//===- ValueNumbering.cpp - Value #'ing Implementation ----------*- C++ -*-===// // // This file implements the non-abstract Value Numbering methods as well as a // default implementation for the analysis group. // //===----------------------------------------------------------------------===// #include "llvm/Analysis/ValueNumbering.h" #include "llvm/Support/InstVisitor.h" #include "llvm/BasicBlock.h" #include "llvm/Pass.h" #include "llvm/Type.h" #include "llvm/iMemory.h" // Register the ValueNumbering interface, providing a nice name to refer to. static RegisterAnalysisGroup X("Value Numbering"); /// ValueNumbering destructor: DO NOT move this to the header file for /// ValueNumbering or else clients of the ValueNumbering class may not depend on /// the ValueNumbering.o file in the current .a file, causing alias analysis /// support to not be included in the tool correctly! /// ValueNumbering::~ValueNumbering() {} //===----------------------------------------------------------------------===// // Basic ValueNumbering Pass Implementation //===----------------------------------------------------------------------===// // // Because of the way .a files work, the implementation of the BasicVN class // MUST be in the ValueNumbering file itself, or else we run the risk of // ValueNumbering being used, but the default implementation not being linked // into the tool that uses it. As such, we register and implement the class // here. // namespace { /// BasicVN - This class is the default implementation of the ValueNumbering /// interface. It walks the SSA def-use chains to trivially identify /// lexically identical expressions. This does not require any ahead of time /// analysis, so it is a very fast default implementation. /// struct BasicVN : public ImmutablePass, public ValueNumbering { /// getEqualNumberNodes - Return nodes with the same value number as the /// specified Value. This fills in the argument vector with any equal /// values. /// /// This is where our implementation is. /// virtual void getEqualNumberNodes(Value *V1, std::vector &RetVals) const; }; // Register this pass... RegisterOpt X("basicvn", "Basic Value Numbering (default GVN impl)"); // Declare that we implement the ValueNumbering interface RegisterAnalysisGroup Y; } // End of anonymous namespace namespace { /// BVNImpl - Implement BasicVN in terms of a visitor class that /// handles the different types of instructions as appropriate. /// struct BVNImpl : public InstVisitor { std::vector &RetVals; BVNImpl(std::vector &RV) : RetVals(RV) {} void handleBinaryInst(Instruction &I); void visitBinaryOperator(BinaryOperator &I) { handleBinaryInst((Instruction&)I); } void visitGetElementPtrInst(GetElementPtrInst &I); void visitCastInst(CastInst &I); void visitShiftInst(ShiftInst &I) { handleBinaryInst((Instruction&)I); } void visitInstruction(Instruction &) { // Cannot value number calls or terminator instructions... } }; } // getEqualNumberNodes - Return nodes with the same value number as the // specified Value. This fills in the argument vector with any equal values. // void BasicVN::getEqualNumberNodes(Value *V, std::vector &RetVals) const{ assert(V->getType() != Type::VoidTy && "Can only value number non-void values!"); // We can only handle the case where I is an instruction! if (Instruction *I = dyn_cast(V)) BVNImpl(RetVals).visit(I); } void BVNImpl::visitCastInst(CastInst &CI) { Instruction &I = (Instruction&)CI; Value *Op = I.getOperand(0); Function *F = I.getParent()->getParent(); for (Value::use_iterator UI = Op->use_begin(), UE = Op->use_end(); UI != UE; ++UI) if (Instruction *Other = dyn_cast(*UI)) // Check to see if this new cast is not I, but has the same operand... if (Other != &I && Other->getOpcode() == I.getOpcode() && Other->getOperand(0) == Op && // Is the operand the same? // Is it embeded in the same function? (This could be false if LHS // is a constant or global!) Other->getParent()->getParent() == F && // Check that the types are the same, since this code handles casts... Other->getType() == I.getType()) { // These instructions are identical. Add to list... RetVals.push_back(Other); } } // isIdenticalBinaryInst - Return true if the two binary instructions are // identical. // static inline bool isIdenticalBinaryInst(const Instruction &I1, const Instruction *I2) { // Is it embeded in the same function? (This could be false if LHS // is a constant or global!) if (I1.getOpcode() != I2->getOpcode() || I1.getParent()->getParent() != I2->getParent()->getParent()) return false; // They are identical if both operands are the same! if (I1.getOperand(0) == I2->getOperand(0) && I1.getOperand(1) == I2->getOperand(1)) return true; // If the instruction is commutative and associative, the instruction can // match if the operands are swapped! // if ((I1.getOperand(0) == I2->getOperand(1) && I1.getOperand(1) == I2->getOperand(0)) && (I1.getOpcode() == Instruction::Add || I1.getOpcode() == Instruction::Mul || I1.getOpcode() == Instruction::And || I1.getOpcode() == Instruction::Or || I1.getOpcode() == Instruction::Xor)) return true; return false; } void BVNImpl::handleBinaryInst(Instruction &I) { Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); Function *F = I.getParent()->getParent(); for (Value::use_iterator UI = LHS->use_begin(), UE = LHS->use_end(); UI != UE; ++UI) if (Instruction *Other = dyn_cast(*UI)) // Check to see if this new binary operator is not I, but same operand... if (Other != &I && isIdenticalBinaryInst(I, Other)) { // These instructions are identical. Handle the situation. RetVals.push_back(Other); } } // IdenticalComplexInst - Return true if the two instructions are the same, by // using a brute force comparison. This is useful for instructions with an // arbitrary number of arguments. // static bool IdenticalComplexInst(const Instruction *I1, const Instruction *I2) { assert(I1->getOpcode() == I2->getOpcode()); // Equal if they are in the same function... return I1->getParent()->getParent() == I2->getParent()->getParent() && // And return the same type... I1->getType() == I2->getType() && // And have the same number of operands... I1->getNumOperands() == I2->getNumOperands() && // And all of the operands are equal. std::equal(I1->op_begin(), I1->op_end(), I2->op_begin()); } void BVNImpl::visitGetElementPtrInst(GetElementPtrInst &I) { Value *Op = I.getOperand(0); Function *F = I.getParent()->getParent(); for (Value::use_iterator UI = Op->use_begin(), UE = Op->use_end(); UI != UE; ++UI) if (GetElementPtrInst *Other = dyn_cast(*UI)) // Check to see if this new getelementptr is not I, but same operand... if (Other != &I && IdenticalComplexInst(&I, Other)) { // These instructions are identical. Handle the situation. RetVals.push_back(Other); } }