Index: clang-tools-extra/clangd/SourceCode.cpp
===================================================================
--- clang-tools-extra/clangd/SourceCode.cpp
+++ clang-tools-extra/clangd/SourceCode.cpp
@@ -58,8 +58,8 @@
   // A codepoint takes two UTF-16 code unit if it's astral (outside BMP).
   // Astral codepoints are encoded as 4 bytes in UTF-8, starting with 11110xxx.
   for (size_t I = 0; I < U8.size();) {
-    unsigned char C = static_cast<unsigned char>(U8[I]);
-    if (LLVM_LIKELY(!(C & 0x100))) { // ASCII or extended ASCII character.
+    unsigned short C = static_cast<unsigned short>(U8[I]);
+    if (LLVM_LIKELY(C <= 255)) { // ASCII or extended ASCII character.
       if (CB(1, 1))
         return true;
       ++I;