reclaim my precious bit in FileInfo by ensuring that ContentCache objects

are 8-byte aligned.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@63630 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/Basic/SourceManager.h b/include/clang/Basic/SourceManager.h
index c21c221b5c5b840680ea6f792f66afc80d33c960..ce2aeccb9044a96bc3b1249a8b0311ba4b3c12d7 100644 (file)
--- a/include/clang/Basic/SourceManager.h
+++ b/include/clang/Basic/SourceManager.h
@@ -144,7 +144,7 @@ namespace SrcMgr {
       FileInfo X;
       X.IncludeLoc = IL.getRawEncoding();
       X.Data = (uintptr_t)Con;
-      assert((X.Data & 3) == 0 &&"ContentCache pointer insufficiently aligned");
+      assert((X.Data & 7) == 0 &&"ContentCache pointer insufficiently aligned");
       assert((unsigned)FileCharacter < 4 && "invalid file character");
       X.Data |= (unsigned)FileCharacter;
       return X;
@@ -154,7 +154,7 @@ namespace SrcMgr {
       return SourceLocation::getFromRawEncoding(IncludeLoc);
     }
     const ContentCache* getContentCache() const {
-      return reinterpret_cast<const ContentCache*>(Data & ~3UL);
+      return reinterpret_cast<const ContentCache*>(Data & ~7UL);
     }
     
     /// getCharacteristic - Return whether this is a system header or not.

diff --git a/lib/Basic/SourceManager.cpp b/lib/Basic/SourceManager.cpp
index 191b6155f0954e280ab39d148f36fc93fb548632..6f78ee175c62f29d31a96e7c0532f53e227e4a49 100644 (file)
--- a/lib/Basic/SourceManager.cpp
+++ b/lib/Basic/SourceManager.cpp
@@ -160,8 +160,12 @@ SourceManager::getOrCreateContentCache(const FileEntry *FileEnt) {
   ContentCache *&Entry = FileInfos[FileEnt];
   if (Entry) return Entry;
   
-  // Nope, create a new Cache entry.
-  Entry = ContentCacheAlloc.Allocate<ContentCache>();
+  // 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);
   new (Entry) ContentCache(FileEnt);
   return Entry;
 }
@@ -171,11 +175,12 @@ SourceManager::getOrCreateContentCache(const FileEntry *FileEnt) {
 ///  memory buffer.  This does no caching.
 const ContentCache*
 SourceManager::createMemBufferContentCache(const MemoryBuffer *Buffer) {
-  // Add a new ContentCache to the MemBufferInfos list and return it.  We
-  // must default construct the object first that the instance actually
-  // stored within MemBufferInfos actually owns the Buffer, and not any
-  // temporary we would use in the call to "push_back".
-  ContentCache *Entry = ContentCacheAlloc.Allocate<ContentCache>();
+  // 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);
   new (Entry) ContentCache();
   MemBufferInfos.push_back(Entry);
   Entry->setBuffer(Buffer);