Index: llvm/include/llvm/Support/Compiler.h
===================================================================
--- llvm/include/llvm/Support/Compiler.h
+++ llvm/include/llvm/Support/Compiler.h
@@ -24,6 +24,13 @@
 
 #if defined(_MSC_VER)
 #include <sal.h>
+
+#if _MSC_VER == 1924
+// See https://developercommunity.visualstudio.com/content/problem/845933/miscompile-boolean-condition-deduced-to-be-always.html
+// and thread "[llvm-dev] Longstanding failing tests - clang-tidy, MachO, Polly"
+// on llvm-dev Jan 21-23 2020.
+#error "MSVC 19.24 version of MSVC is known to miscompile LLVM."
+#endif
 #endif
 
 #ifndef __has_feature