2012-11-03 05:48:17 +08:00
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//===- CostModel.cpp ------ Cost Model Analysis ---------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the cost model analysis. It provides a very basic cost
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2012-12-24 13:51:12 +08:00
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// estimation for LLVM-IR. This analysis uses the services of the codegen
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// to approximate the cost of any IR instruction when lowered to machine
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// instructions. The cost results are unit-less and the cost number represents
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// the throughput of the machine assuming that all loads hit the cache, all
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// branches are predicted, etc. The cost numbers can be added in order to
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// compare two or more transformation alternatives.
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2012-11-03 05:48:17 +08:00
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//
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//===----------------------------------------------------------------------===//
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#define CM_NAME "cost-model"
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#define DEBUG_TYPE CM_NAME
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#include "llvm/Analysis/Passes.h"
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2013-01-07 11:08:10 +08:00
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#include "llvm/Analysis/TargetTransformInfo.h"
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2013-01-02 19:36:10 +08:00
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#include "llvm/IR/Function.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Value.h"
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2012-11-03 05:48:17 +08:00
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#include "llvm/Pass.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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namespace {
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class CostModelAnalysis : public FunctionPass {
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public:
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static char ID; // Class identification, replacement for typeinfo
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CostModelAnalysis() : FunctionPass(ID), F(0), TTI(0) {
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2012-11-03 05:48:17 +08:00
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initializeCostModelAnalysisPass(
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*PassRegistry::getPassRegistry());
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}
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/// Returns the expected cost of the instruction.
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/// Returns -1 if the cost is unknown.
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/// Note, this method does not cache the cost calculation and it
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/// can be expensive in some cases.
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unsigned getInstructionCost(const Instruction *I) const;
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2012-11-03 05:48:17 +08:00
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private:
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virtual void getAnalysisUsage(AnalysisUsage &AU) const;
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virtual bool runOnFunction(Function &F);
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virtual void print(raw_ostream &OS, const Module*) const;
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/// The function that we analyze.
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Function *F;
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/// Target information.
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const TargetTransformInfo *TTI;
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2012-11-03 05:48:17 +08:00
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};
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} // End of anonymous namespace
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// Register this pass.
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char CostModelAnalysis::ID = 0;
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static const char cm_name[] = "Cost Model Analysis";
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INITIALIZE_PASS_BEGIN(CostModelAnalysis, CM_NAME, cm_name, false, true)
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INITIALIZE_PASS_END (CostModelAnalysis, CM_NAME, cm_name, false, true)
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FunctionPass *llvm::createCostModelAnalysisPass() {
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return new CostModelAnalysis();
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}
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void
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CostModelAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesAll();
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}
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bool
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CostModelAnalysis::runOnFunction(Function &F) {
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this->F = &F;
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TTI = getAnalysisIfAvailable<TargetTransformInfo>();
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return false;
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}
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2012-12-04 06:47:12 +08:00
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unsigned CostModelAnalysis::getInstructionCost(const Instruction *I) const {
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if (!TTI)
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return -1;
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switch (I->getOpcode()) {
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case Instruction::Ret:
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case Instruction::PHI:
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case Instruction::Br: {
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return TTI->getCFInstrCost(I->getOpcode());
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}
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case Instruction::Add:
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case Instruction::FAdd:
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case Instruction::Sub:
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case Instruction::FSub:
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case Instruction::Mul:
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case Instruction::FMul:
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case Instruction::UDiv:
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case Instruction::SDiv:
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case Instruction::FDiv:
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case Instruction::URem:
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case Instruction::SRem:
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case Instruction::FRem:
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case Instruction::Shl:
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case Instruction::LShr:
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case Instruction::AShr:
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case Instruction::And:
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case Instruction::Or:
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case Instruction::Xor: {
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return TTI->getArithmeticInstrCost(I->getOpcode(), I->getType());
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}
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case Instruction::Select: {
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const SelectInst *SI = cast<SelectInst>(I);
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Type *CondTy = SI->getCondition()->getType();
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return TTI->getCmpSelInstrCost(I->getOpcode(), I->getType(), CondTy);
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}
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case Instruction::ICmp:
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case Instruction::FCmp: {
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Type *ValTy = I->getOperand(0)->getType();
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return TTI->getCmpSelInstrCost(I->getOpcode(), ValTy);
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}
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case Instruction::Store: {
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const StoreInst *SI = cast<StoreInst>(I);
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Type *ValTy = SI->getValueOperand()->getType();
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return TTI->getMemoryOpCost(I->getOpcode(), ValTy,
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SI->getAlignment(),
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SI->getPointerAddressSpace());
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}
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case Instruction::Load: {
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const LoadInst *LI = cast<LoadInst>(I);
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return TTI->getMemoryOpCost(I->getOpcode(), I->getType(),
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LI->getAlignment(),
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LI->getPointerAddressSpace());
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}
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case Instruction::ZExt:
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case Instruction::SExt:
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case Instruction::FPToUI:
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case Instruction::FPToSI:
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case Instruction::FPExt:
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case Instruction::PtrToInt:
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case Instruction::IntToPtr:
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case Instruction::SIToFP:
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case Instruction::UIToFP:
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case Instruction::Trunc:
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case Instruction::FPTrunc:
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case Instruction::BitCast: {
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Type *SrcTy = I->getOperand(0)->getType();
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return TTI->getCastInstrCost(I->getOpcode(), I->getType(), SrcTy);
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}
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case Instruction::ExtractElement: {
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const ExtractElementInst * EEI = cast<ExtractElementInst>(I);
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ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1));
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unsigned Idx = -1;
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if (CI)
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Idx = CI->getZExtValue();
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return TTI->getVectorInstrCost(I->getOpcode(),
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EEI->getOperand(0)->getType(), Idx);
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}
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case Instruction::InsertElement: {
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const InsertElementInst * IE = cast<InsertElementInst>(I);
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ConstantInt *CI = dyn_cast<ConstantInt>(IE->getOperand(2));
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unsigned Idx = -1;
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if (CI)
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Idx = CI->getZExtValue();
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return TTI->getVectorInstrCost(I->getOpcode(),
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IE->getType(), Idx);
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}
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default:
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// We don't have any information on this instruction.
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return -1;
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}
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}
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void CostModelAnalysis::print(raw_ostream &OS, const Module*) const {
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if (!F)
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return;
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for (Function::iterator B = F->begin(), BE = F->end(); B != BE; ++B) {
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for (BasicBlock::iterator it = B->begin(), e = B->end(); it != e; ++it) {
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Instruction *Inst = it;
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unsigned Cost = getInstructionCost(Inst);
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if (Cost != (unsigned)-1)
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OS << "Cost Model: Found an estimated cost of " << Cost;
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else
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OS << "Cost Model: Unknown cost";
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OS << " for instruction: "<< *Inst << "\n";
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}
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}
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}
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