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
@@ -25,7 +25,13 @@
 namespace sys {
 namespace path {
 
-enum class Style { windows, posix, native };
+enum class Style {
+  native,
+  posix,
+  windows_slash,
+  windows_backslash,
+  windows = windows_backslash, // deprecated
+};
 
 /// Check if \p S uses POSIX path rules.
 constexpr bool is_style_posix(Style S) {
@@ -262,6 +268,17 @@
 /// @param path A path that is transformed to native format.
 void native(SmallVectorImpl<char> &path, Style style = Style::native);
 
+/// For Windows path styles, convert path to use the preferred path separators.
+/// For other styles, do nothing.
+///
+/// @param path A path that is transformed to preferred format.
+inline void make_preferred(SmallVectorImpl<char> &path,
+                           Style style = Style::native) {
+  if (!is_style_windows(style))
+    return;
+  native(path, style);
+}
+
 /// Replaces backslashes with slashes if Windows.
 ///
 /// @param path processed 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
@@ -37,9 +37,12 @@
   using llvm::sys::path::Style;
 
   inline Style real_style(Style style) {
-    if (is_style_posix(style))
-      return Style::posix;
-    return Style::windows;
+    if (style == Style::native) {
+      if (is_style_posix(style))
+        return Style::posix;
+      return Style::windows;
+    }
+    return style;
   }
 
   inline const char *separators(Style style) {
@@ -547,7 +550,9 @@
   if (Path.empty())
     return;
   if (is_style_windows(style)) {
-    std::replace(Path.begin(), Path.end(), '/', '\\');
+    for (char &Ch : Path)
+      if (is_separator(Ch, style))
+        Ch = preferred_separator(style);
     if (Path[0] == '~' && (Path.size() == 1 || is_separator(Path[1], style))) {
       SmallString<128> PathHome;
       home_directory(PathHome);
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
@@ -99,6 +99,7 @@
   EXPECT_FALSE(path::is_separator(' '));
 
   EXPECT_TRUE(path::is_separator('\\', path::Style::windows));
+  EXPECT_TRUE(path::is_separator('\\', path::Style::windows_slash));
   EXPECT_FALSE(path::is_separator('\\', path::Style::posix));
 
   EXPECT_EQ(path::is_style_windows(path::Style::native),
@@ -387,6 +388,8 @@
               testing::ElementsAre("/", ".c", ".d", "..", "."));
   EXPECT_THAT(GetComponents("c:\\c\\e\\foo.txt", path::Style::windows),
               testing::ElementsAre("c:", "\\", "c", "e", "foo.txt"));
+  EXPECT_THAT(GetComponents("c:\\c\\e\\foo.txt", path::Style::windows_slash),
+              testing::ElementsAre("c:", "\\", "c", "e", "foo.txt"));
   EXPECT_THAT(GetComponents("//net/"), testing::ElementsAre("//net", "/"));
   EXPECT_THAT(GetComponents("//net/c/foo.txt"),
               testing::ElementsAre("//net", "/", "c", "foo.txt"));
@@ -1429,10 +1432,25 @@
   for (auto &T : Tests) {
     SmallString<64> Win(std::get<0>(T));
     SmallString<64> Posix(Win);
+    SmallString<64> WinSlash(Win);
     path::native(Win, path::Style::windows);
     path::native(Posix, path::Style::posix);
+    path::native(WinSlash, path::Style::windows_slash);
     EXPECT_EQ(std::get<1>(T), Win);
     EXPECT_EQ(std::get<2>(T), Posix);
+    EXPECT_EQ(std::get<2>(T), WinSlash);
+  }
+
+  for (auto &T : Tests) {
+    SmallString<64> WinBackslash(std::get<0>(T));
+    SmallString<64> Posix(WinBackslash);
+    SmallString<64> WinSlash(WinBackslash);
+    path::make_preferred(WinBackslash, path::Style::windows_backslash);
+    path::make_preferred(Posix, path::Style::posix);
+    path::make_preferred(WinSlash, path::Style::windows_slash);
+    EXPECT_EQ(std::get<1>(T), WinBackslash);
+    EXPECT_EQ(std::get<0>(T), Posix); // Posix remains unchanged here
+    EXPECT_EQ(std::get<2>(T), WinSlash);
   }
 
 #if defined(_WIN32)
@@ -1441,10 +1459,15 @@
 
   const char *Path7a = "~/aaa";
   SmallString<64> Path7(Path7a);
-  path::native(Path7);
+  path::native(Path7, path::Style::windows_backslash);
   EXPECT_TRUE(Path7.endswith("\\aaa"));
   EXPECT_TRUE(Path7.startswith(PathHome));
   EXPECT_EQ(Path7.size(), PathHome.size() + strlen(Path7a + 1));
+  Path7 = Path7a;
+  path::native(Path7, path::Style::windows_slash);
+  EXPECT_TRUE(Path7.endswith("/aaa"));
+  EXPECT_TRUE(Path7.startswith(PathHome));
+  EXPECT_EQ(Path7.size(), PathHome.size() + strlen(Path7a + 1));
 
   const char *Path8a = "~";
   SmallString<64> Path8(Path8a);
@@ -1458,7 +1481,7 @@
 
   const char *Path10a = "aaa/~/b";
   SmallString<64> Path10(Path10a);
-  path::native(Path10);
+  path::native(Path10, path::Style::windows_backslash);
   EXPECT_EQ(Path10, "aaa\\~\\b");
 #endif
 }