1 files changed, 19 insertions, 0 deletions
diff --git a/llvm/lib/VMCore/Dominators.cpp b/llvm/lib/VMCore/Dominators.cpp
index bb73aaf705d..6d0e23d6427 100644
--- a/llvm/lib/VMCore/Dominators.cpp
+++ b/llvm/lib/VMCore/Dominators.cpp
@@ -52,6 +52,25 @@ void DominatorTree::print(raw_ostream &OS, const Module *) const {
   DT->print(OS);
 }
 
+// dominates - Return true if A dominates B. This performs the
+// special checks necessary if A and B are in the same basic block.
+bool DominatorTree::dominates(const Instruction *A, const Instruction *B) const{
+  const BasicBlock *BBA = A->getParent(), *BBB = B->getParent();
+  if (BBA != BBB) return dominates(BBA, BBB);
+  
+  // It is not possible to determine dominance between two PHI nodes 
+  // based on their ordering.
+  if (isa<PHINode>(A) && isa<PHINode>(B)) 
+    return false;
+  
+  // Loop through the basic block until we find A or B.
+  BasicBlock::const_iterator I = BBA->begin();
+  for (; &*I != A && &*I != B; ++I)
+    /*empty*/;
+  
+  return &*I == A;
+}
+
 
 
 //===----------------------------------------------------------------------===//