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