| //===- ValueNumbering.cpp - Value #'ing Implementation ----------*- C++ -*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file was developed by the LLVM research group and is distributed under |
| // the University of Illinois Open Source License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements the non-abstract Value Numbering methods as well as a |
| // default implementation for the analysis group. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Analysis/Passes.h" |
| #include "llvm/Analysis/ValueNumbering.h" |
| #include "llvm/Support/InstVisitor.h" |
| #include "llvm/BasicBlock.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Type.h" |
| using namespace llvm; |
| |
| // Register the ValueNumbering interface, providing a nice name to refer to. |
| static RegisterAnalysisGroup<ValueNumbering> 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<Value*> &RetVals) const; |
| }; |
| |
| // Register this pass... |
| RegisterOpt<BasicVN> |
| X("basicvn", "Basic Value Numbering (default GVN impl)"); |
| |
| // Declare that we implement the ValueNumbering interface |
| RegisterAnalysisGroup<ValueNumbering, BasicVN, true> Y; |
| |
| /// BVNImpl - Implement BasicVN in terms of a visitor class that |
| /// handles the different types of instructions as appropriate. |
| /// |
| struct BVNImpl : public InstVisitor<BVNImpl> { |
| std::vector<Value*> &RetVals; |
| BVNImpl(std::vector<Value*> &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... |
| } |
| }; |
| } |
| |
| ImmutablePass *llvm::createBasicVNPass() { return new BasicVN(); } |
| |
| // 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<Value*> &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<Instruction>(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 (CastInst *Other = dyn_cast<CastInst>(*UI)) |
| // Check that the types are the same, since this code handles casts... |
| if (Other->getType() == I.getType() && |
| // Is it embedded in the same function? (This could be false if LHS |
| // is a constant or global!) |
| Other->getParent()->getParent() == F && |
| // Check to see if this new cast is not I. |
| Other != &I) { |
| // 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 embedded 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, the instruction can match if the |
| // operands are swapped! |
| // |
| if ((I1.getOperand(0) == I2->getOperand(1) && |
| I1.getOperand(1) == I2->getOperand(0)) && |
| I1.isCommutative()) |
| return true; |
| |
| return false; |
| } |
| |
| void BVNImpl::handleBinaryInst(Instruction &I) { |
| Value *LHS = I.getOperand(0); |
| |
| for (Value::use_iterator UI = LHS->use_begin(), UE = LHS->use_end(); |
| UI != UE; ++UI) |
| if (Instruction *Other = dyn_cast<Instruction>(*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 inline 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); |
| |
| // Try to pick a local operand if possible instead of a constant or a global |
| // that might have a lot of uses. |
| for (unsigned i = 1, e = I.getNumOperands(); i != e; ++i) |
| if (isa<Instruction>(I.getOperand(i)) || isa<Argument>(I.getOperand(i))) { |
| Op = I.getOperand(i); |
| break; |
| } |
| |
| for (Value::use_iterator UI = Op->use_begin(), UE = Op->use_end(); |
| UI != UE; ++UI) |
| if (GetElementPtrInst *Other = dyn_cast<GetElementPtrInst>(*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); |
| } |
| } |
| |
| void llvm::BasicValueNumberingStub() { } |