Index: include/llvm/Transforms/Utils/OrderedInstructions.h
===================================================================
--- /dev/null
+++ include/llvm/Transforms/Utils/OrderedInstructions.h
@@ -0,0 +1,45 @@
+//===- llvm/Transforms/Utils/OrderedInstructions.h -------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines an efficient way to check for dominance between 2
+// instructions.
+//
+// This interface dispatches to appropriate dominance check given 2
+// instructions, i.e. in case the instructions are in the same basic block,
+// OrderedBasicBlock (with instruction numbering and caching) are used.
+// Otherwise, dominator tree is used.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_UTILS_ORDEREDINSTRUCTIONS_H
+#define LLVM_TRANSFORMS_UTILS_ORDEREDINSTRUCTIONS_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/Analysis/OrderedBasicBlock.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Operator.h"
+
+namespace llvm {
+
+class OrderedInstructions {
+  /// Used to check dominance for instructions in same basic block.
+  DenseMap<const BasicBlock *, std::unique_ptr<OrderedBasicBlock>> OBBMap;
+
+public:
+  /// Return true if first instruction dominates the second.
+  bool dominates(const Instruction *, const Instruction *,
+                 const DominatorTree *DT);
+
+  /// Invalidate the OrderedBasicBlock cache when its basic block changes.
+  void invalidateBlock(BasicBlock *BB) { OBBMap.erase(BB); }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_TRANSFORMS_UTILS_ORDEREDINSTRUCTIONS_H
Index: lib/Transforms/Utils/CMakeLists.txt
===================================================================
--- lib/Transforms/Utils/CMakeLists.txt
+++ lib/Transforms/Utils/CMakeLists.txt
@@ -37,6 +37,7 @@
   MetaRenamer.cpp
   ModuleUtils.cpp
   NameAnonGlobals.cpp
+  OrderedInstructions.cpp
   PredicateInfo.cpp
   PromoteMemoryToRegister.cpp
   StripGCRelocates.cpp
Index: lib/Transforms/Utils/OrderedInstructions.cpp
===================================================================
--- /dev/null
+++ lib/Transforms/Utils/OrderedInstructions.cpp
@@ -0,0 +1,32 @@
+//===-- OrderedInstructions.cpp - Instruction dominance function ---------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines utility to check dominance information for 2 instructions.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/OrderedInstructions.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "ordered-insts"
+
+bool OrderedInstructions::dominates(const Instruction *InstA,
+                                    const Instruction *InstB,
+                                    const DominatorTree *DT) {
+  const BasicBlock *IBB = InstA->getParent();
+  // Use ordered basic block to do dominance check in case the 2 instructions
+  // are in the same basic block.
+  if (IBB == InstB->getParent()) {
+    auto OBB = OBBMap.find(IBB);
+    if (OBB == OBBMap.end())
+      OBB = OBBMap.insert({IBB, make_unique<OrderedBasicBlock>(IBB)}).first;
+    return OBB->second->dominates(InstA, InstB);
+  } else
+    return DT->dominates(InstA->getParent(), InstB->getParent());
+}
Index: unittests/Transforms/Utils/CMakeLists.txt
===================================================================
--- unittests/Transforms/Utils/CMakeLists.txt
+++ unittests/Transforms/Utils/CMakeLists.txt
@@ -11,5 +11,6 @@
   FunctionComparator.cpp
   IntegerDivision.cpp
   Local.cpp
+  OrderedInstructions.cpp
   ValueMapperTest.cpp
   )
Index: unittests/Transforms/Utils/OrderedInstructions.cpp
===================================================================
--- /dev/null
+++ unittests/Transforms/Utils/OrderedInstructions.cpp
@@ -0,0 +1,51 @@
+//===- OrderedInstructions.cpp - Unit tests for OrderedInstructions  ------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/OrderedInstructions.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/LegacyPassManager.h"
+#include "llvm/IR/Module.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+TEST(OrderedInstructionsTest, DominanceTest) {
+  LLVMContext Ctx;
+  Module M("test", Ctx);
+  IRBuilder<> B(Ctx);
+  FunctionType *FTy =
+      FunctionType::get(Type::getVoidTy(Ctx), {B.getInt8PtrTy()}, false);
+  Function *F = cast<Function>(M.getOrInsertFunction("f", FTy));
+
+  // Create BBX with 2 loads.
+  BasicBlock *BBX = BasicBlock::Create(Ctx, "bbx", F);
+  B.SetInsertPoint(BBX);
+  Argument *PointerArg = &*F->arg_begin();
+  LoadInst *LoadInstX = B.CreateLoad(PointerArg);
+  LoadInst *LoadInstY = B.CreateLoad(PointerArg);
+
+  // Create BBY with 1 load.
+  BasicBlock *BBY = BasicBlock::Create(Ctx, "bby", F);
+  B.SetInsertPoint(BBY);
+  LoadInst *LoadInstZ = B.CreateLoad(PointerArg);
+  B.CreateRet(LoadInstZ);
+  std::unique_ptr<DominatorTree> DT(new DominatorTree(*F));
+  OrderedInstructions OI;
+
+  // Intra-BB dominance test.
+  EXPECT_TRUE(OI.dominates(LoadInstX, LoadInstY, &*DT));
+  EXPECT_FALSE(OI.dominates(LoadInstY, LoadInstX, &*DT));
+
+  // Inter-BB dominance test.
+  EXPECT_TRUE(OI.dominates(LoadInstY, LoadInstZ, &*DT));
+}