--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/tree-ssa/pr90078.C	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,199 @@
+// { dg-do compile }
+// { dg-options "-std=c++14 -O2 -ftemplate-depth=1000000" }
+
+template <class T, int Dim0, int Dim1, int Dim2> struct Tensor3;
+template <class A, class T, int Dim0, int Dim1, int Dim2, char i, char j,
+          char k>
+struct Tensor3_Expr;
+
+template <class T, int Dim0, int Dim1, int Dim2, int Dim3> struct Tensor4;
+template <class A, class T, int Dim0, int Dim1, int Dim2, int Dim3, char i,
+          char j, char k, char l>
+struct Tensor4_Expr;
+
+template <char i, int Dim> struct Index
+{};
+template <const int N> struct Number
+{
+  Number(){};
+  operator int() const { return N; }
+};
+
+template <class T, int Tensor_Dim0, int Tensor_Dim1, int Tensor_Dim2>
+struct Tensor3
+{
+  T data[Tensor_Dim0][Tensor_Dim1][Tensor_Dim2];
+
+  T operator()(const int N1, const int N2, const int N3) const
+  {
+    return data[N1][N2][N3];
+  }
+
+  template <char i, char j, char k, int Dim0, int Dim1, int Dim2>
+  Tensor3_Expr<const Tensor3<T, Tensor_Dim0, Tensor_Dim1, Tensor_Dim2>, T,
+               Dim0, Dim1, Dim2, i, j, k>
+  operator()(const Index<i, Dim0>, const Index<j, Dim1>,
+             const Index<k, Dim2>) const
+  {
+    return Tensor3_Expr<const Tensor3<T, Tensor_Dim0, Tensor_Dim1, Tensor_Dim2>,
+                        T, Dim0, Dim1, Dim2, i, j, k>(*this);
+  }
+};
+
+template <class A, class T, int Dim0, int Dim1, int Dim2, char i, char j,
+          char k>
+struct Tensor3_Expr
+{
+  A iter;
+
+  Tensor3_Expr(const A &a) : iter(a) {}
+  T operator()(const int N1, const int N2, const int N3) const
+  {
+    return iter(N1, N2, N3);
+  }
+};
+
+template <class A, class T, int Tensor_Dim0, int Tensor_Dim1, int Tensor_Dim2,
+          int Dim0, int Dim1, int Dim2, char i, char j, char k>
+struct Tensor3_Expr<Tensor3<A, Tensor_Dim0, Tensor_Dim1, Tensor_Dim2>, T, Dim0,
+                   Dim1, Dim2, i, j, k>
+{
+  Tensor3<A, Tensor_Dim0, Tensor_Dim1, Tensor_Dim2> &iter;
+
+  Tensor3_Expr(Tensor3<A, Tensor_Dim0, Tensor_Dim1, Tensor_Dim2> &a) : iter(a)
+  {}
+  T operator()(const int N1, const int N2, const int N3) const
+  {
+    return iter(N1, N2, N3);
+  }
+};
+
+template <class A, class B, class T, class U, int Dim0, int Dim1, int Dim23,
+          int Dim4, int Dim5, char i, char j, char k, char l, char m>
+struct Tensor3_times_Tensor3_21
+{
+  Tensor3_Expr<A, T, Dim0, Dim1, Dim23, i, j, k> iterA;
+  Tensor3_Expr<B, U, Dim23, Dim4, Dim5, k, l, m> iterB;
+
+  template <int CurrentDim>
+  T eval(const int N1, const int N2, const int N3, const int N4,
+         const Number<CurrentDim> &) const
+  {
+    return iterA(N1, N2, CurrentDim - 1) * iterB(CurrentDim - 1, N3, N4)
+           + eval(N1, N2, N3, N4, Number<CurrentDim - 1>());
+  }
+  T eval(const int N1, const int N2, const int N3, const int N4,
+         const Number<1> &) const
+  {
+    return iterA(N1, N2, 0) * iterB(0, N3, N4);
+  }
+
+  Tensor3_times_Tensor3_21(
+    const Tensor3_Expr<A, T, Dim0, Dim1, Dim23, i, j, k> &a,
+    const Tensor3_Expr<B, U, Dim23, Dim4, Dim5, k, l, m> &b)
+      : iterA(a), iterB(b)
+  {}
+  T operator()(const int &N1, const int &N2, const int &N3,
+               const int &N4) const
+  {
+    return eval(N1, N2, N3, N4, Number<Dim23>());
+  }
+};
+
+template <class A, class B, class T, class U, int Dim0, int Dim1, int Dim23,
+          int Dim4, int Dim5, char i, char j, char k, char l, char m>
+Tensor4_Expr<Tensor3_times_Tensor3_21<A, B, T, U, Dim0, Dim1, Dim23, Dim4,
+                                      Dim5, i, j, k, l, m>,
+             T, Dim0, Dim1, Dim4, Dim5, i, j, l, m>
+operator*(const Tensor3_Expr<A, T, Dim0, Dim1, Dim23, i, j, k> &a,
+          const Tensor3_Expr<B, U, Dim23, Dim4, Dim5, k, l, m> &b)
+{
+  using TensorExpr = Tensor3_times_Tensor3_21<A, B, T, U, Dim0, Dim1, Dim23,
+                                              Dim4, Dim5, i, j, k, l, m>;
+  return Tensor4_Expr<TensorExpr, T, Dim0, Dim1, Dim4, Dim5, i, j, l, m>(
+    TensorExpr(a, b));
+};
+
+template <class T, int Tensor_Dim0, int Tensor_Dim1, int Tensor_Dim2,
+          int Tensor_Dim3>
+struct Tensor4
+{
+  T data[Tensor_Dim0][Tensor_Dim1][Tensor_Dim2][Tensor_Dim3];
+
+  Tensor4() {}
+  T &operator()(const int N1, const int N2, const int N3, const int N4)
+  {
+    return data[N1][N2][N3][N4];
+  }
+
+  template <char i, char j, char k, char l, int Dim0, int Dim1, int Dim2,
+            int Dim3>
+  Tensor4_Expr<Tensor4<T, Tensor_Dim0, Tensor_Dim1, Tensor_Dim2, Tensor_Dim3>,
+               T, Dim0, Dim1, Dim2, Dim3, i, j, k, l>
+  operator()(const Index<i, Dim0>, const Index<j, Dim1>, const Index<k, Dim2>,
+             const Index<l, Dim3>)
+  {
+    return Tensor4_Expr<
+      Tensor4<T, Tensor_Dim0, Tensor_Dim1, Tensor_Dim2, Tensor_Dim3>, T, Dim0,
+      Dim1, Dim2, Dim3, i, j, k, l>(*this);
+  };
+};
+
+template <class A, class T, int Dim0, int Dim1, int Dim2, int Dim3, char i,
+          char j, char k, char l>
+struct Tensor4_Expr
+{
+  A iter;
+
+  Tensor4_Expr(const A &a) : iter(a) {}
+  T operator()(const int N1, const int N2, const int N3, const int N4) const
+  {
+    return iter(N1, N2, N3, N4);
+  }
+};
+
+template <class A, class T, int Dim0, int Dim1, int Dim2, int Dim3, char i,
+          char j, char k, char l>
+struct Tensor4_Expr<Tensor4<A, Dim0, Dim1, Dim2, Dim3>, T, Dim0, Dim1, Dim2,
+                   Dim3, i, j, k, l>
+{
+  Tensor4<A, Dim0, Dim1, Dim2, Dim3> &iter;
+
+  Tensor4_Expr(Tensor4<A, Dim0, Dim1, Dim2, Dim3> &a) : iter(a) {}
+  T operator()(const int N1, const int N2, const int N3, const int N4) const
+  {
+    return iter(N1, N2, N3, N4);
+  }
+
+  template <class B, class U, int Dim1_0, int Dim1_1, int Dim1_2, int Dim1_3,
+            char i_1, char j_1, char k_1, char l_1>
+  auto &operator=(const Tensor4_Expr<B, U, Dim1_0, Dim1_1, Dim1_2, Dim1_3, i_1,
+                                     j_1, k_1, l_1> &rhs)
+  {
+    for(int ii = 0; ii < Dim0; ++ii)
+      for(int jj = 0; jj < Dim1; ++jj)
+        for(int kk = 0; kk < Dim2; ++kk)
+          for(int ll = 0; ll < Dim3; ++ll)
+            {
+              iter(ii, jj, kk, ll) = rhs(ii, jj, kk, ll);
+            }
+    return *this;
+  }
+};
+
+int main()
+{
+  Tensor3<float, 100, 100, 1000> t1;
+  Tensor3<float, 1000, 100, 100> t2;
+
+  Index<'l', 100> l;
+  Index<'m', 100> m;
+  Index<'k', 1000> k;
+  Index<'n', 100> n;
+  Index<'o', 100> o;
+
+  Tensor4<float, 100, 100, 100, 100> res;
+  res(l, m, n, o) = t1(l, m, k) * t2(k, n, o);
+  return 0;
+}
+