diff --git a/llvm/include/llvm/Support/Path.h b/llvm/include/llvm/Support/Path.h
--- a/llvm/include/llvm/Support/Path.h
+++ b/llvm/include/llvm/Support/Path.h
@@ -468,31 +468,6 @@
 /// @result True if the path is absolute, false if it is not.
 bool is_absolute(const Twine &path, Style style = Style::native);
 
-/// Is path absolute using GNU rules?
-///
-/// GNU rules are:
-/// 1) Paths starting with a path separator are absolute.
-/// 2) Windows style paths are also absolute if they start with a character
-///    followed by ':'.
-/// 3) No other paths are absolute.
-///
-/// On Windows style the path "C:\Users\Default" has "C:" as root name and "\"
-/// as root directory.
-///
-/// Hence "C:" on Windows is absolute under GNU rules and not absolute under
-/// C++17 because it has no root directory. Likewise "/" and "\" on Windows are
-/// absolute under GNU and are not absolute under C++17 due to empty root name.
-///
-/// \see has_root_name
-/// \see has_root_directory
-///
-/// @param path Input path.
-/// @param style The style of \p path (e.g. Windows or POSIX). "native" style
-/// means to derive the style from the host.
-/// @result True if the path is absolute following GNU rules, false if it is
-/// not.
-bool is_absolute_gnu(const Twine &path, Style style = Style::native);
-
 /// Is path relative?
 ///
 /// @param path Input path.
diff --git a/llvm/lib/Support/Path.cpp b/llvm/lib/Support/Path.cpp
--- a/llvm/lib/Support/Path.cpp
+++ b/llvm/lib/Support/Path.cpp
@@ -683,24 +683,6 @@
   return rootDir && rootName;
 }
 
-bool is_absolute_gnu(const Twine &path, Style style) {
-  SmallString<128> path_storage;
-  StringRef p = path.toStringRef(path_storage);
-
-  // Handle '/' which is absolute for both Windows and POSIX systems.
-  // Handle '\\' on Windows.
-  if (!p.empty() && is_separator(p.front(), style))
-    return true;
-
-  if (real_style(style) == Style::windows) {
-    // Handle drive letter pattern (a character followed by ':') on Windows.
-    if (p.size() >= 2 && (p[0] && p[1] == ':'))
-      return true;
-  }
-
-  return false;
-}
-
 bool is_relative(const Twine &path, Style style) {
   return !is_absolute(path, style);
 }
diff --git a/llvm/unittests/Support/Path.cpp b/llvm/unittests/Support/Path.cpp
--- a/llvm/unittests/Support/Path.cpp
+++ b/llvm/unittests/Support/Path.cpp
@@ -85,31 +85,6 @@
 #endif
 }
 
-TEST(is_absolute_gnu, Works) {
-  // Test tuple <Path, ExpectedPosixValue, ExpectedWindowsValue>.
-  const std::tuple<StringRef, bool, bool> Paths[] = {
-      std::make_tuple("", false, false),
-      std::make_tuple("/", true, true),
-      std::make_tuple("/foo", true, true),
-      std::make_tuple("\\", false, true),
-      std::make_tuple("\\foo", false, true),
-      std::make_tuple("foo", false, false),
-      std::make_tuple("c", false, false),
-      std::make_tuple("c:", false, true),
-      std::make_tuple("c:\\", false, true),
-      std::make_tuple("!:", false, true),
-      std::make_tuple("xx:", false, false),
-      std::make_tuple("c:abc\\", false, true),
-      std::make_tuple(":", false, false)};
-
-  for (const auto &Path : Paths) {
-    EXPECT_EQ(path::is_absolute_gnu(std::get<0>(Path), path::Style::posix),
-              std::get<1>(Path));
-    EXPECT_EQ(path::is_absolute_gnu(std::get<0>(Path), path::Style::windows),
-              std::get<2>(Path));
-  }
-}
-
 TEST(Support, Path) {
   SmallVector<StringRef, 40> paths;
   paths.push_back("");
@@ -196,7 +171,6 @@
     (void)path::has_extension(*i);
     (void)path::extension(*i);
     (void)path::is_absolute(*i);
-    (void)path::is_absolute_gnu(*i);
     (void)path::is_relative(*i);
 
     SmallString<128> temp_store;