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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 54 : Expected<NativeObjectCache> lto::localCache(StringRef CacheDirectoryPath,
32 : AddBufferFn AddBuffer) {
33 54 : if (std::error_code EC = sys::fs::create_directories(CacheDirectoryPath))
34 0 : return errorCodeToError(EC);
35 :
36 0 : 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 56 : CacheStream(std::unique_ptr<raw_pwrite_stream> OS, AddBufferFn AddBuffer,
78 : sys::fs::TempFile TempFile, std::string EntryPath,
79 : unsigned Task)
80 56 : : NativeObjectStream(std::move(OS)), AddBuffer(std::move(AddBuffer)),
81 : TempFile(std::move(TempFile)), EntryPath(std::move(EntryPath)),
82 112 : Task(Task) {}
83 :
84 168 : ~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 56 : MemoryBuffer::getOpenFile(TempFile.FD, TempFile.TmpName,
91 : /*FileSize*/ -1,
92 56 : /*RequiresNullTerminator*/ false);
93 56 : if (!MBOrErr)
94 0 : 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.
107 112 : Error E = TempFile.keep(EntryPath);
108 112 : 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 56 : if (E)
124 0 : report_fatal_error(Twine("Failed to rename temporary file ") +
125 : TempFile.TmpName + " to " + EntryPath + ": " +
126 0 : toString(std::move(E)) + "\n");
127 :
128 112 : AddBuffer(Task, std::move(*MBOrErr));
129 112 : }
130 56 : };
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 : }
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