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/Passes.h" 21 #include "llvm/Analysis/TargetTransformInfo.h" 22 #include "llvm/IR/Function.h" 23 #include "llvm/IR/PassManager.h" 24 #include "llvm/InitializePasses.h" 25 #include "llvm/Pass.h" 26 #include "llvm/Support/CommandLine.h" 27 #include "llvm/Support/raw_ostream.h" 28 #include "llvm/IR/IntrinsicInst.h" 29 using namespace llvm; 30 31 static cl::opt<TargetTransformInfo::TargetCostKind> CostKind( 32 "cost-kind", cl::desc("Target cost kind"), 33 cl::init(TargetTransformInfo::TCK_RecipThroughput), 34 cl::values(clEnumValN(TargetTransformInfo::TCK_RecipThroughput, 35 "throughput", "Reciprocal throughput"), 36 clEnumValN(TargetTransformInfo::TCK_Latency, 37 "latency", "Instruction latency"), 38 clEnumValN(TargetTransformInfo::TCK_CodeSize, 39 "code-size", "Code size"), 40 clEnumValN(TargetTransformInfo::TCK_SizeAndLatency, 41 "size-latency", "Code size and latency"))); 42 43 static cl::opt<bool> TypeBasedIntrinsicCost("type-based-intrinsic-cost", 44 cl::desc("Calculate intrinsics cost based only on argument types"), 45 cl::init(false)); 46 47 #define CM_NAME "cost-model" 48 #define DEBUG_TYPE CM_NAME 49 50 PreservedAnalyses CostModelPrinterPass::run(Function &F, 51 FunctionAnalysisManager &AM) { 52 auto &TTI = AM.getResult<TargetIRAnalysis>(F); 53 OS << "Printing analysis 'Cost Model Analysis' for function '" << F.getName() << "':\n"; 54 for (BasicBlock &B : F) { 55 for (Instruction &Inst : B) { 56 // TODO: Use a pass parameter instead of cl::opt CostKind to determine 57 // which cost kind to print. 58 InstructionCost Cost; 59 auto *II = dyn_cast<IntrinsicInst>(&Inst); 60 if (II && TypeBasedIntrinsicCost) { 61 IntrinsicCostAttributes ICA(II->getIntrinsicID(), *II, 62 InstructionCost::getInvalid(), true); 63 Cost = TTI.getIntrinsicInstrCost(ICA, CostKind); 64 } 65 else { 66 Cost = TTI.getInstructionCost(&Inst, CostKind); 67 } 68 69 if (auto CostVal = Cost.getValue()) 70 OS << "Cost Model: Found an estimated cost of " << *CostVal; 71 else 72 OS << "Cost Model: Invalid cost"; 73 74 OS << " for instruction: " << Inst << "\n"; 75 } 76 } 77 return PreservedAnalyses::all(); 78 } 79