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/MemoryBuffer.h" 18 #include "llvm/Support/Path.h" 19 #include "llvm/Support/Process.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), EntryPath); 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 sys::fs::TempFile TempFile; 52 std::string EntryPath; 53 unsigned Task; 54 55 CacheStream(std::unique_ptr<raw_pwrite_stream> OS, AddBufferFn AddBuffer, 56 sys::fs::TempFile TempFile, std::string EntryPath, 57 unsigned Task) 58 : NativeObjectStream(std::move(OS)), AddBuffer(std::move(AddBuffer)), 59 TempFile(std::move(TempFile)), EntryPath(std::move(EntryPath)), 60 Task(Task) {} 61 62 ~CacheStream() { 63 // Make sure the stream is closed before committing it. 64 OS.reset(); 65 66 // Open the file first to avoid racing with a cache pruner. 67 ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = 68 MemoryBuffer::getOpenFile(TempFile.FD, TempFile.TmpName, 69 /*FileSize*/ -1, 70 /*RequiresNullTerminator*/ false); 71 if (!MBOrErr) 72 report_fatal_error(Twine("Failed to open new cache file ") + 73 TempFile.TmpName + ": " + 74 MBOrErr.getError().message() + "\n"); 75 76 // On POSIX systems, this will atomically replace the destination if 77 // it already exists. We try to emulate this on Windows, but this may 78 // fail with a permission denied error (for example, if the destination 79 // is currently opened by another process that does not give us the 80 // sharing permissions we need). Since the existing file should be 81 // semantically equivalent to the one we are trying to write, we give 82 // AddBuffer a copy of the bytes we wrote in that case. We do this 83 // instead of just using the existing file, because the pruner might 84 // delete the file before we get a chance to use it. 85 Error E = TempFile.keep(EntryPath); 86 E = handleErrors(std::move(E), [&](const ECError &E) -> Error { 87 std::error_code EC = E.convertToErrorCode(); 88 if (EC != errc::permission_denied) 89 return errorCodeToError(EC); 90 91 auto MBCopy = MemoryBuffer::getMemBufferCopy((*MBOrErr)->getBuffer(), 92 EntryPath); 93 MBOrErr = std::move(MBCopy); 94 95 // FIXME: should we consume the discard error? 96 consumeError(TempFile.discard()); 97 98 return Error::success(); 99 }); 100 101 if (E) 102 report_fatal_error(Twine("Failed to rename temporary file ") + 103 TempFile.TmpName + " to " + EntryPath + ": " + 104 toString(std::move(E)) + "\n"); 105 106 AddBuffer(Task, std::move(*MBOrErr), EntryPath); 107 } 108 }; 109 110 return [=](size_t Task) -> std::unique_ptr<NativeObjectStream> { 111 // Write to a temporary to avoid race condition 112 SmallString<64> TempFilenameModel; 113 sys::path::append(TempFilenameModel, CacheDirectoryPath, "Thin-%%%%%%.tmp.o"); 114 Expected<sys::fs::TempFile> Temp = sys::fs::TempFile::create( 115 TempFilenameModel, sys::fs::owner_read | sys::fs::owner_write); 116 if (!Temp) { 117 errs() << "Error: " << toString(Temp.takeError()) << "\n"; 118 report_fatal_error("ThinLTO: Can't get a temporary file"); 119 } 120 121 // This CacheStream will move the temporary file into the cache when done. 122 return llvm::make_unique<CacheStream>( 123 llvm::make_unique<raw_fd_ostream>(Temp->FD, /* ShouldClose */ false), 124 AddBuffer, std::move(*Temp), EntryPath.str(), Task); 125 }; 126 }; 127 } 128