1 //===- CostModel.cpp ------ Cost Model Analysis ---------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the cost model analysis. It provides a very basic cost
11 // estimation for LLVM-IR. This analysis uses the services of the codegen
12 // to approximate the cost of any IR instruction when lowered to machine
13 // instructions. The cost results are unit-less and the cost number represents
14 // the throughput of the machine assuming that all loads hit the cache, all
15 // branches are predicted, etc. The cost numbers can be added in order to
16 // compare two or more transformation alternatives.
18 //===----------------------------------------------------------------------===//
20 #define CM_NAME "cost-model"
21 #define DEBUG_TYPE CM_NAME
22 #include "llvm/Analysis/Passes.h"
23 #include "llvm/Analysis/TargetTransformInfo.h"
24 #include "llvm/IR/Function.h"
25 #include "llvm/IR/Instructions.h"
26 #include "llvm/IR/IntrinsicInst.h"
27 #include "llvm/IR/Value.h"
28 #include "llvm/Pass.h"
29 #include "llvm/Support/Debug.h"
30 #include "llvm/Support/raw_ostream.h"
34 class CostModelAnalysis : public FunctionPass {
37 static char ID; // Class identification, replacement for typeinfo
38 CostModelAnalysis() : FunctionPass(ID), F(0), TTI(0) {
39 initializeCostModelAnalysisPass(
40 *PassRegistry::getPassRegistry());
43 /// Returns the expected cost of the instruction.
44 /// Returns -1 if the cost is unknown.
45 /// Note, this method does not cache the cost calculation and it
46 /// can be expensive in some cases.
47 unsigned getInstructionCost(const Instruction *I) const;
50 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
51 virtual bool runOnFunction(Function &F);
52 virtual void print(raw_ostream &OS, const Module*) const;
54 /// The function that we analyze.
56 /// Target information.
57 const TargetTransformInfo *TTI;
59 } // End of anonymous namespace
61 // Register this pass.
62 char CostModelAnalysis::ID = 0;
63 static const char cm_name[] = "Cost Model Analysis";
64 INITIALIZE_PASS_BEGIN(CostModelAnalysis, CM_NAME, cm_name, false, true)
65 INITIALIZE_PASS_END (CostModelAnalysis, CM_NAME, cm_name, false, true)
67 FunctionPass *llvm::createCostModelAnalysisPass() {
68 return new CostModelAnalysis();
72 CostModelAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
77 CostModelAnalysis::runOnFunction(Function &F) {
79 TTI = getAnalysisIfAvailable<TargetTransformInfo>();
84 static bool isReverseVectorMask(SmallVector<int, 16> &Mask) {
85 for (unsigned i = 0, MaskSize = Mask.size(); i < MaskSize; ++i)
86 if (Mask[i] > 0 && Mask[i] != (int)(MaskSize - 1 - i))
91 unsigned CostModelAnalysis::getInstructionCost(const Instruction *I) const {
95 switch (I->getOpcode()) {
96 case Instruction::GetElementPtr:{
97 Type *ValTy = I->getOperand(0)->getType()->getPointerElementType();
98 return TTI->getAddressComputationCost(ValTy);
101 case Instruction::Ret:
102 case Instruction::PHI:
103 case Instruction::Br: {
104 return TTI->getCFInstrCost(I->getOpcode());
106 case Instruction::Add:
107 case Instruction::FAdd:
108 case Instruction::Sub:
109 case Instruction::FSub:
110 case Instruction::Mul:
111 case Instruction::FMul:
112 case Instruction::UDiv:
113 case Instruction::SDiv:
114 case Instruction::FDiv:
115 case Instruction::URem:
116 case Instruction::SRem:
117 case Instruction::FRem:
118 case Instruction::Shl:
119 case Instruction::LShr:
120 case Instruction::AShr:
121 case Instruction::And:
122 case Instruction::Or:
123 case Instruction::Xor: {
124 return TTI->getArithmeticInstrCost(I->getOpcode(), I->getType());
126 case Instruction::Select: {
127 const SelectInst *SI = cast<SelectInst>(I);
128 Type *CondTy = SI->getCondition()->getType();
129 return TTI->getCmpSelInstrCost(I->getOpcode(), I->getType(), CondTy);
131 case Instruction::ICmp:
132 case Instruction::FCmp: {
133 Type *ValTy = I->getOperand(0)->getType();
134 return TTI->getCmpSelInstrCost(I->getOpcode(), ValTy);
136 case Instruction::Store: {
137 const StoreInst *SI = cast<StoreInst>(I);
138 Type *ValTy = SI->getValueOperand()->getType();
139 return TTI->getMemoryOpCost(I->getOpcode(), ValTy,
141 SI->getPointerAddressSpace());
143 case Instruction::Load: {
144 const LoadInst *LI = cast<LoadInst>(I);
145 return TTI->getMemoryOpCost(I->getOpcode(), I->getType(),
147 LI->getPointerAddressSpace());
149 case Instruction::ZExt:
150 case Instruction::SExt:
151 case Instruction::FPToUI:
152 case Instruction::FPToSI:
153 case Instruction::FPExt:
154 case Instruction::PtrToInt:
155 case Instruction::IntToPtr:
156 case Instruction::SIToFP:
157 case Instruction::UIToFP:
158 case Instruction::Trunc:
159 case Instruction::FPTrunc:
160 case Instruction::BitCast: {
161 Type *SrcTy = I->getOperand(0)->getType();
162 return TTI->getCastInstrCost(I->getOpcode(), I->getType(), SrcTy);
164 case Instruction::ExtractElement: {
165 const ExtractElementInst * EEI = cast<ExtractElementInst>(I);
166 ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1));
169 Idx = CI->getZExtValue();
170 return TTI->getVectorInstrCost(I->getOpcode(),
171 EEI->getOperand(0)->getType(), Idx);
173 case Instruction::InsertElement: {
174 const InsertElementInst * IE = cast<InsertElementInst>(I);
175 ConstantInt *CI = dyn_cast<ConstantInt>(IE->getOperand(2));
178 Idx = CI->getZExtValue();
179 return TTI->getVectorInstrCost(I->getOpcode(),
182 case Instruction::ShuffleVector: {
183 const ShuffleVectorInst *Shuffle = cast<ShuffleVectorInst>(I);
184 Type *VecTypOp0 = Shuffle->getOperand(0)->getType();
185 unsigned NumVecElems = VecTypOp0->getVectorNumElements();
186 SmallVector<int, 16> Mask = Shuffle->getShuffleMask();
188 if (NumVecElems == Mask.size() && isReverseVectorMask(Mask))
189 return TTI->getShuffleCost(TargetTransformInfo::SK_Reverse, VecTypOp0, 0,
193 case Instruction::Call:
194 if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
195 SmallVector<Type*, 4> Tys;
196 for (unsigned J = 0, JE = II->getNumArgOperands(); J != JE; ++J)
197 Tys.push_back(II->getArgOperand(J)->getType());
199 return TTI->getIntrinsicInstrCost(II->getIntrinsicID(), II->getType(),
204 // We don't have any information on this instruction.
209 void CostModelAnalysis::print(raw_ostream &OS, const Module*) const {
213 for (Function::iterator B = F->begin(), BE = F->end(); B != BE; ++B) {
214 for (BasicBlock::iterator it = B->begin(), e = B->end(); it != e; ++it) {
215 Instruction *Inst = it;
216 unsigned Cost = getInstructionCost(Inst);
217 if (Cost != (unsigned)-1)
218 OS << "Cost Model: Found an estimated cost of " << Cost;
220 OS << "Cost Model: Unknown cost";
222 OS << " for instruction: "<< *Inst << "\n";