LCOV - code coverage report
Current view: top level - lib/LTO - Caching.cpp (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 26 34 76.5 %
Date: 2018-09-23 13:06:45 Functions: 4 4 100.0 %
Legend: Lines: hit not hit

          Line data    Source code
       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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