diff --git a/llvm/lib/Support/NativeFormatting.cpp b/llvm/lib/Support/NativeFormatting.cpp
--- a/llvm/lib/Support/NativeFormatting.cpp
+++ b/llvm/lib/Support/NativeFormatting.cpp
@@ -262,5 +262,11 @@
   case FloatStyle::Percent:
     return 2; // Number of decimal places.
   }
+  // Workaround for MSVC bug in VS2022:
+  // https://developercommunity.visualstudio.com/t/Prev-Issue---with-__assume-isnan-/1597317
+  // llvm_unreachable expands to __assume(false) with MSVC which triggers the
+  // bug.
+#ifndef _MSC_VER
   llvm_unreachable("Unknown FloatStyle enum");
+#endif
 }