r318945 - Avoid copying the data of in-memory preambles

[Ilya Biryukov via cfe-commits]

Author: ibiryukov
Date: Fri Nov 24 05:12:38 2017
New Revision: 318945

URL: http://llvm.org/viewvc/llvm-project?rev=318945&view=rev
Log:
Avoid copying the data of in-memory preambles

Summary: Preambles are large and we should avoid copying them.

Reviewers: bkramer, klimek

Reviewed By: bkramer

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D40302

Modified:
    cfe/trunk/include/clang/Frontend/PrecompiledPreamble.h
    cfe/trunk/lib/Frontend/PrecompiledPreamble.cpp

Modified: cfe/trunk/include/clang/Frontend/PrecompiledPreamble.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Frontend/PrecompiledPreamble.h?rev=318945&r1=318944&r2=318945&view=diff
==============================================================================
--- cfe/trunk/include/clang/Frontend/PrecompiledPreamble.h (original)
+++ cfe/trunk/include/clang/Frontend/PrecompiledPreamble.h Fri Nov 24 05:12:38 2017
@@ -98,6 +98,10 @@ public:
   /// Changes options inside \p CI to use PCH from this preamble. Also remaps
   /// main file to \p MainFileBuffer and updates \p VFS to ensure the preamble
   /// is accessible.
+  /// For in-memory preambles, PrecompiledPreamble instance continues to own
+  /// the MemoryBuffer with the Preamble after this method returns. The caller
+  /// is reponsible for making sure the PrecompiledPreamble instance outlives
+  /// the compiler run and the AST that will be using the PCH.
   void AddImplicitPreamble(CompilerInvocation &CI,
                            IntrusiveRefCntPtr<vfs::FileSystem> &VFS,
                            llvm::MemoryBuffer *MainFileBuffer) const;

Modified: cfe/trunk/lib/Frontend/PrecompiledPreamble.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Frontend/PrecompiledPreamble.cpp?rev=318945&r1=318944&r2=318945&view=diff
==============================================================================
--- cfe/trunk/lib/Frontend/PrecompiledPreamble.cpp (original)
+++ cfe/trunk/lib/Frontend/PrecompiledPreamble.cpp Fri Nov 24 05:12:38 2017
@@ -699,9 +699,7 @@ void PrecompiledPreamble::setupPreambleS
     StringRef PCHPath = getInMemoryPreamblePath();
     PreprocessorOpts.ImplicitPCHInclude = PCHPath;
 
-    // FIMXE(ibiryukov): Preambles can be large. We should allow shared access
-    // to the preamble data instead of copying it here.
-    auto Buf = llvm::MemoryBuffer::getMemBufferCopy(Storage.asMemory().Data);
+    auto Buf = llvm::MemoryBuffer::getMemBuffer(Storage.asMemory().Data);
     VFS = createVFSOverlayForPreamblePCH(PCHPath, std::move(Buf), VFS);
   }
 }