diff --git a/clang/include/clang/Basic/FileManager.h b/clang/include/clang/Basic/FileManager.h
index e83a61d6ff00c..769cfedae6018 100644
--- a/clang/include/clang/Basic/FileManager.h
+++ b/clang/include/clang/Basic/FileManager.h
@@ -319,13 +319,6 @@ class FileManager : public RefCountedBase<FileManager> {
   /// required, which is (almost) never.
   StringRef getCanonicalName(FileEntryRef File);
 
-private:
-  /// Retrieve the canonical name for a given file or directory.
-  ///
-  /// The first param is a key in the CanonicalNames array.
-  StringRef getCanonicalName(const void *Entry, StringRef Name);
-
-public:
   void PrintStats() const;
 
   /// Import statistics from a child FileManager and add them to this current
diff --git a/clang/lib/Basic/FileManager.cpp b/clang/lib/Basic/FileManager.cpp
index 86fe352df0461..f0285f56c9476 100644
--- a/clang/lib/Basic/FileManager.cpp
+++ b/clang/lib/Basic/FileManager.cpp
@@ -618,48 +618,33 @@ void FileManager::GetUniqueIDMapping(
 }
 
 StringRef FileManager::getCanonicalName(DirectoryEntryRef Dir) {
-  return getCanonicalName(Dir, Dir.getName());
-}
+  auto Known = CanonicalNames.find(Dir);
+  if (Known != CanonicalNames.end())
+    return Known->second;
 
-StringRef FileManager::getCanonicalName(FileEntryRef File) {
-  return getCanonicalName(File, File.getName());
+  StringRef CanonicalName(Dir.getName());
+
+  SmallString<4096> CanonicalNameBuf;
+  if (!FS->getRealPath(Dir.getName(), CanonicalNameBuf))
+    CanonicalName = CanonicalNameBuf.str().copy(CanonicalNameStorage);
+
+  CanonicalNames.insert({Dir, CanonicalName});
+  return CanonicalName;
 }
 
-StringRef FileManager::getCanonicalName(const void *Entry, StringRef Name) {
+StringRef FileManager::getCanonicalName(FileEntryRef File) {
   llvm::DenseMap<const void *, llvm::StringRef>::iterator Known =
-      CanonicalNames.find(Entry);
+      CanonicalNames.find(File);
   if (Known != CanonicalNames.end())
     return Known->second;
 
-  // Name comes from FileEntry/DirectoryEntry::getName(), so it is safe to
-  // store it in the DenseMap below.
-  StringRef CanonicalName(Name);
-
-  SmallString<256> AbsPathBuf;
-  SmallString<256> RealPathBuf;
-  if (!FS->getRealPath(Name, RealPathBuf)) {
-    if (is_style_windows(llvm::sys::path::Style::native)) {
-      // For Windows paths, only use the real path if it doesn't resolve
-      // a substitute drive, as those are used to avoid MAX_PATH issues.
-      AbsPathBuf = Name;
-      if (!FS->makeAbsolute(AbsPathBuf)) {
-        if (llvm::sys::path::root_name(RealPathBuf) ==
-            llvm::sys::path::root_name(AbsPathBuf)) {
-          CanonicalName = RealPathBuf.str().copy(CanonicalNameStorage);
-        } else {
-          // Fallback to using the absolute path.
-          // Simplifying /../ is semantically valid on Windows even in the
-          // presence of symbolic links.
-          llvm::sys::path::remove_dots(AbsPathBuf, /*remove_dot_dot=*/true);
-          CanonicalName = AbsPathBuf.str().copy(CanonicalNameStorage);
-        }
-      }
-    } else {
-      CanonicalName = RealPathBuf.str().copy(CanonicalNameStorage);
-    }
-  }
+  StringRef CanonicalName(File.getName());
+
+  SmallString<4096> CanonicalNameBuf;
+  if (!FS->getRealPath(File.getName(), CanonicalNameBuf))
+    CanonicalName = CanonicalNameBuf.str().copy(CanonicalNameStorage);
 
-  CanonicalNames.insert({Entry, CanonicalName});
+  CanonicalNames.insert({File, CanonicalName});
   return CanonicalName;
 }
 
diff --git a/clang/test/Lexer/case-insensitive-include-absolute.c b/clang/test/Lexer/case-insensitive-include-absolute.c
index ef9e131c45df5..4274d05045ecf 100644
--- a/clang/test/Lexer/case-insensitive-include-absolute.c
+++ b/clang/test/Lexer/case-insensitive-include-absolute.c
@@ -1,8 +1,8 @@
 // REQUIRES: case-insensitive-filesystem
 
 // RUN: rm -rf %t && split-file %s %t
-// RUN: sed "s|DIR|%{/t:real}|g" %t/tu.c.in > %t/tu.c
-// RUN: %clang_cc1 -fsyntax-only %t/tu.c 2>&1 | FileCheck %s -DDIR=%{/t:real}
+// RUN: sed "s|DIR|%/t|g" %t/tu.c.in > %t/tu.c
+// RUN: %clang_cc1 -fsyntax-only %t/tu.c 2>&1 | FileCheck %s -DDIR=%/t
 
 //--- header.h
 //--- tu.c.in
diff --git a/clang/test/Lexer/case-insensitive-include-win.c b/clang/test/Lexer/case-insensitive-include-win.c
index ed722feb3d994..6a17d0b552448 100644
--- a/clang/test/Lexer/case-insensitive-include-win.c
+++ b/clang/test/Lexer/case-insensitive-include-win.c
@@ -2,15 +2,9 @@
 // This file should only include code that really needs a Windows host OS to
 // run.
 
-// Note: We must use the real path here, because the logic to detect case
-// mismatches must resolve the real path to figure out the original casing.
-// If we use %t and we are on a substitute drive S: mapping to C:\subst,
-// then we will compare "S:\test.dir\FOO.h" to "C:\subst\test.dir\foo.h"
-// and avoid emitting the diagnostic because the structure is different.
-
 // REQUIRES: system-windows
 // RUN: mkdir -p %t.dir
 // RUN: touch %t.dir/foo.h
-// RUN: not %clang_cl /FI \\?\%{t:real}.dir\FOO.h /WX -fsyntax-only %s 2>&1 | FileCheck %s
+// RUN: not %clang_cl /FI\\?\%t.dir\FOO.h /WX -fsyntax-only %s 2>&1 | FileCheck %s
 
 // CHECK: non-portable path to file '"\\?\
diff --git a/llvm/cmake/modules/AddLLVM.cmake b/llvm/cmake/modules/AddLLVM.cmake
index 52bf7ca0906a3..2360f72e59d08 100644
--- a/llvm/cmake/modules/AddLLVM.cmake
+++ b/llvm/cmake/modules/AddLLVM.cmake
@@ -1887,15 +1887,10 @@ endfunction()
 # use it and can't be in a lit module. Use with make_paths_relative().
 string(CONCAT LLVM_LIT_PATH_FUNCTION
   "# Allow generated file to be relocatable.\n"
-  "import os\n"
-  "import platform\n"
+  "from pathlib import Path\n"
   "def path(p):\n"
   "    if not p: return ''\n"
-  "    # Follows lit.util.abs_path_preserve_drive, which cannot be imported here.\n"
-  "    if platform.system() == 'Windows':\n"
-  "        return os.path.abspath(os.path.join(os.path.dirname(__file__), p))\n"
-  "    else:\n"
-  "        return os.path.realpath(os.path.join(os.path.dirname(__file__), p))\n"
+  "    return str((Path(__file__).parent / p).resolve())\n"
   )
 
 # This function provides an automatic way to 'configure'-like generate a file
diff --git a/llvm/docs/CommandGuide/lit.rst b/llvm/docs/CommandGuide/lit.rst
index 2a0ddd0ea04b4..46c5b9936239e 100644
--- a/llvm/docs/CommandGuide/lit.rst
+++ b/llvm/docs/CommandGuide/lit.rst
@@ -616,16 +616,6 @@ TestRunner.py:
  %/T                     %T but ``\`` is replaced by ``/``
  %{s:basename}           The last path component of %s
  %{t:stem}               The last path component of %t but without the ``.tmp`` extension (alias for %basename_t)
- %{s:real}               %s after expanding all symbolic links and substitute drives
- %{S:real}               %S after expanding all symbolic links and substitute drives
- %{p:real}               %p after expanding all symbolic links and substitute drives
- %{t:real}               %t after expanding all symbolic links and substitute drives
- %{T:real}               %T after expanding all symbolic links and substitute drives
- %{/s:real}              %/s after expanding all symbolic links and substitute drives
- %{/S:real}              %/S after expanding all symbolic links and substitute drives
- %{/p:real}              %/p after expanding all symbolic links and substitute drives
- %{/t:real}              %/t after expanding all symbolic links and substitute drives
- %{/T:real}              %/T after expanding all symbolic links and substitute drives
  %{/s:regex_replacement} %/s but escaped for use in the replacement of a ``s@@@`` command in sed
  %{/S:regex_replacement} %/S but escaped for use in the replacement of a ``s@@@`` command in sed
  %{/p:regex_replacement} %/p but escaped for use in the replacement of a ``s@@@`` command in sed
diff --git a/llvm/docs/TestingGuide.rst b/llvm/docs/TestingGuide.rst
index b6dda6a732405..3a555d6bea5aa 100644
--- a/llvm/docs/TestingGuide.rst
+++ b/llvm/docs/TestingGuide.rst
@@ -757,7 +757,7 @@ RUN lines:
 ``%{fs-sep}``
    Expands to the file system separator, i.e. ``/`` or ``\`` on Windows.
 
-``%/s, %/S, %/t, %/T``
+``%/s, %/S, %/t, %/T:``
 
   Act like the corresponding substitution above but replace any ``\``
   character with a ``/``. This is useful to normalize path separators.
@@ -766,17 +766,7 @@ RUN lines:
 
    Example: ``%/s: C:/Desktop Files/foo_test.s.tmp``
 
-``%{s:real}, %{S:real}, %{t:real}, %{T:real}``
-``%{/s:real}, %{/S:real}, %{/t:real}, %{/T:real}``
-
-  Act like the corresponding substitution, including with ``/``, but use
-  the real path by expanding all symbolic links and substitute drives.
-
-   Example: ``%s:  S:\foo_test.s.tmp``
-
-   Example: ``%{/s:real}: C:/SDrive/foo_test.s.tmp``
-
-``%:s, %:S, %:t, %:T``
+``%:s, %:S, %:t, %:T:``
 
   Act like the corresponding substitution above but remove colons at
   the beginning of Windows paths. This is useful to allow concatenation
diff --git a/llvm/utils/lit/lit/TestRunner.py b/llvm/utils/lit/lit/TestRunner.py
index 16e9c7fbf45c5..48650f5cda9c7 100644
--- a/llvm/utils/lit/lit/TestRunner.py
+++ b/llvm/utils/lit/lit/TestRunner.py
@@ -96,7 +96,7 @@ def change_dir(self, newdir):
         if os.path.isabs(newdir):
             self.cwd = newdir
         else:
-            self.cwd = lit.util.abs_path_preserve_drive(os.path.join(self.cwd, newdir))
+            self.cwd = os.path.realpath(os.path.join(self.cwd, newdir))
 
 
 class TimeoutHelper(object):
@@ -455,7 +455,7 @@ def executeBuiltinMkdir(cmd, cmd_shenv):
         dir = to_unicode(dir) if kIsWindows else to_bytes(dir)
         cwd = to_unicode(cwd) if kIsWindows else to_bytes(cwd)
         if not os.path.isabs(dir):
-            dir = lit.util.abs_path_preserve_drive(os.path.join(cwd, dir))
+            dir = os.path.realpath(os.path.join(cwd, dir))
         if parent:
             lit.util.mkdir_p(dir)
         else:
@@ -501,7 +501,7 @@ def on_rm_error(func, path, exc_info):
         path = to_unicode(path) if kIsWindows else to_bytes(path)
         cwd = to_unicode(cwd) if kIsWindows else to_bytes(cwd)
         if not os.path.isabs(path):
-            path = lit.util.abs_path_preserve_drive(os.path.join(cwd, path))
+            path = os.path.realpath(os.path.join(cwd, path))
         if force and not os.path.exists(path):
             continue
         try:
@@ -1399,11 +1399,19 @@ def getDefaultSubstitutions(test, tmpDir, tmpBase, normalize_slashes=False):
     tmpBaseName = os.path.basename(tmpBase)
     sourceBaseName = os.path.basename(sourcepath)
 
-    substitutions.append(("%{pathsep}", os.pathsep))
-    substitutions.append(("%basename_t", tmpBaseName))
-
-    substitutions.append(("%{s:basename}", sourceBaseName))
-    substitutions.append(("%{t:stem}", tmpBaseName))
+    substitutions.extend(
+        [
+            ("%s", sourcepath),
+            ("%S", sourcedir),
+            ("%p", sourcedir),
+            ("%{pathsep}", os.pathsep),
+            ("%t", tmpName),
+            ("%basename_t", tmpBaseName),
+            ("%T", tmpDir),
+            ("%{s:basename}", sourceBaseName),
+            ("%{t:stem}", tmpBaseName),
+        ]
+    )
 
     substitutions.extend(
         [
@@ -1413,47 +1421,49 @@ def getDefaultSubstitutions(test, tmpDir, tmpBase, normalize_slashes=False):
         ]
     )
 
-    substitutions.append(("%/et", tmpName.replace("\\", "\\\\\\\\\\\\\\\\")))
+    # "%/[STpst]" should be normalized.
+    substitutions.extend(
+        [
+            ("%/s", sourcepath.replace("\\", "/")),
+            ("%/S", sourcedir.replace("\\", "/")),
+            ("%/p", sourcedir.replace("\\", "/")),
+            ("%/t", tmpBase.replace("\\", "/") + ".tmp"),
+            ("%/T", tmpDir.replace("\\", "/")),
+            ("%/et", tmpName.replace("\\", "\\\\\\\\\\\\\\\\")),
+        ]
+    )
 
+    # "%{/[STpst]:regex_replacement}" should be normalized like "%/[STpst]" but we're
+    # also in a regex replacement context of a s@@@ regex.
     def regex_escape(s):
         s = s.replace("@", r"\@")
         s = s.replace("&", r"\&")
         return s
 
-    path_substitutions = [
-        ("s", sourcepath), ("S", sourcedir), ("p", sourcedir),
-        ("t", tmpName), ("T", tmpDir)
-    ]
-    for path_substitution in path_substitutions:
-        letter = path_substitution[0]
-        path = path_substitution[1]
-
-        # Original path variant
-        substitutions.append(("%" + letter, path))
-
-        # Normalized path separator variant
-        substitutions.append(("%/" + letter, path.replace("\\", "/")))
-
-        # realpath variants
-        # Windows paths with substitute drives are not expanded by default
-        # as they are used to avoid MAX_PATH issues, but sometimes we do
-        # need the fully expanded path.
-        real_path = os.path.realpath(path)
-        substitutions.append(("%{" + letter + ":real}", real_path))
-        substitutions.append(("%{/" + letter + ":real}",
-            real_path.replace("\\", "/")))
-
-        # "%{/[STpst]:regex_replacement}" should be normalized like
-        # "%/[STpst]" but we're also in a regex replacement context
-        # of a s@@@ regex.
-        substitutions.append(
-            ("%{/" + letter + ":regex_replacement}",
-            regex_escape(path.replace("\\", "/"))))
-
-        # "%:[STpst]" are normalized paths without colons and without
-        # a leading slash.
-        substitutions.append(("%:" + letter, colonNormalizePath(path)))
+    substitutions.extend(
+        [
+            ("%{/s:regex_replacement}", regex_escape(sourcepath.replace("\\", "/"))),
+            ("%{/S:regex_replacement}", regex_escape(sourcedir.replace("\\", "/"))),
+            ("%{/p:regex_replacement}", regex_escape(sourcedir.replace("\\", "/"))),
+            (
+                "%{/t:regex_replacement}",
+                regex_escape(tmpBase.replace("\\", "/")) + ".tmp",
+            ),
+            ("%{/T:regex_replacement}", regex_escape(tmpDir.replace("\\", "/"))),
+        ]
+    )
 
+    # "%:[STpst]" are normalized paths without colons and without a leading
+    # slash.
+    substitutions.extend(
+        [
+            ("%:s", colonNormalizePath(sourcepath)),
+            ("%:S", colonNormalizePath(sourcedir)),
+            ("%:p", colonNormalizePath(sourcedir)),
+            ("%:t", colonNormalizePath(tmpBase + ".tmp")),
+            ("%:T", colonNormalizePath(tmpDir)),
+        ]
+    )
     return substitutions
 
 
diff --git a/llvm/utils/lit/lit/builtin_commands/diff.py b/llvm/utils/lit/lit/builtin_commands/diff.py
index fbf4eb0e137b3..3a91920f9b5ed 100644
--- a/llvm/utils/lit/lit/builtin_commands/diff.py
+++ b/llvm/utils/lit/lit/builtin_commands/diff.py
@@ -281,7 +281,7 @@ def main(argv):
     try:
         for file in args:
             if file != "-" and not os.path.isabs(file):
-                file = util.abs_path_preserve_drive(file)
+                file = os.path.realpath(os.path.join(os.getcwd(), file))
 
             if flags.recursive_diff:
                 if file == "-":
diff --git a/llvm/utils/lit/lit/discovery.py b/llvm/utils/lit/lit/discovery.py
index 2e7f90c6bb0c9..a0a2549d8df99 100644
--- a/llvm/utils/lit/lit/discovery.py
+++ b/llvm/utils/lit/lit/discovery.py
@@ -7,7 +7,7 @@
 import sys
 
 from lit.TestingConfig import TestingConfig
-from lit import LitConfig, Test, util
+from lit import LitConfig, Test
 
 
 def chooseConfigFileFromDir(dir, config_names):
@@ -56,7 +56,7 @@ def search1(path):
         # configuration to load instead.
         config_map = litConfig.params.get("config_map")
         if config_map:
-            cfgpath = util.abs_path_preserve_drive(cfgpath)
+            cfgpath = os.path.realpath(cfgpath)
             target = config_map.get(os.path.normcase(cfgpath))
             if target:
                 cfgpath = target
@@ -67,13 +67,13 @@ def search1(path):
 
         cfg = TestingConfig.fromdefaults(litConfig)
         cfg.load_from_path(cfgpath, litConfig)
-        source_root = util.abs_path_preserve_drive(cfg.test_source_root or path)
-        exec_root = util.abs_path_preserve_drive(cfg.test_exec_root or path)
+        source_root = os.path.realpath(cfg.test_source_root or path)
+        exec_root = os.path.realpath(cfg.test_exec_root or path)
         return Test.TestSuite(cfg.name, source_root, exec_root, cfg), ()
 
     def search(path):
         # Check for an already instantiated test suite.
-        real_path = util.abs_path_preserve_drive(path)
+        real_path = os.path.realpath(path)
         res = cache.get(real_path)
         if res is None:
             cache[real_path] = res = search1(path)
diff --git a/llvm/utils/lit/lit/util.py b/llvm/utils/lit/lit/util.py
index b03fd8bc22693..bd32d760f8ff1 100644
--- a/llvm/utils/lit/lit/util.py
+++ b/llvm/utils/lit/lit/util.py
@@ -128,23 +128,6 @@ def usable_core_count():
 
     return n
 
-def abs_path_preserve_drive(path):
-    """Return the absolute path without resolving drive mappings on Windows.
-
-    """
-    if platform.system() == "Windows":
-        # Windows has limitations on path length (MAX_PATH) that
-        # can be worked around using substitute drives, which map
-        # a drive letter to a longer path on another drive.
-        # Since Python 3.8, os.path.realpath resolves sustitute drives,
-        # so we should not use it. In Python 3.7, os.path.realpath
-        # was implemented as os.path.abspath.
-        return os.path.abspath(path)
-    else:
-        # On UNIX, the current directory always has symbolic links resolved,
-        # so any program accepting relative paths cannot preserve symbolic
-        # links in paths and we should always use os.path.realpath.
-        return os.path.realpath(path)
 
 def mkdir(path):
     try:
diff --git a/llvm/utils/lit/tests/Inputs/config-map-discovery/driver.py b/llvm/utils/lit/tests/Inputs/config-map-discovery/driver.py
index 50ad2cd65cb1b..d22b84d6a15cf 100644
--- a/llvm/utils/lit/tests/Inputs/config-map-discovery/driver.py
+++ b/llvm/utils/lit/tests/Inputs/config-map-discovery/driver.py
@@ -2,7 +2,8 @@
 import os
 import sys
 
-main_config = lit.util.abs_path_preserve_drive(sys.argv[1])
+main_config = sys.argv[1]
+main_config = os.path.realpath(main_config)
 main_config = os.path.normcase(main_config)
 
 config_map = {main_config: sys.argv[2]}
diff --git a/llvm/utils/lit/tests/Inputs/config-map-discovery/lit.alt.cfg b/llvm/utils/lit/tests/Inputs/config-map-discovery/lit.alt.cfg
index 27860e192fdc1..c7b303f50a05c 100644
--- a/llvm/utils/lit/tests/Inputs/config-map-discovery/lit.alt.cfg
+++ b/llvm/utils/lit/tests/Inputs/config-map-discovery/lit.alt.cfg
@@ -5,5 +5,5 @@ config.suffixes = ['.txt']
 config.test_format = lit.formats.ShTest()
 
 import os
-config.test_exec_root = os.path.dirname(lit.util.abs_path_preserve_drive(__file__))
+config.test_exec_root = os.path.realpath(os.path.dirname(__file__))
 config.test_source_root = os.path.join(config.test_exec_root, "tests")
diff --git a/llvm/utils/lit/tests/Inputs/use-llvm-tool-required/lit.cfg b/llvm/utils/lit/tests/Inputs/use-llvm-tool-required/lit.cfg
index 5062e38c82f14..e41207bc2f05d 100644
--- a/llvm/utils/lit/tests/Inputs/use-llvm-tool-required/lit.cfg
+++ b/llvm/utils/lit/tests/Inputs/use-llvm-tool-required/lit.cfg
@@ -1,5 +1,4 @@
 import lit.formats
-import lit.util
 
 config.name = "use-llvm-tool-required"
 config.suffixes = [".txt"]
@@ -8,7 +7,7 @@ config.test_source_root = None
 config.test_exec_root = None
 import os.path
 
-config.llvm_tools_dir = os.path.dirname(lit.util.abs_path_preserve_drive(__file__))
+config.llvm_tools_dir = os.path.realpath(os.path.dirname(__file__))
 import lit.llvm
 
 lit.llvm.initialize(lit_config, config)
diff --git a/llvm/utils/lit/tests/Inputs/use-llvm-tool/lit.cfg b/llvm/utils/lit/tests/Inputs/use-llvm-tool/lit.cfg
index 2a52db2183edf..8fe62d98c1349 100644
--- a/llvm/utils/lit/tests/Inputs/use-llvm-tool/lit.cfg
+++ b/llvm/utils/lit/tests/Inputs/use-llvm-tool/lit.cfg
@@ -1,5 +1,4 @@
 import lit.formats
-import lit.util
 
 config.name = "use-llvm-tool"
 config.suffixes = [".txt"]
@@ -8,7 +7,7 @@ config.test_source_root = None
 config.test_exec_root = None
 import os.path
 
-this_dir = os.path.dirname(lit.util.abs_path_preserve_drive(__file__))
+this_dir = os.path.realpath(os.path.dirname(__file__))
 config.llvm_tools_dir = os.path.join(this_dir, "build")
 import lit.llvm
 
diff --git a/llvm/utils/llvm-lit/llvm-lit.in b/llvm/utils/llvm-lit/llvm-lit.in
index 0b6683b6b6230..33ec8017cf05f 100755
--- a/llvm/utils/llvm-lit/llvm-lit.in
+++ b/llvm/utils/llvm-lit/llvm-lit.in
@@ -8,7 +8,7 @@ config_map = {}
 
 def map_config(source_dir, site_config):
     global config_map
-    source_dir = os.path.abspath(source_dir)
+    source_dir = os.path.realpath(source_dir)
     source_dir = os.path.normcase(source_dir)
     site_config = os.path.normpath(site_config)
     config_map[source_dir] = site_config