand(1), RI); + PropogateRelation(SCI->getSwappedCondition(), + SCI->getOperand(1), SCI->getOperand(0), RI); + + } else { // If we know the condition is false... + // We know the opposite of the condition is true... + Instruction::BinaryOps C = SCI->getInverseCondition(); + + PropogateRelation(C, SCI->getOperand(0), SCI->getOperand(1), RI); + PropogateRelation(SetCondInst::getSwappedCondition(C), + SCI->getOperand(1), SCI->getOperand(0), RI); + } + } + } + } + + // Propogate information about Op0 to Op1 & visa versa + PropogateRelation(Instruction::SetEQ, Op0, Op1, RI); + PropogateRelation(Instruction::SetEQ, Op1, Op0, RI); +} + + +// PropogateRelation - We know that the specified relation is true in all of the +// blocks in the specified region. Propogate the information about Op0 and +// anything derived from it into this region. +// +void CEE::PropogateRelation(Instruction::BinaryOps 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 PropogateRelation. + // + if (isa(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 propogating, ignore this info. Something bad must have happened! + // + if (Op1R.contradicts(Opcode, VI)) { + Op1R.contradicts(Opcode, VI); + std::cerr << "Contradiction found for opcode: " + << Instruction::getOpcodeName(Opcode) << "\n"; + Op1R.print(std::cerr); + return; + } + + // If the information propogted is new, then we want process the uses of this + // instruction to propogate the information down to them. + // + if (Op1R.incorporate(Opcode, VI)) + UpdateUsersOfValue(Op0, RI); +} + + +// UpdateUsersOfValue - The information about V in this region has been updated. +// Propogate 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(*I)) { + // If this is an instruction using a value that we know something about, + // try to propogate information to the value produced by the + // instruction. We can only do this if it is an instruction we can + // propogate 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 (DS->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 (SetCondInst *SCI = dyn_cast(Inst)) { + // See if we can figure out a result for this instruction... + Relation::KnownResult Result = getSetCCResult(SCI, RI); + if (Result != Relation::Unknown) { + PropogateEquality(SCI, Result ? ConstantBool::True : ConstantBool::False, + 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 cannonicalizing 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 = VI.getBounds().getSingleElement(); + + // 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 &Relationships = VI.getRelationships(); + for (unsigned i = 0, e = Relationships.size(); i != e; ++i) + if (Relationships[i].getRelation() == Instruction::SetEQ) { + 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 (SetCondInst *SCI = dyn_cast(Inst)) { + // Try to simplify a setcc instruction based on inherited information + Relation::KnownResult Result = getSetCCResult(SCI, RI); + if (Result != Relation::Unknown) { + DEBUG(std::cerr << "Replacing setcc with " << Result + << " constant: " << SCI); + + SCI->replaceAllUsesWith(ConstantBool::get((bool)Result)); + // The instruction is now dead, remove it from the program. + SCI->getParent()->getInstList().erase(SCI); + ++NumSetCCRemoved; + Changed = true; + } + } + } + + return Changed; +} + +// SimplifyInstruction - Inspect the operands of the instruction, converting +// them to their cannonical 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. + DEBUG(std::cerr << "In Inst: " << I << " Replacing operand #" << i + << " with " << Repl << "\n"); + I->setOperand(i, Repl); + Changed = true; + ++NumOperandsCann; + } + + return Changed; +} + + +// SimplifySetCC - Try to simplify a setcc instruction based on information +// inherited from a dominating setcc instruction. V is one of the operands to +// the setcc 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::getSetCCResult(SetCondInst *SCI, + const RegionInfo &RI) { + Value *Op0 = SCI->getOperand(0), *Op1 = SCI->getOperand(1); + Instruction::BinaryOps Opcode = SCI->getOpcode(); + + if (isa(Op0)) { + if (isa(Op1)) { + if (Constant *Result = ConstantFoldInstruction(SCI)) { + // Wow, this is easy, directly eliminate the SetCondInst. + DEBUG(std::cerr << "Replacing setcc with constant fold: " << SCI); + return cast(Result)->getValue() + ? Relation::KnownTrue : Relation::KnownFalse; + } + } else { + // We want to swap this instruction so that operand #0 is the constant. + std::swap(Op0, Op1); + Opcode = SCI->getSwappedCondition(); + } + } + + // 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 setcc. + // + if (ConstantIntegral *C = dyn_cast(Op1)) { + // Check to see if we already know the result of this comparison... + ConstantRange R = ConstantRange(Opcode, C); + 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(Opcode); + } + } + return Result; +} + +//===----------------------------------------------------------------------===// +// Relation Implementation +//===----------------------------------------------------------------------===// + +// CheckCondition - Return true if the specified condition is false. Bound may +// be null. +static bool CheckCondition(Constant *Bound, Constant *C, + Instruction::BinaryOps BO) { + assert(C != 0 && "C is not specified!"); + if (Bound == 0) return false; + + ConstantBool *Val; + switch (BO) { + default: assert(0 && "Unknown Condition code!"); + case Instruction::SetEQ: Val = *Bound == *C; break; + case Instruction::SetNE: Val = *Bound != *C; break; + case Instruction::SetLT: Val = *Bound < *C; break; + case Instruction::SetGT: Val = *Bound > *C; break; + case Instruction::SetLE: Val = *Bound <= *C; break; + case Instruction::SetGE: Val = *Bound >= *C; break; + } + + // ConstantHandling code may not succeed in the comparison... + if (Val == 0) return false; + return !Val->getValue(); // Return true if the condition is false... +} + +// contradicts - Return true if the relationship specified by the operand +// contradicts already known information. +// +bool Relation::contradicts(Instruction::BinaryOps 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 (ConstantIntegral *C = dyn_cast(Val)) + if (ConstantRange(Op, C).intersectWith(VI.getBounds()).isEmptySet()) + return true; + + switch (Rel) { + default: assert(0 && "Unknown Relationship code!"); + case Instruction::Add: return false; // Nothing known, nothing contradicts + case Instruction::SetEQ: + return Op == Instruction::SetLT || Op == Instruction::SetGT || + Op == Instruction::SetNE; + case Instruction::SetNE: return Op == Instruction::SetEQ; + case Instruction::SetLE: return Op == Instruction::SetGT; + case Instruction::SetGE: return Op == Instruction::SetLT; + case Instruction::SetLT: + return Op == Instruction::SetEQ || Op == Instruction::SetGT || + Op == Instruction::SetGE; + case Instruction::SetGT: + return Op == Instruction::SetEQ || Op == Instruction::SetLT || + Op == Instruction::SetLE; + } +} + +// 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(Instruction::BinaryOps 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 (ConstantIntegral *C = dyn_cast(Val)) + VI.getBounds() = ConstantRange(Op, C).intersectWith(VI.getBounds()); + + switch (Rel) { + default: assert(0 && "Unknown prior value!"); + case Instruction::Add: Rel = Op; return true; + case Instruction::SetEQ: return false; // Nothing is more precise + case Instruction::SetNE: return false; // Nothing is more precise + case Instruction::SetLT: return false; // Nothing is more precise + case Instruction::SetGT: return false; // Nothing is more precise + case Instruction::SetLE: + if (Op == Instruction::SetEQ || Op == Instruction::SetLT) { + Rel = Op; + return true; + } else if (Op == Instruction::SetNE) { + Rel = Instruction::SetLT; + return true; + } + return false; + case Instruction::SetGE: return Op == Instruction::SetLT; + if (Op == Instruction::SetEQ || Op == Instruction::SetGT) { + Rel = Op; + return true; + } else if (Op == Instruction::SetNE) { + Rel = Instruction::SetGT; + 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(Instruction::BinaryOps Op) const { + if (Rel == Op) return KnownTrue; + if (Rel == SetCondInst::getInverseCondition(Op)) return KnownFalse; + + switch (Rel) { + default: assert(0 && "Unknown prior value!"); + case Instruction::SetEQ: + if (Op == Instruction::SetLE || Op == Instruction::SetGE) return KnownTrue; + if (Op == Instruction::SetLT || Op == Instruction::SetGT) return KnownFalse; + break; + case Instruction::SetLT: + if (Op == Instruction::SetNE || Op == Instruction::SetLE) return KnownTrue; + if (Op == Instruction::SetEQ) return KnownFalse; + break; + case Instruction::SetGT: + if (Op == Instruction::SetNE || Op == Instruction::SetGE) return KnownTrue; + if (Op == Instruction::SetEQ) return KnownFalse; + break; + case Instruction::SetNE: + case Instruction::SetLE: + case Instruction::SetGE: + case Instruction::Add: + 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::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::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 Instruction::SetEQ: OS << "== "; break; + case Instruction::SetNE: OS << "!= "; break; + case Instruction::SetLT: OS << "< "; break; + case Instruction::SetGT: OS << "> "; break; + case Instruction::SetLE: OS << "<= "; break; + case Instruction::SetGE: OS << ">= "; break; + } + + WriteAsOperand(OS, Val); + OS << "\n"; +} + +void Relation::dump() const { print(std::cerr); } +void ValueInfo::dump() const { print(std::cerr, 0); }