--- /dev/null
+//===- 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 <algorithm>
+
+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<Relation> 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<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 Relation's, 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(), 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(), 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<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; }
+
+ 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<Value*, unsigned> RankMap;
+ std::map<BasicBlock*, RegionInfo> 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<DominatorSet>();
+ AU.addRequired<DominatorTree>();
+ };
+
+ // 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<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) || isa<GlobalValue>(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);
+
+ 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<CEE> 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<DominatorSet>();
+ DT = &getAnalysis<DominatorTree>();
+
+ std::set<BasicBlock*> 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<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(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<BranchInst>(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<BranchInst>(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<SetCondInst>(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<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++;
+}
+
+
+// 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<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() == 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<ConstantBool>(Op1)) {
+
+ 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->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<BinaryOperator>(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<SetCondInst>(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<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 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<Instruction>(*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<SetCondInst>(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<Relation> &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<SetCondInst>(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<Constant>(Op0)) {
+ if (isa<Constant>(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<ConstantBool>(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<ConstantIntegral>(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<ConstantIntegral>(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<ConstantIntegral>(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<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 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); }
projects / oota-llvm.git / commitdiff