lib/Transforms/Scalar/PredicateSimplifier.cpp - platform/external/llvm - Gitiles

 //===-- PredicateSimplifier.cpp - Path Sensitive Simplifier -----------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file was developed by Nick Lewycky and is distributed under the
 // University of Illinois Open Source License. See LICENSE.TXT for details.
 //
 //===------------------------------------------------------------------===//
 //
 // Path-sensitive optimizer. In a branch where x == y, replace uses of
 // x with y. Permits further optimization, such as the elimination of
 // the unreachable call:
 //
 // void test(int *p, int *q)
 // {
 //   if (p != q)
 //     return;
 //
 //   if (*p != *q)
 //     foo(); // unreachable
 // }
 //
 //===------------------------------------------------------------------===//
 //
 // This optimization works by substituting %q for %p when protected by a
 // conditional that assures us of that fact. Properties are stored as
 // relationships between two values.
 //
 //===------------------------------------------------------------------===//

 #define DEBUG_TYPE "predsimplify"
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Constants.h"
 #include "llvm/Instructions.h"
 #include "llvm/Pass.h"
 #include "llvm/ADT/EquivalenceClasses.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Analysis/Dominators.h"
 #include "llvm/Support/CFG.h"
 #include "llvm/Support/Debug.h"
 #include <iostream>
 using namespace llvm;

 namespace {
   Statistic<>
   NumVarsReplaced("predsimplify", "Number of argument substitutions");
   Statistic<>
   NumInstruction("predsimplify", "Number of instructions removed");
   Statistic<>
   NumSwitchCases("predsimplify", "Number of switch cases removed");
   Statistic<>
   NumBranches("predsimplify", "Number of branches made unconditional");

   /// Used for choosing the canonical Value in a synonym set.
   /// Leaves the better one in V1. Returns whether a swap took place.
   static void order(Value *&V1, Value *&V2) {
     if (isa<Constant>(V2)) {
       if (!isa<Constant>(V1)) {
         std::swap(V1, V2);
         return;
       }
     } else if (isa<Argument>(V2)) {
       if (!isa<Constant>(V1) && !isa<Argument>(V1)) {
         std::swap(V1, V2);
         return;
       }
     }
     if (User *U1 = dyn_cast<User>(V1)) {
       for (User::const_op_iterator I = U1->op_begin(), E = U1->op_end();
            I != E; ++I) {
         if (*I == V2) {
           std::swap(V1, V2);
           return;
         }
       }
     }
     return;
   }

   /// Represents the set of equivalent Value*s and provides insertion
   /// and fast lookup. Also stores the set of inequality relationships.
   class PropertySet {
     struct Property;
     class EquivalenceClasses<Value *> union_find;
   public:
     typedef std::vector<Property>::iterator       PropertyIterator;
     typedef std::vector<Property>::const_iterator ConstPropertyIterator;

     enum Ops {
       EQ,
       NE
     };

     Value *canonicalize(Value *V) const {
       Value *C = lookup(V);
       return C ? C : V;
     }

     Value *lookup(Value *V) const {
       EquivalenceClasses<Value *>::member_iterator SI =
           union_find.findLeader(V);
       if (SI == union_find.member_end()) return NULL;
       return *SI;
     }

     bool empty() const {
       return union_find.empty();
     }

     void addEqual(Value *V1, Value *V2) {
       // If %x = 0. and %y = -0., seteq %x, %y is true, but
       // copysign(%x) is not the same as copysign(%y).
       if (V2->getType()->isFloatingPoint()) return;

       order(V1, V2);
       if (isa<Constant>(V2)) return; // refuse to set false == true.

       DEBUG(std::cerr << "equal: " << *V1 << " and " << *V2 << "\n");
       union_find.unionSets(V1, V2);
       addImpliedProperties(EQ, V1, V2);
     }

     void addNotEqual(Value *V1, Value *V2) {
       // If %x = NAN then seteq %x, %x is false.
       if (V2->getType()->isFloatingPoint()) return;

       DEBUG(std::cerr << "not equal: " << *V1 << " and " << *V2 << "\n");
       if (findProperty(NE, V1, V2) != Properties.end())
         return; // found.

       // Add the property.
       Properties.push_back(Property(NE, V1, V2));
       addImpliedProperties(NE, V1, V2);
     }

     PropertyIterator findProperty(Ops Opcode, Value *V1, Value *V2) {
       assert(Opcode != EQ && "Can't findProperty on EQ."
              "Use the lookup method instead.");

       V1 = canonicalize(V1);
       V2 = canonicalize(V2);

       // Does the property already exist?
       for (PropertyIterator I = Properties.begin(), E = Properties.end();
            I != E; ++I) {
         if (I->Opcode != Opcode) continue;

         I->V1 = canonicalize(I->V1);
         I->V2 = canonicalize(I->V2);
         if ((I->V1 == V1 && I->V2 == V2) ||
             (I->V1 == V2 && I->V2 == V1)) {
           return I; // Found.
         }
       }
       return Properties.end();
     }

     ConstPropertyIterator
     findProperty(Ops Opcode, Value *V1, Value *V2) const {
       assert(Opcode != EQ && "Can't findProperty on EQ."
              "Use the lookup method instead.");

       V1 = canonicalize(V1);
       V2 = canonicalize(V2);

       // Does the property already exist?
       for (ConstPropertyIterator I = Properties.begin(),
            E = Properties.end(); I != E; ++I) {
         if (I->Opcode != Opcode) continue;

         Value *v1 = canonicalize(I->V1),
               *v2 = canonicalize(I->V2);
         if ((v1 == V1 && v2 == V2) ||
             (v1 == V2 && v2 == V1)) {
           return I; // Found.
         }
       }
       return Properties.end();
     }

   private:
     // Represents Head OP [Tail1, Tail2, ...]
     // For example: %x != %a, %x != %b.
     struct Property {
       Property(Ops opcode, Value *v1, Value *v2)
         : Opcode(opcode), V1(v1), V2(v2)
       { assert(opcode != EQ && "Equality belongs in the synonym set, "
                "not a property."); }

       Ops Opcode;
       Value *V1, *V2;
     };

     void add(Ops Opcode, Value *V1, Value *V2, bool invert) {
       switch (Opcode) {
         case EQ:
           if (invert) addNotEqual(V1, V2);
           else        addEqual(V1, V2);
           break;
         case NE:
           if (invert) addEqual(V1, V2);
           else        addNotEqual(V1, V2);
           break;
         default:
           assert(0 && "Unknown property opcode.");
       }
     }

     // Finds the properties implied by a equivalence and adds them too.
     // Example: ("seteq %a, %b", true,  EQ) --> (%a, %b, EQ)
     //          ("seteq %a, %b", false, EQ) --> (%a, %b, NE)
     void addImpliedProperties(Ops Opcode, Value *V1, Value *V2) {
       order(V1, V2);

       if (BinaryOperator *BO = dyn_cast<BinaryOperator>(V2)) {
         switch (BO->getOpcode()) {
         case Instruction::SetEQ:
           if (V1 == ConstantBool::True)
             add(Opcode, BO->getOperand(0), BO->getOperand(1), false);
           if (V1 == ConstantBool::False)
             add(Opcode, BO->getOperand(0), BO->getOperand(1), true);
           break;
         case Instruction::SetNE:
           if (V1 == ConstantBool::True)
             add(Opcode, BO->getOperand(0), BO->getOperand(1), true);
           if (V1 == ConstantBool::False)
             add(Opcode, BO->getOperand(0), BO->getOperand(1), false);
           break;
         case Instruction::SetLT:
         case Instruction::SetGT:
           if (V1 == ConstantBool::True)
             add(Opcode, BO->getOperand(0), BO->getOperand(1), true);
           break;
         case Instruction::SetLE:
         case Instruction::SetGE:
           if (V1 == ConstantBool::False)
             add(Opcode, BO->getOperand(0), BO->getOperand(1), true);
           break;
         case Instruction::And:
           if (V1 == ConstantBool::True) {
             add(Opcode, ConstantBool::True, BO->getOperand(0), false);
             add(Opcode, ConstantBool::True, BO->getOperand(1), false);
           }
           break;
         case Instruction::Or:
           if (V1 == ConstantBool::False) {
             add(Opcode, ConstantBool::False, BO->getOperand(0), false);
             add(Opcode, ConstantBool::False, BO->getOperand(1), false);
           }
           break;
         case Instruction::Xor:
           if (V1 == ConstantBool::True) {
             if (BO->getOperand(0) == ConstantBool::True)
               add(Opcode, ConstantBool::False, BO->getOperand(1), false);
             if (BO->getOperand(1) == ConstantBool::True)
               add(Opcode, ConstantBool::False, BO->getOperand(0), false);
           }
           if (V1 == ConstantBool::False) {
             if (BO->getOperand(0) == ConstantBool::True)
               add(Opcode, ConstantBool::True, BO->getOperand(1), false);
             if (BO->getOperand(1) == ConstantBool::True)
               add(Opcode, ConstantBool::True, BO->getOperand(0), false);
           }
           break;
         default:
           break;
         }
       } else if (SelectInst *SI = dyn_cast<SelectInst>(V2)) {
         if (Opcode != EQ && Opcode != NE) return;

         ConstantBool *True  = (Opcode==EQ) ? ConstantBool::True
                                            : ConstantBool::False,
                      *False = (Opcode==EQ) ? ConstantBool::False
                                            : ConstantBool::True;

         if (V1 == SI->getTrueValue())
           addEqual(SI->getCondition(), True);
         else if (V1 == SI->getFalseValue())
           addEqual(SI->getCondition(), False);
         else if (Opcode == EQ)
           assert("Result of select not equal to either value.");
       }
     }

   public:
 #ifdef DEBUG
     void debug(std::ostream &os) const {
       for (EquivalenceClasses<Value*>::iterator I = union_find.begin(),
            E = union_find.end(); I != E; ++I) {
         if (!I->isLeader()) continue;
         for (EquivalenceClasses<Value*>::member_iterator MI =
              union_find.member_begin(I); MI != union_find.member_end(); ++MI)
           std::cerr << **MI << " ";
         std::cerr << "\n--\n";
       }
     }
 #endif

     std::vector<Property> Properties;
   };

   /// PredicateSimplifier - This class is a simplifier that replaces
   /// one equivalent variable with another. It also tracks what
   /// can't be equal and will solve setcc instructions when possible.
   class PredicateSimplifier : public FunctionPass {
   public:
     bool runOnFunction(Function &F);
     virtual void getAnalysisUsage(AnalysisUsage &AU) const;

   private:
     // Try to replace the Use of the instruction with something simpler.
     Value *resolve(SetCondInst *SCI, const PropertySet &);
     Value *resolve(BinaryOperator *BO, const PropertySet &);
     Value *resolve(SelectInst *SI, const PropertySet &);
     Value *resolve(Value *V, const PropertySet &);

     // Used by terminator instructions to proceed from the current basic
     // block to the next. Verifies that "current" dominates "next",
     // then calls visitBasicBlock.
     void proceedToSuccessor(PropertySet &CurrentPS, PropertySet &NextPS,
                   DominatorTree::Node *Current, DominatorTree::Node *Next);
     void proceedToSuccessor(PropertySet &CurrentPS,
                   DominatorTree::Node *Current, DominatorTree::Node *Next);

     // Visits each instruction in the basic block.
     void visitBasicBlock(DominatorTree::Node *DTNode,
                          PropertySet &KnownProperties);

     // For each instruction, add the properties to KnownProperties.
     void visit(Instruction *I, DominatorTree::Node *, PropertySet &);
     void visit(TerminatorInst *TI, DominatorTree::Node *, PropertySet &);
     void visit(BranchInst *BI, DominatorTree::Node *, PropertySet &);
     void visit(SwitchInst *SI, DominatorTree::Node *, PropertySet);
     void visit(LoadInst *LI, DominatorTree::Node *, PropertySet &);
     void visit(StoreInst *SI, DominatorTree::Node *, PropertySet &);
     void visit(BinaryOperator *BO, DominatorTree::Node *, PropertySet &);

     DominatorTree *DT;
     bool modified;
   };

   RegisterPass<PredicateSimplifier> X("predsimplify",
                                       "Predicate Simplifier");
 }

 FunctionPass *llvm::createPredicateSimplifierPass() {
   return new PredicateSimplifier();
 }

 bool PredicateSimplifier::runOnFunction(Function &F) {
   DT = &getAnalysis<DominatorTree>();

   modified = false;
   PropertySet KnownProperties;
   visitBasicBlock(DT->getRootNode(), KnownProperties);
   return modified;
 }

 void PredicateSimplifier::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addRequired<DominatorTree>();
 }

 // resolve catches cases addProperty won't because it wasn't used as a
 // condition in the branch, and that visit won't, because the instruction
 // was defined outside of the scope that the properties apply to.
 Value *PredicateSimplifier::resolve(SetCondInst *SCI,
                                     const PropertySet &KP) {
   // Attempt to resolve the SetCondInst to a boolean.

   Value *SCI0 = resolve(SCI->getOperand(0), KP),
         *SCI1 = resolve(SCI->getOperand(1), KP);
   PropertySet::ConstPropertyIterator NE =
                    KP.findProperty(PropertySet::NE, SCI0, SCI1);

   if (NE != KP.Properties.end()) {
     switch (SCI->getOpcode()) {
       case Instruction::SetEQ:
         return ConstantBool::False;
       case Instruction::SetNE:
         return ConstantBool::True;
       case Instruction::SetLE:
       case Instruction::SetGE:
       case Instruction::SetLT:
       case Instruction::SetGT:
         break;
       default:
         assert(0 && "Unknown opcode in SetCondInst.");
         break;
     }
   }

   ConstantIntegral *CI1 = dyn_cast<ConstantIntegral>(SCI0),
                    *CI2 = dyn_cast<ConstantIntegral>(SCI1);

   if (!CI1 || !CI2) return SCI;

   switch(SCI->getOpcode()) {
     case Instruction::SetLE:
     case Instruction::SetGE:
     case Instruction::SetEQ:
       if (CI1->getRawValue() == CI2->getRawValue())
         return ConstantBool::True;
       else
         return ConstantBool::False;
     case Instruction::SetLT:
     case Instruction::SetGT:
     case Instruction::SetNE:
       if (CI1->getRawValue() == CI2->getRawValue())
         return ConstantBool::False;
       else
         return ConstantBool::True;
     default:
       assert(0 && "Unknown opcode in SetContInst.");
       break;
   }
 }

 Value *PredicateSimplifier::resolve(BinaryOperator *BO,
                                     const PropertySet &KP) {
   if (SetCondInst *SCI = dyn_cast<SetCondInst>(BO))
     return resolve(SCI, KP);

   DEBUG(std::cerr << "BO->getOperand(1) = " << *BO->getOperand(1) << "\n");

   Value *lhs = resolve(BO->getOperand(0), KP),
         *rhs = resolve(BO->getOperand(1), KP);
   ConstantIntegral *CI1 = dyn_cast<ConstantIntegral>(lhs);
   ConstantIntegral *CI2 = dyn_cast<ConstantIntegral>(rhs);

   DEBUG(std::cerr << "resolveBO: lhs = " << *lhs
                   << ", rhs = " << *rhs << "\n");
   if (CI1) DEBUG(std::cerr << "CI1 = " << *CI1);
   if (CI2) DEBUG(std::cerr << "CI2 = " << *CI2);

   if (!CI1 || !CI2) return BO;

   Value *V = ConstantExpr::get(BO->getOpcode(), CI1, CI2);
   if (V) return V;
   return BO;
 }

 Value *PredicateSimplifier::resolve(SelectInst *SI, const PropertySet &KP) {
   Value *Condition = resolve(SI->getCondition(), KP);
   if (Condition == ConstantBool::True)
     return resolve(SI->getTrueValue(), KP);
   else if (Condition == ConstantBool::False)
     return resolve(SI->getFalseValue(), KP);
   return SI;
 }

 Value *PredicateSimplifier::resolve(Value *V, const PropertySet &KP) {
   if (isa<Constant>(V) || isa<BasicBlock>(V) || KP.empty()) return V;

   V = KP.canonicalize(V);

   DEBUG(std::cerr << "peering into " << *V << "\n");

   if (BinaryOperator *BO = dyn_cast<BinaryOperator>(V))
     return resolve(BO, KP);
   else if (SelectInst *SI = dyn_cast<SelectInst>(V))
     return resolve(SI, KP);

   return V;
 }

 void PredicateSimplifier::visitBasicBlock(DominatorTree::Node *DTNode,
                                           PropertySet &KnownProperties) {
   BasicBlock *BB = DTNode->getBlock();
   for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
     visit(I, DTNode, KnownProperties);
   }
 }

 void PredicateSimplifier::visit(Instruction *I, DominatorTree::Node *DTNode,
                                 PropertySet &KnownProperties) {
   DEBUG(std::cerr << "Considering instruction " << *I << "\n");
   DEBUG(KnownProperties.debug(std::cerr));

   // Try to replace whole instruction.
   Value *V = resolve(I, KnownProperties);
   assert(V && "resolve not supposed to return NULL.");
   if (V != I) {
     modified = true;
     ++NumInstruction;
     I->replaceAllUsesWith(V);
     I->eraseFromParent();
     return;
   }

   // Try to substitute operands.
   for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
     Value *Oper = I->getOperand(i);
     Value *V = resolve(Oper, KnownProperties);
     assert(V && "resolve not supposed to return NULL.");
     if (V != Oper) {
       modified = true;
       ++NumVarsReplaced;
       DEBUG(std::cerr << "resolving " << *I);
       I->setOperand(i, V);
       DEBUG(std::cerr << "into " << *I);
     }
   }

   if (TerminatorInst *TI = dyn_cast<TerminatorInst>(I))
     visit(TI, DTNode, KnownProperties);
   else if (LoadInst *LI = dyn_cast<LoadInst>(I))
     visit(LI, DTNode, KnownProperties);
   else if (StoreInst *SI = dyn_cast<StoreInst>(I))
     visit(SI, DTNode, KnownProperties);
   else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I))
     visit(BO, DTNode, KnownProperties);
 }

 void PredicateSimplifier::proceedToSuccessor(PropertySet &CurrentPS,
     PropertySet &NextPS, DominatorTree::Node *Current,
     DominatorTree::Node *Next) {
   if (Next->getBlock()->getSinglePredecessor() == Current->getBlock())
     proceedToSuccessor(NextPS, Current, Next);
   else
     proceedToSuccessor(CurrentPS, Current, Next);
 }

 void PredicateSimplifier::proceedToSuccessor(PropertySet &KP,
     DominatorTree::Node *Current, DominatorTree::Node *Next) {
   if (Current->properlyDominates(Next))
     visitBasicBlock(Next, KP);
 }

 void PredicateSimplifier::visit(TerminatorInst *TI,
                                 DominatorTree::Node *Node, PropertySet &KP){
   if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
     visit(BI, Node, KP);
     return;
   }
   if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
     visit(SI, Node, KP);
     return;
   }

   for (unsigned i = 0, E = TI->getNumSuccessors(); i != E; ++i) {
     BasicBlock *BB = TI->getSuccessor(i);
     PropertySet KPcopy(KP);
     proceedToSuccessor(KPcopy, Node, DT->getNode(TI->getSuccessor(i)));
   }
 }

 void PredicateSimplifier::visit(BranchInst *BI,
                                 DominatorTree::Node *Node, PropertySet &KP){
   if (BI->isUnconditional()) {
     proceedToSuccessor(KP, Node, DT->getNode(BI->getSuccessor(0)));
     return;
   }

   Value *Condition = BI->getCondition();

   BasicBlock *TrueDest  = BI->getSuccessor(0),
              *FalseDest = BI->getSuccessor(1);

   if (Condition == ConstantBool::True) {
     FalseDest->removePredecessor(BI->getParent());
     BI->setUnconditionalDest(TrueDest);
     modified = true;
     ++NumBranches;
     proceedToSuccessor(KP, Node, DT->getNode(TrueDest));
     return;
   } else if (Condition == ConstantBool::False) {
     TrueDest->removePredecessor(BI->getParent());
     BI->setUnconditionalDest(FalseDest);
     modified = true;
     ++NumBranches;
     proceedToSuccessor(KP, Node, DT->getNode(FalseDest));
     return;
   }

   PropertySet TrueProperties(KP), FalseProperties(KP);
   DEBUG(std::cerr << "true set:\n");
   TrueProperties.addEqual(ConstantBool::True,   Condition);
   DEBUG(TrueProperties.debug(std::cerr));
   DEBUG(std::cerr << "false set:\n");
   FalseProperties.addEqual(ConstantBool::False, Condition);
   DEBUG(FalseProperties.debug(std::cerr));

   PropertySet KPcopy(KP);
   proceedToSuccessor(KP,     TrueProperties,  Node, DT->getNode(TrueDest));
   proceedToSuccessor(KPcopy, FalseProperties, Node, DT->getNode(FalseDest));
 }

 void PredicateSimplifier::visit(SwitchInst *SI,
                              DominatorTree::Node *DTNode, PropertySet KP) {
   Value *Condition = SI->getCondition();
   DEBUG(assert(Condition == KP.canonicalize(Condition) &&
                "Instruction wasn't already canonicalized?"));

   // If there's an NEProperty covering this SwitchInst, we may be able to
   // eliminate one of the cases.
   for (PropertySet::ConstPropertyIterator I = KP.Properties.begin(),
        E = KP.Properties.end(); I != E; ++I) {
     if (I->Opcode != PropertySet::NE) continue;
     Value *V1 = KP.canonicalize(I->V1),
           *V2 = KP.canonicalize(I->V2);
     if (V1 != Condition && V2 != Condition) continue;

     // Is one side a number?
     ConstantInt *CI = dyn_cast<ConstantInt>(KP.canonicalize(I->V1));
     if (!CI)     CI = dyn_cast<ConstantInt>(KP.canonicalize(I->V2));

     if (CI) {
       unsigned i = SI->findCaseValue(CI);
       if (i != 0) {
         SI->getSuccessor(i)->removePredecessor(SI->getParent());
         SI->removeCase(i);
         modified = true;
         ++NumSwitchCases;
       }
     }
   }

   // Set the EQProperty in each of the cases BBs,
   // and the NEProperties in the default BB.
   PropertySet DefaultProperties(KP);

   DominatorTree::Node *Node        = DT->getNode(SI->getParent()),
                       *DefaultNode = DT->getNode(SI->getSuccessor(0));
   if (!Node->dominates(DefaultNode)) DefaultNode = NULL;

   for (unsigned I = 1, E = SI->getNumCases(); I < E; ++I) {
     ConstantInt *CI = SI->getCaseValue(I);

     BasicBlock *SuccBB = SI->getSuccessor(I);
     PropertySet copy(KP);
     if (SuccBB->getSinglePredecessor()) {
       PropertySet NewProperties(KP);
       NewProperties.addEqual(Condition, CI);
       proceedToSuccessor(copy, NewProperties, DTNode, DT->getNode(SuccBB));
     } else
       proceedToSuccessor(copy, DTNode, DT->getNode(SuccBB));

     if (DefaultNode)
       DefaultProperties.addNotEqual(Condition, CI);
   }

   if (DefaultNode)
     proceedToSuccessor(DefaultProperties, DTNode, DefaultNode);
 }

 void PredicateSimplifier::visit(LoadInst *LI,
                                 DominatorTree::Node *, PropertySet &KP) {
   Value *Ptr = LI->getPointerOperand();
   KP.addNotEqual(Constant::getNullValue(Ptr->getType()), Ptr);
 }

 void PredicateSimplifier::visit(StoreInst *SI,
                                 DominatorTree::Node *, PropertySet &KP) {
   Value *Ptr = SI->getPointerOperand();
   KP.addNotEqual(Constant::getNullValue(Ptr->getType()), Ptr);
 }

 void PredicateSimplifier::visit(BinaryOperator *BO,
                                 DominatorTree::Node *, PropertySet &KP) {
   Instruction::BinaryOps ops = BO->getOpcode();

   switch (ops) {
     case Instruction::Div:
     case Instruction::Rem: {
       Value *Divisor = BO->getOperand(1);
       KP.addNotEqual(Constant::getNullValue(Divisor->getType()), Divisor);
       break;
     }
     default:
       break;
   }

   // Some other things we could do:
   // In f=x*y, if x != 1 && y != 1 then f != x && f != y.
   // In f=x+y, if x != 0 then f != y and if y != 0 then f != x.
 }
	//===-- PredicateSimplifier.cpp - Path Sensitive Simplifier -----------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file was developed by Nick Lewycky and is distributed under the
	// University of Illinois Open Source License. See LICENSE.TXT for details.
	//
	//===------------------------------------------------------------------===//
	//
	// Path-sensitive optimizer. In a branch where x == y, replace uses of
	// x with y. Permits further optimization, such as the elimination of
	// the unreachable call:
	//
	// void test(int p, int q)
	// {
	// if (p != q)
	// return;
	//
	// if (p != q)
	// foo(); // unreachable
	// }
	//
	//===------------------------------------------------------------------===//
	//
	// This optimization works by substituting %q for %p when protected by a
	// conditional that assures us of that fact. Properties are stored as
	// relationships between two values.
	//
	//===------------------------------------------------------------------===//

	#define DEBUG_TYPE "predsimplify"
	#include "llvm/Transforms/Scalar.h"
	#include "llvm/Constants.h"
	#include "llvm/Instructions.h"
	#include "llvm/Pass.h"
	#include "llvm/ADT/EquivalenceClasses.h"
	#include "llvm/ADT/Statistic.h"
	#include "llvm/ADT/STLExtras.h"
	#include "llvm/Analysis/Dominators.h"
	#include "llvm/Support/CFG.h"
	#include "llvm/Support/Debug.h"
	#include <iostream>
	using namespace llvm;

	namespace {
	Statistic<>
	NumVarsReplaced("predsimplify", "Number of argument substitutions");
	Statistic<>
	NumInstruction("predsimplify", "Number of instructions removed");
	Statistic<>
	NumSwitchCases("predsimplify", "Number of switch cases removed");
	Statistic<>
	NumBranches("predsimplify", "Number of branches made unconditional");

	/// Used for choosing the canonical Value in a synonym set.
	/// Leaves the better one in V1. Returns whether a swap took place.
	static void order(Value &V1, Value &V2) {
	if (isa<Constant>(V2)) {
	if (!isa<Constant>(V1)) {
	std::swap(V1, V2);
	return;
	}
	} else if (isa<Argument>(V2)) {
	if (!isa<Constant>(V1) && !isa<Argument>(V1)) {
	std::swap(V1, V2);
	return;
	}
	}
	if (User *U1 = dyn_cast<User>(V1)) {
	for (User::const_op_iterator I = U1->op_begin(), E = U1->op_end();
	I != E; ++I) {
	if (*I == V2) {
	std::swap(V1, V2);
	return;
	}
	}
	}
	return;
	}

	/// Represents the set of equivalent Value*s and provides insertion
	/// and fast lookup. Also stores the set of inequality relationships.
	class PropertySet {
	struct Property;
	class EquivalenceClasses<Value *> union_find;
	public:
	typedef std::vector<Property>::iterator PropertyIterator;
	typedef std::vector<Property>::const_iterator ConstPropertyIterator;

	enum Ops {
	EQ,
	NE
	};

	Value canonicalize(Value V) const {
	Value *C = lookup(V);
	return C ? C : V;
	}

	Value lookup(Value V) const {
	EquivalenceClasses<Value *>::member_iterator SI =
	union_find.findLeader(V);
	if (SI == union_find.member_end()) return NULL;
	return *SI;
	}

	bool empty() const {
	return union_find.empty();
	}

	void addEqual(Value V1, Value V2) {
	// If %x = 0. and %y = -0., seteq %x, %y is true, but
	// copysign(%x) is not the same as copysign(%y).
	if (V2->getType()->isFloatingPoint()) return;

	order(V1, V2);
	if (isa<Constant>(V2)) return; // refuse to set false == true.

	DEBUG(std::cerr << "equal: " << V1 << " and " << V2 << "\n");
	union_find.unionSets(V1, V2);
	addImpliedProperties(EQ, V1, V2);
	}

	void addNotEqual(Value V1, Value V2) {
	// If %x = NAN then seteq %x, %x is false.
	if (V2->getType()->isFloatingPoint()) return;

	DEBUG(std::cerr << "not equal: " << V1 << " and " << V2 << "\n");
	if (findProperty(NE, V1, V2) != Properties.end())
	return; // found.

	// Add the property.
	Properties.push_back(Property(NE, V1, V2));
	addImpliedProperties(NE, V1, V2);
	}

	PropertyIterator findProperty(Ops Opcode, Value V1, Value V2) {
	assert(Opcode != EQ && "Can't findProperty on EQ."
	"Use the lookup method instead.");

	V1 = canonicalize(V1);
	V2 = canonicalize(V2);

	// Does the property already exist?
	for (PropertyIterator I = Properties.begin(), E = Properties.end();
	I != E; ++I) {
	if (I->Opcode != Opcode) continue;

	I->V1 = canonicalize(I->V1);
	I->V2 = canonicalize(I->V2);
	if ((I->V1 == V1 && I->V2 == V2) \|\|
	(I->V1 == V2 && I->V2 == V1)) {
	return I; // Found.
	}
	}
	return Properties.end();
	}

	ConstPropertyIterator
	findProperty(Ops Opcode, Value V1, Value V2) const {
	assert(Opcode != EQ && "Can't findProperty on EQ."
	"Use the lookup method instead.");

	V1 = canonicalize(V1);
	V2 = canonicalize(V2);

	// Does the property already exist?
	for (ConstPropertyIterator I = Properties.begin(),
	E = Properties.end(); I != E; ++I) {
	if (I->Opcode != Opcode) continue;

	Value *v1 = canonicalize(I->V1),
	*v2 = canonicalize(I->V2);
	if ((v1 == V1 && v2 == V2) \|\|
	(v1 == V2 && v2 == V1)) {
	return I; // Found.
	}
	}
	return Properties.end();
	}

	private:
	// Represents Head OP [Tail1, Tail2, ...]
	// For example: %x != %a, %x != %b.
	struct Property {
	Property(Ops opcode, Value v1, Value v2)
	: Opcode(opcode), V1(v1), V2(v2)
	{ assert(opcode != EQ && "Equality belongs in the synonym set, "
	"not a property."); }

	Ops Opcode;
	Value V1, V2;
	};

	void add(Ops Opcode, Value V1, Value V2, bool invert) {
	switch (Opcode) {
	case EQ:
	if (invert) addNotEqual(V1, V2);
	else addEqual(V1, V2);
	break;
	case NE:
	if (invert) addEqual(V1, V2);
	else addNotEqual(V1, V2);
	break;
	default:
	assert(0 && "Unknown property opcode.");
	}
	}

	// Finds the properties implied by a equivalence and adds them too.
	// Example: ("seteq %a, %b", true, EQ) --> (%a, %b, EQ)
	// ("seteq %a, %b", false, EQ) --> (%a, %b, NE)
	void addImpliedProperties(Ops Opcode, Value V1, Value V2) {
	order(V1, V2);

	if (BinaryOperator *BO = dyn_cast<BinaryOperator>(V2)) {
	switch (BO->getOpcode()) {
	case Instruction::SetEQ:
	if (V1 == ConstantBool::True)
	add(Opcode, BO->getOperand(0), BO->getOperand(1), false);
	if (V1 == ConstantBool::False)
	add(Opcode, BO->getOperand(0), BO->getOperand(1), true);
	break;
	case Instruction::SetNE:
	if (V1 == ConstantBool::True)
	add(Opcode, BO->getOperand(0), BO->getOperand(1), true);
	if (V1 == ConstantBool::False)
	add(Opcode, BO->getOperand(0), BO->getOperand(1), false);
	break;
	case Instruction::SetLT:
	case Instruction::SetGT:
	if (V1 == ConstantBool::True)
	add(Opcode, BO->getOperand(0), BO->getOperand(1), true);
	break;
	case Instruction::SetLE:
	case Instruction::SetGE:
	if (V1 == ConstantBool::False)
	add(Opcode, BO->getOperand(0), BO->getOperand(1), true);
	break;
	case Instruction::And:
	if (V1 == ConstantBool::True) {
	add(Opcode, ConstantBool::True, BO->getOperand(0), false);
	add(Opcode, ConstantBool::True, BO->getOperand(1), false);
	}
	break;
	case Instruction::Or:
	if (V1 == ConstantBool::False) {
	add(Opcode, ConstantBool::False, BO->getOperand(0), false);
	add(Opcode, ConstantBool::False, BO->getOperand(1), false);
	}
	break;
	case Instruction::Xor:
	if (V1 == ConstantBool::True) {
	if (BO->getOperand(0) == ConstantBool::True)
	add(Opcode, ConstantBool::False, BO->getOperand(1), false);
	if (BO->getOperand(1) == ConstantBool::True)
	add(Opcode, ConstantBool::False, BO->getOperand(0), false);
	}
	if (V1 == ConstantBool::False) {
	if (BO->getOperand(0) == ConstantBool::True)
	add(Opcode, ConstantBool::True, BO->getOperand(1), false);
	if (BO->getOperand(1) == ConstantBool::True)
	add(Opcode, ConstantBool::True, BO->getOperand(0), false);
	}
	break;
	default:
	break;
	}
	} else if (SelectInst *SI = dyn_cast<SelectInst>(V2)) {
	if (Opcode != EQ && Opcode != NE) return;

	ConstantBool *True = (Opcode==EQ) ? ConstantBool::True
	: ConstantBool::False,
	*False = (Opcode==EQ) ? ConstantBool::False
	: ConstantBool::True;

	if (V1 == SI->getTrueValue())
	addEqual(SI->getCondition(), True);
	else if (V1 == SI->getFalseValue())
	addEqual(SI->getCondition(), False);
	else if (Opcode == EQ)
	assert("Result of select not equal to either value.");
	}
	}

	public:
	#ifdef DEBUG
	void debug(std::ostream &os) const {
	for (EquivalenceClasses<Value*>::iterator I = union_find.begin(),
	E = union_find.end(); I != E; ++I) {
	if (!I->isLeader()) continue;
	for (EquivalenceClasses<Value*>::member_iterator MI =
	union_find.member_begin(I); MI != union_find.member_end(); ++MI)
	std::cerr << **MI << " ";
	std::cerr << "\n--\n";
	}
	}
	#endif

	std::vector<Property> Properties;
	};

	/// PredicateSimplifier - This class is a simplifier that replaces
	/// one equivalent variable with another. It also tracks what
	/// can't be equal and will solve setcc instructions when possible.
	class PredicateSimplifier : public FunctionPass {
	public:
	bool runOnFunction(Function &F);
	virtual void getAnalysisUsage(AnalysisUsage &AU) const;

	private:
	// Try to replace the Use of the instruction with something simpler.
	Value resolve(SetCondInst SCI, const PropertySet &);
	Value resolve(BinaryOperator BO, const PropertySet &);
	Value resolve(SelectInst SI, const PropertySet &);
	Value resolve(Value V, const PropertySet &);

	// Used by terminator instructions to proceed from the current basic
	// block to the next. Verifies that "current" dominates "next",
	// then calls visitBasicBlock.
	void proceedToSuccessor(PropertySet &CurrentPS, PropertySet &NextPS,
	DominatorTree::Node Current, DominatorTree::Node Next);
	void proceedToSuccessor(PropertySet &CurrentPS,
	DominatorTree::Node Current, DominatorTree::Node Next);

	// Visits each instruction in the basic block.
	void visitBasicBlock(DominatorTree::Node *DTNode,
	PropertySet &KnownProperties);

	// For each instruction, add the properties to KnownProperties.
	void visit(Instruction I, DominatorTree::Node , PropertySet &);
	void visit(TerminatorInst TI, DominatorTree::Node , PropertySet &);
	void visit(BranchInst BI, DominatorTree::Node , PropertySet &);
	void visit(SwitchInst SI, DominatorTree::Node , PropertySet);
	void visit(LoadInst LI, DominatorTree::Node , PropertySet &);
	void visit(StoreInst SI, DominatorTree::Node , PropertySet &);
	void visit(BinaryOperator BO, DominatorTree::Node , PropertySet &);

	DominatorTree *DT;
	bool modified;
	};

	RegisterPass<PredicateSimplifier> X("predsimplify",
	"Predicate Simplifier");
	}

	FunctionPass *llvm::createPredicateSimplifierPass() {
	return new PredicateSimplifier();
	}

	bool PredicateSimplifier::runOnFunction(Function &F) {
	DT = &getAnalysis<DominatorTree>();

	modified = false;
	PropertySet KnownProperties;
	visitBasicBlock(DT->getRootNode(), KnownProperties);
	return modified;
	}

	void PredicateSimplifier::getAnalysisUsage(AnalysisUsage &AU) const {
	AU.addRequired<DominatorTree>();
	}

	// resolve catches cases addProperty won't because it wasn't used as a
	// condition in the branch, and that visit won't, because the instruction
	// was defined outside of the scope that the properties apply to.
	Value PredicateSimplifier::resolve(SetCondInst SCI,
	const PropertySet &KP) {
	// Attempt to resolve the SetCondInst to a boolean.

	Value *SCI0 = resolve(SCI->getOperand(0), KP),
	*SCI1 = resolve(SCI->getOperand(1), KP);
	PropertySet::ConstPropertyIterator NE =
	KP.findProperty(PropertySet::NE, SCI0, SCI1);

	if (NE != KP.Properties.end()) {
	switch (SCI->getOpcode()) {
	case Instruction::SetEQ:
	return ConstantBool::False;
	case Instruction::SetNE:
	return ConstantBool::True;
	case Instruction::SetLE:
	case Instruction::SetGE:
	case Instruction::SetLT:
	case Instruction::SetGT:
	break;
	default:
	assert(0 && "Unknown opcode in SetCondInst.");
	break;
	}
	}

	ConstantIntegral *CI1 = dyn_cast<ConstantIntegral>(SCI0),
	*CI2 = dyn_cast<ConstantIntegral>(SCI1);

	if (!CI1 \|\| !CI2) return SCI;

	switch(SCI->getOpcode()) {
	case Instruction::SetLE:
	case Instruction::SetGE:
	case Instruction::SetEQ:
	if (CI1->getRawValue() == CI2->getRawValue())
	return ConstantBool::True;
	else
	return ConstantBool::False;
	case Instruction::SetLT:
	case Instruction::SetGT:
	case Instruction::SetNE:
	if (CI1->getRawValue() == CI2->getRawValue())
	return ConstantBool::False;
	else
	return ConstantBool::True;
	default:
	assert(0 && "Unknown opcode in SetContInst.");
	break;
	}
	}

	Value PredicateSimplifier::resolve(BinaryOperator BO,
	const PropertySet &KP) {
	if (SetCondInst *SCI = dyn_cast<SetCondInst>(BO))
	return resolve(SCI, KP);

	DEBUG(std::cerr << "BO->getOperand(1) = " << *BO->getOperand(1) << "\n");

	Value *lhs = resolve(BO->getOperand(0), KP),
	*rhs = resolve(BO->getOperand(1), KP);
	ConstantIntegral *CI1 = dyn_cast<ConstantIntegral>(lhs);
	ConstantIntegral *CI2 = dyn_cast<ConstantIntegral>(rhs);

	DEBUG(std::cerr << "resolveBO: lhs = " << *lhs
	<< ", rhs = " << *rhs << "\n");
	if (CI1) DEBUG(std::cerr << "CI1 = " << *CI1);
	if (CI2) DEBUG(std::cerr << "CI2 = " << *CI2);

	if (!CI1 \|\| !CI2) return BO;

	Value *V = ConstantExpr::get(BO->getOpcode(), CI1, CI2);
	if (V) return V;
	return BO;
	}

	Value PredicateSimplifier::resolve(SelectInst SI, const PropertySet &KP) {
	Value *Condition = resolve(SI->getCondition(), KP);
	if (Condition == ConstantBool::True)
	return resolve(SI->getTrueValue(), KP);
	else if (Condition == ConstantBool::False)
	return resolve(SI->getFalseValue(), KP);
	return SI;
	}

	Value PredicateSimplifier::resolve(Value V, const PropertySet &KP) {
	if (isa<Constant>(V) \|\| isa<BasicBlock>(V) \|\| KP.empty()) return V;

	V = KP.canonicalize(V);

	DEBUG(std::cerr << "peering into " << *V << "\n");

	if (BinaryOperator *BO = dyn_cast<BinaryOperator>(V))
	return resolve(BO, KP);
	else if (SelectInst *SI = dyn_cast<SelectInst>(V))
	return resolve(SI, KP);

	return V;
	}

	void PredicateSimplifier::visitBasicBlock(DominatorTree::Node *DTNode,
	PropertySet &KnownProperties) {
	BasicBlock *BB = DTNode->getBlock();
	for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
	visit(I, DTNode, KnownProperties);
	}
	}

	void PredicateSimplifier::visit(Instruction I, DominatorTree::Node DTNode,
	PropertySet &KnownProperties) {
	DEBUG(std::cerr << "Considering instruction " << *I << "\n");
	DEBUG(KnownProperties.debug(std::cerr));

	// Try to replace whole instruction.
	Value *V = resolve(I, KnownProperties);
	assert(V && "resolve not supposed to return NULL.");
	if (V != I) {
	modified = true;
	++NumInstruction;
	I->replaceAllUsesWith(V);
	I->eraseFromParent();
	return;
	}

	// Try to substitute operands.
	for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
	Value *Oper = I->getOperand(i);
	Value *V = resolve(Oper, KnownProperties);
	assert(V && "resolve not supposed to return NULL.");
	if (V != Oper) {
	modified = true;
	++NumVarsReplaced;
	DEBUG(std::cerr << "resolving " << *I);
	I->setOperand(i, V);
	DEBUG(std::cerr << "into " << *I);
	}
	}

	if (TerminatorInst *TI = dyn_cast<TerminatorInst>(I))
	visit(TI, DTNode, KnownProperties);
	else if (LoadInst *LI = dyn_cast<LoadInst>(I))
	visit(LI, DTNode, KnownProperties);
	else if (StoreInst *SI = dyn_cast<StoreInst>(I))
	visit(SI, DTNode, KnownProperties);
	else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I))
	visit(BO, DTNode, KnownProperties);
	}

	void PredicateSimplifier::proceedToSuccessor(PropertySet &CurrentPS,
	PropertySet &NextPS, DominatorTree::Node *Current,
	DominatorTree::Node *Next) {
	if (Next->getBlock()->getSinglePredecessor() == Current->getBlock())
	proceedToSuccessor(NextPS, Current, Next);
	else
	proceedToSuccessor(CurrentPS, Current, Next);
	}

	void PredicateSimplifier::proceedToSuccessor(PropertySet &KP,
	DominatorTree::Node Current, DominatorTree::Node Next) {
	if (Current->properlyDominates(Next))
	visitBasicBlock(Next, KP);
	}

	void PredicateSimplifier::visit(TerminatorInst *TI,
	DominatorTree::Node *Node, PropertySet &KP){
	if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
	visit(BI, Node, KP);
	return;
	}
	if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
	visit(SI, Node, KP);
	return;
	}

	for (unsigned i = 0, E = TI->getNumSuccessors(); i != E; ++i) {
	BasicBlock *BB = TI->getSuccessor(i);
	PropertySet KPcopy(KP);
	proceedToSuccessor(KPcopy, Node, DT->getNode(TI->getSuccessor(i)));
	}
	}

	void PredicateSimplifier::visit(BranchInst *BI,
	DominatorTree::Node *Node, PropertySet &KP){
	if (BI->isUnconditional()) {
	proceedToSuccessor(KP, Node, DT->getNode(BI->getSuccessor(0)));
	return;
	}

	Value *Condition = BI->getCondition();

	BasicBlock *TrueDest = BI->getSuccessor(0),
	*FalseDest = BI->getSuccessor(1);

	if (Condition == ConstantBool::True) {
	FalseDest->removePredecessor(BI->getParent());
	BI->setUnconditionalDest(TrueDest);
	modified = true;
	++NumBranches;
	proceedToSuccessor(KP, Node, DT->getNode(TrueDest));
	return;
	} else if (Condition == ConstantBool::False) {
	TrueDest->removePredecessor(BI->getParent());
	BI->setUnconditionalDest(FalseDest);
	modified = true;
	++NumBranches;
	proceedToSuccessor(KP, Node, DT->getNode(FalseDest));
	return;
	}

	PropertySet TrueProperties(KP), FalseProperties(KP);
	DEBUG(std::cerr << "true set:\n");
	TrueProperties.addEqual(ConstantBool::True, Condition);
	DEBUG(TrueProperties.debug(std::cerr));
	DEBUG(std::cerr << "false set:\n");
	FalseProperties.addEqual(ConstantBool::False, Condition);
	DEBUG(FalseProperties.debug(std::cerr));

	PropertySet KPcopy(KP);
	proceedToSuccessor(KP, TrueProperties, Node, DT->getNode(TrueDest));
	proceedToSuccessor(KPcopy, FalseProperties, Node, DT->getNode(FalseDest));
	}

	void PredicateSimplifier::visit(SwitchInst *SI,
	DominatorTree::Node *DTNode, PropertySet KP) {
	Value *Condition = SI->getCondition();
	DEBUG(assert(Condition == KP.canonicalize(Condition) &&
	"Instruction wasn't already canonicalized?"));

	// If there's an NEProperty covering this SwitchInst, we may be able to
	// eliminate one of the cases.
	for (PropertySet::ConstPropertyIterator I = KP.Properties.begin(),
	E = KP.Properties.end(); I != E; ++I) {
	if (I->Opcode != PropertySet::NE) continue;
	Value *V1 = KP.canonicalize(I->V1),
	*V2 = KP.canonicalize(I->V2);
	if (V1 != Condition && V2 != Condition) continue;

	// Is one side a number?
	ConstantInt *CI = dyn_cast<ConstantInt>(KP.canonicalize(I->V1));
	if (!CI) CI = dyn_cast<ConstantInt>(KP.canonicalize(I->V2));

	if (CI) {
	unsigned i = SI->findCaseValue(CI);
	if (i != 0) {
	SI->getSuccessor(i)->removePredecessor(SI->getParent());
	SI->removeCase(i);
	modified = true;
	++NumSwitchCases;
	}
	}
	}

	// Set the EQProperty in each of the cases BBs,
	// and the NEProperties in the default BB.
	PropertySet DefaultProperties(KP);

	DominatorTree::Node *Node = DT->getNode(SI->getParent()),
	*DefaultNode = DT->getNode(SI->getSuccessor(0));
	if (!Node->dominates(DefaultNode)) DefaultNode = NULL;

	for (unsigned I = 1, E = SI->getNumCases(); I < E; ++I) {
	ConstantInt *CI = SI->getCaseValue(I);

	BasicBlock *SuccBB = SI->getSuccessor(I);
	PropertySet copy(KP);
	if (SuccBB->getSinglePredecessor()) {
	PropertySet NewProperties(KP);
	NewProperties.addEqual(Condition, CI);
	proceedToSuccessor(copy, NewProperties, DTNode, DT->getNode(SuccBB));
	} else
	proceedToSuccessor(copy, DTNode, DT->getNode(SuccBB));

	if (DefaultNode)
	DefaultProperties.addNotEqual(Condition, CI);
	}

	if (DefaultNode)
	proceedToSuccessor(DefaultProperties, DTNode, DefaultNode);
	}

	void PredicateSimplifier::visit(LoadInst *LI,
	DominatorTree::Node *, PropertySet &KP) {
	Value *Ptr = LI->getPointerOperand();
	KP.addNotEqual(Constant::getNullValue(Ptr->getType()), Ptr);
	}

	void PredicateSimplifier::visit(StoreInst *SI,
	DominatorTree::Node *, PropertySet &KP) {
	Value *Ptr = SI->getPointerOperand();
	KP.addNotEqual(Constant::getNullValue(Ptr->getType()), Ptr);
	}

	void PredicateSimplifier::visit(BinaryOperator *BO,
	DominatorTree::Node *, PropertySet &KP) {
	Instruction::BinaryOps ops = BO->getOpcode();

	switch (ops) {
	case Instruction::Div:
	case Instruction::Rem: {
	Value *Divisor = BO->getOperand(1);
	KP.addNotEqual(Constant::getNullValue(Divisor->getType()), Divisor);
	break;
	}
	default:
	break;
	}

	// Some other things we could do:
	// In f=x*y, if x != 1 && y != 1 then f != x && f != y.
	// In f=x+y, if x != 0 then f != y and if y != 0 then f != x.
	}