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"
22 #include "llvm/Support/Compiler.h"
25 // Register the ValueNumbering interface, providing a nice name to refer to.
26 static RegisterAnalysisGroup<ValueNumbering> X("Value Numbering");
28 /// ValueNumbering destructor: DO NOT move this to the header file for
29 /// ValueNumbering or else clients of the ValueNumbering class may not depend on
30 /// the ValueNumbering.o file in the current .a file, causing alias analysis
31 /// support to not be included in the tool correctly!
33 ValueNumbering::~ValueNumbering() {}
35 //===----------------------------------------------------------------------===//
36 // Basic ValueNumbering Pass Implementation
37 //===----------------------------------------------------------------------===//
39 // Because of the way .a files work, the implementation of the BasicVN class
40 // MUST be in the ValueNumbering file itself, or else we run the risk of
41 // ValueNumbering being used, but the default implementation not being linked
42 // into the tool that uses it. As such, we register and implement the class
47 /// BasicVN - This class is the default implementation of the ValueNumbering
48 /// interface. It walks the SSA def-use chains to trivially identify
49 /// lexically identical expressions. This does not require any ahead of time
50 /// analysis, so it is a very fast default implementation.
52 struct VISIBILITY_HIDDEN BasicVN
53 : public ImmutablePass, public ValueNumbering {
54 /// getEqualNumberNodes - Return nodes with the same value number as the
55 /// specified Value. This fills in the argument vector with any equal
58 /// This is where our implementation is.
60 virtual void getEqualNumberNodes(Value *V1,
61 std::vector<Value*> &RetVals) const;
64 // Register this pass...
66 X("basicvn", "Basic Value Numbering (default GVN impl)");
68 // Declare that we implement the ValueNumbering interface
69 RegisterAnalysisGroup<ValueNumbering, true> Y(X);
71 /// BVNImpl - Implement BasicVN in terms of a visitor class that
72 /// handles the different types of instructions as appropriate.
74 struct VISIBILITY_HIDDEN BVNImpl : public InstVisitor<BVNImpl> {
75 std::vector<Value*> &RetVals;
76 BVNImpl(std::vector<Value*> &RV) : RetVals(RV) {}
78 void visitCastInst(CastInst &I);
79 void visitGetElementPtrInst(GetElementPtrInst &I);
80 void visitCmpInst(CmpInst &I);
82 void handleBinaryInst(Instruction &I);
83 void visitBinaryOperator(Instruction &I) { handleBinaryInst(I); }
84 void visitShiftInst(Instruction &I) { handleBinaryInst(I); }
85 void visitExtractElementInst(Instruction &I) { handleBinaryInst(I); }
87 void handleTernaryInst(Instruction &I);
88 void visitSelectInst(Instruction &I) { handleTernaryInst(I); }
89 void visitInsertElementInst(Instruction &I) { handleTernaryInst(I); }
90 void visitShuffleVectorInst(Instruction &I) { handleTernaryInst(I); }
91 void visitInstruction(Instruction &) {
92 // Cannot value number calls or terminator instructions.
97 ImmutablePass *llvm::createBasicVNPass() { return new BasicVN(); }
99 // getEqualNumberNodes - Return nodes with the same value number as the
100 // specified Value. This fills in the argument vector with any equal values.
102 void BasicVN::getEqualNumberNodes(Value *V, std::vector<Value*> &RetVals) const{
103 assert(V->getType() != Type::VoidTy &&
104 "Can only value number non-void values!");
105 // We can only handle the case where I is an instruction!
106 if (Instruction *I = dyn_cast<Instruction>(V))
107 BVNImpl(RetVals).visit(I);
110 void BVNImpl::visitCastInst(CastInst &CI) {
111 Instruction &I = (Instruction&)CI;
112 Value *Op = I.getOperand(0);
113 Function *F = I.getParent()->getParent();
115 for (Value::use_iterator UI = Op->use_begin(), UE = Op->use_end();
117 if (CastInst *Other = dyn_cast<CastInst>(*UI))
118 // Check that the opcode is the same
119 if (Other->getOpcode() == Instruction::CastOps(I.getOpcode()) &&
120 // Check that the destination types are the same
121 Other->getType() == I.getType() &&
122 // Is it embedded in the same function? (This could be false if LHS
123 // is a constant or global!)
124 Other->getParent()->getParent() == F &&
125 // Check to see if this new cast is not I.
127 // These instructions are identical. Add to list...
128 RetVals.push_back(Other);
132 void BVNImpl::visitCmpInst(CmpInst &CI1) {
133 Value *LHS = CI1.getOperand(0);
134 for (Value::use_iterator UI = LHS->use_begin(), UE = LHS->use_end();
136 if (CmpInst *CI2 = dyn_cast<CmpInst>(*UI))
137 // Check to see if this compare instruction is not CI, but same opcode,
138 // same predicate, and in the same function.
139 if (CI2 != &CI1 && CI2->getOpcode() == CI1.getOpcode() &&
140 CI2->getPredicate() == CI1.getPredicate() &&
141 CI2->getParent()->getParent() == CI1.getParent()->getParent())
142 // If the operands are the same
143 if ((CI2->getOperand(0) == CI1.getOperand(0) &&
144 CI2->getOperand(1) == CI1.getOperand(1)) ||
145 // Or the compare is commutative and the operands are reversed
146 (CI1.isCommutative() &&
147 CI2->getOperand(0) == CI1.getOperand(1) &&
148 CI2->getOperand(1) == CI1.getOperand(0)))
149 // Then the instructiosn are identical, add to list.
150 RetVals.push_back(CI2);
155 // isIdenticalBinaryInst - Return true if the two binary instructions are
158 static inline bool isIdenticalBinaryInst(const Instruction &I1,
159 const Instruction *I2) {
160 // Is it embedded in the same function? (This could be false if LHS
161 // is a constant or global!)
162 if (I1.getOpcode() != I2->getOpcode() ||
163 I1.getParent()->getParent() != I2->getParent()->getParent())
166 // If they are CmpInst instructions, check their predicates
167 if (CmpInst *CI1 = dyn_cast<CmpInst>(&const_cast<Instruction&>(I1)))
168 if (CI1->getPredicate() != cast<CmpInst>(I2)->getPredicate())
171 // They are identical if both operands are the same!
172 if (I1.getOperand(0) == I2->getOperand(0) &&
173 I1.getOperand(1) == I2->getOperand(1))
176 // If the instruction is commutative, the instruction can match if the
177 // operands are swapped!
179 if ((I1.getOperand(0) == I2->getOperand(1) &&
180 I1.getOperand(1) == I2->getOperand(0)) &&
187 // isIdenticalTernaryInst - Return true if the two ternary instructions are
190 static inline bool isIdenticalTernaryInst(const Instruction &I1,
191 const Instruction *I2) {
192 // Is it embedded in the same function? (This could be false if LHS
193 // is a constant or global!)
194 if (I1.getParent()->getParent() != I2->getParent()->getParent())
197 // They are identical if all operands are the same!
198 return I1.getOperand(0) == I2->getOperand(0) &&
199 I1.getOperand(1) == I2->getOperand(1) &&
200 I1.getOperand(2) == I2->getOperand(2);
205 void BVNImpl::handleBinaryInst(Instruction &I) {
206 Value *LHS = I.getOperand(0);
208 for (Value::use_iterator UI = LHS->use_begin(), UE = LHS->use_end();
210 if (Instruction *Other = dyn_cast<Instruction>(*UI))
211 // Check to see if this new binary operator is not I, but same operand...
212 if (Other != &I && isIdenticalBinaryInst(I, Other)) {
213 // These instructions are identical. Handle the situation.
214 RetVals.push_back(Other);
218 // IdenticalComplexInst - Return true if the two instructions are the same, by
219 // using a brute force comparison. This is useful for instructions with an
220 // arbitrary number of arguments.
222 static inline bool IdenticalComplexInst(const Instruction *I1,
223 const Instruction *I2) {
224 assert(I1->getOpcode() == I2->getOpcode());
225 // Equal if they are in the same function...
226 return I1->getParent()->getParent() == I2->getParent()->getParent() &&
227 // And return the same type...
228 I1->getType() == I2->getType() &&
229 // And have the same number of operands...
230 I1->getNumOperands() == I2->getNumOperands() &&
231 // And all of the operands are equal.
232 std::equal(I1->op_begin(), I1->op_end(), I2->op_begin());
235 void BVNImpl::visitGetElementPtrInst(GetElementPtrInst &I) {
236 Value *Op = I.getOperand(0);
238 // Try to pick a local operand if possible instead of a constant or a global
239 // that might have a lot of uses.
240 for (unsigned i = 1, e = I.getNumOperands(); i != e; ++i)
241 if (isa<Instruction>(I.getOperand(i)) || isa<Argument>(I.getOperand(i))) {
242 Op = I.getOperand(i);
246 for (Value::use_iterator UI = Op->use_begin(), UE = Op->use_end();
248 if (GetElementPtrInst *Other = dyn_cast<GetElementPtrInst>(*UI))
249 // Check to see if this new getelementptr is not I, but same operand...
250 if (Other != &I && IdenticalComplexInst(&I, Other)) {
251 // These instructions are identical. Handle the situation.
252 RetVals.push_back(Other);
256 void BVNImpl::handleTernaryInst(Instruction &I) {
257 Value *Op0 = I.getOperand(0);
258 Instruction *OtherInst;
260 for (Value::use_iterator UI = Op0->use_begin(), UE = Op0->use_end();
262 if ((OtherInst = dyn_cast<Instruction>(*UI)) &&
263 OtherInst->getOpcode() == I.getOpcode()) {
264 // Check to see if this new select is not I, but has the same operands.
265 if (OtherInst != &I && isIdenticalTernaryInst(I, OtherInst)) {
266 // These instructions are identical. Handle the situation.
267 RetVals.push_back(OtherInst);
274 // Ensure that users of ValueNumbering.h will link with this file
275 DEFINING_FILE_FOR(BasicValueNumbering)