diff options
Diffstat (limited to 'src/rustllvm/PassWrapper.cpp')
| -rw-r--r-- | src/rustllvm/PassWrapper.cpp | 461 |
1 files changed, 461 insertions, 0 deletions
diff --git a/src/rustllvm/PassWrapper.cpp b/src/rustllvm/PassWrapper.cpp index 2f966e5a1c5..e37f048dd47 100644 --- a/src/rustllvm/PassWrapper.cpp +++ b/src/rustllvm/PassWrapper.cpp @@ -26,7 +26,11 @@ #include "llvm/Transforms/IPO/PassManagerBuilder.h" #if LLVM_VERSION_GE(4, 0) +#include "llvm/Object/ModuleSummaryIndexObjectFile.h" #include "llvm/Transforms/IPO/AlwaysInliner.h" +#include "llvm/Transforms/IPO/FunctionImport.h" +#include "llvm/Transforms/Utils/FunctionImportUtils.h" +#include "llvm/LTO/LTO.h" #endif #include "llvm-c/Transforms/PassManagerBuilder.h" @@ -102,6 +106,19 @@ extern "C" void LLVMRustAddPass(LLVMPassManagerRef PMR, LLVMPassRef RustPass) { PMB->add(Pass); } +extern "C" +bool LLVMRustPassManagerBuilderPopulateThinLTOPassManager( + LLVMPassManagerBuilderRef PMBR, + LLVMPassManagerRef PMR +) { +#if LLVM_VERSION_GE(4, 0) + unwrap(PMBR)->populateThinLTOPassManager(*unwrap(PMR)); + return true; +#else + return false; +#endif +} + #ifdef LLVM_COMPONENT_X86 #define SUBTARGET_X86 SUBTARGET(X86) #else @@ -740,3 +757,447 @@ extern "C" void LLVMRustSetModulePIELevel(LLVMModuleRef M) { unwrap(M)->setPIELevel(PIELevel::Level::Large); #endif } + +extern "C" bool +LLVMRustThinLTOAvailable() { +#if LLVM_VERSION_GE(4, 0) + return true; +#else + return false; +#endif +} + +#if LLVM_VERSION_GE(4, 0) + +// Here you'll find an implementation of ThinLTO as used by the Rust compiler +// right now. This ThinLTO support is only enabled on "recent ish" versions of +// LLVM, and otherwise it's just blanket rejected from other compilers. +// +// Most of this implementation is straight copied from LLVM. At the time of +// this writing it wasn't *quite* suitable to reuse more code from upstream +// for our purposes, but we should strive to upstream this support once it's +// ready to go! I figure we may want a bit of testing locally first before +// sending this upstream to LLVM. I hear though they're quite eager to receive +// feedback like this! +// +// If you're reading this code and wondering "what in the world" or you're +// working "good lord by LLVM upgrade is *still* failing due to these bindings" +// then fear not! (ok maybe fear a little). All code here is mostly based +// on `lib/LTO/ThinLTOCodeGenerator.cpp` in LLVM. +// +// You'll find that the general layout here roughly corresponds to the `run` +// method in that file as well as `ProcessThinLTOModule`. Functions are +// specifically commented below as well, but if you're updating this code +// or otherwise trying to understand it, the LLVM source will be useful in +// interpreting the mysteries within. +// +// Otherwise I'll apologize in advance, it probably requires a relatively +// significant investment on your part to "truly understand" what's going on +// here. Not saying I do myself, but it took me awhile staring at LLVM's source +// and various online resources about ThinLTO to make heads or tails of all +// this. + +extern "C" bool +LLVMRustWriteThinBitcodeToFile(LLVMPassManagerRef PMR, + LLVMModuleRef M, + const char *BcFile) { + llvm::legacy::PassManager *PM = unwrap<llvm::legacy::PassManager>(PMR); + std::error_code EC; + llvm::raw_fd_ostream bc(BcFile, EC, llvm::sys::fs::F_None); + if (EC) { + LLVMRustSetLastError(EC.message().c_str()); + return false; + } + PM->add(createWriteThinLTOBitcodePass(bc)); + PM->run(*unwrap(M)); + delete PM; + return true; +} + +// This is a shared data structure which *must* be threadsafe to share +// read-only amongst threads. This also corresponds basically to the arguments +// of the `ProcessThinLTOModule` function in the LLVM source. +struct LLVMRustThinLTOData { + // The combined index that is the global analysis over all modules we're + // performing ThinLTO for. This is mostly managed by LLVM. + ModuleSummaryIndex Index; + + // All modules we may look at, stored as in-memory serialized versions. This + // is later used when inlining to ensure we can extract any module to inline + // from. + StringMap<MemoryBufferRef> ModuleMap; + + // A set that we manage of everything we *don't* want internalized. Note that + // this includes all transitive references right now as well, but it may not + // always! + DenseSet<GlobalValue::GUID> GUIDPreservedSymbols; + + // Not 100% sure what these are, but they impact what's internalized and + // what's inlined across modules, I believe. + StringMap<FunctionImporter::ImportMapTy> ImportLists; + StringMap<FunctionImporter::ExportSetTy> ExportLists; + StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries; +}; + +// Just an argument to the `LLVMRustCreateThinLTOData` function below. +struct LLVMRustThinLTOModule { + const char *identifier; + const char *data; + size_t len; +}; + +// This is copied from `lib/LTO/ThinLTOCodeGenerator.cpp`, not sure what it +// does. +static const GlobalValueSummary * +getFirstDefinitionForLinker(const GlobalValueSummaryList &GVSummaryList) { + auto StrongDefForLinker = llvm::find_if( + GVSummaryList, [](const std::unique_ptr<GlobalValueSummary> &Summary) { + auto Linkage = Summary->linkage(); + return !GlobalValue::isAvailableExternallyLinkage(Linkage) && + !GlobalValue::isWeakForLinker(Linkage); + }); + if (StrongDefForLinker != GVSummaryList.end()) + return StrongDefForLinker->get(); + + auto FirstDefForLinker = llvm::find_if( + GVSummaryList, [](const std::unique_ptr<GlobalValueSummary> &Summary) { + auto Linkage = Summary->linkage(); + return !GlobalValue::isAvailableExternallyLinkage(Linkage); + }); + if (FirstDefForLinker == GVSummaryList.end()) + return nullptr; + return FirstDefForLinker->get(); +} + +// This is a helper function we added that isn't present in LLVM's source. +// +// The way LTO works in Rust is that we typically have a number of symbols that +// we know ahead of time need to be preserved. We want to ensure that ThinLTO +// doesn't accidentally internalize any of these and otherwise is always +// ready to keep them linking correctly. +// +// This function will recursively walk the `GUID` provided and all of its +// references, as specified in the `Index`. In other words, we're taking a +// `GUID` as input, adding it to `Preserved`, and then taking all `GUID` +// items that the input references and recursing. +static void +addPreservedGUID(const ModuleSummaryIndex &Index, + DenseSet<GlobalValue::GUID> &Preserved, + GlobalValue::GUID GUID) { + if (Preserved.count(GUID)) + return; + Preserved.insert(GUID); + + auto SummaryList = Index.findGlobalValueSummaryList(GUID); + if (SummaryList == Index.end()) + return; + for (auto &Summary : SummaryList->second) { + for (auto &Ref : Summary->refs()) { + if (Ref.isGUID()) { + addPreservedGUID(Index, Preserved, Ref.getGUID()); + } else { + auto Value = Ref.getValue(); + addPreservedGUID(Index, Preserved, Value->getGUID()); + } + } + + GlobalValueSummary *GVSummary = Summary.get(); + if (isa<FunctionSummary>(GVSummary)) { + FunctionSummary *FS = cast<FunctionSummary>(GVSummary); + for (auto &Call: FS->calls()) { + if (Call.first.isGUID()) { + addPreservedGUID(Index, Preserved, Call.first.getGUID()); + } else { + auto Value = Call.first.getValue(); + addPreservedGUID(Index, Preserved, Value->getGUID()); + } + } + for (auto &GUID: FS->type_tests()) { + addPreservedGUID(Index, Preserved, GUID); + } + } + } +} + +// The main entry point for creating the global ThinLTO analysis. The structure +// here is basically the same as before threads are spawned in the `run` +// function of `lib/LTO/ThinLTOCodeGenerator.cpp`. +extern "C" LLVMRustThinLTOData* +LLVMRustCreateThinLTOData(LLVMRustThinLTOModule *modules, + int num_modules, + const char **preserved_symbols, + int num_symbols) { + auto Ret = llvm::make_unique<LLVMRustThinLTOData>(); + + // Load each module's summary and merge it into one combined index + for (int i = 0; i < num_modules; i++) { + auto module = &modules[i]; + StringRef buffer(module->data, module->len); + MemoryBufferRef mem_buffer(buffer, module->identifier); + + Ret->ModuleMap[module->identifier] = mem_buffer; + + Expected<std::unique_ptr<object::ModuleSummaryIndexObjectFile>> ObjOrErr = + object::ModuleSummaryIndexObjectFile::create(mem_buffer); + if (!ObjOrErr) { + LLVMRustSetLastError(toString(ObjOrErr.takeError()).c_str()); + return nullptr; + } + auto Index = (*ObjOrErr)->takeIndex(); + Ret->Index.mergeFrom(std::move(Index), i); + } + + // Collect for each module the list of function it defines (GUID -> Summary) + Ret->Index.collectDefinedGVSummariesPerModule(Ret->ModuleToDefinedGVSummaries); + + // Convert the preserved symbols set from string to GUID, this is then needed + // for internalization. We use `addPreservedGUID` to include any transitively + // used symbol as well. + for (int i = 0; i < num_symbols; i++) { + addPreservedGUID(Ret->Index, + Ret->GUIDPreservedSymbols, + GlobalValue::getGUID(preserved_symbols[i])); + } + + // Collect the import/export lists for all modules from the call-graph in the + // combined index + // + // This is copied from `lib/LTO/ThinLTOCodeGenerator.cpp` + computeDeadSymbols(Ret->Index, Ret->GUIDPreservedSymbols); + ComputeCrossModuleImport( + Ret->Index, + Ret->ModuleToDefinedGVSummaries, + Ret->ImportLists, + Ret->ExportLists + ); + + // Resolve LinkOnce/Weak symbols, this has to be computed early be cause it + // impacts the caching. + // + // This is copied from `lib/LTO/ThinLTOCodeGenerator.cpp` + StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR; + DenseMap<GlobalValue::GUID, const GlobalValueSummary *> PrevailingCopy; + for (auto &I : Ret->Index) { + if (I.second.size() > 1) + PrevailingCopy[I.first] = getFirstDefinitionForLinker(I.second); + } + auto isPrevailing = [&](GlobalValue::GUID GUID, const GlobalValueSummary *S) { + const auto &Prevailing = PrevailingCopy.find(GUID); + if (Prevailing == PrevailingCopy.end()) + return true; + return Prevailing->second == S; + }; + auto recordNewLinkage = [&](StringRef ModuleIdentifier, + GlobalValue::GUID GUID, + GlobalValue::LinkageTypes NewLinkage) { + ResolvedODR[ModuleIdentifier][GUID] = NewLinkage; + }; + thinLTOResolveWeakForLinkerInIndex(Ret->Index, isPrevailing, recordNewLinkage); + auto isExported = [&](StringRef ModuleIdentifier, GlobalValue::GUID GUID) { + const auto &ExportList = Ret->ExportLists.find(ModuleIdentifier); + return (ExportList != Ret->ExportLists.end() && + ExportList->second.count(GUID)) || + Ret->GUIDPreservedSymbols.count(GUID); + }; + thinLTOInternalizeAndPromoteInIndex(Ret->Index, isExported); + + return Ret.release(); +} + +extern "C" void +LLVMRustFreeThinLTOData(LLVMRustThinLTOData *Data) { + delete Data; +} + +// Below are the various passes that happen *per module* when doing ThinLTO. +// +// In other words, these are the functions that are all run concurrently +// with one another, one per module. The passes here correspond to the analysis +// passes in `lib/LTO/ThinLTOCodeGenerator.cpp`, currently found in the +// `ProcessThinLTOModule` function. Here they're split up into separate steps +// so rustc can save off the intermediate bytecode between each step. + +extern "C" bool +LLVMRustPrepareThinLTORename(const LLVMRustThinLTOData *Data, LLVMModuleRef M) { + Module &Mod = *unwrap(M); + if (renameModuleForThinLTO(Mod, Data->Index)) { + LLVMRustSetLastError("renameModuleForThinLTO failed"); + return false; + } + return true; +} + +extern "C" bool +LLVMRustPrepareThinLTOResolveWeak(const LLVMRustThinLTOData *Data, LLVMModuleRef M) { + Module &Mod = *unwrap(M); + const auto &DefinedGlobals = Data->ModuleToDefinedGVSummaries.lookup(Mod.getModuleIdentifier()); + thinLTOResolveWeakForLinkerModule(Mod, DefinedGlobals); + return true; +} + +extern "C" bool +LLVMRustPrepareThinLTOInternalize(const LLVMRustThinLTOData *Data, LLVMModuleRef M) { + Module &Mod = *unwrap(M); + const auto &DefinedGlobals = Data->ModuleToDefinedGVSummaries.lookup(Mod.getModuleIdentifier()); + thinLTOInternalizeModule(Mod, DefinedGlobals); + return true; +} + +extern "C" bool +LLVMRustPrepareThinLTOImport(const LLVMRustThinLTOData *Data, LLVMModuleRef M) { + Module &Mod = *unwrap(M); + const auto &ImportList = Data->ImportLists.lookup(Mod.getModuleIdentifier()); + auto Loader = [&](StringRef Identifier) { + const auto &Memory = Data->ModuleMap.lookup(Identifier); + auto &Context = Mod.getContext(); + return getLazyBitcodeModule(Memory, Context, true, true); + }; + FunctionImporter Importer(Data->Index, Loader); + Expected<bool> Result = Importer.importFunctions(Mod, ImportList); + if (!Result) { + LLVMRustSetLastError(toString(Result.takeError()).c_str()); + return false; + } + return true; +} + +// This struct and various functions are sort of a hack right now, but the +// problem is that we've got in-memory LLVM modules after we generate and +// optimize all codegen-units for one compilation in rustc. To be compatible +// with the LTO support above we need to serialize the modules plus their +// ThinLTO summary into memory. +// +// This structure is basically an owned version of a serialize module, with +// a ThinLTO summary attached. +struct LLVMRustThinLTOBuffer { + std::string data; +}; + +extern "C" LLVMRustThinLTOBuffer* +LLVMRustThinLTOBufferCreate(LLVMModuleRef M) { + auto Ret = llvm::make_unique<LLVMRustThinLTOBuffer>(); + { + raw_string_ostream OS(Ret->data); + { + legacy::PassManager PM; + PM.add(createWriteThinLTOBitcodePass(OS)); + PM.run(*unwrap(M)); + } + } + return Ret.release(); +} + +extern "C" void +LLVMRustThinLTOBufferFree(LLVMRustThinLTOBuffer *Buffer) { + delete Buffer; +} + +extern "C" const void* +LLVMRustThinLTOBufferPtr(const LLVMRustThinLTOBuffer *Buffer) { + return Buffer->data.data(); +} + +extern "C" size_t +LLVMRustThinLTOBufferLen(const LLVMRustThinLTOBuffer *Buffer) { + return Buffer->data.length(); +} + +// This is what we used to parse upstream bitcode for actual ThinLTO +// processing. We'll call this once per module optimized through ThinLTO, and +// it'll be called concurrently on many threads. +extern "C" LLVMModuleRef +LLVMRustParseBitcodeForThinLTO(LLVMContextRef Context, + const char *data, + size_t len, + const char *identifier) { + StringRef Data(data, len); + MemoryBufferRef Buffer(Data, identifier); + unwrap(Context)->enableDebugTypeODRUniquing(); + Expected<std::unique_ptr<Module>> SrcOrError = + parseBitcodeFile(Buffer, *unwrap(Context)); + if (!SrcOrError) { + LLVMRustSetLastError(toString(SrcOrError.takeError()).c_str()); + return nullptr; + } + return wrap(std::move(*SrcOrError).release()); +} + +#else + +extern "C" bool +LLVMRustWriteThinBitcodeToFile(LLVMPassManagerRef PMR, + LLVMModuleRef M, + const char *BcFile) { + llvm_unreachable("ThinLTO not available"); +} + +struct LLVMRustThinLTOData { +}; + +struct LLVMRustThinLTOModule { +}; + +extern "C" LLVMRustThinLTOData* +LLVMRustCreateThinLTOData(LLVMRustThinLTOModule *modules, + int num_modules, + const char **preserved_symbols, + int num_symbols) { + llvm_unreachable("ThinLTO not available"); +} + +extern "C" bool +LLVMRustPrepareThinLTORename(const LLVMRustThinLTOData *Data, LLVMModuleRef M) { + llvm_unreachable("ThinLTO not available"); +} + +extern "C" bool +LLVMRustPrepareThinLTOResolveWeak(const LLVMRustThinLTOData *Data, LLVMModuleRef M) { + llvm_unreachable("ThinLTO not available"); +} + +extern "C" bool +LLVMRustPrepareThinLTOInternalize(const LLVMRustThinLTOData *Data, LLVMModuleRef M) { + llvm_unreachable("ThinLTO not available"); +} + +extern "C" bool +LLVMRustPrepareThinLTOImport(const LLVMRustThinLTOData *Data, LLVMModuleRef M) { + llvm_unreachable("ThinLTO not available"); +} + +extern "C" void +LLVMRustFreeThinLTOData(LLVMRustThinLTOData *Data) { + llvm_unreachable("ThinLTO not available"); +} + +struct LLVMRustThinLTOBuffer { +}; + +extern "C" LLVMRustThinLTOBuffer* +LLVMRustThinLTOBufferCreate(LLVMModuleRef M) { + llvm_unreachable("ThinLTO not available"); +} + +extern "C" void +LLVMRustThinLTOBufferFree(LLVMRustThinLTOBuffer *Buffer) { + llvm_unreachable("ThinLTO not available"); +} + +extern "C" const void* +LLVMRustThinLTOBufferPtr(const LLVMRustThinLTOBuffer *Buffer) { + llvm_unreachable("ThinLTO not available"); +} + +extern "C" size_t +LLVMRustThinLTOBufferLen(const LLVMRustThinLTOBuffer *Buffer) { + llvm_unreachable("ThinLTO not available"); +} + +extern "C" LLVMModuleRef +LLVMRustParseBitcodeForThinLTO(LLVMContextRef Context, + const char *data, + size_t len, + const char *identifier) { + llvm_unreachable("ThinLTO not available"); +} +#endif // LLVM_VERSION_GE(4, 0) |