From 1e65707aa20603fc2ee9c2ac21c466ef57d23e10 Mon Sep 17 00:00:00 2001
From: Charles Schlosser <cs.schlosser@gmail.com>
Date: Wed, 23 Jul 2025 22:26:40 +0000
Subject: [PATCH] Suppress Warray-bounds warning in generic ploaduSegment, fix
 edge case for vectorized cast

---
 Eigen/src/Core/CoreEvaluators.h    |  6 +++---
 Eigen/src/Core/GenericPacketMath.h | 11 +++++++----
 test/packet_segment.cpp            | 16 ++++++++++++++++
 3 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/Eigen/src/Core/CoreEvaluators.h b/Eigen/src/Core/CoreEvaluators.h
index 63f1895d2..ec731acd5 100644
--- a/Eigen/src/Core/CoreEvaluators.h
+++ b/Eigen/src/Core/CoreEvaluators.h
@@ -707,7 +707,7 @@ struct unary_evaluator<CwiseUnaryOp<core_cast_op<SrcType, DstType>, ArgType>, In
     Index packetOffset = offset * PacketSize;
     Index actualRow = IsRowMajor ? row : row + packetOffset;
     Index actualCol = IsRowMajor ? col + packetOffset : col;
-    eigen_assert(check_array_bounds(actualRow, actualCol, 0, count) && "Array index out of bounds");
+    eigen_assert(check_array_bounds(actualRow, actualCol, begin, count) && "Array index out of bounds");
     return m_argImpl.template packetSegment<LoadMode, PacketType>(actualRow, actualCol, begin, count);
   }
   template <int LoadMode, typename PacketType = SrcPacketType>
@@ -715,8 +715,8 @@ struct unary_evaluator<CwiseUnaryOp<core_cast_op<SrcType, DstType>, ArgType>, In
                                                                     Index offset) const {
     constexpr int PacketSize = unpacket_traits<PacketType>::size;
     Index packetOffset = offset * PacketSize;
-    Index actualIndex = index + packetOffset + begin;
-    eigen_assert(check_array_bounds(actualIndex, 0, count) && "Array index out of bounds");
+    Index actualIndex = index + packetOffset;
+    eigen_assert(check_array_bounds(actualIndex, begin, count) && "Array index out of bounds");
     return m_argImpl.template packetSegment<LoadMode, PacketType>(actualIndex, begin, count);
   }
 
diff --git a/Eigen/src/Core/GenericPacketMath.h b/Eigen/src/Core/GenericPacketMath.h
index e1d62fa17..de599a15c 100644
--- a/Eigen/src/Core/GenericPacketMath.h
+++ b/Eigen/src/Core/GenericPacketMath.h
@@ -1596,9 +1596,10 @@ EIGEN_DEVICE_FUNC inline Packet ploaduSegment(const typename unpacket_traits<Pac
   using Scalar = typename unpacket_traits<Packet>::type;
   constexpr Index PacketSize = unpacket_traits<Packet>::size;
   eigen_assert((begin >= 0 && count >= 0 && begin + count <= PacketSize) && "invalid range");
-  Scalar aux[PacketSize];
-  memset(static_cast<void*>(aux), 0x00, sizeof(Scalar) * PacketSize);
-  smart_copy(from + begin, from + begin + count, aux + begin);
+  Scalar aux[PacketSize] = {};
+  for (Index k = begin; k < begin + count; k++) {
+    aux[k] = from[k];
+  }
   return ploadu<Packet>(aux);
 }
 
@@ -1619,7 +1620,9 @@ EIGEN_DEVICE_FUNC inline void pstoreuSegment(Scalar* to, const Packet& from, Ind
   eigen_assert((begin >= 0 && count >= 0 && begin + count <= PacketSize) && "invalid range");
   Scalar aux[PacketSize];
   pstoreu<Scalar, Packet>(aux, from);
-  smart_copy(aux + begin, aux + begin + count, to + begin);
+  for (Index k = begin; k < begin + count; k++) {
+    to[k] = aux[k];
+  }
 }
 
 /** \internal copy the packet \a from in the range [begin, begin + count) to \a *to.
diff --git a/test/packet_segment.cpp b/test/packet_segment.cpp
index 6fa6a290d..8a5469cb4 100644
--- a/test/packet_segment.cpp
+++ b/test/packet_segment.cpp
@@ -142,6 +142,21 @@ struct packet_segment_test_driver<Scalar, 1> {
   static void run() {}
 };
 
+template <bool Enable = internal::packet_traits<half>::Vectorizable>
+void testReverseEdgeCase() {
+  // this reversed cast uses a non-zero offset for ploadSegment
+  Index size = 16 * internal::packet_traits<half>::size + 1;
+  VectorX<half> v1(size);
+  VectorX<float> v2(size), v3(size);
+  v1.setRandom();
+  v2 = v1.reverse().cast<float>();
+  v3 = v1.cast<float>().reverse();
+  VERIFY_IS_EQUAL(v2, v3);
+}
+
+template <>
+void testReverseEdgeCase<false>() {}
+
 template <typename Scalar>
 void test_packet_segment() {
   packet_segment_test_driver<Scalar, internal::packet_traits<Scalar>::size>::run();
@@ -164,5 +179,6 @@ EIGEN_DECLARE_TEST(packet_segment) {
     test_packet_segment<double>();
     test_packet_segment<std::complex<float>>();
     test_packet_segment<std::complex<double>>();
+    testReverseEdgeCase();
   }
 }