1 //===- CostModel.cpp ------ Cost Model Analysis ---------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file defines the cost model analysis. It provides a very basic cost 10 // estimation for LLVM-IR. This analysis uses the services of the codegen 11 // to approximate the cost of any IR instruction when lowered to machine 12 // instructions. The cost results are unit-less and the cost number represents 13 // the throughput of the machine assuming that all loads hit the cache, all 14 // branches are predicted, etc. The cost numbers can be added in order to 15 // compare two or more transformation alternatives. 16 // 17 //===----------------------------------------------------------------------===// 18 19 #include "llvm/Analysis/CostModel.h" 20 #include "llvm/Analysis/TargetTransformInfo.h" 21 #include "llvm/IR/Function.h" 22 #include "llvm/IR/IntrinsicInst.h" 23 #include "llvm/IR/PassManager.h" 24 #include "llvm/Pass.h" 25 #include "llvm/Support/CommandLine.h" 26 #include "llvm/Support/raw_ostream.h" 27 using namespace llvm; 28 29 static cl::opt<TargetTransformInfo::TargetCostKind> CostKind( 30 "cost-kind", cl::desc("Target cost kind"), 31 cl::init(TargetTransformInfo::TCK_RecipThroughput), 32 cl::values(clEnumValN(TargetTransformInfo::TCK_RecipThroughput, 33 "throughput", "Reciprocal throughput"), 34 clEnumValN(TargetTransformInfo::TCK_Latency, 35 "latency", "Instruction latency"), 36 clEnumValN(TargetTransformInfo::TCK_CodeSize, 37 "code-size", "Code size"), 38 clEnumValN(TargetTransformInfo::TCK_SizeAndLatency, 39 "size-latency", "Code size and latency"))); 40 41 static cl::opt<bool> TypeBasedIntrinsicCost("type-based-intrinsic-cost", 42 cl::desc("Calculate intrinsics cost based only on argument types"), 43 cl::init(false)); 44 45 #define CM_NAME "cost-model" 46 #define DEBUG_TYPE CM_NAME 47 48 PreservedAnalyses CostModelPrinterPass::run(Function &F, 49 FunctionAnalysisManager &AM) { 50 auto &TTI = AM.getResult<TargetIRAnalysis>(F); 51 OS << "Printing analysis 'Cost Model Analysis' for function '" << F.getName() << "':\n"; 52 for (BasicBlock &B : F) { 53 for (Instruction &Inst : B) { 54 // TODO: Use a pass parameter instead of cl::opt CostKind to determine 55 // which cost kind to print. 56 InstructionCost Cost; 57 auto *II = dyn_cast<IntrinsicInst>(&Inst); 58 if (II && TypeBasedIntrinsicCost) { 59 IntrinsicCostAttributes ICA(II->getIntrinsicID(), *II, 60 InstructionCost::getInvalid(), true); 61 Cost = TTI.getIntrinsicInstrCost(ICA, CostKind); 62 } 63 else { 64 Cost = TTI.getInstructionCost(&Inst, CostKind); 65 } 66 67 if (auto CostVal = Cost.getValue()) 68 OS << "Cost Model: Found an estimated cost of " << *CostVal; 69 else 70 OS << "Cost Model: Invalid cost"; 71 72 OS << " for instruction: " << Inst << "\n"; 73 } 74 } 75 return PreservedAnalyses::all(); 76 } 77