From 21cd3fe20990a5ac1d683806f605110962aac3f1 Mon Sep 17 00:00:00 2001
From: Charles Schlosser <charless@vt.edu>
Date: Mon, 10 Jul 2023 17:40:17 +0000
Subject: [PATCH] Optimize check_rows_cols_for_overflow

---
 Eigen/src/Core/PlainObjectBase.h            | 43 +++++++++++++++------
 Eigen/src/Core/util/XprHelper.h             |  4 +-
 unsupported/Eigen/CXX11/src/Tensor/Tensor.h |  2 +-
 3 files changed, 35 insertions(+), 14 deletions(-)

diff --git a/Eigen/src/Core/PlainObjectBase.h b/Eigen/src/Core/PlainObjectBase.h
index 1b8630460..ba6e51d31 100644
--- a/Eigen/src/Core/PlainObjectBase.h
+++ b/Eigen/src/Core/PlainObjectBase.h
@@ -28,21 +28,40 @@ namespace Eigen {
 
 namespace internal {
 
-template<int MaxSizeAtCompileTime> struct check_rows_cols_for_overflow {
+template <int MaxSizeAtCompileTime, int MaxRowsAtCompileTime, int MaxColsAtCompileTime>
+struct check_rows_cols_for_overflow {
+  EIGEN_STATIC_ASSERT(MaxRowsAtCompileTime * MaxColsAtCompileTime == MaxSizeAtCompileTime,YOU MADE A PROGRAMMING MISTAKE)
   template <typename Index>
   EIGEN_DEVICE_FUNC static EIGEN_ALWAYS_INLINE constexpr void run(Index, Index) {}
 };
 
-template<> struct check_rows_cols_for_overflow<Dynamic> {
+template <int MaxRowsAtCompileTime>
+struct check_rows_cols_for_overflow<Dynamic, MaxRowsAtCompileTime, Dynamic> {
+  template <typename Index>
+  EIGEN_DEVICE_FUNC static EIGEN_ALWAYS_INLINE constexpr void run(Index, Index cols) {
+    constexpr Index MaxIndex = NumTraits<Index>::highest();
+    bool error = cols > MaxIndex / MaxRowsAtCompileTime;
+    if (error) throw_std_bad_alloc();
+  }
+};
+
+template <int MaxColsAtCompileTime>
+struct check_rows_cols_for_overflow<Dynamic, Dynamic, MaxColsAtCompileTime> {
+  template <typename Index>
+  EIGEN_DEVICE_FUNC static EIGEN_ALWAYS_INLINE constexpr void run(Index rows, Index) {
+    constexpr Index MaxIndex = NumTraits<Index>::highest();
+    bool error = rows > MaxIndex / MaxColsAtCompileTime;
+    if (error) throw_std_bad_alloc();
+  }
+};
+
+template <>
+struct check_rows_cols_for_overflow<Dynamic, Dynamic, Dynamic> {
   template <typename Index>
   EIGEN_DEVICE_FUNC static EIGEN_ALWAYS_INLINE constexpr void run(Index rows, Index cols) {
-    // http://hg.mozilla.org/mozilla-central/file/6c8a909977d3/xpcom/ds/CheckedInt.h#l242
-    // we assume Index is signed
-    Index max_index = (std::size_t(1) << (8 * sizeof(Index) - 1)) - 1; // assume Index is signed
-    bool error = (rows == 0 || cols == 0) ? false
-               : (rows > max_index / cols);
-    if (error)
-      throw_std_bad_alloc();
+    constexpr Index MaxIndex = NumTraits<Index>::highest();
+    bool error = cols == 0 ? false : (rows > MaxIndex / cols);
+    if (error) throw_std_bad_alloc();
   }
 };
 
@@ -268,7 +287,7 @@ class PlainObjectBase : public internal::dense_xpr_base<Derived>::type
                    && internal::check_implication(RowsAtCompileTime==Dynamic && MaxRowsAtCompileTime!=Dynamic, rows<=MaxRowsAtCompileTime)
                    && internal::check_implication(ColsAtCompileTime==Dynamic && MaxColsAtCompileTime!=Dynamic, cols<=MaxColsAtCompileTime)
                    && rows>=0 && cols>=0 && "Invalid sizes when resizing a matrix or array.");
-      internal::check_rows_cols_for_overflow<MaxSizeAtCompileTime>::run(rows, cols);
+      internal::check_rows_cols_for_overflow<MaxSizeAtCompileTime, MaxRowsAtCompileTime, MaxColsAtCompileTime>::run(rows, cols);
       #ifdef EIGEN_INITIALIZE_COEFFS
         Index size = rows*cols;
         bool size_changed = size != this->size();
@@ -340,7 +359,7 @@ class PlainObjectBase : public internal::dense_xpr_base<Derived>::type
     EIGEN_STRONG_INLINE void resizeLike(const EigenBase<OtherDerived>& _other)
     {
       const OtherDerived& other = _other.derived();
-      internal::check_rows_cols_for_overflow<MaxSizeAtCompileTime>::run(other.rows(), other.cols());
+      internal::check_rows_cols_for_overflow<MaxSizeAtCompileTime, MaxRowsAtCompileTime, MaxColsAtCompileTime>::run(other.rows(), other.cols());
       const Index othersize = other.rows()*other.cols();
       if(RowsAtCompileTime == 1)
       {
@@ -965,7 +984,7 @@ struct conservative_resize_like_impl
           && (( Derived::IsRowMajor && _this.cols() == cols) ||  // row-major and we change only the number of rows
               (!Derived::IsRowMajor && _this.rows() == rows) ))  // column-major and we change only the number of columns
     {
-      internal::check_rows_cols_for_overflow<Derived::MaxSizeAtCompileTime>::run(rows, cols);
+      internal::check_rows_cols_for_overflow<Derived::MaxSizeAtCompileTime, Derived::MaxRowsAtCompileTime, Derived::MaxColsAtCompileTime>::run(rows, cols);
       _this.derived().m_storage.conservativeResize(rows*cols,rows,cols);
     }
     else
diff --git a/Eigen/src/Core/util/XprHelper.h b/Eigen/src/Core/util/XprHelper.h
index ccc6d4313..d8ac1b340 100644
--- a/Eigen/src/Core/util/XprHelper.h
+++ b/Eigen/src/Core/util/XprHelper.h
@@ -311,7 +311,9 @@ constexpr inline unsigned compute_matrix_flags(int Options) {
 }
 
 constexpr inline int size_at_compile_time(int rows, int cols) {
-  return (rows==Dynamic || cols==Dynamic) ? Dynamic : rows * cols;
+  if (rows == 0 || cols == 0) return 0;
+  if (rows == Dynamic || cols == Dynamic) return Dynamic;
+  return rows * cols;
 }
 
 template<typename XprType> struct size_of_xpr_at_compile_time
diff --git a/unsupported/Eigen/CXX11/src/Tensor/Tensor.h b/unsupported/Eigen/CXX11/src/Tensor/Tensor.h
index b830984f7..f873f2b9f 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/Tensor.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/Tensor.h
@@ -360,7 +360,7 @@ class Tensor : public TensorBase<Tensor<Scalar_, NumIndices_, Options_, IndexTyp
       int i;
       Index size = Index(1);
       for (i = 0; i < NumIndices; i++) {
-        internal::check_rows_cols_for_overflow<Dynamic>::run(size, dimensions[i]);
+        internal::check_rows_cols_for_overflow<Dynamic, Dynamic, Dynamic>::run(size, dimensions[i]);
         size *= dimensions[i];
       }
       #ifdef EIGEN_INITIALIZE_COEFFS