LLVM  15.0.0git
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  Twine TempFilePrefixRef,
31  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) -> Expected<AddStreamFn> {
41  // This choice of file name allows the cache to be pruned (see pruneCache()
42  // in include/llvm/Support/CachePruning.h).
43  SmallString<64> EntryPath;
44  sys::path::append(EntryPath, CacheDirectoryPath, "llvmcache-" + Key);
45  // First, see if we have a cache hit.
46  SmallString<64> ResultPath;
48  Twine(EntryPath), sys::fs::OF_UpdateAtime, &ResultPath);
49  std::error_code EC;
50  if (FDOrErr) {
52  MemoryBuffer::getOpenFile(*FDOrErr, EntryPath,
53  /*FileSize=*/-1,
54  /*RequiresNullTerminator=*/false);
55  sys::fs::closeFile(*FDOrErr);
56  if (MBOrErr) {
57  AddBuffer(Task, std::move(*MBOrErr));
58  return AddStreamFn();
59  }
60  EC = MBOrErr.getError();
61  } else {
62  EC = errorToErrorCode(FDOrErr.takeError());
63  }
64 
65  // On Windows we can fail to open a cache file with a permission denied
66  // error. This generally means that another process has requested to delete
67  // the file while it is still open, but it could also mean that another
68  // process has opened the file without the sharing permissions we need.
69  // Since the file is probably being deleted we handle it in the same way as
70  // if the file did not exist at all.
72  return createStringError(EC, Twine("Failed to open cache file ") +
73  EntryPath + ": " + EC.message() + "\n");
74 
75  // This file stream is responsible for commiting the resulting file to the
76  // cache and calling AddBuffer to add it to the link.
77  struct CacheStream : CachedFileStream {
78  AddBufferFn AddBuffer;
79  sys::fs::TempFile TempFile;
80  unsigned Task;
81 
82  CacheStream(std::unique_ptr<raw_pwrite_stream> OS, AddBufferFn AddBuffer,
83  sys::fs::TempFile TempFile, std::string EntryPath,
84  unsigned Task)
85  : CachedFileStream(std::move(OS), std::move(EntryPath)),
86  AddBuffer(std::move(AddBuffer)), TempFile(std::move(TempFile)),
87  Task(Task) {}
88 
89  ~CacheStream() {
90  // TODO: Manually commit rather than using non-trivial destructor,
91  // allowing to replace report_fatal_errors with a return Error.
92 
93  // Make sure the stream is closed before committing it.
94  OS.reset();
95 
96  // Open the file first to avoid racing with a cache pruner.
99  sys::fs::convertFDToNativeFile(TempFile.FD), ObjectPathName,
100  /*FileSize=*/-1, /*RequiresNullTerminator=*/false);
101  if (!MBOrErr)
102  report_fatal_error(Twine("Failed to open new cache file ") +
103  TempFile.TmpName + ": " +
104  MBOrErr.getError().message() + "\n");
105 
106  // On POSIX systems, this will atomically replace the destination if
107  // it already exists. We try to emulate this on Windows, but this may
108  // fail with a permission denied error (for example, if the destination
109  // is currently opened by another process that does not give us the
110  // sharing permissions we need). Since the existing file should be
111  // semantically equivalent to the one we are trying to write, we give
112  // AddBuffer a copy of the bytes we wrote in that case. We do this
113  // instead of just using the existing file, because the pruner might
114  // delete the file before we get a chance to use it.
115  Error E = TempFile.keep(ObjectPathName);
116  E = handleErrors(std::move(E), [&](const ECError &E) -> Error {
117  std::error_code EC = E.convertToErrorCode();
118  if (EC != errc::permission_denied)
119  return errorCodeToError(EC);
120 
121  auto MBCopy = MemoryBuffer::getMemBufferCopy((*MBOrErr)->getBuffer(),
122  ObjectPathName);
123  MBOrErr = std::move(MBCopy);
124 
125  // FIXME: should we consume the discard error?
126  consumeError(TempFile.discard());
127 
128  return Error::success();
129  });
130 
131  if (E)
132  report_fatal_error(Twine("Failed to rename temporary file ") +
133  TempFile.TmpName + " to " + ObjectPathName + ": " +
134  toString(std::move(E)) + "\n");
135 
136  AddBuffer(Task, std::move(*MBOrErr));
137  }
138  };
139 
140  return [=](size_t Task) -> Expected<std::unique_ptr<CachedFileStream>> {
141  // Create the cache directory if not already done. Doing this lazily
142  // ensures the filesystem isn't mutated until the cache is.
143  if (std::error_code EC = sys::fs::create_directories(
144  CacheDirectoryPath, /*IgnoreExisting=*/true))
145  return errorCodeToError(EC);
146 
147  // Write to a temporary to avoid race condition
148  SmallString<64> TempFilenameModel;
149  sys::path::append(TempFilenameModel, CacheDirectoryPath,
150  TempFilePrefix + "-%%%%%%.tmp.o");
152  TempFilenameModel, sys::fs::owner_read | sys::fs::owner_write);
153  if (!Temp)
155  toString(Temp.takeError()) + ": " + CacheName +
156  ": Can't get a temporary file");
157 
158  // This CacheStream will move the temporary file into the cache when done.
159  return std::make_unique<CacheStream>(
160  std::make_unique<raw_fd_ostream>(Temp->FD, /* ShouldClose */ false),
161  AddBuffer, std::move(*Temp), std::string(EntryPath.str()), Task);
162  };
163  };
164 }
MemoryBuffer.h
llvm
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:17
llvm::handleErrors
Error handleErrors(Error E, HandlerTs &&... Hs)
Pass the ErrorInfo(s) contained in E to their respective handlers.
Definition: Error.h:943
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)
Given an already-open file descriptor, read the file and return a MemoryBuffer.
Definition: MemoryBuffer.cpp:498
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::AddStreamFn
std::function< Expected< std::unique_ptr< CachedFileStream > >(unsigned Task)> AddStreamFn
This type defines the callback to add a file that is generated on the fly.
Definition: Caching.h:42
llvm::AddBufferFn
std::function< void(unsigned Task, std::unique_ptr< MemoryBuffer > MB)> AddBufferFn
This type defines the callback to add a pre-existing file (e.g.
Definition: Caching.h:62
llvm::Error::success
static ErrorSuccess success()
Create a success value.
Definition: Error.h:329
Errc.h
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:1141
llvm::consumeError
void consumeError(Error Err)
Consume a Error without doing anything.
Definition: Error.h:1043
llvm::sys::fs::TempFile::discard
Error discard()
Definition: Path.cpp:1221
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:90
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:963
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:143
llvm::sys::fs::TempFile::keep
Error keep(const Twine &Name)
Definition: Path.cpp:1249
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::localCache
Expected< FileCache > localCache(Twine CacheNameRef, Twine TempFilePrefixRef, Twine CacheDirectoryPathRef, AddBufferFn AddBuffer=[](size_t Task, 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::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::sys::fs::closeFile
std::error_code closeFile(file_t &F)
Close the file object.
llvm::StringRef
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:58
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:83
llvm::createStringError
Error createStringError(std::error_code EC, char const *Fmt, const Ts &... Vals)
Create formatted StringError object.
Definition: Error.h:1239
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::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:96
llvm::Expected::takeError
Error takeError()
Take ownership of the stored error.
Definition: Error.h:597
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:1324
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:138
llvm::sys::fs::TempFile::FD
int FD
Definition: FileSystem.h:867