Revert "[X86][EVEX512] Restrict attaching EVEX512 for default CPU only, NFCI (llvm#65920)"

  breaks qmcpack

This reverts commit 8a58407.

Change-Id: Ife1e7e0c5e9ab5a2349b57dde856cae023579b7a

Author: ronlieb

llvm/lib/Target/X86/X86Subtarget.cpp

@@ -273,23 +273,18 @@ void X86Subtarget::initSubtargetFeatures(StringRef CPU, StringRef TuneCPU,
   if (!FS.empty())
     FullFS = (Twine(FullFS) + "," + FS).str();
 
-  // Attach EVEX512 feature when we have AVX512 features with a default CPU.
-  // "pentium4" is default CPU for 32-bit targets.
-  // "x86-64" is default CPU for 64-bit targets.
-  if (CPU == "generic" || CPU == "pentium4" || CPU == "x86-64") {
-    size_t posNoEVEX512 = FS.rfind("-evex512");
-    // Make sure we won't be cheated by "-avx512fp16".
-    size_t posNoAVX512F = FS.endswith("-avx512f") ? FS.size() - 8
-                                                  : FS.rfind("-avx512f,");
-    size_t posEVEX512 = FS.rfind("+evex512");
-    // Any AVX512XXX will enable AVX512F.
-    size_t posAVX512F = FS.rfind("+avx512");
-
-    if (posAVX512F != StringRef::npos &&
-        (posNoAVX512F == StringRef::npos || posNoAVX512F < posAVX512F))
-      if (posEVEX512 == StringRef::npos && posNoEVEX512 == StringRef::npos)
-        FullFS += ",+evex512";
-  }
+  // Attach EVEX512 feature when we have AVX512 features and EVEX512 is not set.
+  size_t posNoEVEX512 = FS.rfind("-evex512");
+  // Make sure we won't be cheated by "-avx512fp16".
+  size_t posNoAVX512F = FS.endswith("-avx512f") ? FS.size() - 8
+                                                : FS.rfind("-avx512f,");
+  size_t posEVEX512 = FS.rfind("+evex512");
+  size_t posAVX512F = FS.rfind("+avx512"); // Any AVX512XXX will enable AVX512F.
+
+  if (posAVX512F != StringRef::npos &&
+      (posNoAVX512F == StringRef::npos || posNoAVX512F < posAVX512F))
+    if (posEVEX512 == StringRef::npos && posNoEVEX512 == StringRef::npos)
+      FullFS += ",+evex512";
 
   // Parse features string and set the CPU.
   ParseSubtargetFeatures(CPU, TuneCPU, FullFS);