1 //===- ValueNumbering.cpp - Value #'ing Implementation ----------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the non-abstract Value Numbering methods as well as a
11 // default implementation for the analysis group.
13 //===----------------------------------------------------------------------===//
15 #include "llvm/Analysis/ValueNumbering.h"
16 #include "llvm/Support/InstVisitor.h"
17 #include "llvm/BasicBlock.h"
18 #include "llvm/Pass.h"
19 #include "llvm/Type.h"
20 #include "llvm/iMemory.h"
22 // Register the ValueNumbering interface, providing a nice name to refer to.
23 static RegisterAnalysisGroup<ValueNumbering> X("Value Numbering");
25 /// ValueNumbering destructor: DO NOT move this to the header file for
26 /// ValueNumbering or else clients of the ValueNumbering class may not depend on
27 /// the ValueNumbering.o file in the current .a file, causing alias analysis
28 /// support to not be included in the tool correctly!
30 ValueNumbering::~ValueNumbering() {}
32 //===----------------------------------------------------------------------===//
33 // Basic ValueNumbering Pass Implementation
34 //===----------------------------------------------------------------------===//
36 // Because of the way .a files work, the implementation of the BasicVN class
37 // MUST be in the ValueNumbering file itself, or else we run the risk of
38 // ValueNumbering being used, but the default implementation not being linked
39 // into the tool that uses it. As such, we register and implement the class
43 /// BasicVN - This class is the default implementation of the ValueNumbering
44 /// interface. It walks the SSA def-use chains to trivially identify
45 /// lexically identical expressions. This does not require any ahead of time
46 /// analysis, so it is a very fast default implementation.
48 struct BasicVN : public ImmutablePass, public ValueNumbering {
49 /// getEqualNumberNodes - Return nodes with the same value number as the
50 /// specified Value. This fills in the argument vector with any equal
53 /// This is where our implementation is.
55 virtual void getEqualNumberNodes(Value *V1,
56 std::vector<Value*> &RetVals) const;
59 // Register this pass...
61 X("basicvn", "Basic Value Numbering (default GVN impl)");
63 // Declare that we implement the ValueNumbering interface
64 RegisterAnalysisGroup<ValueNumbering, BasicVN, true> Y;
65 } // End of anonymous namespace
68 /// BVNImpl - Implement BasicVN in terms of a visitor class that
69 /// handles the different types of instructions as appropriate.
71 struct BVNImpl : public InstVisitor<BVNImpl> {
72 std::vector<Value*> &RetVals;
73 BVNImpl(std::vector<Value*> &RV) : RetVals(RV) {}
75 void handleBinaryInst(Instruction &I);
76 void visitBinaryOperator(BinaryOperator &I) {
77 handleBinaryInst((Instruction&)I);
79 void visitGetElementPtrInst(GetElementPtrInst &I);
80 void visitCastInst(CastInst &I);
81 void visitShiftInst(ShiftInst &I) { handleBinaryInst((Instruction&)I); }
82 void visitInstruction(Instruction &) {
83 // Cannot value number calls or terminator instructions...
88 // getEqualNumberNodes - Return nodes with the same value number as the
89 // specified Value. This fills in the argument vector with any equal values.
91 void BasicVN::getEqualNumberNodes(Value *V, std::vector<Value*> &RetVals) const{
92 assert(V->getType() != Type::VoidTy &&
93 "Can only value number non-void values!");
94 // We can only handle the case where I is an instruction!
95 if (Instruction *I = dyn_cast<Instruction>(V))
96 BVNImpl(RetVals).visit(I);
99 void BVNImpl::visitCastInst(CastInst &CI) {
100 Instruction &I = (Instruction&)CI;
101 Value *Op = I.getOperand(0);
102 Function *F = I.getParent()->getParent();
104 for (Value::use_iterator UI = Op->use_begin(), UE = Op->use_end();
106 if (Instruction *Other = dyn_cast<Instruction>(*UI))
107 // Check to see if this new cast is not I, but has the same operand...
108 if (Other != &I && Other->getOpcode() == I.getOpcode() &&
109 Other->getOperand(0) == Op && // Is the operand the same?
110 // Is it embedded in the same function? (This could be false if LHS
111 // is a constant or global!)
112 Other->getParent()->getParent() == F &&
114 // Check that the types are the same, since this code handles casts...
115 Other->getType() == I.getType()) {
117 // These instructions are identical. Add to list...
118 RetVals.push_back(Other);
123 // isIdenticalBinaryInst - Return true if the two binary instructions are
126 static inline bool isIdenticalBinaryInst(const Instruction &I1,
127 const Instruction *I2) {
128 // Is it embedded in the same function? (This could be false if LHS
129 // is a constant or global!)
130 if (I1.getOpcode() != I2->getOpcode() ||
131 I1.getParent()->getParent() != I2->getParent()->getParent())
134 // They are identical if both operands are the same!
135 if (I1.getOperand(0) == I2->getOperand(0) &&
136 I1.getOperand(1) == I2->getOperand(1))
139 // If the instruction is commutative, the instruction can match if the
140 // operands are swapped!
142 if ((I1.getOperand(0) == I2->getOperand(1) &&
143 I1.getOperand(1) == I2->getOperand(0)) &&
150 void BVNImpl::handleBinaryInst(Instruction &I) {
151 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
152 Function *F = I.getParent()->getParent();
154 for (Value::use_iterator UI = LHS->use_begin(), UE = LHS->use_end();
156 if (Instruction *Other = dyn_cast<Instruction>(*UI))
157 // Check to see if this new binary operator is not I, but same operand...
158 if (Other != &I && isIdenticalBinaryInst(I, Other)) {
159 // These instructions are identical. Handle the situation.
160 RetVals.push_back(Other);
164 // IdenticalComplexInst - Return true if the two instructions are the same, by
165 // using a brute force comparison. This is useful for instructions with an
166 // arbitrary number of arguments.
168 static bool IdenticalComplexInst(const Instruction *I1, const Instruction *I2) {
169 assert(I1->getOpcode() == I2->getOpcode());
170 // Equal if they are in the same function...
171 return I1->getParent()->getParent() == I2->getParent()->getParent() &&
172 // And return the same type...
173 I1->getType() == I2->getType() &&
174 // And have the same number of operands...
175 I1->getNumOperands() == I2->getNumOperands() &&
176 // And all of the operands are equal.
177 std::equal(I1->op_begin(), I1->op_end(), I2->op_begin());
180 void BVNImpl::visitGetElementPtrInst(GetElementPtrInst &I) {
181 Value *Op = I.getOperand(0);
182 Function *F = I.getParent()->getParent();
184 for (Value::use_iterator UI = Op->use_begin(), UE = Op->use_end();
186 if (GetElementPtrInst *Other = dyn_cast<GetElementPtrInst>(*UI))
187 // Check to see if this new getelementptr is not I, but same operand...
188 if (Other != &I && IdenticalComplexInst(&I, Other)) {
189 // These instructions are identical. Handle the situation.
190 RetVals.push_back(Other);