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Summary: The cumulative size of the bitcode files for a very large application can be huge, particularly with -g. In a distributed build environment, all of these files must be sent to the remote build node that performs the thin link step, and this can exceed size limits. The thin link actually only needs the summary along with a bitcode symbol table. Until we have a proper bitcode symbol table, simply stripping the debug metadata results in significant size reduction. Add support for an option to additionally emit minimized bitcode modules, just for use in the thin link step, which for now just strips all debug metadata. I plan to add a cc1 option so this can be invoked easily during the compile step. However, care must be taken to ensure that these minimized thin link bitcode files produce the same index as with the original bitcode files, as these original bitcode files will be used in the backends. Specifically: 1) The module hash used for caching is typically produced by hashing the written bitcode, and we want to include the hash that would correspond to the original bitcode file. This is because we want to ensure that changes in the stripped portions affect caching. Added plumbing to emit the same module hash in the minimized thin link bitcode file. 2) The module paths in the index are constructed from the module ID of each thin linked bitcode, and typically is automatically generated from the input file path. This is the path used for finding the modules to import from, and obviously we need this to point to the original bitcode files. Added gold-plugin support to take a suffix replacement during the thin link that is used to override the identifier on the MemoryBufferRef constructed from the loaded thin link bitcode file. The assumption is that the build system can specify that the minimized bitcode file has a name that is similar but uses a different suffix (e.g. out.thinlink.bc instead of out.o). Added various tests to ensure that we get identical index files out of the thin link step. Reviewers: mehdi_amini, pcc Subscribers: Prazek, llvm-commits Differential Revision: https://reviews.llvm.org/D31027 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@298638 91177308-0d34-0410-b5e6-96231b3b80d8
100 lines
3.6 KiB
C++
100 lines
3.6 KiB
C++
//===- ModuleSummaryIndexObjectFile.h - Summary index file implementation -=//
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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 declares the ModuleSummaryIndexObjectFile template class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_OBJECT_MODULESUMMARYINDEXOBJECTFILE_H
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#define LLVM_OBJECT_MODULESUMMARYINDEXOBJECTFILE_H
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#include "llvm/IR/DiagnosticInfo.h"
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#include "llvm/Object/SymbolicFile.h"
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namespace llvm {
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class ModuleSummaryIndex;
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class Module;
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namespace object {
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class ObjectFile;
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/// This class is used to read just the module summary index related
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/// sections out of the given object (which may contain a single module's
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/// bitcode or be a combined index bitcode file). It builds a ModuleSummaryIndex
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/// object.
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class ModuleSummaryIndexObjectFile : public SymbolicFile {
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std::unique_ptr<ModuleSummaryIndex> Index;
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public:
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ModuleSummaryIndexObjectFile(MemoryBufferRef Object,
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std::unique_ptr<ModuleSummaryIndex> I);
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~ModuleSummaryIndexObjectFile() override;
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// TODO: Walk through GlobalValueMap entries for symbols.
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// However, currently these interfaces are not used by any consumers.
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void moveSymbolNext(DataRefImpl &Symb) const override {
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llvm_unreachable("not implemented");
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}
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std::error_code printSymbolName(raw_ostream &OS,
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DataRefImpl Symb) const override {
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llvm_unreachable("not implemented");
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return std::error_code();
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}
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uint32_t getSymbolFlags(DataRefImpl Symb) const override {
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llvm_unreachable("not implemented");
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return 0;
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}
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basic_symbol_iterator symbol_begin() const override {
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llvm_unreachable("not implemented");
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return basic_symbol_iterator(BasicSymbolRef());
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}
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basic_symbol_iterator symbol_end() const override {
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llvm_unreachable("not implemented");
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return basic_symbol_iterator(BasicSymbolRef());
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}
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const ModuleSummaryIndex &getIndex() const {
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return const_cast<ModuleSummaryIndexObjectFile *>(this)->getIndex();
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}
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ModuleSummaryIndex &getIndex() { return *Index; }
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std::unique_ptr<ModuleSummaryIndex> takeIndex();
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static inline bool classof(const Binary *v) {
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return v->isModuleSummaryIndex();
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}
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/// \brief Finds and returns bitcode embedded in the given object file, or an
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/// error code if not found.
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static ErrorOr<MemoryBufferRef> findBitcodeInObject(const ObjectFile &Obj);
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/// \brief Finds and returns bitcode in the given memory buffer (which may
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/// be either a bitcode file or a native object file with embedded bitcode),
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/// or an error code if not found.
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static ErrorOr<MemoryBufferRef>
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findBitcodeInMemBuffer(MemoryBufferRef Object);
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/// \brief Parse module summary index in the given memory buffer.
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/// Return new ModuleSummaryIndexObjectFile instance containing parsed module
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/// summary/index.
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static Expected<std::unique_ptr<ModuleSummaryIndexObjectFile>>
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create(MemoryBufferRef Object);
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};
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}
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/// Parse the module summary index out of an IR file and return the module
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/// summary index object if found, or nullptr if not. If Identifier is
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/// non-empty, it is used as the module ID (module path) in the resulting
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/// index. This can be used when the index is being read from a file
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/// containing minimized bitcode just for the thin link.
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Expected<std::unique_ptr<ModuleSummaryIndex>>
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getModuleSummaryIndexForFile(StringRef Path, StringRef Identifier = "");
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}
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#endif
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