1 //===-Caching.cpp - LLVM Link Time Optimizer Cache Handling ---------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file implements the Caching for ThinLTO. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "llvm/LTO/Caching.h" 14 #include "llvm/ADT/StringExtras.h" 15 #include "llvm/Support/Errc.h" 16 #include "llvm/Support/FileSystem.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 SmallString<64> ResultPath; 43 Expected<sys::fs::file_t> FDOrErr = sys::fs::openNativeFileForRead( 44 Twine(EntryPath), sys::fs::OF_UpdateAtime, &ResultPath); 45 std::error_code EC; 46 if (FDOrErr) { 47 ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = 48 MemoryBuffer::getOpenFile(*FDOrErr, EntryPath, 49 /*FileSize=*/-1, 50 /*RequiresNullTerminator=*/false); 51 sys::fs::closeFile(*FDOrErr); 52 if (MBOrErr) { 53 AddBuffer(Task, std::move(*MBOrErr)); 54 return AddStreamFn(); 55 } 56 EC = MBOrErr.getError(); 57 } else { 58 EC = errorToErrorCode(FDOrErr.takeError()); 59 } 60 61 // On Windows we can fail to open a cache file with a permission denied 62 // error. This generally means that another process has requested to delete 63 // the file while it is still open, but it could also mean that another 64 // process has opened the file without the sharing permissions we need. 65 // Since the file is probably being deleted we handle it in the same way as 66 // if the file did not exist at all. 67 if (EC != errc::no_such_file_or_directory && EC != errc::permission_denied) 68 report_fatal_error(Twine("Failed to open cache file ") + EntryPath + 69 ": " + EC.message() + "\n"); 70 71 // This native object stream is responsible for commiting the resulting 72 // file to the cache and calling AddBuffer to add it to the link. 73 struct CacheStream : NativeObjectStream { 74 AddBufferFn AddBuffer; 75 sys::fs::TempFile TempFile; 76 std::string EntryPath; 77 unsigned Task; 78 79 CacheStream(std::unique_ptr<raw_pwrite_stream> OS, AddBufferFn AddBuffer, 80 sys::fs::TempFile TempFile, std::string EntryPath, 81 unsigned Task) 82 : NativeObjectStream(std::move(OS)), AddBuffer(std::move(AddBuffer)), 83 TempFile(std::move(TempFile)), EntryPath(std::move(EntryPath)), 84 Task(Task) {} 85 86 ~CacheStream() { 87 // Make sure the stream is closed before committing it. 88 OS.reset(); 89 90 // Open the file first to avoid racing with a cache pruner. 91 ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = 92 MemoryBuffer::getOpenFile( 93 sys::fs::convertFDToNativeFile(TempFile.FD), TempFile.TmpName, 94 /*FileSize=*/-1, /*RequiresNullTerminator=*/false); 95 if (!MBOrErr) 96 report_fatal_error(Twine("Failed to open new cache file ") + 97 TempFile.TmpName + ": " + 98 MBOrErr.getError().message() + "\n"); 99 100 // On POSIX systems, this will atomically replace the destination if 101 // it already exists. We try to emulate this on Windows, but this may 102 // fail with a permission denied error (for example, if the destination 103 // is currently opened by another process that does not give us the 104 // sharing permissions we need). Since the existing file should be 105 // semantically equivalent to the one we are trying to write, we give 106 // AddBuffer a copy of the bytes we wrote in that case. We do this 107 // instead of just using the existing file, because the pruner might 108 // delete the file before we get a chance to use it. 109 Error E = TempFile.keep(EntryPath); 110 E = handleErrors(std::move(E), [&](const ECError &E) -> Error { 111 std::error_code EC = E.convertToErrorCode(); 112 if (EC != errc::permission_denied) 113 return errorCodeToError(EC); 114 115 auto MBCopy = MemoryBuffer::getMemBufferCopy((*MBOrErr)->getBuffer(), 116 EntryPath); 117 MBOrErr = std::move(MBCopy); 118 119 // FIXME: should we consume the discard error? 120 consumeError(TempFile.discard()); 121 122 return Error::success(); 123 }); 124 125 if (E) 126 report_fatal_error(Twine("Failed to rename temporary file ") + 127 TempFile.TmpName + " to " + EntryPath + ": " + 128 toString(std::move(E)) + "\n"); 129 130 AddBuffer(Task, std::move(*MBOrErr)); 131 } 132 }; 133 134 return [=](size_t Task) -> std::unique_ptr<NativeObjectStream> { 135 // Write to a temporary to avoid race condition 136 SmallString<64> TempFilenameModel; 137 sys::path::append(TempFilenameModel, CacheDirectoryPath, "Thin-%%%%%%.tmp.o"); 138 Expected<sys::fs::TempFile> Temp = sys::fs::TempFile::create( 139 TempFilenameModel, sys::fs::owner_read | sys::fs::owner_write); 140 if (!Temp) { 141 errs() << "Error: " << toString(Temp.takeError()) << "\n"; 142 report_fatal_error("ThinLTO: Can't get a temporary file"); 143 } 144 145 // This CacheStream will move the temporary file into the cache when done. 146 return std::make_unique<CacheStream>( 147 std::make_unique<raw_fd_ostream>(Temp->FD, /* ShouldClose */ false), 148 AddBuffer, std::move(*Temp), std::string(EntryPath.str()), Task); 149 }; 150 }; 151 } 152