Index: llvm/test/tools/llvm-ar/case-detection.test
===================================================================
--- llvm/test/tools/llvm-ar/case-detection.test
+++ llvm/test/tools/llvm-ar/case-detection.test
@@ -0,0 +1,7 @@
+-- Test CamelCase Lib.exe to ensure detection works properly
+
+RUN: yaml2obj %S/Inputs/coff.yaml -o %t.obj
+RUN: rm -rf %t1
+RUN: mkdir %t1
+RUN: cp llvm-ar %t1/Lib
+RUN: %t1/Lib /OUT:%t.lib %t.obj
Index: llvm/tools/llvm-ar/llvm-ar.cpp
===================================================================
--- llvm/tools/llvm-ar/llvm-ar.cpp
+++ llvm/tools/llvm-ar/llvm-ar.cpp
@@ -863,11 +863,11 @@
   llvm::InitializeAllAsmParsers();
 
   StringRef Stem = sys::path::stem(ToolName);
-  if (Stem.find("dlltool") != StringRef::npos)
+  if (Stem.find_lower("dlltool") != StringRef::npos)
     return dlltoolDriverMain(makeArrayRef(argv, argc));
 
-  if (Stem.find("ranlib") == StringRef::npos &&
-      Stem.find("lib") != StringRef::npos)
+  if (Stem.find_lower("ranlib") == StringRef::npos &&
+      Stem.find_lower("lib") != StringRef::npos)
     return libDriverMain(makeArrayRef(argv, argc));
 
   SmallVector<const char *, 256> Argv;
@@ -900,9 +900,9 @@
     "  This program archives bitcode files into single libraries\n"
   );
 
-  if (Stem.find("ranlib") != StringRef::npos)
+  if (Stem.find_lower("ranlib") != StringRef::npos)
     return ranlib_main();
-  if (Stem.find("ar") != StringRef::npos)
+  if (Stem.find_lower("ar") != StringRef::npos)
     return ar_main();
   fail("Not ranlib, ar, lib or dlltool!");
 }