LLVM  16.0.0git
Caching.cpp
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1 //===-Caching.cpp - LLVM Local File Cache ---------------------------------===//
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 localCache function, which simplifies creating,
10 // adding to, and querying a local file system cache. localCache takes care of
11 // periodically pruning older files from the cache using a CachePruningPolicy.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/Support/Caching.h"
16 #include "llvm/Support/Errc.h"
19 #include "llvm/Support/Path.h"
20 
21 #if !defined(_MSC_VER) && !defined(__MINGW32__)
22 #include <unistd.h>
23 #else
24 #include <io.h>
25 #endif
26 
27 using namespace llvm;
28 
30  const Twine &TempFilePrefixRef,
31  const Twine &CacheDirectoryPathRef,
32  AddBufferFn AddBuffer) {
33 
34  // Create local copies which are safely captured-by-copy in lambdas
35  SmallString<64> CacheName, TempFilePrefix, CacheDirectoryPath;
36  CacheNameRef.toVector(CacheName);
37  TempFilePrefixRef.toVector(TempFilePrefix);
38  CacheDirectoryPathRef.toVector(CacheDirectoryPath);
39 
40  return [=](unsigned Task, StringRef Key,
42  // This choice of file name allows the cache to be pruned (see pruneCache()
43  // in include/llvm/Support/CachePruning.h).
44  SmallString<64> EntryPath;
45  sys::path::append(EntryPath, CacheDirectoryPath, "llvmcache-" + Key);
46  // First, see if we have a cache hit.
47  SmallString<64> ResultPath;
49  Twine(EntryPath), sys::fs::OF_UpdateAtime, &ResultPath);
50  std::error_code EC;
51  if (FDOrErr) {
53  MemoryBuffer::getOpenFile(*FDOrErr, EntryPath,
54  /*FileSize=*/-1,
55  /*RequiresNullTerminator=*/false);
56  sys::fs::closeFile(*FDOrErr);
57  if (MBOrErr) {
58  AddBuffer(Task, ModuleName, std::move(*MBOrErr));
59  return AddStreamFn();
60  }
61  EC = MBOrErr.getError();
62  } else {
63  EC = errorToErrorCode(FDOrErr.takeError());
64  }
65 
66  // On Windows we can fail to open a cache file with a permission denied
67  // error. This generally means that another process has requested to delete
68  // the file while it is still open, but it could also mean that another
69  // process has opened the file without the sharing permissions we need.
70  // Since the file is probably being deleted we handle it in the same way as
71  // if the file did not exist at all.
73  return createStringError(EC, Twine("Failed to open cache file ") +
74  EntryPath + ": " + EC.message() + "\n");
75 
76  // This file stream is responsible for commiting the resulting file to the
77  // cache and calling AddBuffer to add it to the link.
78  struct CacheStream : CachedFileStream {
79  AddBufferFn AddBuffer;
80  sys::fs::TempFile TempFile;
81  std::string ModuleName;
82  unsigned Task;
83 
84  CacheStream(std::unique_ptr<raw_pwrite_stream> OS, AddBufferFn AddBuffer,
85  sys::fs::TempFile TempFile, std::string EntryPath,
86  std::string ModuleName, unsigned Task)
87  : CachedFileStream(std::move(OS), std::move(EntryPath)),
88  AddBuffer(std::move(AddBuffer)), TempFile(std::move(TempFile)),
89  ModuleName(ModuleName), Task(Task) {}
90 
91  ~CacheStream() {
92  // TODO: Manually commit rather than using non-trivial destructor,
93  // allowing to replace report_fatal_errors with a return Error.
94 
95  // Make sure the stream is closed before committing it.
96  OS.reset();
97 
98  // Open the file first to avoid racing with a cache pruner.
101  sys::fs::convertFDToNativeFile(TempFile.FD), ObjectPathName,
102  /*FileSize=*/-1, /*RequiresNullTerminator=*/false);
103  if (!MBOrErr)
104  report_fatal_error(Twine("Failed to open new cache file ") +
105  TempFile.TmpName + ": " +
106  MBOrErr.getError().message() + "\n");
107 
108  // On POSIX systems, this will atomically replace the destination if
109  // it already exists. We try to emulate this on Windows, but this may
110  // fail with a permission denied error (for example, if the destination
111  // is currently opened by another process that does not give us the
112  // sharing permissions we need). Since the existing file should be
113  // semantically equivalent to the one we are trying to write, we give
114  // AddBuffer a copy of the bytes we wrote in that case. We do this
115  // instead of just using the existing file, because the pruner might
116  // delete the file before we get a chance to use it.
117  Error E = TempFile.keep(ObjectPathName);
118  E = handleErrors(std::move(E), [&](const ECError &E) -> Error {
119  std::error_code EC = E.convertToErrorCode();
120  if (EC != errc::permission_denied)
121  return errorCodeToError(EC);
122 
123  auto MBCopy = MemoryBuffer::getMemBufferCopy((*MBOrErr)->getBuffer(),
124  ObjectPathName);
125  MBOrErr = std::move(MBCopy);
126 
127  // FIXME: should we consume the discard error?
128  consumeError(TempFile.discard());
129 
130  return Error::success();
131  });
132 
133  if (E)
134  report_fatal_error(Twine("Failed to rename temporary file ") +
135  TempFile.TmpName + " to " + ObjectPathName + ": " +
136  toString(std::move(E)) + "\n");
137 
138  AddBuffer(Task, ModuleName, std::move(*MBOrErr));
139  }
140  };
141 
142  return [=](size_t Task, const Twine &ModuleName)
143  -> Expected<std::unique_ptr<CachedFileStream>> {
144  // Create the cache directory if not already done. Doing this lazily
145  // ensures the filesystem isn't mutated until the cache is.
146  if (std::error_code EC = sys::fs::create_directories(
147  CacheDirectoryPath, /*IgnoreExisting=*/true))
148  return errorCodeToError(EC);
149 
150  // Write to a temporary to avoid race condition
151  SmallString<64> TempFilenameModel;
152  sys::path::append(TempFilenameModel, CacheDirectoryPath,
153  TempFilePrefix + "-%%%%%%.tmp.o");
155  TempFilenameModel, sys::fs::owner_read | sys::fs::owner_write);
156  if (!Temp)
158  toString(Temp.takeError()) + ": " + CacheName +
159  ": Can't get a temporary file");
160 
161  // This CacheStream will move the temporary file into the cache when done.
162  return std::make_unique<CacheStream>(
163  std::make_unique<raw_fd_ostream>(Temp->FD, /* ShouldClose */ false),
164  AddBuffer, std::move(*Temp), std::string(EntryPath.str()),
165  ModuleName.str(), Task);
166  };
167  };
168 }
MemoryBuffer.h
llvm
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
llvm::handleErrors
Error handleErrors(Error E, HandlerTs &&... Hs)
Pass the ErrorInfo(s) contained in E to their respective handlers.
Definition: Error.h:942
FileSystem.h
llvm::sys::fs::TempFile::TmpName
std::string TmpName
Definition: FileSystem.h:864
llvm::CachedFileStream
This class wraps an output stream for a file.
Definition: Caching.h:28
Path.h
llvm::Error::success
static ErrorSuccess success()
Create a success value.
Definition: Error.h:329
Errc.h
llvm::AddBufferFn
std::function< void(unsigned Task, const Twine &ModuleName, std::unique_ptr< MemoryBuffer > MB)> AddBufferFn
This type defines the callback to add a pre-existing file (e.g.
Definition: Caching.h:64
llvm::errc::no_such_file_or_directory
@ no_such_file_or_directory
llvm::Expected
Tagged union holding either a T or a Error.
Definition: APFloat.h:41
llvm::ECError
This class wraps a std::error_code in a Error.
Definition: Error.h:1140
llvm::consumeError
void consumeError(Error Err)
Consume a Error without doing anything.
Definition: Error.h:1042
llvm::sys::fs::TempFile::discard
Error discard()
Definition: Path.cpp:1234
llvm::errc::permission_denied
@ permission_denied
llvm::sys::path::append
void append(SmallVectorImpl< char > &path, const Twine &a, const Twine &b="", const Twine &c="", const Twine &d="")
Append to path.
Definition: Path.cpp:456
Caching.h
E
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
llvm::errorCodeToError
Error errorCodeToError(std::error_code EC)
Helper for converting an std::error_code to a Error.
Definition: Error.cpp:92
llvm::AMDGPU::PALMD::Key
Key
PAL metadata keys.
Definition: AMDGPUMetadata.h:486
llvm::ErrorOr::getError
std::error_code getError() const
Definition: ErrorOr.h:153
llvm::sys::fs::create_directories
std::error_code create_directories(const Twine &path, bool IgnoreExisting=true, perms Perms=owner_all|group_all)
Create all the non-existent directories in path.
Definition: Path.cpp:967
llvm::report_fatal_error
void report_fatal_error(Error Err, bool gen_crash_diag=true)
Report a serious error, calling any installed error handler.
Definition: Error.cpp:145
llvm::sys::fs::TempFile::keep
Error keep(const Twine &Name)
Definition: Path.cpp:1262
llvm::sys::fs::openNativeFileForRead
Expected< file_t > openNativeFileForRead(const Twine &Name, OpenFlags Flags=OF_None, SmallVectorImpl< char > *RealPath=nullptr)
Opens the file with the given name in a read-only mode, returning its open file descriptor.
llvm::SmallString< 64 >
llvm::sys::fs::owner_write
@ owner_write
Definition: FileSystem.h:89
move
compiles ldr LCPI1_0 ldr ldr mov lsr tst moveq r1 ldr LCPI1_1 and r0 bx lr It would be better to do something like to fold the shift into the conditional move
Definition: README.txt:546
llvm::Twine::toVector
void toVector(SmallVectorImpl< char > &Out) const
Append the concatenated string into the given SmallString or SmallVector.
Definition: Twine.cpp:32
llvm::AddStreamFn
std::function< Expected< std::unique_ptr< CachedFileStream > >(unsigned Task, const Twine &ModuleName)> AddStreamFn
This type defines the callback to add a file that is generated on the fly.
Definition: Caching.h:42
ModuleName
Definition: ItaniumDemangle.h:999
llvm::sys::fs::closeFile
std::error_code closeFile(file_t &F)
Close the file object.
llvm::localCache
Expected< FileCache > localCache(const Twine &CacheNameRef, const Twine &TempFilePrefixRef, const Twine &CacheDirectoryPathRef, AddBufferFn AddBuffer=[](size_t Task, const Twine &ModuleName, std::unique_ptr< MemoryBuffer > MB) {})
Create a local file system cache which uses the given cache name, temporary file prefix,...
Definition: Caching.cpp:29
llvm::StringRef
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
llvm::sys::fs::OF_UpdateAtime
@ OF_UpdateAtime
Force files Atime to be updated on access.
Definition: FileSystem.h:785
llvm::sys::fs::convertFDToNativeFile
file_t convertFDToNativeFile(int FD)
Converts from a Posix file descriptor number to a native file handle.
Definition: FileSystem.h:993
llvm::Twine
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
llvm::createStringError
Error createStringError(std::error_code EC, char const *Fmt, const Ts &... Vals)
Create formatted StringError object.
Definition: Error.h:1238
llvm::toString
const char * toString(DWARFSectionKind Kind)
Definition: DWARFUnitIndex.h:67
llvm::Error
Lightweight error class with error context and mandatory checking.
Definition: Error.h:155
llvm::errc::io_error
@ io_error
llvm::sys::fs::owner_read
@ owner_read
Definition: FileSystem.h:88
llvm::MemoryBuffer::getOpenFile
static ErrorOr< std::unique_ptr< MemoryBuffer > > getOpenFile(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize, bool RequiresNullTerminator=true, bool IsVolatile=false, Optional< Align > Alignment=None)
Given an already-open file descriptor, read the file and return a MemoryBuffer.
Definition: MemoryBuffer.cpp:513
llvm::SmallString::str
StringRef str() const
Explicit conversion to StringRef.
Definition: SmallString.h:260
llvm::errorToErrorCode
std::error_code errorToErrorCode(Error Err)
Helper for converting an ECError to a std::error_code.
Definition: Error.cpp:98
llvm::Expected::takeError
Error takeError()
Take ownership of the stored error.
Definition: Error.h:596
llvm::ErrorOr
Represents either an error or a value T.
Definition: ErrorOr.h:56
llvm::sys::fs::TempFile
Represents a temporary file.
Definition: FileSystem.h:850
llvm::sys::fs::TempFile::create
static Expected< TempFile > create(const Twine &Model, unsigned Mode=all_read|all_write, OpenFlags ExtraFlags=OF_None)
This creates a temporary file with createUniqueFile and schedules it for deletion with sys::RemoveFil...
Definition: Path.cpp:1337
llvm::MemoryBuffer::getMemBufferCopy
static std::unique_ptr< MemoryBuffer > getMemBufferCopy(StringRef InputData, const Twine &BufferName="")
Open the specified memory range as a MemoryBuffer, copying the contents and taking ownership of it.
Definition: MemoryBuffer.cpp:140
llvm::sys::fs::TempFile::FD
int FD
Definition: FileSystem.h:867