Use intrusive refcounted pointers to manage RopeRefCountString lifetime.

std::shared_ptr<char []> would be even nicer, but shared_ptr doesn't work
with arrays :(

No functionality change.

llvm-svn: 217798

clang/include/clang/Rewrite/Core/RewriteRope.h

@@ -14,6 +14,7 @@
 #ifndef LLVM_CLANG_REWRITE_CORE_REWRITEROPE_H
 #define LLVM_CLANG_REWRITE_CORE_REWRITEROPE_H
 
+#include "llvm/ADT/IntrusiveRefCntPtr.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Compiler.h"
 #include <cassert>
@@ -34,11 +35,10 @@ namespace clang {
     unsigned RefCount;
     char Data[1];  //  Variable sized.
 
-    void addRef() {
-      ++RefCount;
-    }
+    void Retain() { ++RefCount; }
 
-    void dropRef() {
+    void Release() {
+      assert(RefCount > 0 && "Reference count is already zero.");
       if (--RefCount == 0)
         delete [] (char*)this;
     }
@@ -57,39 +57,15 @@ namespace clang {
   /// that both refer to the same underlying RopeRefCountString (just with
   /// different offsets) which is a nice constant time operation.
   struct RopePiece {
-    RopeRefCountString *StrData;
+    llvm::IntrusiveRefCntPtr<RopeRefCountString> StrData;
     unsigned StartOffs;
     unsigned EndOffs;
 
     RopePiece() : StrData(nullptr), StartOffs(0), EndOffs(0) {}
 
-    RopePiece(RopeRefCountString *Str, unsigned Start, unsigned End)
-      : StrData(Str), StartOffs(Start), EndOffs(End) {
-      if (StrData)
-        StrData->addRef();
-    }
-    RopePiece(const RopePiece &RP)
-      : StrData(RP.StrData), StartOffs(RP.StartOffs), EndOffs(RP.EndOffs) {
-      if (StrData)
-        StrData->addRef();
-    }
-
-    ~RopePiece() {
-      if (StrData)
-        StrData->dropRef();
-    }
-
-    void operator=(const RopePiece &RHS) {
-      if (StrData != RHS.StrData) {
-        if (StrData)
-          StrData->dropRef();
-        StrData = RHS.StrData;
-        if (StrData)
-          StrData->addRef();
-      }
-      StartOffs = RHS.StartOffs;
-      EndOffs = RHS.EndOffs;
-    }
+    RopePiece(llvm::IntrusiveRefCntPtr<RopeRefCountString> Str, unsigned Start,
+              unsigned End)
+        : StrData(std::move(Str)), StartOffs(Start), EndOffs(End) {}
 
     const char &operator[](unsigned Offset) const {
       return StrData->Data[Offset+StartOffs];
@@ -191,7 +167,7 @@ class RewriteRope {
 
   /// We allocate space for string data out of a buffer of size AllocChunkSize.
   /// This keeps track of how much space is left.
-  RopeRefCountString *AllocBuffer;
+  llvm::IntrusiveRefCntPtr<RopeRefCountString> AllocBuffer;
   unsigned AllocOffs;
   enum { AllocChunkSize = 4080 };
 
@@ -201,12 +177,6 @@ public:
     : Chunks(RHS.Chunks), AllocBuffer(nullptr), AllocOffs(AllocChunkSize) {
   }
 
-  ~RewriteRope() {
-    // If we had an allocation buffer, drop our reference to it.
-    if (AllocBuffer)
-      AllocBuffer->dropRef();
-  }
-
   typedef RopePieceBTree::iterator iterator;
   typedef RopePieceBTree::iterator const_iterator;
   iterator begin() const { return Chunks.begin(); }

clang/lib/Rewrite/RewriteRope.cpp

@@ -788,18 +788,14 @@ RopePiece RewriteRope::MakeRopeString(const char *Start, const char *End) {
   // Otherwise, this was a small request but we just don't have space for it
   // Make a new chunk and share it with later allocations.
 
-  if (AllocBuffer)
-    AllocBuffer->dropRef();
-
   unsigned AllocSize = offsetof(RopeRefCountString, Data) + AllocChunkSize;
-  AllocBuffer = reinterpret_cast<RopeRefCountString *>(new char[AllocSize]);
-  AllocBuffer->RefCount = 0;
-  memcpy(AllocBuffer->Data, Start, Len);
+  RopeRefCountString *Res =
+      reinterpret_cast<RopeRefCountString *>(new char[AllocSize]);
+  Res->RefCount = 0;
+  memcpy(Res->Data, Start, Len);
+  AllocBuffer = Res;
   AllocOffs = Len;
 
-  // Start out the new allocation with a refcount of 1, since we have an
-  // internal reference to it.
-  AllocBuffer->addRef();
   return RopePiece(AllocBuffer, 0, Len);
 }