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 #if !defined(_MSC_VER) && !defined(__MINGW32__) 23 #include <unistd.h> 24 #else 25 #include <io.h> 26 #endif 27 28 using namespace llvm; 29 using namespace llvm::lto; 30 31 Expected<NativeObjectCache> lto::localCache(StringRef CacheDirectoryPath, 32 AddBufferFn AddBuffer) { 33 if (std::error_code EC = sys::fs::create_directories(CacheDirectoryPath)) 34 return errorCodeToError(EC); 35 36 return [=](unsigned Task, StringRef Key) -> AddStreamFn { 37 // This choice of file name allows the cache to be pruned (see pruneCache() 38 // in include/llvm/Support/CachePruning.h). 39 SmallString<64> EntryPath; 40 sys::path::append(EntryPath, CacheDirectoryPath, "llvmcache-" + Key); 41 // First, see if we have a cache hit. 42 int FD; 43 SmallString<64> ResultPath; 44 std::error_code EC = sys::fs::openFileForRead( 45 Twine(EntryPath), FD, sys::fs::OF_UpdateAtime, &ResultPath); 46 if (!EC) { 47 ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = 48 MemoryBuffer::getOpenFile(FD, EntryPath, 49 /*FileSize*/ -1, 50 /*RequiresNullTerminator*/ false); 51 close(FD); 52 if (MBOrErr) { 53 AddBuffer(Task, std::move(*MBOrErr)); 54 return AddStreamFn(); 55 } 56 EC = MBOrErr.getError(); 57 } 58 59 // On Windows we can fail to open a cache file with a permission denied 60 // error. This generally means that another process has requested to delete 61 // the file while it is still open, but it could also mean that another 62 // process has opened the file without the sharing permissions we need. 63 // Since the file is probably being deleted we handle it in the same way as 64 // if the file did not exist at all. 65 if (EC != errc::no_such_file_or_directory && EC != errc::permission_denied) 66 report_fatal_error(Twine("Failed to open cache file ") + EntryPath + 67 ": " + EC.message() + "\n"); 68 69 // This native object stream is responsible for commiting the resulting 70 // file to the cache and calling AddBuffer to add it to the link. 71 struct CacheStream : NativeObjectStream { 72 AddBufferFn AddBuffer; 73 sys::fs::TempFile TempFile; 74 std::string EntryPath; 75 unsigned Task; 76 77 CacheStream(std::unique_ptr<raw_pwrite_stream> OS, AddBufferFn AddBuffer, 78 sys::fs::TempFile TempFile, std::string EntryPath, 79 unsigned Task) 80 : NativeObjectStream(std::move(OS)), AddBuffer(std::move(AddBuffer)), 81 TempFile(std::move(TempFile)), EntryPath(std::move(EntryPath)), 82 Task(Task) {} 83 84 ~CacheStream() { 85 // Make sure the stream is closed before committing it. 86 OS.reset(); 87 88 // Open the file first to avoid racing with a cache pruner. 89 ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = 90 MemoryBuffer::getOpenFile(TempFile.FD, TempFile.TmpName, 91 /*FileSize*/ -1, 92 /*RequiresNullTerminator*/ false); 93 if (!MBOrErr) 94 report_fatal_error(Twine("Failed to open new cache file ") + 95 TempFile.TmpName + ": " + 96 MBOrErr.getError().message() + "\n"); 97 98 // On POSIX systems, this will atomically replace the destination if 99 // it already exists. We try to emulate this on Windows, but this may 100 // fail with a permission denied error (for example, if the destination 101 // is currently opened by another process that does not give us the 102 // sharing permissions we need). Since the existing file should be 103 // semantically equivalent to the one we are trying to write, we give 104 // AddBuffer a copy of the bytes we wrote in that case. We do this 105 // instead of just using the existing file, because the pruner might 106 // delete the file before we get a chance to use it. 107 Error E = TempFile.keep(EntryPath); 108 E = handleErrors(std::move(E), [&](const ECError &E) -> Error { 109 std::error_code EC = E.convertToErrorCode(); 110 if (EC != errc::permission_denied) 111 return errorCodeToError(EC); 112 113 auto MBCopy = MemoryBuffer::getMemBufferCopy((*MBOrErr)->getBuffer(), 114 EntryPath); 115 MBOrErr = std::move(MBCopy); 116 117 // FIXME: should we consume the discard error? 118 consumeError(TempFile.discard()); 119 120 return Error::success(); 121 }); 122 123 if (E) 124 report_fatal_error(Twine("Failed to rename temporary file ") + 125 TempFile.TmpName + " to " + EntryPath + ": " + 126 toString(std::move(E)) + "\n"); 127 128 AddBuffer(Task, std::move(*MBOrErr)); 129 } 130 }; 131 132 return [=](size_t Task) -> std::unique_ptr<NativeObjectStream> { 133 // Write to a temporary to avoid race condition 134 SmallString<64> TempFilenameModel; 135 sys::path::append(TempFilenameModel, CacheDirectoryPath, "Thin-%%%%%%.tmp.o"); 136 Expected<sys::fs::TempFile> Temp = sys::fs::TempFile::create( 137 TempFilenameModel, sys::fs::owner_read | sys::fs::owner_write); 138 if (!Temp) { 139 errs() << "Error: " << toString(Temp.takeError()) << "\n"; 140 report_fatal_error("ThinLTO: Can't get a temporary file"); 141 } 142 143 // This CacheStream will move the temporary file into the cache when done. 144 return llvm::make_unique<CacheStream>( 145 llvm::make_unique<raw_fd_ostream>(Temp->FD, /* ShouldClose */ false), 146 AddBuffer, std::move(*Temp), EntryPath.str(), Task); 147 }; 148 }; 149 } 150