BMI2 support is indicated in bit eight of EBX, not nine.
See Intel SDM, Vol 2A, Table 3-8:
https://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-vol-2a-manual.pdf#page=296

Differential Revision: https://reviews.llvm.org/D65766

llvm-svn: 367929
diff --git a/llvm/lib/Support/Host.cpp b/llvm/lib/Support/Host.cpp
index d491912..3ad1495 100644
--- a/llvm/lib/Support/Host.cpp
+++ b/llvm/lib/Support/Host.cpp
@@ -1034,7 +1034,7 @@
     setFeature(X86::FEATURE_BMI);
   if (HasLeaf7 && ((EBX >> 5) & 1) && HasAVX)
     setFeature(X86::FEATURE_AVX2);
-  if (HasLeaf7 && ((EBX >> 9) & 1))
+  if (HasLeaf7 && ((EBX >> 8) & 1))
     setFeature(X86::FEATURE_BMI2);
   if (HasLeaf7 && ((EBX >> 16) & 1) && HasAVX512Save)
     setFeature(X86::FEATURE_AVX512F);