503 lines
19 KiB
C++
503 lines
19 KiB
C++
//===- FunctionImport.cpp - ThinLTO Summary-based Function Import ---------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements Function import based on summaries.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/IPO/FunctionImport.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/StringSet.h"
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#include "llvm/IR/AutoUpgrade.h"
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#include "llvm/IR/DiagnosticPrinter.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/Module.h"
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#include "llvm/IRReader/IRReader.h"
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#include "llvm/Linker/Linker.h"
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#include "llvm/Object/ModuleSummaryIndexObjectFile.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/SourceMgr.h"
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#include "llvm/Transforms/Utils/FunctionImportUtils.h"
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#define DEBUG_TYPE "function-import"
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using namespace llvm;
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STATISTIC(NumImported, "Number of functions imported");
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/// Limit on instruction count of imported functions.
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static cl::opt<unsigned> ImportInstrLimit(
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"import-instr-limit", cl::init(100), cl::Hidden, cl::value_desc("N"),
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cl::desc("Only import functions with less than N instructions"));
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static cl::opt<float>
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ImportInstrFactor("import-instr-evolution-factor", cl::init(0.7),
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cl::Hidden, cl::value_desc("x"),
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cl::desc("As we import functions, multiply the "
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"`import-instr-limit` threshold by this factor "
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"before processing newly imported functions"));
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static cl::opt<bool> PrintImports("print-imports", cl::init(false), cl::Hidden,
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cl::desc("Print imported functions"));
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// Load lazily a module from \p FileName in \p Context.
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static std::unique_ptr<Module> loadFile(const std::string &FileName,
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LLVMContext &Context) {
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SMDiagnostic Err;
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DEBUG(dbgs() << "Loading '" << FileName << "'\n");
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// Metadata isn't loaded until functions are imported, to minimize
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// the memory overhead.
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std::unique_ptr<Module> Result =
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getLazyIRFileModule(FileName, Err, Context,
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/* ShouldLazyLoadMetadata = */ true);
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if (!Result) {
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Err.print("function-import", errs());
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report_fatal_error("Abort");
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}
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return Result;
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}
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namespace {
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/// Given a list of possible callee implementation for a call site, select one
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/// that fits the \p Threshold.
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///
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/// FIXME: select "best" instead of first that fits. But what is "best"?
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/// - The smallest: more likely to be inlined.
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/// - The one with the least outgoing edges (already well optimized).
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/// - One from a module already being imported from in order to reduce the
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/// number of source modules parsed/linked.
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/// - One that has PGO data attached.
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/// - [insert you fancy metric here]
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static const FunctionSummary *
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selectCallee(const GlobalValueInfoList &CalleeInfoList, unsigned Threshold) {
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auto It = llvm::find_if(
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CalleeInfoList, [&](const std::unique_ptr<GlobalValueInfo> &GlobInfo) {
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assert(GlobInfo->summary() &&
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"We should not have a Global Info without summary");
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auto *Summary = cast<FunctionSummary>(GlobInfo->summary());
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if (GlobalValue::isWeakAnyLinkage(Summary->linkage()))
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return false;
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if (Summary->instCount() > Threshold)
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return false;
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return true;
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});
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if (It == CalleeInfoList.end())
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return nullptr;
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return cast<FunctionSummary>((*It)->summary());
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}
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/// Return the summary for the function \p GUID that fits the \p Threshold, or
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/// null if there's no match.
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static const FunctionSummary *selectCallee(GlobalValue::GUID GUID,
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unsigned Threshold,
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const ModuleSummaryIndex &Index) {
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auto CalleeInfoList = Index.findGlobalValueInfoList(GUID);
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if (CalleeInfoList == Index.end()) {
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return nullptr; // This function does not have a summary
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}
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return selectCallee(CalleeInfoList->second, Threshold);
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}
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/// Return true if the global \p GUID is exported by module \p ExportModulePath.
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static bool isGlobalExported(const ModuleSummaryIndex &Index,
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StringRef ExportModulePath,
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GlobalValue::GUID GUID) {
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auto CalleeInfoList = Index.findGlobalValueInfoList(GUID);
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if (CalleeInfoList == Index.end())
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// This global does not have a summary, it is not part of the ThinLTO
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// process
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return false;
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auto DefinedInCalleeModule = llvm::find_if(
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CalleeInfoList->second,
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[&](const std::unique_ptr<GlobalValueInfo> &GlobInfo) {
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auto *Summary = GlobInfo->summary();
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assert(Summary && "Unexpected GlobalValueInfo without summary");
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return Summary->modulePath() == ExportModulePath;
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});
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return (DefinedInCalleeModule != CalleeInfoList->second.end());
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}
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using EdgeInfo = std::pair<const FunctionSummary *, unsigned /* Threshold */>;
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/// Compute the list of functions to import for a given caller. Mark these
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/// imported functions and the symbols they reference in their source module as
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/// exported from their source module.
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static void computeImportForFunction(
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StringRef ModulePath, const FunctionSummary &Summary,
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const ModuleSummaryIndex &Index, unsigned Threshold,
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const std::map<GlobalValue::GUID, FunctionSummary *> &DefinedFunctions,
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SmallVectorImpl<EdgeInfo> &Worklist,
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FunctionImporter::ImportMapTy &ImportsForModule,
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StringMap<FunctionImporter::ExportSetTy> &ExportLists) {
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for (auto &Edge : Summary.calls()) {
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auto GUID = Edge.first;
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DEBUG(dbgs() << " edge -> " << GUID << " Threshold:" << Threshold << "\n");
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if (DefinedFunctions.count(GUID)) {
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DEBUG(dbgs() << "ignored! Target already in destination module.\n");
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continue;
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}
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auto *CalleeSummary = selectCallee(GUID, Threshold, Index);
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if (!CalleeSummary) {
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DEBUG(dbgs() << "ignored! No qualifying callee with summary found.\n");
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continue;
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}
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assert(CalleeSummary->instCount() <= Threshold &&
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"selectCallee() didn't honor the threshold");
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auto &ProcessedThreshold =
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ImportsForModule[CalleeSummary->modulePath()][GUID];
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/// Since the traversal of the call graph is DFS, we can revisit a function
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/// a second time with a higher threshold. In this case, it is added back to
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/// the worklist with the new threshold.
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if (ProcessedThreshold && ProcessedThreshold > Threshold) {
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DEBUG(dbgs() << "ignored! Target was already seen with Threshold "
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<< ProcessedThreshold << "\n");
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continue;
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}
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// Mark this function as imported in this module, with the current Threshold
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ProcessedThreshold = Threshold;
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// Make exports in the source module.
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auto ExportModulePath = CalleeSummary->modulePath();
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auto ExportList = ExportLists[ExportModulePath];
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ExportList.insert(GUID);
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// Mark all functions and globals referenced by this function as exported to
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// the outside if they are defined in the same source module.
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for (auto &Edge : CalleeSummary->calls()) {
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auto CalleeGUID = Edge.first;
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if (isGlobalExported(Index, ExportModulePath, CalleeGUID))
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ExportList.insert(CalleeGUID);
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}
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for (auto &GUID : CalleeSummary->refs()) {
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if (isGlobalExported(Index, ExportModulePath, GUID))
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ExportList.insert(GUID);
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}
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// Insert the newly imported function to the worklist.
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Worklist.push_back(std::make_pair(CalleeSummary, Threshold));
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}
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}
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/// Given the list of globals defined in a module, compute the list of imports
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/// as well as the list of "exports", i.e. the list of symbols referenced from
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/// another module (that may require promotion).
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static void ComputeImportForModule(
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StringRef ModulePath,
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const std::map<GlobalValue::GUID, FunctionSummary *> &DefinedFunctions,
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const ModuleSummaryIndex &Index,
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FunctionImporter::ImportMapTy &ImportsForModule,
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StringMap<FunctionImporter::ExportSetTy> &ExportLists) {
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// Worklist contains the list of function imported in this module, for which
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// we will analyse the callees and may import further down the callgraph.
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SmallVector<EdgeInfo, 128> Worklist;
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// Populate the worklist with the import for the functions in the current
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// module
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for (auto &FuncInfo : DefinedFunctions) {
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auto *Summary = FuncInfo.second;
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DEBUG(dbgs() << "Initalize import for " << FuncInfo.first << "\n");
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computeImportForFunction(ModulePath, *Summary, Index, ImportInstrLimit,
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DefinedFunctions, Worklist, ImportsForModule,
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ExportLists);
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}
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while (!Worklist.empty()) {
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auto FuncInfo = Worklist.pop_back_val();
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auto *Summary = FuncInfo.first;
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auto Threshold = FuncInfo.second;
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// Process the newly imported functions and add callees to the worklist.
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// Adjust the threshold
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Threshold = Threshold * ImportInstrFactor;
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computeImportForFunction(ModulePath, *Summary, Index, Threshold,
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DefinedFunctions, Worklist, ImportsForModule,
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ExportLists);
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}
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}
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} // anonymous namespace
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/// Compute all the import and export for every module in the Index.
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void llvm::ComputeCrossModuleImport(
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const ModuleSummaryIndex &Index,
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StringMap<FunctionImporter::ImportMapTy> &ImportLists,
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StringMap<FunctionImporter::ExportSetTy> &ExportLists) {
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auto ModuleCount = Index.modulePaths().size();
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// Collect for each module the list of function it defines.
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// GUID -> Summary
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StringMap<std::map<GlobalValue::GUID, FunctionSummary *>>
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Module2FunctionInfoMap(ModuleCount);
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for (auto &GlobalList : Index) {
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auto GUID = GlobalList.first;
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for (auto &GlobInfo : GlobalList.second) {
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auto *Summary = dyn_cast_or_null<FunctionSummary>(GlobInfo->summary());
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if (!Summary)
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/// Ignore global variable, focus on functions
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continue;
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DEBUG(dbgs() << "Adding definition: Module '" << Summary->modulePath()
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<< "' defines '" << GUID << "'\n");
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Module2FunctionInfoMap[Summary->modulePath()][GUID] = Summary;
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}
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}
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// For each module that has function defined, compute the import/export lists.
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for (auto &DefinedFunctions : Module2FunctionInfoMap) {
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auto &ImportsForModule = ImportLists[DefinedFunctions.first()];
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DEBUG(dbgs() << "Computing import for Module '" << DefinedFunctions.first()
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<< "'\n");
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ComputeImportForModule(DefinedFunctions.first(), DefinedFunctions.second,
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Index, ImportsForModule, ExportLists);
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}
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#ifndef NDEBUG
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DEBUG(dbgs() << "Import/Export lists for " << ImportLists.size()
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<< " modules:\n");
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for (auto &ModuleImports : ImportLists) {
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auto ModName = ModuleImports.first();
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auto &Exports = ExportLists[ModName];
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DEBUG(dbgs() << "* Module " << ModName << " exports " << Exports.size()
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<< " functions. Imports from " << ModuleImports.second.size()
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<< " modules.\n");
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for (auto &Src : ModuleImports.second) {
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auto SrcModName = Src.first();
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DEBUG(dbgs() << " - " << Src.second.size() << " functions imported from "
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<< SrcModName << "\n");
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}
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}
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#endif
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}
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// Automatically import functions in Module \p DestModule based on the summaries
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// index.
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//
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bool FunctionImporter::importFunctions(
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Module &DestModule, const FunctionImporter::ImportMapTy &ImportList) {
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DEBUG(dbgs() << "Starting import for Module "
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<< DestModule.getModuleIdentifier() << "\n");
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unsigned ImportedCount = 0;
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// Linker that will be used for importing function
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Linker TheLinker(DestModule);
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// Do the actual import of functions now, one Module at a time
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std::set<StringRef> ModuleNameOrderedList;
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for (auto &FunctionsToImportPerModule : ImportList) {
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ModuleNameOrderedList.insert(FunctionsToImportPerModule.first());
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}
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for (auto &Name : ModuleNameOrderedList) {
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// Get the module for the import
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const auto &FunctionsToImportPerModule = ImportList.find(Name);
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assert(FunctionsToImportPerModule != ImportList.end());
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std::unique_ptr<Module> SrcModule = ModuleLoader(Name);
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assert(&DestModule.getContext() == &SrcModule->getContext() &&
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"Context mismatch");
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// If modules were created with lazy metadata loading, materialize it
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// now, before linking it (otherwise this will be a noop).
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SrcModule->materializeMetadata();
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UpgradeDebugInfo(*SrcModule);
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auto &ImportGUIDs = FunctionsToImportPerModule->second;
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// Find the globals to import
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DenseSet<const GlobalValue *> GlobalsToImport;
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for (auto &GV : *SrcModule) {
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if (!GV.hasName())
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continue;
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auto GUID = GV.getGUID();
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auto Import = ImportGUIDs.count(GUID);
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DEBUG(dbgs() << (Import ? "Is" : "Not") << " importing " << GUID << " "
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<< GV.getName() << " from " << SrcModule->getSourceFileName()
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<< "\n");
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if (Import) {
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GV.materialize();
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GlobalsToImport.insert(&GV);
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}
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}
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for (auto &GV : SrcModule->aliases()) {
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if (!GV.hasName())
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continue;
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auto GUID = GV.getGUID();
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auto Import = ImportGUIDs.count(GUID);
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DEBUG(dbgs() << (Import ? "Is" : "Not") << " importing " << GUID << " "
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<< GV.getName() << " from " << SrcModule->getSourceFileName()
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<< "\n");
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if (Import) {
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// Alias can't point to "available_externally". However when we import
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// linkOnceODR the linkage does not change. So we import the alias
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// and aliasee only in this case.
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const GlobalObject *GO = GV.getBaseObject();
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if (!GO->hasLinkOnceODRLinkage())
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continue;
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GV.materialize();
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GlobalsToImport.insert(&GV);
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GlobalsToImport.insert(GO);
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}
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}
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for (auto &GV : SrcModule->globals()) {
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if (!GV.hasName())
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continue;
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auto GUID = GV.getGUID();
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auto Import = ImportGUIDs.count(GUID);
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DEBUG(dbgs() << (Import ? "Is" : "Not") << " importing " << GUID << " "
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<< GV.getName() << " from " << SrcModule->getSourceFileName()
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<< "\n");
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if (Import) {
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GV.materialize();
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GlobalsToImport.insert(&GV);
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}
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}
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// Link in the specified functions.
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if (renameModuleForThinLTO(*SrcModule, Index, &GlobalsToImport))
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return true;
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if (PrintImports) {
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for (const auto *GV : GlobalsToImport)
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dbgs() << DestModule.getSourceFileName() << ": Import " << GV->getName()
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<< " from " << SrcModule->getSourceFileName() << "\n";
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}
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if (TheLinker.linkInModule(std::move(SrcModule), Linker::Flags::None,
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&GlobalsToImport))
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report_fatal_error("Function Import: link error");
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ImportedCount += GlobalsToImport.size();
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}
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NumImported += ImportedCount;
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DEBUG(dbgs() << "Imported " << ImportedCount << " functions for Module "
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<< DestModule.getModuleIdentifier() << "\n");
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return ImportedCount;
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}
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/// Summary file to use for function importing when using -function-import from
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/// the command line.
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static cl::opt<std::string>
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SummaryFile("summary-file",
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cl::desc("The summary file to use for function importing."));
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static void diagnosticHandler(const DiagnosticInfo &DI) {
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raw_ostream &OS = errs();
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DiagnosticPrinterRawOStream DP(OS);
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DI.print(DP);
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OS << '\n';
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}
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/// Parse the summary index out of an IR file and return the summary
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/// index object if found, or nullptr if not.
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static std::unique_ptr<ModuleSummaryIndex>
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getModuleSummaryIndexForFile(StringRef Path, std::string &Error,
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DiagnosticHandlerFunction DiagnosticHandler) {
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std::unique_ptr<MemoryBuffer> Buffer;
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ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
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MemoryBuffer::getFile(Path);
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if (std::error_code EC = BufferOrErr.getError()) {
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Error = EC.message();
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return nullptr;
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}
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Buffer = std::move(BufferOrErr.get());
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ErrorOr<std::unique_ptr<object::ModuleSummaryIndexObjectFile>> ObjOrErr =
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object::ModuleSummaryIndexObjectFile::create(Buffer->getMemBufferRef(),
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DiagnosticHandler);
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if (std::error_code EC = ObjOrErr.getError()) {
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Error = EC.message();
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return nullptr;
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}
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return (*ObjOrErr)->takeIndex();
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}
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namespace {
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/// Pass that performs cross-module function import provided a summary file.
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class FunctionImportPass : public ModulePass {
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/// Optional module summary index to use for importing, otherwise
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/// the summary-file option must be specified.
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const ModuleSummaryIndex *Index;
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public:
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/// Pass identification, replacement for typeid
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static char ID;
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/// Specify pass name for debug output
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const char *getPassName() const override {
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return "Function Importing";
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}
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explicit FunctionImportPass(const ModuleSummaryIndex *Index = nullptr)
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: ModulePass(ID), Index(Index) {}
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bool runOnModule(Module &M) override {
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if (SummaryFile.empty() && !Index)
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report_fatal_error("error: -function-import requires -summary-file or "
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"file from frontend\n");
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std::unique_ptr<ModuleSummaryIndex> IndexPtr;
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if (!SummaryFile.empty()) {
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if (Index)
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report_fatal_error("error: -summary-file and index from frontend\n");
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std::string Error;
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IndexPtr =
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getModuleSummaryIndexForFile(SummaryFile, Error, diagnosticHandler);
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if (!IndexPtr) {
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errs() << "Error loading file '" << SummaryFile << "': " << Error
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<< "\n";
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return false;
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}
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Index = IndexPtr.get();
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}
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// First step is collecting the import/export lists
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// The export list is not used yet, but could limit the amount of renaming
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// performed in renameModuleForThinLTO()
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StringMap<FunctionImporter::ImportMapTy> ImportLists;
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StringMap<FunctionImporter::ExportSetTy> ExportLists;
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ComputeCrossModuleImport(*Index, ImportLists, ExportLists);
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auto &ImportList = ImportLists[M.getModuleIdentifier()];
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// Next we need to promote to global scope and rename any local values that
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// are potentially exported to other modules.
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if (renameModuleForThinLTO(M, *Index, nullptr)) {
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errs() << "Error renaming module\n";
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return false;
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}
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// Perform the import now.
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auto ModuleLoader = [&M](StringRef Identifier) {
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return loadFile(Identifier, M.getContext());
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};
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FunctionImporter Importer(*Index, ModuleLoader);
|
|
return Importer.importFunctions(M, ImportList);
|
|
}
|
|
};
|
|
} // anonymous namespace
|
|
|
|
char FunctionImportPass::ID = 0;
|
|
INITIALIZE_PASS_BEGIN(FunctionImportPass, "function-import",
|
|
"Summary Based Function Import", false, false)
|
|
INITIALIZE_PASS_END(FunctionImportPass, "function-import",
|
|
"Summary Based Function Import", false, false)
|
|
|
|
namespace llvm {
|
|
Pass *createFunctionImportPass(const ModuleSummaryIndex *Index = nullptr) {
|
|
return new FunctionImportPass(Index);
|
|
}
|
|
}
|