Simplify preprocessor logic

Author: kimwalisch

Diff for: libpopcnt.h

@@ -102,7 +102,7 @@
   #define HAVE_AVX512
 #endif
 
-/* Windows: MSVC compatible compilers */
+/* MSVC compatible compilers (Windows) */
 #if defined(_MSC_VER) && \
     defined(HAVE_CPUID)
   /* clang-cl (LLVM 10 from 2020) requires /arch:AVX2 or
@@ -117,15 +117,14 @@
     #endif
   /* MSVC 2017 or later does not require
    * /arch:AVX2 or /arch:AVX512 */
-  #elif (_MSC_VER >= 1910)
+  #elif _MSC_VER >= 1910
     #define HAVE_AVX2
     #define HAVE_AVX512
   #endif
-#else /* Unix-like OSes */
+#else /* Clang (Unix-like OSes) */
   #if defined(HAVE_CPUID) && \
       CLANG_PREREQ(3, 8) && \
       __has_attribute(target) && \
-    (!defined(_MSC_VER) || defined(__AVX2__)) && \
     (!defined(__apple_build_version__) || __apple_build_version__ >= 8000000)
     #define HAVE_AVX2
     #define HAVE_AVX512