305 lines · cpp
1//===------ PerfMonitor.cpp - Generate a run-time performance monitor. -======//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-exception6//7//===----------------------------------------------------------------------===//8//9//===----------------------------------------------------------------------===//10 11#include "polly/CodeGen/PerfMonitor.h"12#include "polly/CodeGen/RuntimeDebugBuilder.h"13#include "polly/ScopInfo.h"14#include "llvm/ADT/Twine.h"15#include "llvm/IR/IntrinsicsX86.h"16#include "llvm/IR/Module.h"17#include "llvm/TargetParser/Triple.h"18 19using namespace llvm;20using namespace polly;21 22Function *PerfMonitor::getAtExit() {23 const char *Name = "atexit";24 Function *F = M->getFunction(Name);25 26 if (!F) {27 GlobalValue::LinkageTypes Linkage = Function::ExternalLinkage;28 FunctionType *Ty =29 FunctionType::get(Builder.getInt32Ty(), {Builder.getPtrTy()}, false);30 F = Function::Create(Ty, Linkage, Name, M);31 }32 33 return F;34}35 36void PerfMonitor::addToGlobalConstructors(Function *Fn) {37 const char *Name = "llvm.global_ctors";38 GlobalVariable *GV = M->getGlobalVariable(Name);39 std::vector<Constant *> V;40 41 if (GV) {42 Constant *Array = GV->getInitializer();43 for (Value *X : Array->operand_values())44 V.push_back(cast<Constant>(X));45 GV->eraseFromParent();46 }47 48 StructType *ST =49 StructType::get(Builder.getInt32Ty(), Fn->getType(), Builder.getPtrTy());50 51 V.push_back(52 ConstantStruct::get(ST, Builder.getInt32(10), Fn,53 ConstantPointerNull::get(Builder.getPtrTy())));54 ArrayType *Ty = ArrayType::get(ST, V.size());55 56 GV = new GlobalVariable(*M, Ty, true, GlobalValue::AppendingLinkage,57 ConstantArray::get(Ty, V), Name, nullptr,58 GlobalVariable::NotThreadLocal);59}60 61Function *PerfMonitor::getRDTSCP() {62 return Intrinsic::getOrInsertDeclaration(M, Intrinsic::x86_rdtscp);63}64 65PerfMonitor::PerfMonitor(const Scop &S, Module *M)66 : M(M), Builder(M->getContext()), S(S) {67 if (M->getTargetTriple().getArch() == llvm::Triple::x86_64)68 Supported = true;69 else70 Supported = false;71}72 73static void TryRegisterGlobal(Module *M, const char *Name,74 Constant *InitialValue, Value **Location) {75 *Location = M->getGlobalVariable(Name);76 77 if (!*Location)78 *Location = new GlobalVariable(79 *M, InitialValue->getType(), true, GlobalValue::WeakAnyLinkage,80 InitialValue, Name, nullptr, GlobalVariable::InitialExecTLSModel);81}82 83// Generate a unique name that is usable as a LLVM name for a scop to name its84// performance counter.85static std::string GetScopUniqueVarname(const Scop &S) {86 std::string EntryString, ExitString;87 std::tie(EntryString, ExitString) = S.getEntryExitStr();88 89 return (Twine("__polly_perf_in_") + S.getFunction().getName() + "_from__" +90 EntryString + "__to__" + ExitString)91 .str();92}93 94void PerfMonitor::addScopCounter() {95 const std::string varname = GetScopUniqueVarname(S);96 TryRegisterGlobal(M, (varname + "_cycles").c_str(), Builder.getInt64(0),97 &CyclesInCurrentScopPtr);98 99 TryRegisterGlobal(M, (varname + "_trip_count").c_str(), Builder.getInt64(0),100 &TripCountForCurrentScopPtr);101}102 103void PerfMonitor::addGlobalVariables() {104 TryRegisterGlobal(M, "__polly_perf_cycles_total_start", Builder.getInt64(0),105 &CyclesTotalStartPtr);106 107 TryRegisterGlobal(M, "__polly_perf_initialized", Builder.getInt1(false),108 &AlreadyInitializedPtr);109 110 TryRegisterGlobal(M, "__polly_perf_cycles_in_scops", Builder.getInt64(0),111 &CyclesInScopsPtr);112 113 TryRegisterGlobal(M, "__polly_perf_cycles_in_scop_start", Builder.getInt64(0),114 &CyclesInScopStartPtr);115}116 117static const char *InitFunctionName = "__polly_perf_init";118static const char *FinalReportingFunctionName = "__polly_perf_final";119 120static BasicBlock *FinalStartBB = nullptr;121static ReturnInst *ReturnFromFinal = nullptr;122 123Function *PerfMonitor::insertFinalReporting() {124 // Create new function.125 GlobalValue::LinkageTypes Linkage = Function::WeakODRLinkage;126 FunctionType *Ty = FunctionType::get(Builder.getVoidTy(), {}, false);127 Function *ExitFn =128 Function::Create(Ty, Linkage, FinalReportingFunctionName, M);129 FinalStartBB = BasicBlock::Create(M->getContext(), "start", ExitFn);130 Builder.SetInsertPoint(FinalStartBB);131 132 if (!Supported) {133 RuntimeDebugBuilder::createCPUPrinter(134 Builder, "Polly runtime information generation not supported\n");135 Builder.CreateRetVoid();136 return ExitFn;137 }138 139 // Measure current cycles and compute final timings.140 Function *RDTSCPFn = getRDTSCP();141 142 Type *Int64Ty = Builder.getInt64Ty();143 Value *CurrentCycles =144 Builder.CreateExtractValue(Builder.CreateCall(RDTSCPFn), {0});145 Value *CyclesStart = Builder.CreateLoad(Int64Ty, CyclesTotalStartPtr, true);146 Value *CyclesTotal = Builder.CreateSub(CurrentCycles, CyclesStart);147 Value *CyclesInScops = Builder.CreateLoad(Int64Ty, CyclesInScopsPtr, true);148 149 // Print the runtime information.150 RuntimeDebugBuilder::createCPUPrinter(Builder, "Polly runtime information\n");151 RuntimeDebugBuilder::createCPUPrinter(Builder, "-------------------------\n");152 RuntimeDebugBuilder::createCPUPrinter(Builder, "Total: ", CyclesTotal, "\n");153 RuntimeDebugBuilder::createCPUPrinter(Builder, "Scops: ", CyclesInScops,154 "\n");155 156 // Print the preamble for per-scop information.157 RuntimeDebugBuilder::createCPUPrinter(Builder, "\n");158 RuntimeDebugBuilder::createCPUPrinter(Builder, "Per SCoP information\n");159 RuntimeDebugBuilder::createCPUPrinter(Builder, "--------------------\n");160 161 RuntimeDebugBuilder::createCPUPrinter(162 Builder, "scop function, "163 "entry block name, exit block name, total time, trip count\n");164 ReturnFromFinal = Builder.CreateRetVoid();165 return ExitFn;166}167 168void PerfMonitor::AppendScopReporting() {169 if (!Supported)170 return;171 172 assert(FinalStartBB && "Expected FinalStartBB to be initialized by "173 "PerfMonitor::insertFinalReporting.");174 assert(ReturnFromFinal && "Expected ReturnFromFinal to be initialized by "175 "PerfMonitor::insertFinalReporting.");176 177 Builder.SetInsertPoint(FinalStartBB);178 ReturnFromFinal->eraseFromParent();179 180 Type *Int64Ty = Builder.getInt64Ty();181 Value *CyclesInCurrentScop =182 Builder.CreateLoad(Int64Ty, this->CyclesInCurrentScopPtr, true);183 184 Value *TripCountForCurrentScop =185 Builder.CreateLoad(Int64Ty, this->TripCountForCurrentScopPtr, true);186 187 std::string EntryName, ExitName;188 std::tie(EntryName, ExitName) = S.getEntryExitStr();189 190 // print in CSV for easy parsing with other tools.191 RuntimeDebugBuilder::createCPUPrinter(192 Builder, S.getFunction().getName(), ", ", EntryName, ", ", ExitName, ", ",193 CyclesInCurrentScop, ", ", TripCountForCurrentScop, "\n");194 195 ReturnFromFinal = Builder.CreateRetVoid();196}197 198static Function *FinalReporting = nullptr;199 200void PerfMonitor::initialize() {201 addGlobalVariables();202 addScopCounter();203 204 // Ensure that we only add the final reporting function once.205 // On later invocations, append to the reporting function.206 if (!FinalReporting) {207 FinalReporting = insertFinalReporting();208 209 Function *InitFn = insertInitFunction(FinalReporting);210 addToGlobalConstructors(InitFn);211 }212 213 AppendScopReporting();214}215 216Function *PerfMonitor::insertInitFunction(Function *FinalReporting) {217 // Insert function definition and BBs.218 GlobalValue::LinkageTypes Linkage = Function::WeakODRLinkage;219 FunctionType *Ty = FunctionType::get(Builder.getVoidTy(), {}, false);220 Function *InitFn = Function::Create(Ty, Linkage, InitFunctionName, M);221 BasicBlock *Start = BasicBlock::Create(M->getContext(), "start", InitFn);222 BasicBlock *EarlyReturn =223 BasicBlock::Create(M->getContext(), "earlyreturn", InitFn);224 BasicBlock *InitBB = BasicBlock::Create(M->getContext(), "initbb", InitFn);225 226 Builder.SetInsertPoint(Start);227 228 // Check if this function was already run. If yes, return.229 //230 // In case profiling has been enabled in multiple translation units, the231 // initializer function will be added to the global constructors list of232 // each translation unit. When merging translation units, the global233 // constructor lists are just appended, such that the initializer will appear234 // multiple times. To avoid initializations being run multiple times (and235 // especially to avoid that atExitFn is called more than once), we bail236 // out if the initializer is run more than once.237 Value *HasRunBefore =238 Builder.CreateLoad(Builder.getInt1Ty(), AlreadyInitializedPtr);239 Builder.CreateCondBr(HasRunBefore, EarlyReturn, InitBB);240 Builder.SetInsertPoint(EarlyReturn);241 Builder.CreateRetVoid();242 243 // Keep track that this function has been run once.244 Builder.SetInsertPoint(InitBB);245 Value *True = Builder.getInt1(true);246 Builder.CreateStore(True, AlreadyInitializedPtr);247 248 // Register the final reporting function with atexit().249 Value *FinalReportingPtr =250 Builder.CreatePointerCast(FinalReporting, Builder.getPtrTy());251 Function *AtExitFn = getAtExit();252 Builder.CreateCall(AtExitFn, {FinalReportingPtr});253 254 if (Supported) {255 // Read the currently cycle counter and store the result for later.256 Function *RDTSCPFn = getRDTSCP();257 Value *CurrentCycles =258 Builder.CreateExtractValue(Builder.CreateCall(RDTSCPFn), {0});259 Builder.CreateStore(CurrentCycles, CyclesTotalStartPtr, true);260 }261 Builder.CreateRetVoid();262 263 return InitFn;264}265 266void PerfMonitor::insertRegionStart(Instruction *InsertBefore) {267 if (!Supported)268 return;269 270 Builder.SetInsertPoint(InsertBefore->getIterator());271 Function *RDTSCPFn = getRDTSCP();272 Value *CurrentCycles =273 Builder.CreateExtractValue(Builder.CreateCall(RDTSCPFn), {0});274 Builder.CreateStore(CurrentCycles, CyclesInScopStartPtr, true);275}276 277void PerfMonitor::insertRegionEnd(Instruction *InsertBefore) {278 if (!Supported)279 return;280 281 Builder.SetInsertPoint(InsertBefore->getIterator());282 Function *RDTSCPFn = getRDTSCP();283 Type *Int64Ty = Builder.getInt64Ty();284 LoadInst *CyclesStart =285 Builder.CreateLoad(Int64Ty, CyclesInScopStartPtr, true);286 Value *CurrentCycles =287 Builder.CreateExtractValue(Builder.CreateCall(RDTSCPFn), {0});288 Value *CyclesInScop = Builder.CreateSub(CurrentCycles, CyclesStart);289 Value *CyclesInScops = Builder.CreateLoad(Int64Ty, CyclesInScopsPtr, true);290 CyclesInScops = Builder.CreateAdd(CyclesInScops, CyclesInScop);291 Builder.CreateStore(CyclesInScops, CyclesInScopsPtr, true);292 293 Value *CyclesInCurrentScop =294 Builder.CreateLoad(Int64Ty, CyclesInCurrentScopPtr, true);295 CyclesInCurrentScop = Builder.CreateAdd(CyclesInCurrentScop, CyclesInScop);296 Builder.CreateStore(CyclesInCurrentScop, CyclesInCurrentScopPtr, true);297 298 Value *TripCountForCurrentScop =299 Builder.CreateLoad(Int64Ty, TripCountForCurrentScopPtr, true);300 TripCountForCurrentScop =301 Builder.CreateAdd(TripCountForCurrentScop, Builder.getInt64(1));302 Builder.CreateStore(TripCountForCurrentScop, TripCountForCurrentScopPtr,303 true);304}305