Add a FunctionImporter helper to perform summary-based cross-module function importing
Summary:
This is a helper to perform cross-module import for ThinLTO. Right now
it is importing naively every possible called functions.
Reviewers: tejohnson
Subscribers: dexonsmith, llvm-commits
Differential Revision: http://reviews.llvm.org/D14914
From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 253954
diff --git a/llvm/lib/Transforms/IPO/CMakeLists.txt b/llvm/lib/Transforms/IPO/CMakeLists.txt
index 8c777548..ba77477 100644
--- a/llvm/lib/Transforms/IPO/CMakeLists.txt
+++ b/llvm/lib/Transforms/IPO/CMakeLists.txt
@@ -6,6 +6,7 @@
ElimAvailExtern.cpp
ExtractGV.cpp
FunctionAttrs.cpp
+ FunctionImport.cpp
GlobalDCE.cpp
GlobalOpt.cpp
IPConstantPropagation.cpp
diff --git a/llvm/lib/Transforms/IPO/FunctionImport.cpp b/llvm/lib/Transforms/IPO/FunctionImport.cpp
new file mode 100644
index 0000000..7257967
--- /dev/null
+++ b/llvm/lib/Transforms/IPO/FunctionImport.cpp
@@ -0,0 +1,239 @@
+//===- FunctionImport.cpp - ThinLTO Summary-based Function Import ---------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements Function import based on summaries.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/IPO/FunctionImport.h"
+
+#include "llvm/ADT/StringSet.h"
+#include "llvm/IR/AutoUpgrade.h"
+#include "llvm/IR/DiagnosticPrinter.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IRReader/IRReader.h"
+#include "llvm/Linker/Linker.h"
+#include "llvm/Object/FunctionIndexObjectFile.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/SourceMgr.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "function-import"
+
+// Load lazily a module from \p FileName in \p Context.
+static std::unique_ptr<Module> loadFile(const std::string &FileName,
+ LLVMContext &Context) {
+ SMDiagnostic Err;
+ DEBUG(dbgs() << "Loading '" << FileName << "'\n");
+ std::unique_ptr<Module> Result = getLazyIRFileModule(FileName, Err, Context);
+ if (!Result) {
+ Err.print("function-import", errs());
+ return nullptr;
+ }
+
+ Result->materializeMetadata();
+ UpgradeDebugInfo(*Result);
+
+ return Result;
+}
+
+// Get a Module for \p FileName from the cache, or load it lazily.
+Module &FunctionImporter::getOrLoadModule(StringRef FileName) {
+ auto &Module = ModuleMap[FileName];
+ if (!Module)
+ Module = loadFile(FileName, Context);
+ return *Module;
+}
+
+// Automatically import functions in Module \p M based on the summaries index.
+//
+// The current implementation imports every called functions that exists in the
+// summaries index.
+bool FunctionImporter::importFunctions(Module &M) {
+ assert(&Context == &M.getContext());
+
+ bool Changed = false;
+
+ /// First step is collecting the called functions and the one defined in this
+ /// module.
+ StringSet<> CalledFunctions;
+ for (auto &F : M) {
+ if (F.isDeclaration() || F.hasFnAttribute(Attribute::OptimizeNone))
+ continue;
+ for (auto &BB : F) {
+ for (auto &I : BB) {
+ if (isa<CallInst>(I)) {
+ DEBUG(dbgs() << "Found a call: '" << I << "'\n");
+ auto CalledFunction = cast<CallInst>(I).getCalledFunction();
+ if (CalledFunction && CalledFunction->hasName() &&
+ CalledFunction->isDeclaration())
+ CalledFunctions.insert(CalledFunction->getName());
+ }
+ }
+ }
+ }
+
+ /// Second step: for every call to an external function, try to import it.
+
+ // Linker that will be used for importing function
+ Linker L(&M, DiagnosticHandler);
+
+ /// Insert initial called function set in a worklist, so that we can add
+ /// transively called functions when importing.
+ SmallVector<StringRef, 64> Worklist;
+ for (auto &CalledFunction : CalledFunctions)
+ Worklist.push_back(CalledFunction.first());
+
+ while (!Worklist.empty()) {
+ auto CalledFunctionName = Worklist.pop_back_val();
+ DEBUG(dbgs() << "Process import for " << CalledFunctionName << "\n");
+
+ // Try to get a summary for this function call.
+ auto InfoList = Index.findFunctionInfoList(CalledFunctionName);
+ if (InfoList == Index.end()) {
+ DEBUG(dbgs() << "No summary for " << CalledFunctionName
+ << " Ignoring.\n");
+ continue;
+ }
+ assert(!InfoList->second.empty() && "No summary, error at import?");
+
+ // Comdat can have multiple entries, FIXME: what do we do with them?
+ auto &Info = InfoList->second[0];
+ assert(Info && "Nullptr in list, error importing summaries?\n");
+
+ auto *Summary = Info->functionSummary();
+ if (!Summary) {
+ // FIXME: in case we are lazyloading summaries, we can do it now.
+ dbgs() << "Missing summary for " << CalledFunctionName
+ << ", error at import?\n";
+ llvm_unreachable("Missing summary");
+ }
+
+ //
+ // No profitability notion right now, just import all the time...
+ //
+
+ // Get the module path from the summary.
+ auto FileName = Summary->modulePath();
+ DEBUG(dbgs() << "Importing " << CalledFunctionName << " from " << FileName
+ << "\n");
+
+ // Get the module for the import (potentially from the cache).
+ auto &Module = getOrLoadModule(FileName);
+
+ // The function that we will import!
+ GlobalValue *SGV = Module.getNamedValue(CalledFunctionName);
+ Function *F = dyn_cast<Function>(SGV);
+ if (!F && isa<GlobalAlias>(SGV)) {
+ auto *SGA = dyn_cast<GlobalAlias>(SGV);
+ F = dyn_cast<Function>(SGA->getBaseObject());
+ }
+ if (!F) {
+ errs() << "Can't load function '" << CalledFunctionName << "' in Module '"
+ << FileName << "', error in the summary?\n";
+ llvm_unreachable("Can't load function in Module");
+ }
+
+ // We cannot import weak_any functions without possibly affecting the
+ // order they are seen and selected by the linker, changing program
+ // semantics.
+ if (F->hasWeakAnyLinkage()) {
+ DEBUG(dbgs() << "Ignoring import request for weak-any function "
+ << CalledFunctionName << " from " << FileName << "\n");
+ continue;
+ }
+
+ // Link in the specified function.
+ if (L.linkInModule(&Module, Linker::Flags::None, &Index, F))
+ report_fatal_error("Function Import: link error");
+
+ // TODO: Process the newly imported function and add callees to the
+ // worklist.
+
+ Changed = true;
+ }
+ return Changed;
+}
+
+/// Summary file to use for function importing when using -function-import from
+/// the command line.
+static cl::opt<std::string>
+ SummaryFile("summary-file",
+ cl::desc("The summary file to use for function importing."));
+
+static void diagnosticHandler(const DiagnosticInfo &DI) {
+ raw_ostream &OS = errs();
+ DiagnosticPrinterRawOStream DP(OS);
+ DI.print(DP);
+ OS << '\n';
+}
+
+/// Parse the function index out of an IR file and return the function
+/// index object if found, or nullptr if not.
+static std::unique_ptr<FunctionInfoIndex>
+getFunctionIndexForFile(StringRef Path, std::string &Error,
+ DiagnosticHandlerFunction DiagnosticHandler) {
+ std::unique_ptr<MemoryBuffer> Buffer;
+ ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
+ MemoryBuffer::getFile(Path);
+ if (std::error_code EC = BufferOrErr.getError()) {
+ Error = EC.message();
+ return nullptr;
+ }
+ Buffer = std::move(BufferOrErr.get());
+ ErrorOr<std::unique_ptr<object::FunctionIndexObjectFile>> ObjOrErr =
+ object::FunctionIndexObjectFile::create(Buffer->getMemBufferRef(),
+ DiagnosticHandler);
+ if (std::error_code EC = ObjOrErr.getError()) {
+ Error = EC.message();
+ return nullptr;
+ }
+ return (*ObjOrErr)->takeIndex();
+}
+
+/// Pass that performs cross-module function import provided a summary file.
+class FunctionImportPass : public ModulePass {
+
+public:
+ /// Pass identification, replacement for typeid
+ static char ID;
+
+ explicit FunctionImportPass() : ModulePass(ID) {}
+
+ bool runOnModule(Module &M) override {
+ if (SummaryFile.empty()) {
+ report_fatal_error("error: -function-import requires -summary-file\n");
+ }
+ std::string Error;
+ std::unique_ptr<FunctionInfoIndex> Index =
+ getFunctionIndexForFile(SummaryFile, Error, diagnosticHandler);
+ if (!Index) {
+ errs() << "Error loading file '" << SummaryFile << "': " << Error << "\n";
+ return false;
+ }
+
+ // Perform the import now.
+ FunctionImporter Importer(M.getContext(), *Index, diagnosticHandler);
+ return Importer.importFunctions(M);
+
+ return false;
+ }
+};
+
+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() { return new FunctionImportPass(); }
+}
diff --git a/llvm/lib/Transforms/IPO/IPO.cpp b/llvm/lib/Transforms/IPO/IPO.cpp
index 97e4584..379af30 100644
--- a/llvm/lib/Transforms/IPO/IPO.cpp
+++ b/llvm/lib/Transforms/IPO/IPO.cpp
@@ -48,6 +48,7 @@
initializeBarrierNoopPass(Registry);
initializeEliminateAvailableExternallyPass(Registry);
initializeSampleProfileLoaderPass(Registry);
+ initializeFunctionImportPassPass(Registry);
}
void LLVMInitializeIPO(LLVMPassRegistryRef R) {
diff --git a/llvm/lib/Transforms/IPO/LLVMBuild.txt b/llvm/lib/Transforms/IPO/LLVMBuild.txt
index 2311e27..c14b6b7 100644
--- a/llvm/lib/Transforms/IPO/LLVMBuild.txt
+++ b/llvm/lib/Transforms/IPO/LLVMBuild.txt
@@ -20,4 +20,4 @@
name = IPO
parent = Transforms
library_name = ipo
-required_libraries = Analysis Core InstCombine ProfileData Scalar Support TransformUtils Vectorize
+required_libraries = Analysis Core InstCombine Linker ProfileData Scalar Support TransformUtils Vectorize