Sweep stale FIXME/TODO comments in Core

libeigen/eigen!2446

Co-authored-by: Rasmus Munk Larsen <rmlarsen@gmail.com>

Eigen/src/Core/Block.h

diff --git a/Eigen/src/Core/Block.h b/Eigen/src/Core/Block.h
index c2d8bea..7dcf909 100644
--- a/Eigen/src/Core/Block.h
+++ b/Eigen/src/Core/Block.h
@@ -392,8 +392,7 @@
   EIGEN_DEVICE_FUNC constexpr StorageIndex startCol() const noexcept { return m_startCol.value(); }
 
 #ifndef __SUNPRO_CC
-  // FIXME sunstudio is not friendly with the above friend...
-  // META-FIXME there is no 'friend' keyword around here. Is this obsolete?
+  // Historical workaround for SunStudio's handling of the access specifier here.
  protected:
 #endif
 

Eigen/src/Core/PartialReduxEvaluator.h

diff --git a/Eigen/src/Core/PartialReduxEvaluator.h b/Eigen/src/Core/PartialReduxEvaluator.h
index d2c5851..18aeca3 100644
--- a/Eigen/src/Core/PartialReduxEvaluator.h
+++ b/Eigen/src/Core/PartialReduxEvaluator.h
@@ -199,10 +199,9 @@
     using BinaryOp = typename MemberOp::BinaryOp;
     using Impl = internal::packetwise_redux_impl<BinaryOp, PanelEvaluator>;
 
-    // FIXME
-    // See bug 1612, currently if PacketSize==1 (i.e. complex<double> with 128bits registers) then the storage-order of
-    // panel get reversed and methods like packetByOuterInner do not make sense anymore in this context. So let's just
-    // by pass "vectorization" in this case:
+    // Workaround for issue 1612 (closed): when PacketSize==1 (i.e. complex<double> with 128bits registers) the
+    // storage-order of panel gets reversed and methods like packetByOuterInner do not make sense in this context, so
+    // bypass "vectorization":
     EIGEN_IF_CONSTEXPR(PacketSize == 1) return internal::pset1<PacketType>(coeff(idx));
 
     Index startRow = Direction == Vertical ? 0 : idx;

Eigen/src/Core/Reshaped.h

diff --git a/Eigen/src/Core/Reshaped.h b/Eigen/src/Core/Reshaped.h
index 5763d6a..c3b4d56 100644
--- a/Eigen/src/Core/Reshaped.h
+++ b/Eigen/src/Core/Reshaped.h
@@ -349,8 +349,6 @@
 
   EIGEN_DEVICE_FUNC constexpr explicit reshaped_evaluator(const XprType& xpr)
       : mapbase_evaluator<XprType, typename XprType::PlainObject>(xpr) {
-    // TODO: for the 3.4 release, this should be turned to an internal assertion, but let's keep it as is for the beta
-    // lifetime
     eigen_assert(((std::uintptr_t(xpr.data()) % plain_enum_max(1, evaluator<XprType>::Alignment)) == 0) &&
                  "data is not aligned");
   }

Eigen/src/Core/util/Constants.h

diff --git a/Eigen/src/Core/util/Constants.h b/Eigen/src/Core/util/Constants.h
index 205bb9a..3a8c40f 100644
--- a/Eigen/src/Core/util/Constants.h
+++ b/Eigen/src/Core/util/Constants.h
@@ -76,7 +76,7 @@
 /** \ingroup flags
  * \deprecated
  * means the expression should be evaluated before any assignment */
-EIGEN_DEPRECATED constexpr unsigned int EvalBeforeAssigningBit = 0x4;  // FIXME deprecated
+EIGEN_DEPRECATED constexpr unsigned int EvalBeforeAssigningBit = 0x4;
 
 /** \ingroup flags
  *