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/MemoryBuffer.h" 17#include "llvm/Support/Path.h" 18#include "llvm/Support/Process.h" 19#include "llvm/Support/raw_ostream.h" 20 21#if !defined(_MSC_VER) && !defined(__MINGW32__) 22#include <unistd.h> 23#else 24#include <io.h> 25#endif 26 27using namespace llvm; 28using namespace llvm::lto; 29 30Expected<NativeObjectCache> lto::localCache(StringRef CacheDirectoryPath, 31 AddBufferFn AddBuffer) { 32 if (std::error_code EC = sys::fs::create_directories(CacheDirectoryPath)) 33 return errorCodeToError(EC); 34 35 return [=](unsigned Task, StringRef Key) -> AddStreamFn { 36 // This choice of file name allows the cache to be pruned (see pruneCache() 37 // in include/llvm/Support/CachePruning.h). 38 SmallString<64> EntryPath; 39 sys::path::append(EntryPath, CacheDirectoryPath, "llvmcache-" + Key); 40 // First, see if we have a cache hit. 41 SmallString<64> ResultPath; 42 Expected<sys::fs::file_t> FDOrErr = sys::fs::openNativeFileForRead( 43 Twine(EntryPath), sys::fs::OF_UpdateAtime, &ResultPath); 44 std::error_code EC; 45 if (FDOrErr) { 46 ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = 47 MemoryBuffer::getOpenFile(*FDOrErr, EntryPath, 48 /*FileSize=*/-1, 49 /*RequiresNullTerminator=*/false); 50 sys::fs::closeFile(*FDOrErr); 51 if (MBOrErr) { 52 AddBuffer(Task, std::move(*MBOrErr)); 53 return AddStreamFn(); 54 } 55 EC = MBOrErr.getError(); 56 } else { 57 EC = errorToErrorCode(FDOrErr.takeError()); 58 } 59 60 // On Windows we can fail to open a cache file with a permission denied 61 // error. This generally means that another process has requested to delete 62 // the file while it is still open, but it could also mean that another 63 // process has opened the file without the sharing permissions we need. 64 // Since the file is probably being deleted we handle it in the same way as 65 // if the file did not exist at all. 66 if (EC != errc::no_such_file_or_directory && EC != errc::permission_denied) 67 report_fatal_error(Twine("Failed to open cache file ") + EntryPath + 68 ": " + EC.message() + "\n"); 69 70 // This native object stream is responsible for commiting the resulting 71 // file to the cache and calling AddBuffer to add it to the link. 72 struct CacheStream : NativeObjectStream { 73 AddBufferFn AddBuffer; 74 sys::fs::TempFile TempFile; 75 std::string EntryPath; 76 unsigned Task; 77 78 CacheStream(std::unique_ptr<raw_pwrite_stream> OS, AddBufferFn AddBuffer, 79 sys::fs::TempFile TempFile, std::string EntryPath, 80 unsigned Task) 81 : NativeObjectStream(std::move(OS)), AddBuffer(std::move(AddBuffer)), 82 TempFile(std::move(TempFile)), EntryPath(std::move(EntryPath)), 83 Task(Task) {} 84 85 ~CacheStream() { 86 // Make sure the stream is closed before committing it. 87 OS.reset(); 88 89 // Open the file first to avoid racing with a cache pruner. 90 ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = 91 MemoryBuffer::getOpenFile( 92 sys::fs::convertFDToNativeFile(TempFile.FD), TempFile.TmpName, 93 /*FileSize=*/-1, /*RequiresNullTerminator=*/false); 94 if (!MBOrErr) 95 report_fatal_error(Twine("Failed to open new cache file ") + 96 TempFile.TmpName + ": " + 97 MBOrErr.getError().message() + "\n"); 98 99 // On POSIX systems, this will atomically replace the destination if 100 // it already exists. We try to emulate this on Windows, but this may 101 // fail with a permission denied error (for example, if the destination 102 // is currently opened by another process that does not give us the 103 // sharing permissions we need). Since the existing file should be 104 // semantically equivalent to the one we are trying to write, we give 105 // AddBuffer a copy of the bytes we wrote in that case. We do this 106 // instead of just using the existing file, because the pruner might 107 // delete the file before we get a chance to use it. 108 Error E = TempFile.keep(EntryPath); 109 E = handleErrors(std::move(E), [&](const ECError &E) -> Error { 110 std::error_code EC = E.convertToErrorCode(); 111 if (EC != errc::permission_denied) 112 return errorCodeToError(EC); 113 114 auto MBCopy = MemoryBuffer::getMemBufferCopy((*MBOrErr)->getBuffer(), 115 EntryPath); 116 MBOrErr = std::move(MBCopy); 117 118 // FIXME: should we consume the discard error? 119 consumeError(TempFile.discard()); 120 121 return Error::success(); 122 }); 123 124 if (E) 125 report_fatal_error(Twine("Failed to rename temporary file ") + 126 TempFile.TmpName + " to " + EntryPath + ": " + 127 toString(std::move(E)) + "\n"); 128 129 AddBuffer(Task, std::move(*MBOrErr)); 130 } 131 }; 132 133 return [=](size_t Task) -> std::unique_ptr<NativeObjectStream> { 134 // Write to a temporary to avoid race condition 135 SmallString<64> TempFilenameModel; 136 sys::path::append(TempFilenameModel, CacheDirectoryPath, "Thin-%%%%%%.tmp.o"); 137 Expected<sys::fs::TempFile> Temp = sys::fs::TempFile::create( 138 TempFilenameModel, sys::fs::owner_read | sys::fs::owner_write); 139 if (!Temp) { 140 errs() << "Error: " << toString(Temp.takeError()) << "\n"; 141 report_fatal_error("ThinLTO: Can't get a temporary file"); 142 } 143 144 // This CacheStream will move the temporary file into the cache when done. 145 return std::make_unique<CacheStream>( 146 std::make_unique<raw_fd_ostream>(Temp->FD, /* ShouldClose */ false), 147 AddBuffer, std::move(*Temp), EntryPath.str(), Task); 148 }; 149 }; 150} 151