1 //===-Caching.cpp - LLVM Link Time Optimizer Cache Handling ---------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file implements the Caching for ThinLTO. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/LTO/Caching.h" 15 #include "llvm/ADT/StringExtras.h" 16 #include "llvm/Support/Errc.h" 17 #include "llvm/Support/FileSystem.h" 18 #include "llvm/Support/MemoryBuffer.h" 19 #include "llvm/Support/Path.h" 20 #include "llvm/Support/raw_ostream.h" 21 22 using namespace llvm; 23 using namespace llvm::lto; 24 25 Expected<NativeObjectCache> lto::localCache(StringRef CacheDirectoryPath, 26 AddBufferFn AddBuffer) { 27 if (std::error_code EC = sys::fs::create_directories(CacheDirectoryPath)) 28 return errorCodeToError(EC); 29 30 return [=](unsigned Task, StringRef Key) -> AddStreamFn { 31 // This choice of file name allows the cache to be pruned (see pruneCache() 32 // in include/llvm/Support/CachePruning.h). 33 SmallString<64> EntryPath; 34 sys::path::append(EntryPath, CacheDirectoryPath, "llvmcache-" + Key); 35 // First, see if we have a cache hit. 36 ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = 37 MemoryBuffer::getFile(EntryPath); 38 if (MBOrErr) { 39 AddBuffer(Task, std::move(*MBOrErr)); 40 return AddStreamFn(); 41 } 42 43 if (MBOrErr.getError() != errc::no_such_file_or_directory) 44 report_fatal_error(Twine("Failed to open cache file ") + EntryPath + 45 ": " + MBOrErr.getError().message() + "\n"); 46 47 // This native object stream is responsible for commiting the resulting 48 // file to the cache and calling AddBuffer to add it to the link. 49 struct CacheStream : NativeObjectStream { 50 AddBufferFn AddBuffer; 51 std::string TempFilename; 52 std::string EntryPath; 53 unsigned Task; 54 55 CacheStream(std::unique_ptr<raw_pwrite_stream> OS, AddBufferFn AddBuffer, 56 std::string TempFilename, std::string EntryPath, 57 unsigned Task) 58 : NativeObjectStream(std::move(OS)), AddBuffer(std::move(AddBuffer)), 59 TempFilename(std::move(TempFilename)), 60 EntryPath(std::move(EntryPath)), Task(Task) {} 61 62 ~CacheStream() { 63 // FIXME: This code could race with the cache pruner, but it is unlikely 64 // that the cache pruner will choose to remove a newly created file. 65 66 // Make sure the file is closed before committing it. 67 OS.reset(); 68 // This is atomic on POSIX systems. 69 if (auto EC = sys::fs::rename(TempFilename, EntryPath)) 70 report_fatal_error(Twine("Failed to rename temporary file ") + 71 TempFilename + ": " + EC.message() + "\n"); 72 73 ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = 74 MemoryBuffer::getFile(EntryPath); 75 if (!MBOrErr) 76 report_fatal_error(Twine("Failed to open cache file ") + EntryPath + 77 ": " + MBOrErr.getError().message() + "\n"); 78 AddBuffer(Task, std::move(*MBOrErr)); 79 } 80 }; 81 82 return [=](size_t Task) -> std::unique_ptr<NativeObjectStream> { 83 // Write to a temporary to avoid race condition 84 int TempFD; 85 SmallString<64> TempFilenameModel, TempFilename; 86 sys::path::append(TempFilenameModel, CacheDirectoryPath, "Thin-%%%%%%.tmp.o"); 87 std::error_code EC = 88 sys::fs::createUniqueFile(TempFilenameModel, TempFD, TempFilename, 89 sys::fs::owner_read | sys::fs::owner_write); 90 if (EC) { 91 errs() << "Error: " << EC.message() << "\n"; 92 report_fatal_error("ThinLTO: Can't get a temporary file"); 93 } 94 95 // This CacheStream will move the temporary file into the cache when done. 96 return llvm::make_unique<CacheStream>( 97 llvm::make_unique<raw_fd_ostream>(TempFD, /* ShouldClose */ true), 98 AddBuffer, TempFilename.str(), EntryPath.str(), Task); 99 }; 100 }; 101 } 102