Author: tejohnson Date: Wed Dec 28 12:00:08 2016 New Revision: 290674 URL: http://llvm.org/viewvc/llvm-project?rev=290674&view=rev Log: [ThinLTO] No need to rediscover imports in distributed backend
Summary: We can simply import all external values with summaries included in the individual index file created for the distributed backend job, as only those are added to the individual index file created by the WriteIndexesThinBackend (in addition to summaries for the original module, which are skipped here). While computing the cross module imports on this index would come to the same conclusion as the original thin link import logic, it is unnecessary work. And when tuning, it avoids the need to pass the same function importing parameters (e.g. -import-instr-limit) to both the thin link and the backends (otherwise they won't make the same decisions). Reviewers: mehdi_amini, pcc Subscribers: cfe-commits Differential Revision: https://reviews.llvm.org/D28139 Modified: cfe/trunk/lib/CodeGen/BackendUtil.cpp Modified: cfe/trunk/lib/CodeGen/BackendUtil.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/BackendUtil.cpp?rev=290674&r1=290673&r2=290674&view=diff ============================================================================== --- cfe/trunk/lib/CodeGen/BackendUtil.cpp (original) +++ cfe/trunk/lib/CodeGen/BackendUtil.cpp Wed Dec 28 12:00:08 2016 @@ -863,11 +863,23 @@ static void runThinLTOBackend(const Code ModuleToDefinedGVSummaries; CombinedIndex->collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries); - // FIXME: We could simply import the modules mentioned in the combined index - // here. + // We can simply import the values mentioned in the combined index, since + // we should only invoke this using the individual indexes written out + // via a WriteIndexesThinBackend. FunctionImporter::ImportMapTy ImportList; - ComputeCrossModuleImportForModule(M->getModuleIdentifier(), *CombinedIndex, - ImportList); + for (auto &GlobalList : *CombinedIndex) { + auto GUID = GlobalList.first; + assert(GlobalList.second.size() == 1 && + "Expected individual combined index to have one summary per GUID"); + auto &Summary = GlobalList.second[0]; + // Skip the summaries for the importing module. These are included to + // e.g. record required linkage changes. + if (Summary->modulePath() == M->getModuleIdentifier()) + continue; + // Doesn't matter what value we plug in to the map, just needs an entry + // to provoke importing by thinBackend. + ImportList[Summary->modulePath()][GUID] = 1; + } std::vector<std::unique_ptr<llvm::MemoryBuffer>> OwnedImports; MapVector<llvm::StringRef, llvm::BitcodeModule> ModuleMap; _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits