Index: llvm/include/llvm/Support/TypeSize.h
===================================================================
--- llvm/include/llvm/Support/TypeSize.h
+++ llvm/include/llvm/Support/TypeSize.h
@@ -177,7 +177,7 @@
   ScalarTy Value;         // The value at the univeriate dimension.
   unsigned UnivariateDim; // The univeriate dimension.
 
-  UnivariateLinearPolyBase(ScalarTy &Val, unsigned UnivariateDim)
+  UnivariateLinearPolyBase(ScalarTy Val, unsigned UnivariateDim)
       : Value(Val), UnivariateDim(UnivariateDim) {}
 
   friend LeafTy &operator+=(LeafTy &LHS, const LeafTy &RHS) {
@@ -235,6 +235,18 @@
   ScalarTy getValue(unsigned Dim) const {
     return Dim == UnivariateDim ? Value : 0;
   }
+
+  /// Add \p RHS to the value at the univariate dimension.
+  LeafTy getWithIncrement(ScalarTy RHS) {
+    return static_cast<LeafTy>(
+        UnivariateLinearPolyBase(Value + RHS, UnivariateDim));
+  }
+
+  /// Subtract \p RHS from the value at the univariate dimension.
+  LeafTy getWithDecrement(ScalarTy RHS) {
+    return static_cast<LeafTy>(
+        UnivariateLinearPolyBase(Value - RHS, UnivariateDim));
+  }
 };
 
 
@@ -253,6 +265,11 @@
 /// fixed-sized or it is scalable-sized, but it cannot be both.
 template <typename LeafTy>
 class LinearPolySize : public UnivariateLinearPolyBase<LeafTy> {
+  // Make the parent class a friend, so that it can access the protected
+  // conversion/copy-constructor for UnivariatePolyBase<LeafTy> ->
+  // LinearPolySize<LeafTy>.
+  friend class UnivariateLinearPolyBase<LeafTy>;
+
 public:
   using ScalarTy = typename UnivariateLinearPolyBase<LeafTy>::ScalarTy;
   enum Dims : unsigned { FixedDim = 0, ScalableDim = 1 };
@@ -261,7 +278,11 @@
   LinearPolySize(ScalarTy MinVal, Dims D)
       : UnivariateLinearPolyBase<LeafTy>(MinVal, D) {}
 
+  LinearPolySize(const UnivariateLinearPolyBase<LeafTy> &V)
+      : UnivariateLinearPolyBase<LeafTy>(V) {}
+
 public:
+
   static LeafTy getFixed(ScalarTy MinVal) {
     return static_cast<LeafTy>(LinearPolySize(MinVal, FixedDim));
   }
Index: llvm/unittests/Support/LinearPolyBaseTest.cpp
===================================================================
--- llvm/unittests/Support/LinearPolyBaseTest.cpp
+++ llvm/unittests/Support/LinearPolyBaseTest.cpp
@@ -135,6 +135,11 @@
   Univariate3D X(42, 0);
   X += Univariate3D(42, 0);
   EXPECT_EQ(X, Univariate3D(84, 0));
+
+  // Test 'getWithIncrement' method
+  EXPECT_EQ(Univariate3D(42, 0).getWithIncrement(1), Univariate3D(43, 0));
+  EXPECT_EQ(Univariate3D(42, 1).getWithIncrement(2), Univariate3D(44, 1));
+  EXPECT_EQ(Univariate3D(42, 2).getWithIncrement(3), Univariate3D(45, 2));
 }
 
 TEST(UnivariateLinearPolyBase, Univariate3D_Sub) {
@@ -148,6 +153,11 @@
   Univariate3D X(84, 0);
   X -= Univariate3D(42, 0);
   EXPECT_EQ(X, Univariate3D(42, 0));
+
+  // Test 'getWithDecrement' method
+  EXPECT_EQ(Univariate3D(43, 0).getWithDecrement(1), Univariate3D(42, 0));
+  EXPECT_EQ(Univariate3D(44, 1).getWithDecrement(2), Univariate3D(42, 1));
+  EXPECT_EQ(Univariate3D(45, 2).getWithDecrement(3), Univariate3D(42, 2));
 }
 
 TEST(UnivariateLinearPolyBase, Univariate3D_Scale) {