diff --git a/llvm/include/llvm/ADT/StringExtras.h b/llvm/include/llvm/ADT/StringExtras.h
--- a/llvm/include/llvm/ADT/StringExtras.h
+++ b/llvm/include/llvm/ADT/StringExtras.h
@@ -67,11 +67,8 @@
 /// If \p C is not a valid hex digit, -1U is returned.
 inline unsigned hexDigitValue(char C) {
   struct HexTable {
-    unsigned LUT[255] = {};
+    unsigned LUT[255] = {static_cast<unsigned>(-1)};
     constexpr HexTable() {
-      // Default initialize everything to invalid.
-      for (int i = 0; i < 255; ++i)
-        LUT[i] = -1U;
       // Initialize `0`-`9`.
       for (int i = 0; i < 10; ++i)
         LUT['0' + i] = i;