diff --git a/Eigen/src/Core/arch/NEON/Complex.h b/Eigen/src/Core/arch/NEON/Complex.h
index 1445c6246..7855e4e8b 100644
--- a/Eigen/src/Core/arch/NEON/Complex.h
+++ b/Eigen/src/Core/arch/NEON/Complex.h
@@ -461,7 +461,7 @@ EIGEN_INSTANTIATE_COMPLEX_MATH_FUNCS(Packet1cf)
 EIGEN_INSTANTIATE_COMPLEX_MATH_FUNCS(Packet2cf)
 
 //---------- double ----------
-#if EIGEN_ARCH_ARM64 && !EIGEN_APPLE_DOUBLE_NEON_BUG
+#if EIGEN_ARCH_ARM64
 
 inline uint64x2_t p2ul_CONJ_XOR() {
   static const uint64_t p2ul_conj_XOR_DATA[] = {0x0, 0x8000000000000000};
diff --git a/Eigen/src/Core/arch/NEON/MathFunctions.h b/Eigen/src/Core/arch/NEON/MathFunctions.h
index ed421821e..1e947af33 100644
--- a/Eigen/src/Core/arch/NEON/MathFunctions.h
+++ b/Eigen/src/Core/arch/NEON/MathFunctions.h
@@ -52,7 +52,7 @@ EIGEN_STRONG_INLINE Packet4bf pldexp(const Packet4bf& a, const Packet4bf& expone
 
 //---------- double ----------
 
-#if EIGEN_ARCH_ARM64 && !EIGEN_APPLE_DOUBLE_NEON_BUG
+#if EIGEN_ARCH_ARM64
 
 EIGEN_INSTANTIATE_GENERIC_MATH_FUNCS_DOUBLE(Packet2d)
 
diff --git a/Eigen/src/Core/arch/NEON/PacketMath.h b/Eigen/src/Core/arch/NEON/PacketMath.h
index 79f44d5d1..f0309882e 100644
--- a/Eigen/src/Core/arch/NEON/PacketMath.h
+++ b/Eigen/src/Core/arch/NEON/PacketMath.h
@@ -4955,18 +4955,7 @@ EIGEN_STRONG_INLINE Packet4bf pnegate<Packet4bf>(const Packet4bf& a) {
 
 //---------- double ----------
 
-// Clang 3.5 in the iOS toolchain has an ICE triggered by NEON intrinsics for double.
-// Confirmed at least with __apple_build_version__ = 6000054.
-#if EIGEN_COMP_CLANGAPPLE
-// Let's hope that by the time __apple_build_version__ hits the 601* range, the bug will be fixed.
-// https://gist.github.com/yamaya/2924292 suggests that the 3 first digits are only updated with
-// major toolchain updates.
-#define EIGEN_APPLE_DOUBLE_NEON_BUG (EIGEN_COMP_CLANGAPPLE < 6010000)
-#else
-#define EIGEN_APPLE_DOUBLE_NEON_BUG 0
-#endif
-
-#if EIGEN_ARCH_ARM64 && !EIGEN_APPLE_DOUBLE_NEON_BUG
+#if EIGEN_ARCH_ARM64
 
 #if EIGEN_COMP_GNUC
 // Bug 907: workaround missing declarations of the following two functions in the ADK
@@ -5043,7 +5032,7 @@ struct packet_traits<double> : default_packet_traits {
 
     HasDiv = 1,
 
-#if EIGEN_ARCH_ARM64 && !EIGEN_APPLE_DOUBLE_NEON_BUG
+#if EIGEN_ARCH_ARM64
     HasExp = 1,
     HasLog = 1,
     HasLog10 = 1,
@@ -5390,7 +5379,7 @@ EIGEN_STRONG_INLINE Packet2d psqrt(const Packet2d& _x) {
   return vsqrtq_f64(_x);
 }
 
-#endif  // EIGEN_ARCH_ARM64 && !EIGEN_APPLE_DOUBLE_NEON_BUG
+#endif  // EIGEN_ARCH_ARM64
 
 // Do we have an fp16 types and supporting Neon intrinsics?
 #if EIGEN_HAS_ARM64_FP16_VECTOR_ARITHMETIC
diff --git a/Eigen/src/Core/util/Assert.h b/Eigen/src/Core/util/Assert.h
index 07c4f43a1..22a87e140 100644
--- a/Eigen/src/Core/util/Assert.h
+++ b/Eigen/src/Core/util/Assert.h
@@ -41,13 +41,13 @@
 
 #ifndef EIGEN_HAS_BUILTIN_FILE
 // Clang can check if __builtin_FILE() is supported.
-// GCC > 5, MSVC 2019 14.26 (1926) all have __builtin_FILE().
+// Supported GCC versions and MSVC 2019 14.26 (1926) all have __builtin_FILE().
 //
 // For NVCC, it's more complicated.  Through trial-and-error:
 //   - nvcc+gcc supports __builtin_FILE() on host, and on device after CUDA 11.
 //   - nvcc+msvc supports __builtin_FILE() only after CUDA 11.
-#if (EIGEN_HAS_BUILTIN(__builtin_FILE) && (EIGEN_COMP_CLANG || !defined(EIGEN_CUDA_ARCH))) ||            \
-    (EIGEN_GNUC_STRICT_AT_LEAST(5, 0, 0) && (EIGEN_COMP_NVCC >= 110000 || !defined(EIGEN_CUDA_ARCH))) || \
+#if (EIGEN_HAS_BUILTIN(__builtin_FILE) && (EIGEN_COMP_CLANG || !defined(EIGEN_CUDA_ARCH))) || \
+    (EIGEN_COMP_GNUC_STRICT && (EIGEN_COMP_NVCC >= 110000 || !defined(EIGEN_CUDA_ARCH))) ||   \
     (EIGEN_COMP_MSVC >= 1926 && (!EIGEN_COMP_NVCC || EIGEN_COMP_NVCC >= 110000))
 #define EIGEN_HAS_BUILTIN_FILE 1
 #else
diff --git a/Eigen/src/Core/util/ConfigureVectorization.h b/Eigen/src/Core/util/ConfigureVectorization.h
index 7ea2b3c77..87e7fad59 100644
--- a/Eigen/src/Core/util/ConfigureVectorization.h
+++ b/Eigen/src/Core/util/ConfigureVectorization.h
@@ -360,9 +360,8 @@
 // so, to avoid compile errors when windows.h is included after Eigen/Core, ensure intrinsics are extern "C" here too.
 // notice that since these are C headers, the extern "C" is theoretically needed anyways.
 extern "C" {
-// In theory we should only include immintrin.h and not the other *mmintrin.h header files directly.
-// Doing so triggers some issues with ICC. However old gcc versions may not have this file, thus:
-#if EIGEN_COMP_ICC >= 1110 || EIGEN_COMP_EMSCRIPTEN
+// ICC and Emscripten need the umbrella header instead of direct *mmintrin.h includes.
+#if EIGEN_COMP_ICC || EIGEN_COMP_EMSCRIPTEN
 #include <immintrin.h>
 #else
 #include <mmintrin.h>
@@ -525,7 +524,7 @@ extern "C" {
 #define EIGEN_VECTORIZE_FMA
 #endif
 
-#if defined(__F16C__) && !defined(EIGEN_GPUCC) && (!EIGEN_COMP_CLANG_STRICT || EIGEN_CLANG_STRICT_AT_LEAST(3, 8, 0))
+#if defined(__F16C__) && !defined(EIGEN_GPUCC)
 // We can use the optimized fp16 to float and float to fp16 conversion routines
 #define EIGEN_HAS_FP16_C
 
diff --git a/Eigen/src/Core/util/Macros.h b/Eigen/src/Core/util/Macros.h
index f9776a5de..87cd6242b 100644
--- a/Eigen/src/Core/util/Macros.h
+++ b/Eigen/src/Core/util/Macros.h
@@ -734,7 +734,7 @@
 // supported by Eigen do not define _MSVC_LANG, so use Eigen's minimum standard.
 #if EIGEN_COMP_MSVC_LANG > 0
 #define EIGEN_CPLUSPLUS EIGEN_COMP_MSVC_LANG
-#elif EIGEN_COMP_MSVC >= 1900
+#elif EIGEN_COMP_MSVC
 #define EIGEN_CPLUSPLUS 201402L
 #elif defined(__cplusplus)
 #define EIGEN_CPLUSPLUS __cplusplus
@@ -809,8 +809,8 @@
 //       See https://gitlab.com/libeigen/eigen/-/issues/2575
 // Does the compiler support C++17 if constexpr?
 #ifndef EIGEN_HAS_CXX17_IFCONSTEXPR
-#if EIGEN_MAX_CPP_VER >= 17 && EIGEN_COMP_CXXVER >= 17 &&                                                            \
-    ((EIGEN_COMP_MSVC >= 1911) || (EIGEN_GNUC_STRICT_AT_LEAST(7, 0, 0)) || (EIGEN_CLANG_STRICT_AT_LEAST(3, 9, 0)) || \
+#if EIGEN_MAX_CPP_VER >= 17 && EIGEN_COMP_CXXVER >= 17 &&                                             \
+    ((EIGEN_COMP_MSVC >= 1911) || (EIGEN_GNUC_STRICT_AT_LEAST(7, 0, 0)) || EIGEN_COMP_CLANG_STRICT || \
      (EIGEN_COMP_CLANGAPPLE && EIGEN_COMP_CLANGAPPLE >= 10000000))
 #define EIGEN_HAS_CXX17_IFCONSTEXPR 1
 #endif
diff --git a/Eigen/src/Core/util/Memory.h b/Eigen/src/Core/util/Memory.h
index cb7f1e3ef..d1066d0f5 100644
--- a/Eigen/src/Core/util/Memory.h
+++ b/Eigen/src/Core/util/Memory.h
@@ -64,8 +64,7 @@
 // set_is_malloc_allowed() function.
 #ifndef EIGEN_AVOID_THREAD_LOCAL
 
-#if ((EIGEN_COMP_GNUC) || __has_feature(cxx_thread_local) || EIGEN_COMP_MSVC >= 1900) && \
-    !defined(EIGEN_GPU_COMPILE_PHASE)
+#if !defined(EIGEN_GPU_COMPILE_PHASE)
 #define EIGEN_MALLOC_CHECK_THREAD_LOCAL thread_local
 #else
 #define EIGEN_MALLOC_CHECK_THREAD_LOCAL
diff --git a/Eigen/src/LU/arch/InverseSize4.h b/Eigen/src/LU/arch/InverseSize4.h
index 94c80429b..f32915bd9 100644
--- a/Eigen/src/LU/arch/InverseSize4.h
+++ b/Eigen/src/LU/arch/InverseSize4.h
@@ -166,7 +166,7 @@ struct compute_inverse_size4<Architecture::Target, float, MatrixType, ResultType
   }
 };
 
-#if !(defined EIGEN_VECTORIZE_NEON && !(EIGEN_ARCH_ARM64 && !EIGEN_APPLE_DOUBLE_NEON_BUG))
+#if !defined(EIGEN_VECTORIZE_NEON) || EIGEN_ARCH_ARM64
 // same algorithm as above, except that each operand is split into
 // halves for two registers to hold.
 template <typename MatrixType, typename ResultType>
diff --git a/Eigen/src/ThreadPool/ThreadLocal.h b/Eigen/src/ThreadPool/ThreadLocal.h
index e2b35621f..4ba7cea59 100644
--- a/Eigen/src/ThreadPool/ThreadLocal.h
+++ b/Eigen/src/ThreadPool/ThreadLocal.h
@@ -19,22 +19,18 @@
 
 #else
 
-#if ((EIGEN_COMP_GNUC) || __has_feature(cxx_thread_local) || EIGEN_COMP_MSVC)
 #define EIGEN_THREAD_LOCAL static thread_local
-#endif
 
 // Disable TLS for Apple and Android builds with older toolchains.
 #if defined(__APPLE__)
 // Included for TARGET_OS_IPHONE, __IPHONE_OS_VERSION_MIN_REQUIRED,
-// __IPHONE_8_0.
+// __IPHONE_9_0.
 #include <Availability.h>
 #include <TargetConditionals.h>
 #endif
 // Checks whether the `thread_local` storage duration specifier is supported.
-#if EIGEN_COMP_CLANGAPPLE && \
-    ((EIGEN_COMP_CLANGAPPLE < 8000042) || (TARGET_OS_IPHONE && __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_9_0))
-// Notes: Xcode's clang did not support `thread_local` until version
-// 8, and even then not for all iOS < 9.0.
+#if EIGEN_COMP_CLANGAPPLE && TARGET_OS_IPHONE && __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_9_0
+// Notes: `thread_local` is not supported for all iOS < 9.0.
 #undef EIGEN_THREAD_LOCAL
 
 #elif defined(__ANDROID__) && EIGEN_COMP_CLANG
diff --git a/test/fastmath.cpp b/test/fastmath.cpp
index 334f84a55..deec4966b 100644
--- a/test/fastmath.cpp
+++ b/test/fastmath.cpp
@@ -18,23 +18,6 @@ void check(bool b, bool ref) {
     std::cout << " BAD ";
 }
 
-#if EIGEN_COMP_MSVC && EIGEN_COMP_MSVC < 1800
-namespace std {
-template <typename T>
-bool(isfinite)(T x) {
-  return _finite(x);
-}
-template <typename T>
-bool(isnan)(T x) {
-  return _isnan(x);
-}
-template <typename T>
-bool(isinf)(T x) {
-  return _fpclass(x) == _FPCLASS_NINF || _fpclass(x) == _FPCLASS_PINF;
-}
-}  // namespace std
-#endif
-
 template <typename T>
 void check_inf_nan(bool dryrun) {
   Matrix<T, Dynamic, 1> m(10);