1 files changed, 29 insertions, 0 deletions
diff --git a/llvm/lib/Analysis/PostDominators.cpp b/llvm/lib/Analysis/PostDominators.cpp
index 4afe22bd5342a..f01d51504d7cd 100644
--- a/llvm/lib/Analysis/PostDominators.cpp
+++ b/llvm/lib/Analysis/PostDominators.cpp
@@ -12,7 +12,9 @@
 
 #include "llvm/Analysis/PostDominators.h"
 #include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
 #include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/raw_ostream.h"
 
@@ -32,6 +34,11 @@ static constexpr bool ExpensiveChecksEnabled = false;
 
 char PostDominatorTreeWrapperPass::ID = 0;
 
+PostDominatorTreeWrapperPass::PostDominatorTreeWrapperPass()
+    : FunctionPass(ID) {
+  initializePostDominatorTreeWrapperPassPass(*PassRegistry::getPassRegistry());
+}
+
 INITIALIZE_PASS(PostDominatorTreeWrapperPass, "postdomtree",
                 "Post-Dominator Tree Construction", true, true)
 
@@ -44,6 +51,28 @@ bool PostDominatorTree::invalidate(Function &F, const PreservedAnalyses &PA,
            PAC.preservedSet<CFGAnalyses>());
 }
 
+bool PostDominatorTree::dominates(const Instruction *I1,
+                                  const Instruction *I2) const {
+  assert(I1 && I2 && "Expecting valid I1 and I2");
+
+  const BasicBlock *BB1 = I1->getParent();
+  const BasicBlock *BB2 = I2->getParent();
+
+  if (BB1 != BB2)
+    return Base::dominates(BB1, BB2);
+
+  // PHINodes in a block are unordered.
+  if (isa<PHINode>(I1) && isa<PHINode>(I2))
+    return false;
+
+  // Loop through the basic block until we find I1 or I2.
+  BasicBlock::const_iterator I = BB1->begin();
+  for (; &*I != I1 && &*I != I2; ++I)
+    /*empty*/;
+
+  return &*I == I2;
+}
+
 bool PostDominatorTreeWrapperPass::runOnFunction(Function &F) {
   DT.recalculate(F);
   return false;