Index: lld/COFF/Driver.cpp
===================================================================
--- lld/COFF/Driver.cpp
+++ lld/COFF/Driver.cpp
@@ -104,10 +104,9 @@
 
 // Drop directory components and replace extension with ".exe" or ".dll".
 static std::string getOutputPath(StringRef path) {
-  auto p = path.find_last_of("\\/");
-  StringRef s = (p == StringRef::npos) ? path : path.substr(p + 1);
-  const char* e = config->dll ? ".dll" : ".exe";
-  return (s.substr(0, s.rfind('.')) + e).str();
+  SmallString<128> outputPath = sys::path::filename(path);
+  sys::path::replace_extension(outputPath, config->dll ? ".dll" : ".exe");
+  return outputPath.str();
 }
 
 // Returns true if S matches /crtend.?\.o$/.
Index: llvm/include/llvm/Support/Path.h
===================================================================
--- llvm/include/llvm/Support/Path.h
+++ llvm/include/llvm/Support/Path.h
@@ -121,6 +121,8 @@
 
 /// Remove the last component from \a path unless it is the root dir.
 ///
+/// Similar to the POSIX "dirname" utility.
+///
 /// @code
 ///   directory/filename.cpp => directory/
 ///   directory/             => directory
@@ -295,7 +297,7 @@
 ///
 /// @param path Input path.
 /// @result The filename part of \a path. This is defined as the last component
-///         of \a path.
+///         of \a path. Similar to the POSIX "basename" utility.
 StringRef filename(StringRef path, Style style = Style::native);
 
 /// Get stem.