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diff --git a/llvm/include/llvm/CodeGen/GlobalISel/CSEMIRBuilder.h b/llvm/include/llvm/CodeGen/GlobalISel/CSEMIRBuilder.h
new file mode 100644
index 00000000000..a8fb736ebbb
--- /dev/null
+++ b/llvm/include/llvm/CodeGen/GlobalISel/CSEMIRBuilder.h
@@ -0,0 +1,110 @@
+//===-- llvm/CodeGen/GlobalISel/CSEMIRBuilder.h  --*- C++ -*-==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+/// This file implements a version of MachineIRBuilder which CSEs insts within
+/// a MachineBasicBlock.
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_CODEGEN_GLOBALISEL_CSEMIRBUILDER_H
+#define LLVM_CODEGEN_GLOBALISEL_CSEMIRBUILDER_H
+
+#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
+#include "llvm/CodeGen/GlobalISel/Utils.h"
+
+namespace llvm {
+
+/// Defines a builder that does CSE of MachineInstructions using GISelCSEInfo.
+/// Eg usage.
+///
+///
+/// GISelCSEInfo *Info =
+/// &getAnalysis<GISelCSEAnalysisWrapperPass>().getCSEInfo(); CSEMIRBuilder
+/// CB(Builder.getState()); CB.setCSEInfo(Info); auto A = CB.buildConstant(s32,
+/// 42); auto B = CB.buildConstant(s32, 42); assert(A == B); unsigned CReg =
+/// MRI.createGenericVirtualRegister(s32); auto C = CB.buildConstant(CReg, 42);
+/// assert(C->getOpcode() == TargetOpcode::COPY);
+/// Explicitly passing in a register would materialize a copy if possible.
+/// CSEMIRBuilder also does trivial constant folding for binary ops.
+class CSEMIRBuilder : public MachineIRBuilder {
+
+  /// Returns true if A dominates B (within the same basic block).
+  /// Both iterators must be in the same basic block.
+  //
+  // TODO: Another approach for checking dominance is having two iterators and
+  // making them go towards each other until they meet or reach begin/end. Which
+  // approach is better? Should this even change dynamically? For G_CONSTANTS
+  // most of which will be at the top of the BB, the top down approach would be
+  // a better choice. Does IRTranslator placing constants at the beginning still
+  // make sense? Should this change based on Opcode?
+  bool dominates(MachineBasicBlock::const_iterator A,
+                 MachineBasicBlock::const_iterator B) const;
+
+  /// For given ID, find a machineinstr in the CSE Map. If found, check if it
+  /// dominates the current insertion point and if not, move it just before the
+  /// current insertion point and return it. If not found, return Null
+  /// MachineInstrBuilder.
+  MachineInstrBuilder getDominatingInstrForID(FoldingSetNodeID &ID,
+                                              void *&NodeInsertPos);
+  /// Simple check if we can CSE (we have the CSEInfo) or if this Opcode is
+  /// safe to CSE.
+  bool canPerformCSEForOpc(unsigned Opc) const;
+
+  void profileDstOp(const DstOp &Op, GISelInstProfileBuilder &B) const;
+
+  void profileDstOps(ArrayRef<DstOp> Ops, GISelInstProfileBuilder &B) const {
+    for (const DstOp &Op : Ops)
+      profileDstOp(Op, B);
+  }
+
+  void profileSrcOp(const SrcOp &Op, GISelInstProfileBuilder &B) const;
+
+  void profileSrcOps(ArrayRef<SrcOp> Ops, GISelInstProfileBuilder &B) const {
+    for (const SrcOp &Op : Ops)
+      profileSrcOp(Op, B);
+  }
+
+  void profileMBBOpcode(GISelInstProfileBuilder &B, unsigned Opc) const;
+
+  void profileEverything(unsigned Opc, ArrayRef<DstOp> DstOps,
+                         ArrayRef<SrcOp> SrcOps, Optional<unsigned> Flags,
+                         GISelInstProfileBuilder &B) const;
+
+  // Takes a MachineInstrBuilder and inserts it into the CSEMap using the
+  // NodeInsertPos.
+  MachineInstrBuilder memoizeMI(MachineInstrBuilder MIB, void *NodeInsertPos);
+
+  // If we have can CSE an instruction, but still need to materialize to a VReg,
+  // we emit a copy from the CSE'd inst to the VReg.
+  MachineInstrBuilder generateCopiesIfRequired(ArrayRef<DstOp> DstOps,
+                                               MachineInstrBuilder &MIB);
+
+  // If we have can CSE an instruction, but still need to materialize to a VReg,
+  // check if we can generate copies. It's not possible to return a single MIB,
+  // while emitting copies to multiple vregs.
+  bool checkCopyToDefsPossible(ArrayRef<DstOp> DstOps);
+
+public:
+  // Pull in base class constructors.
+  using MachineIRBuilder::MachineIRBuilder;
+  // Unhide buildInstr
+  MachineInstrBuilder buildInstr(unsigned Opc, ArrayRef<DstOp> DstOps,
+                                 ArrayRef<SrcOp> SrcOps,
+                                 Optional<unsigned> Flag = None) override;
+  // Bring in the other overload from the base class.
+  using MachineIRBuilder::buildConstant;
+
+  MachineInstrBuilder buildConstant(const DstOp &Res,
+                                    const ConstantInt &Val) override;
+
+  // Bring in the other overload from the base class.
+  using MachineIRBuilder::buildFConstant;
+  MachineInstrBuilder buildFConstant(const DstOp &Res,
+                                     const ConstantFP &Val) override;
+};
+} // namespace llvm
+#endif