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

1 files changed, 12 insertions, 7 deletions

diff --git a/lib/Basic/SourceManager.cpp b/lib/Basic/SourceManager.cpp
index 191b6155f0..6f78ee175c 100644
--- 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);