Remove _m_prefetchw() in favor of supporting only _mm_prefetch() or __builtin_prefetch()

Supporting _m_prefetchw() (officially part of 3DNOW) across various compilers and platforms turns out to be difficult. This change removes the explicit _m_prefetchw call aimed at MSVC compilers given that it causes issues in clang / chromium compilations.

PiperOrigin-RevId: 509632497
Change-Id: Ib1b6b2cf667cbc1af5ed6651cd9aa0294a9265b6

absl/base/prefetch.h

@@ -34,7 +34,6 @@
     (defined(_M_X64) || defined(_M_IX86))
     (defined(_M_X64) || defined(_M_IX86))
 #include <intrin.h>
 #include <intrin.h>
 #pragma intrinsic(_mm_prefetch)
 #pragma intrinsic(_mm_prefetch)
-#pragma intrinsic(_m_prefetchw)
 #endif
 #endif
 
 
 namespace absl {
 namespace absl {
@@ -176,10 +175,6 @@ inline void PrefetchToLocalCacheNta(const void* addr) {
 inline void PrefetchToLocalCacheForWrite(const void* addr) {
 inline void PrefetchToLocalCacheForWrite(const void* addr) {
 #if defined(_MM_HINT_ET0)
 #if defined(_MM_HINT_ET0)
   _mm_prefetch(reinterpret_cast<const char*>(addr), _MM_HINT_ET0);
   _mm_prefetch(reinterpret_cast<const char*>(addr), _MM_HINT_ET0);
-#elif defined(_MSC_VER) && _MSC_VER >= 1900 && \
-    (defined(_M_X64) || defined(_M_IX86))
-  // MSVC 2015 and up on x86/x64 supports prefetchw (feature listed as 3DNOW)
-  _m_prefetchw(const_cast<void*>(addr));
 #elif !defined(_MSC_VER) && defined(__x86_64__)
 #elif !defined(_MSC_VER) && defined(__x86_64__)
   // _MM_HINT_ET0 is not universally supported. As we commented further
   // _MM_HINT_ET0 is not universally supported. As we commented further
   // up, PREFETCHW is recognized as a no-op on older Intel processors
   // up, PREFETCHW is recognized as a no-op on older Intel processors