Automerge: [clang][bytecode] Add Block::movePointersTo (#163795)

which moves all the block's pointers to a new block.

Author: tbaederr

clang/lib/AST/ByteCode/InterpBlock.cpp

@@ -100,6 +100,19 @@ bool Block::hasPointer(const Pointer *P) const {
 }
 #endif
 
+void Block::movePointersTo(Block *B) {
+  assert(B != this);
+
+  while (Pointers) {
+    Pointer *P = Pointers;
+
+    this->removePointer(P);
+    P->BS.Pointee = B;
+    B->addPointer(P);
+  }
+  assert(!this->hasPointers());
+}
+
 DeadBlock::DeadBlock(DeadBlock *&Root, Block *Blk)
     : Root(Root), B(~0u, Blk->Desc, Blk->isExtern(), Blk->IsStatic,
                     Blk->isWeak(), Blk->isDummy(), /*IsDead=*/true) {

clang/lib/AST/ByteCode/InterpBlock.h

@@ -92,6 +92,8 @@ class Block final {
   bool isInitialized() const { return IsInitialized; }
   /// The Evaluation ID this block was created in.
   unsigned getEvalID() const { return EvalID; }
+  /// Move all pointers from this block to \param B.
+  void movePointersTo(Block *B);
 
   /// Returns a pointer to the stored data.
   /// You are allowed to read Desc->getSize() bytes from this address.

clang/lib/AST/ByteCode/Program.cpp

@@ -226,11 +226,7 @@ UnsignedOrNone Program::createGlobal(const ValueDecl *VD, const Expr *Init) {
         Globals[PIdx] = NewGlobal;
         // All pointers pointing to the previous extern decl now point to the
         // new decl.
-        for (Pointer *Ptr = RedeclBlock->Pointers; Ptr; Ptr = Ptr->BS.Next) {
-          RedeclBlock->removePointer(Ptr);
-          Ptr->BS.Pointee = NewGlobal->block();
-          NewGlobal->block()->addPointer(Ptr);
-        }
+        RedeclBlock->movePointersTo(NewGlobal->block());
       }
     }
     PIdx = *Idx;