On Wed, Apr 16, 2014 at 2:31 AM, Evgeniy Stepanov <[email protected] > wrote:
> I see a flood of warnings in GCC 4.8 build about unused attribute > being unused. Looks like GCC does not need or understand this > attribute on member declarations. Do we need a new macro like > LLVM_ATTRIBUTE_UNUSED_MEMBER ? > Someone else mentioned this, but I can't reproduce it. I suspect it just needs the attribute in a different place, but I don't know how to debug it because I don't see it... Let me try more extreme measures. > > [44/588] Building CXX object > tools/clang/lib/Lex/CMakeFiles/clangLex.dir/PreprocessorLexer.cpp.o > In file included from ../tools/clang/lib/Lex/PreprocessorLexer.cpp:15:0: > ../tools/clang/include/clang/Basic/SourceManager.h:100:56: warning: > ‘__unused__’ attribute ignored [-Wattributes] > LLVM_ATTRIBUTE_UNUSED llvm::AlignedCharArray<8, 1> NonceAligner; > ^ > > On Wed, Apr 16, 2014 at 1:34 AM, Chandler Carruth <[email protected]> > wrote: > > Author: chandlerc > > Date: Tue Apr 15 16:34:12 2014 > > New Revision: 206324 > > > > URL: http://llvm.org/viewvc/llvm-project?rev=206324&view=rev > > Log: > > [Allocator] Make the ContentCache object actually carry the 8-byte > > alignment constraint rather than using the allocator function's over > > alignment "feature". This was the only use of the "feature" which I plan > > to remove next. =] Attaching the alignment to the type seems cleaner and > > more principled anyways. > > > > Modified: > > cfe/trunk/include/clang/Basic/SourceManager.h > > cfe/trunk/lib/Basic/SourceManager.cpp > > > > Modified: cfe/trunk/include/clang/Basic/SourceManager.h > > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/SourceManager.h?rev=206324&r1=206323&r2=206324&view=diff > > > ============================================================================== > > --- cfe/trunk/include/clang/Basic/SourceManager.h (original) > > +++ cfe/trunk/include/clang/Basic/SourceManager.h Tue Apr 15 16:34:12 > 2014 > > @@ -44,6 +44,7 @@ > > #include "llvm/ADT/IntrusiveRefCntPtr.h" > > #include "llvm/ADT/PointerIntPair.h" > > #include "llvm/ADT/PointerUnion.h" > > +#include "llvm/Support/AlignOf.h" > > #include "llvm/Support/Allocator.h" > > #include "llvm/Support/DataTypes.h" > > #include "llvm/Support/MemoryBuffer.h" > > @@ -89,6 +90,15 @@ namespace SrcMgr { > > DoNotFreeFlag = 0x02 > > }; > > > > + // Note that the first member of this class is an aligned character > buffer > > + // to ensure that this class has an alignment of 8 bytes. This > wastes > > + // 8 bytes for every ContentCache object, but each of these > corresponds to > > + // a file loaded into memory, so the 8 bytes doesn't seem terribly > > + // important. It is quite awkward to fit this aligner into any > other part > > + // of the class due to the lack of portable ways to combine it with > other > > + // members. > > + llvm::AlignedCharArray<8, 1> NonceAligner LLVM_ATTRIBUTE_UNUSED; > > + > > /// \brief The actual buffer containing the characters from the > input > > /// file. > > /// > > @@ -224,6 +234,11 @@ namespace SrcMgr { > > ContentCache &operator=(const ContentCache& RHS) > LLVM_DELETED_FUNCTION; > > }; > > > > + // Assert that the \c ContentCache objects will always be 8-byte > aligned so > > + // that we can pack 3 bits of integer into pointers to such objects. > > + static_assert(llvm::AlignOf<ContentCache>::Alignment >= 8, > > + "ContentCache must be 8-byte aligned."); > > + > > /// \brief Information about a FileID, basically just the logical file > > /// that it represents and include stack information. > > /// > > > > Modified: cfe/trunk/lib/Basic/SourceManager.cpp > > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Basic/SourceManager.cpp?rev=206324&r1=206323&r2=206324&view=diff > > > ============================================================================== > > --- cfe/trunk/lib/Basic/SourceManager.cpp (original) > > +++ cfe/trunk/lib/Basic/SourceManager.cpp Tue Apr 15 16:34:12 2014 > > @@ -436,12 +436,8 @@ SourceManager::getOrCreateContentCache(c > > ContentCache *&Entry = FileInfos[FileEnt]; > > if (Entry) return Entry; > > > > - // Nope, create a new Cache entry. Make sure it is at least 8-byte > aligned > > - // so that FileInfo can use the low 3 bits of the pointer for its own > > - // nefarious purposes. > > - unsigned EntryAlign = llvm::AlignOf<ContentCache>::Alignment; > > - EntryAlign = std::max(8U, EntryAlign); > > - Entry = ContentCacheAlloc.Allocate<ContentCache>(1, EntryAlign); > > + // Nope, create a new Cache entry. > > + Entry = ContentCacheAlloc.Allocate<ContentCache>(); > > > > if (OverriddenFilesInfo) { > > // If the file contents are overridden with contents from another > file, > > @@ -468,12 +464,8 @@ SourceManager::getOrCreateContentCache(c > > /// memory buffer. This does no caching. > > const ContentCache* > > SourceManager::createMemBufferContentCache(const MemoryBuffer *Buffer) { > > - // Add a new ContentCache to the MemBufferInfos list and return it. > Make sure > > - // it is at least 8-byte aligned so that FileInfo can use the low 3 > bits of > > - // the pointer for its own nefarious purposes. > > - unsigned EntryAlign = llvm::AlignOf<ContentCache>::Alignment; > > - EntryAlign = std::max(8U, EntryAlign); > > - ContentCache *Entry = ContentCacheAlloc.Allocate<ContentCache>(1, > EntryAlign); > > + // Add a new ContentCache to the MemBufferInfos list and return it. > > + ContentCache *Entry = ContentCacheAlloc.Allocate<ContentCache>(); > > new (Entry) ContentCache(); > > MemBufferInfos.push_back(Entry); > > Entry->setBuffer(Buffer); > > > > > > _______________________________________________ > > cfe-commits mailing list > > [email protected] > > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits > > _______________________________________________ > cfe-commits mailing list > [email protected] > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits >
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