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diff --git a/llvm/lib/Analysis/OrderedInstructions.cpp b/llvm/lib/Analysis/OrderedInstructions.cpp
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+++ b/llvm/lib/Analysis/OrderedInstructions.cpp
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+//===-- OrderedInstructions.cpp - Instruction dominance function ---------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines utility to check dominance relation of 2 instructions.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/OrderedInstructions.h"
+using namespace llvm;
+
+bool OrderedInstructions::localDominates(const Instruction *InstA,
+                                         const Instruction *InstB) const {
+  assert(InstA->getParent() == InstB->getParent() &&
+         "Instructions must be in the same basic block");
+
+  const BasicBlock *IBB = InstA->getParent();
+  auto OBB = OBBMap.find(IBB);
+  if (OBB == OBBMap.end())
+    OBB = OBBMap.insert({IBB, std::make_unique<OrderedBasicBlock>(IBB)}).first;
+  return OBB->second->dominates(InstA, InstB);
+}
+
+/// Given 2 instructions, use OrderedBasicBlock to check for dominance relation
+/// if the instructions are in the same basic block, Otherwise, use dominator
+/// tree.
+bool OrderedInstructions::dominates(const Instruction *InstA,
+                                    const Instruction *InstB) const {
+  // Use ordered basic block to do dominance check in case the 2 instructions
+  // are in the same basic block.
+  if (InstA->getParent() == InstB->getParent())
+    return localDominates(InstA, InstB);
+  return DT->dominates(InstA->getParent(), InstB->getParent());
+}
+
+bool OrderedInstructions::dfsBefore(const Instruction *InstA,
+                                    const Instruction *InstB) const {
+  // Use ordered basic block in case the 2 instructions are in the same basic
+  // block.
+  if (InstA->getParent() == InstB->getParent())
+    return localDominates(InstA, InstB);
+
+  DomTreeNode *DA = DT->getNode(InstA->getParent());
+  DomTreeNode *DB = DT->getNode(InstB->getParent());
+  return DA->getDFSNumIn() < DB->getDFSNumIn();
+}