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/Passes.h"
16 #include "llvm/Analysis/ValueNumbering.h"
17 #include "llvm/Support/InstVisitor.h"
18 #include "llvm/BasicBlock.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/Pass.h"
21 #include "llvm/Type.h"
24 // Register the ValueNumbering interface, providing a nice name to refer to.
25 static RegisterAnalysisGroup<ValueNumbering> X("Value Numbering");
27 /// ValueNumbering destructor: DO NOT move this to the header file for
28 /// ValueNumbering or else clients of the ValueNumbering class may not depend on
29 /// the ValueNumbering.o file in the current .a file, causing alias analysis
30 /// support to not be included in the tool correctly!
32 ValueNumbering::~ValueNumbering() {}
34 //===----------------------------------------------------------------------===//
35 // Basic ValueNumbering Pass Implementation
36 //===----------------------------------------------------------------------===//
38 // Because of the way .a files work, the implementation of the BasicVN class
39 // MUST be in the ValueNumbering file itself, or else we run the risk of
40 // ValueNumbering being used, but the default implementation not being linked
41 // into the tool that uses it. As such, we register and implement the class
46 /// BasicVN - This class is the default implementation of the ValueNumbering
47 /// interface. It walks the SSA def-use chains to trivially identify
48 /// lexically identical expressions. This does not require any ahead of time
49 /// analysis, so it is a very fast default implementation.
51 struct BasicVN : public ImmutablePass, public ValueNumbering {
52 /// getEqualNumberNodes - Return nodes with the same value number as the
53 /// specified Value. This fills in the argument vector with any equal
56 /// This is where our implementation is.
58 virtual void getEqualNumberNodes(Value *V1,
59 std::vector<Value*> &RetVals) const;
62 // Register this pass...
64 X("basicvn", "Basic Value Numbering (default GVN impl)");
66 // Declare that we implement the ValueNumbering interface
67 RegisterAnalysisGroup<ValueNumbering, true> Y(X);
69 /// BVNImpl - Implement BasicVN in terms of a visitor class that
70 /// handles the different types of instructions as appropriate.
72 struct BVNImpl : public InstVisitor<BVNImpl> {
73 std::vector<Value*> &RetVals;
74 BVNImpl(std::vector<Value*> &RV) : RetVals(RV) {}
76 void visitCastInst(CastInst &I);
77 void visitGetElementPtrInst(GetElementPtrInst &I);
78 void visitCmpInst(CmpInst &I);
80 void handleBinaryInst(Instruction &I);
81 void visitBinaryOperator(Instruction &I) { handleBinaryInst(I); }
82 void visitShiftInst(Instruction &I) { handleBinaryInst(I); }
83 void visitExtractElementInst(Instruction &I) { handleBinaryInst(I); }
85 void handleTernaryInst(Instruction &I);
86 void visitSelectInst(Instruction &I) { handleTernaryInst(I); }
87 void visitInsertElementInst(Instruction &I) { handleTernaryInst(I); }
88 void visitShuffleVectorInst(Instruction &I) { handleTernaryInst(I); }
89 void visitInstruction(Instruction &) {
90 // Cannot value number calls or terminator instructions.
95 ImmutablePass *llvm::createBasicVNPass() { return new BasicVN(); }
97 // getEqualNumberNodes - Return nodes with the same value number as the
98 // specified Value. This fills in the argument vector with any equal values.
100 void BasicVN::getEqualNumberNodes(Value *V, std::vector<Value*> &RetVals) const{
101 assert(V->getType() != Type::VoidTy &&
102 "Can only value number non-void values!");
103 // We can only handle the case where I is an instruction!
104 if (Instruction *I = dyn_cast<Instruction>(V))
105 BVNImpl(RetVals).visit(I);
108 void BVNImpl::visitCastInst(CastInst &CI) {
109 Instruction &I = (Instruction&)CI;
110 Value *Op = I.getOperand(0);
111 Function *F = I.getParent()->getParent();
113 for (Value::use_iterator UI = Op->use_begin(), UE = Op->use_end();
115 if (CastInst *Other = dyn_cast<CastInst>(*UI))
116 // Check that the types are the same, since this code handles casts...
117 if (Other->getType() == I.getType() &&
118 // Is it embedded in the same function? (This could be false if LHS
119 // is a constant or global!)
120 Other->getParent()->getParent() == F &&
121 // Check to see if this new cast is not I.
123 // These instructions are identical. Add to list...
124 RetVals.push_back(Other);
128 void BVNImpl::visitCmpInst(CmpInst &CI1) {
129 Value *LHS = CI1.getOperand(0);
130 for (Value::use_iterator UI = LHS->use_begin(), UE = LHS->use_end();
132 if (CmpInst *CI2 = dyn_cast<CmpInst>(*UI))
133 // Check to see if this compare instruction is not CI, but same opcode,
134 // same predicate, and in the same function.
135 if (CI2 != &CI1 && CI2->getOpcode() == CI1.getOpcode() &&
136 CI2->getPredicate() == CI1.getPredicate() &&
137 CI2->getParent()->getParent() == CI1.getParent()->getParent())
138 // If the operands are the same
139 if ((CI2->getOperand(0) == CI1.getOperand(0) &&
140 CI2->getOperand(1) == CI1.getOperand(1)) ||
141 // Or the compare is commutative and the operands are reversed
142 (CI1.isCommutative() &&
143 CI2->getOperand(0) == CI1.getOperand(1) &&
144 CI2->getOperand(1) == CI1.getOperand(0)))
145 // Then the instructiosn are identical, add to list.
146 RetVals.push_back(CI2);
151 // isIdenticalBinaryInst - Return true if the two binary instructions are
154 static inline bool isIdenticalBinaryInst(const Instruction &I1,
155 const Instruction *I2) {
156 // Is it embedded in the same function? (This could be false if LHS
157 // is a constant or global!)
158 if (I1.getOpcode() != I2->getOpcode() ||
159 I1.getParent()->getParent() != I2->getParent()->getParent())
162 // They are identical if both operands are the same!
163 if (I1.getOperand(0) == I2->getOperand(0) &&
164 I1.getOperand(1) == I2->getOperand(1))
167 // If the instruction is commutative, the instruction can match if the
168 // operands are swapped!
170 if ((I1.getOperand(0) == I2->getOperand(1) &&
171 I1.getOperand(1) == I2->getOperand(0)) &&
178 // isIdenticalTernaryInst - Return true if the two ternary instructions are
181 static inline bool isIdenticalTernaryInst(const Instruction &I1,
182 const Instruction *I2) {
183 // Is it embedded in the same function? (This could be false if LHS
184 // is a constant or global!)
185 if (I1.getParent()->getParent() != I2->getParent()->getParent())
188 // They are identical if all operands are the same!
189 return I1.getOperand(0) == I2->getOperand(0) &&
190 I1.getOperand(1) == I2->getOperand(1) &&
191 I1.getOperand(2) == I2->getOperand(2);
196 void BVNImpl::handleBinaryInst(Instruction &I) {
197 Value *LHS = I.getOperand(0);
199 for (Value::use_iterator UI = LHS->use_begin(), UE = LHS->use_end();
201 if (Instruction *Other = dyn_cast<Instruction>(*UI))
202 // Check to see if this new binary operator is not I, but same operand...
203 if (Other != &I && isIdenticalBinaryInst(I, Other)) {
204 // These instructions are identical. Handle the situation.
205 RetVals.push_back(Other);
209 // IdenticalComplexInst - Return true if the two instructions are the same, by
210 // using a brute force comparison. This is useful for instructions with an
211 // arbitrary number of arguments.
213 static inline bool IdenticalComplexInst(const Instruction *I1,
214 const Instruction *I2) {
215 assert(I1->getOpcode() == I2->getOpcode());
216 // Equal if they are in the same function...
217 return I1->getParent()->getParent() == I2->getParent()->getParent() &&
218 // And return the same type...
219 I1->getType() == I2->getType() &&
220 // And have the same number of operands...
221 I1->getNumOperands() == I2->getNumOperands() &&
222 // And all of the operands are equal.
223 std::equal(I1->op_begin(), I1->op_end(), I2->op_begin());
226 void BVNImpl::visitGetElementPtrInst(GetElementPtrInst &I) {
227 Value *Op = I.getOperand(0);
229 // Try to pick a local operand if possible instead of a constant or a global
230 // that might have a lot of uses.
231 for (unsigned i = 1, e = I.getNumOperands(); i != e; ++i)
232 if (isa<Instruction>(I.getOperand(i)) || isa<Argument>(I.getOperand(i))) {
233 Op = I.getOperand(i);
237 for (Value::use_iterator UI = Op->use_begin(), UE = Op->use_end();
239 if (GetElementPtrInst *Other = dyn_cast<GetElementPtrInst>(*UI))
240 // Check to see if this new getelementptr is not I, but same operand...
241 if (Other != &I && IdenticalComplexInst(&I, Other)) {
242 // These instructions are identical. Handle the situation.
243 RetVals.push_back(Other);
247 void BVNImpl::handleTernaryInst(Instruction &I) {
248 Value *Op0 = I.getOperand(0);
249 Instruction *OtherInst;
251 for (Value::use_iterator UI = Op0->use_begin(), UE = Op0->use_end();
253 if ((OtherInst = dyn_cast<Instruction>(*UI)) &&
254 OtherInst->getOpcode() == I.getOpcode()) {
255 // Check to see if this new select is not I, but has the same operands.
256 if (OtherInst != &I && isIdenticalTernaryInst(I, OtherInst)) {
257 // These instructions are identical. Handle the situation.
258 RetVals.push_back(OtherInst);
265 // Ensure that users of ValueNumbering.h will link with this file
266 DEFINING_FILE_FOR(BasicValueNumbering)