1 //===- FunctionImport.cpp - ThinLTO Summary-based Function Import ---------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements Function import based on summaries.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/Transforms/IPO/FunctionImport.h"
16 #include "llvm/ADT/StringSet.h"
17 #include "llvm/IR/AutoUpgrade.h"
18 #include "llvm/IR/DiagnosticPrinter.h"
19 #include "llvm/IR/IntrinsicInst.h"
20 #include "llvm/IR/Module.h"
21 #include "llvm/IRReader/IRReader.h"
22 #include "llvm/Linker/Linker.h"
23 #include "llvm/Object/FunctionIndexObjectFile.h"
24 #include "llvm/Support/CommandLine.h"
25 #include "llvm/Support/Debug.h"
26 #include "llvm/Support/SourceMgr.h"
29 #define DEBUG_TYPE "function-import"
31 /// Limit on instruction count of imported functions.
32 static cl::opt<unsigned> ImportInstrLimit(
33 "import-instr-limit", cl::init(100), cl::Hidden, cl::value_desc("N"),
34 cl::desc("Only import functions with less than N instructions"));
36 // Load lazily a module from \p FileName in \p Context.
37 static std::unique_ptr<Module> loadFile(const std::string &FileName,
38 LLVMContext &Context) {
40 DEBUG(dbgs() << "Loading '" << FileName << "'\n");
41 std::unique_ptr<Module> Result = getLazyIRFileModule(FileName, Err, Context);
43 Err.print("function-import", errs());
47 Result->materializeMetadata();
48 UpgradeDebugInfo(*Result);
53 // Get a Module for \p FileName from the cache, or load it lazily.
54 Module &FunctionImporter::getOrLoadModule(StringRef FileName) {
55 auto &Module = ModuleMap[FileName];
57 Module = loadFile(FileName, Context);
61 /// Walk through the instructions in \p F looking for external
62 /// calls not already in the \p CalledFunctions set. If any are
63 /// found they are added to the \p Worklist for importing.
64 static void findExternalCalls(const Function &F, StringSet<> &CalledFunctions,
65 SmallVector<StringRef, 64> &Worklist) {
68 if (isa<CallInst>(I)) {
69 DEBUG(dbgs() << "Found a call: '" << I << "'\n");
70 auto CalledFunction = cast<CallInst>(I).getCalledFunction();
71 // Insert any new external calls that have not already been
72 // added to set/worklist.
73 if (CalledFunction && CalledFunction->hasName() &&
74 CalledFunction->isDeclaration() &&
75 !CalledFunctions.count(CalledFunction->getName())) {
76 CalledFunctions.insert(CalledFunction->getName());
77 Worklist.push_back(CalledFunction->getName());
84 // Automatically import functions in Module \p M based on the summaries index.
86 // The current implementation imports every called functions that exists in the
88 bool FunctionImporter::importFunctions(Module &M) {
89 assert(&Context == &M.getContext());
93 /// First step is collecting the called external functions.
94 StringSet<> CalledFunctions;
95 SmallVector<StringRef, 64> Worklist;
97 if (F.isDeclaration() || F.hasFnAttribute(Attribute::OptimizeNone))
99 findExternalCalls(F, CalledFunctions, Worklist);
102 /// Second step: for every call to an external function, try to import it.
104 // Linker that will be used for importing function
105 Linker L(&M, DiagnosticHandler);
107 while (!Worklist.empty()) {
108 auto CalledFunctionName = Worklist.pop_back_val();
109 DEBUG(dbgs() << "Process import for " << CalledFunctionName << "\n");
111 // Try to get a summary for this function call.
112 auto InfoList = Index.findFunctionInfoList(CalledFunctionName);
113 if (InfoList == Index.end()) {
114 DEBUG(dbgs() << "No summary for " << CalledFunctionName
118 assert(!InfoList->second.empty() && "No summary, error at import?");
120 // Comdat can have multiple entries, FIXME: what do we do with them?
121 auto &Info = InfoList->second[0];
122 assert(Info && "Nullptr in list, error importing summaries?\n");
124 auto *Summary = Info->functionSummary();
126 // FIXME: in case we are lazyloading summaries, we can do it now.
127 dbgs() << "Missing summary for " << CalledFunctionName
128 << ", error at import?\n";
129 llvm_unreachable("Missing summary");
132 if (Summary->instCount() > ImportInstrLimit) {
133 dbgs() << "Skip import of " << CalledFunctionName << " with "
134 << Summary->instCount() << " instructions (limit "
135 << ImportInstrLimit << ")\n";
140 // No profitability notion right now, just import all the time...
143 // Get the module path from the summary.
144 auto FileName = Summary->modulePath();
145 DEBUG(dbgs() << "Importing " << CalledFunctionName << " from " << FileName
148 // Get the module for the import (potentially from the cache).
149 auto &Module = getOrLoadModule(FileName);
151 // The function that we will import!
152 GlobalValue *SGV = Module.getNamedValue(CalledFunctionName);
153 StringRef ImportFunctionName = CalledFunctionName;
155 // Might be local in source Module, promoted/renamed in dest Module M.
156 std::pair<StringRef, StringRef> Split =
157 CalledFunctionName.split(".llvm.");
158 SGV = Module.getNamedValue(Split.first);
160 // Assert that Split.second is module id
162 assert(!Split.second.getAsInteger(10, ModuleId));
163 assert(ModuleId == Index.getModuleId(FileName));
166 Function *F = dyn_cast<Function>(SGV);
167 if (!F && isa<GlobalAlias>(SGV)) {
168 auto *SGA = dyn_cast<GlobalAlias>(SGV);
169 F = dyn_cast<Function>(SGA->getBaseObject());
170 ImportFunctionName = F->getName();
173 errs() << "Can't load function '" << CalledFunctionName << "' in Module '"
174 << FileName << "', error in the summary?\n";
175 llvm_unreachable("Can't load function in Module");
178 // We cannot import weak_any functions/aliases without possibly affecting
179 // the order they are seen and selected by the linker, changing program
181 if (SGV->hasWeakAnyLinkage()) {
182 DEBUG(dbgs() << "Ignoring import request for weak-any "
183 << (isa<Function>(SGV) ? "function " : "alias ")
184 << CalledFunctionName << " from " << FileName << "\n");
188 // Link in the specified function.
189 if (L.linkInModule(&Module, Linker::Flags::None, &Index, F))
190 report_fatal_error("Function Import: link error");
192 // Process the newly imported function and add callees to the worklist.
193 GlobalValue *NewGV = M.getNamedValue(ImportFunctionName);
195 Function *NewF = dyn_cast<Function>(NewGV);
197 findExternalCalls(*NewF, CalledFunctions, Worklist);
204 /// Summary file to use for function importing when using -function-import from
205 /// the command line.
206 static cl::opt<std::string>
207 SummaryFile("summary-file",
208 cl::desc("The summary file to use for function importing."));
210 static void diagnosticHandler(const DiagnosticInfo &DI) {
211 raw_ostream &OS = errs();
212 DiagnosticPrinterRawOStream DP(OS);
217 /// Parse the function index out of an IR file and return the function
218 /// index object if found, or nullptr if not.
219 static std::unique_ptr<FunctionInfoIndex>
220 getFunctionIndexForFile(StringRef Path, std::string &Error,
221 DiagnosticHandlerFunction DiagnosticHandler) {
222 std::unique_ptr<MemoryBuffer> Buffer;
223 ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
224 MemoryBuffer::getFile(Path);
225 if (std::error_code EC = BufferOrErr.getError()) {
226 Error = EC.message();
229 Buffer = std::move(BufferOrErr.get());
230 ErrorOr<std::unique_ptr<object::FunctionIndexObjectFile>> ObjOrErr =
231 object::FunctionIndexObjectFile::create(Buffer->getMemBufferRef(),
233 if (std::error_code EC = ObjOrErr.getError()) {
234 Error = EC.message();
237 return (*ObjOrErr)->takeIndex();
240 /// Pass that performs cross-module function import provided a summary file.
241 class FunctionImportPass : public ModulePass {
244 /// Pass identification, replacement for typeid
247 explicit FunctionImportPass() : ModulePass(ID) {}
249 bool runOnModule(Module &M) override {
250 if (SummaryFile.empty()) {
251 report_fatal_error("error: -function-import requires -summary-file\n");
254 std::unique_ptr<FunctionInfoIndex> Index =
255 getFunctionIndexForFile(SummaryFile, Error, diagnosticHandler);
257 errs() << "Error loading file '" << SummaryFile << "': " << Error << "\n";
261 // Perform the import now.
262 FunctionImporter Importer(M.getContext(), *Index, diagnosticHandler);
263 return Importer.importFunctions(M);
269 char FunctionImportPass::ID = 0;
270 INITIALIZE_PASS_BEGIN(FunctionImportPass, "function-import",
271 "Summary Based Function Import", false, false)
272 INITIALIZE_PASS_END(FunctionImportPass, "function-import",
273 "Summary Based Function Import", false, false)
276 Pass *createFunctionImportPass() { return new FunctionImportPass(); }