[Support] Support both Windows and Posix paths on both platforms.

Previously which path syntax we supported dependend on what
platform we were compiling LLVM on.  While this is normally
desirable, there are situations where we need to be able to
handle a path that we know was generated on a remote host.
Remote debugging, for example, or parsing debug info.

99% of the code in LLVM for handling paths was platform
agnostic and literally just a few branches were gated behind
pre-processor checks, so this changes those sites to use
runtime checks instead, and adds a flag to every path
API that allows one to override the host native syntax.

Differential Revision: https://reviews.llvm.org/D30858

llvm-svn: 298004

1 files changed, 202 insertions, 223 deletions

diff --git a/llvm/lib/Support/Path.cpp b/llvm/lib/Support/Path.cpp
index 26b3eadb289..ffb8ab22088 100644
--- a/llvm/lib/Support/Path.cpp
+++ b/llvm/lib/Support/Path.cpp
@@ -34,16 +34,29 @@ using namespace llvm::support::endian;
 namespace {
   using llvm::StringRef;
   using llvm::sys::path::is_separator;
+  using llvm::sys::path::Style;
 
+  inline Style real_style(Style style) {
 #ifdef LLVM_ON_WIN32
-  const char *separators = "\\/";
-  const char preferred_separator = '\\';
+    return (style == Style::posix) ? Style::posix : Style::windows;
 #else
-  const char  separators = '/';
-  const char preferred_separator = '/';
+    return (style == Style::windows) ? Style::windows : Style::posix;
 #endif
+  }
+
+  inline const char *separators(Style style) {
+    if (real_style(style) == Style::windows)
+      return "\\/";
+    return "/";
+  }
 
-  StringRef find_first_component(StringRef path) {
+  inline char preferred_separator(Style style) {
+    if (real_style(style) == Style::windows)
+      return '\\';
+    return '/';
+  }
+
+  StringRef find_first_component(StringRef path, Style style) {
     // Look for this first component in the following order.
     // * empty (in this case we return an empty string)
     // * either C: or {//,\\}net.
@@ -53,96 +66,85 @@ namespace {
     if (path.empty())
       return path;
 
-#ifdef LLVM_ON_WIN32
-    // C:
-    if (path.size() >= 2 && std::isalpha(static_cast<unsigned char>(path[0])) &&
-        path[1] == ':')
-      return path.substr(0, 2);
-#endif
+    if (real_style(style) == Style::windows) {
+      // C:
+      if (path.size() >= 2 &&
+          std::isalpha(static_cast<unsigned char>(path[0])) && path[1] == ':')
+        return path.substr(0, 2);
+    }
 
     // //net
-    if ((path.size() > 2) &&
-        is_separator(path[0]) &&
-        path[0] == path[1] &&
-        !is_separator(path[2])) {
+    if ((path.size() > 2) && is_separator(path[0], style) &&
+        path[0] == path[1] && !is_separator(path[2], style)) {
       // Find the next directory separator.
-      size_t end = path.find_first_of(separators, 2);
+      size_t end = path.find_first_of(separators(style), 2);
       return path.substr(0, end);
     }
 
     // {/,\}
-    if (is_separator(path[0]))
+    if (is_separator(path[0], style))
       return path.substr(0, 1);
 
     // * {file,directory}name
-    size_t end = path.find_first_of(separators);
+    size_t end = path.find_first_of(separators(style));
     return path.substr(0, end);
   }
 
-  size_t filename_pos(StringRef str) {
-    if (str.size() == 2 &&
-        is_separator(str[0]) &&
-        str[0] == str[1])
+  size_t filename_pos(StringRef str, Style style) {
+    if (str.size() == 2 && is_separator(str[0], style) && str[0] == str[1])
       return 0;
 
-    if (str.size() > 0 && is_separator(str[str.size() - 1]))
+    if (str.size() > 0 && is_separator(str[str.size() - 1], style))
       return str.size() - 1;
 
-    size_t pos = str.find_last_of(separators, str.size() - 1);
+    size_t pos = str.find_last_of(separators(style), str.size() - 1);
 
-#ifdef LLVM_ON_WIN32
-    if (pos == StringRef::npos)
-      pos = str.find_last_of(':', str.size() - 2);
-#endif
+    if (real_style(style) == Style::windows) {
+      if (pos == StringRef::npos)
+        pos = str.find_last_of(':', str.size() - 2);
+    }
 
-    if (pos == StringRef::npos ||
-        (pos == 1 && is_separator(str[0])))
+    if (pos == StringRef::npos || (pos == 1 && is_separator(str[0], style)))
       return 0;
 
     return pos + 1;
   }
 
-  size_t root_dir_start(StringRef str) {
+  size_t root_dir_start(StringRef str, Style style) {
     // case "c:/"
-#ifdef LLVM_ON_WIN32
-    if (str.size() > 2 &&
-        str[1] == ':' &&
-        is_separator(str[2]))
-      return 2;
-#endif
+    if (real_style(style) == Style::windows) {
+      if (str.size() > 2 && str[1] == ':' && is_separator(str[2], style))
+        return 2;
+    }
 
     // case "//"
-    if (str.size() == 2 &&
-        is_separator(str[0]) &&
-        str[0] == str[1])
+    if (str.size() == 2 && is_separator(str[0], style) && str[0] == str[1])
       return StringRef::npos;
 
     // case "//net"
-    if (str.size() > 3 &&
-        is_separator(str[0]) &&
-        str[0] == str[1] &&
-        !is_separator(str[2])) {
-      return str.find_first_of(separators, 2);
+    if (str.size() > 3 && is_separator(str[0], style) && str[0] == str[1] &&
+        !is_separator(str[2], style)) {
+      return str.find_first_of(separators(style), 2);
     }
 
     // case "/"
-    if (str.size() > 0 && is_separator(str[0]))
+    if (str.size() > 0 && is_separator(str[0], style))
       return 0;
 
     return StringRef::npos;
   }
 
-  size_t parent_path_end(StringRef path) {
-    size_t end_pos = filename_pos(path);
+  size_t parent_path_end(StringRef path, Style style) {
+    size_t end_pos = filename_pos(path, style);
 
-    bool filename_was_sep = path.size() > 0 && is_separator(path[end_pos]);
+    bool filename_was_sep =
+        path.size() > 0 && is_separator(path[end_pos], style);
 
     // Skip separators except for root dir.
-    size_t root_dir_pos = root_dir_start(path.substr(0, end_pos));
+    size_t root_dir_pos = root_dir_start(path.substr(0, end_pos), style);
 
-    while(end_pos > 0 &&
-          (end_pos - 1) != root_dir_pos &&
-          is_separator(path[end_pos - 1]))
+    while (end_pos > 0 && (end_pos - 1) != root_dir_pos &&
+           is_separator(path[end_pos - 1], style))
       --end_pos;
 
     if (end_pos == 1 && root_dir_pos == 0 && filename_was_sep)
@@ -230,11 +232,12 @@ namespace llvm {
 namespace sys  {
 namespace path {
 
-const_iterator begin(StringRef path) {
+const_iterator begin(StringRef path, Style style) {
   const_iterator i;
   i.Path      = path;
-  i.Component = find_first_component(path);
+  i.Component = find_first_component(path, style);
   i.Position  = 0;
+  i.S = style;
   return i;
 }
 
@@ -259,27 +262,21 @@ const_iterator &const_iterator::operator++() {
 
   // Both POSIX and Windows treat paths that begin with exactly two separators
   // specially.
-  bool was_net = Component.size() > 2 &&
-    is_separator(Component[0]) &&
-    Component[1] == Component[0] &&
-    !is_separator(Component[2]);
+  bool was_net = Component.size() > 2 && is_separator(Component[0], S) &&
+                 Component[1] == Component[0] && !is_separator(Component[2], S);
 
   // Handle separators.
-  if (is_separator(Path[Position])) {
+  if (is_separator(Path[Position], S)) {
     // Root dir.
-    if (was_net
-#ifdef LLVM_ON_WIN32
+    if (was_net ||
         // c:/
-        || Component.endswith(":")
-#endif
-        ) {
+        (real_style(S) == Style::windows && Component.endswith(":"))) {
       Component = Path.substr(Position, 1);
       return *this;
     }
 
     // Skip extra separators.
-    while (Position != Path.size() &&
-           is_separator(Path[Position])) {
+    while (Position != Path.size() && is_separator(Path[Position], S)) {
       ++Position;
     }
 
@@ -292,7 +289,7 @@ const_iterator &const_iterator::operator++() {
   }
 
   // Find next component.
-  size_t end_pos = Path.find_first_of(separators, Position);
+  size_t end_pos = Path.find_first_of(separators(S), Position);
   Component = Path.slice(Position, end_pos);
 
   return *this;
@@ -306,10 +303,11 @@ ptrdiff_t const_iterator::operator-(const const_iterator &RHS) const {
   return Position - RHS.Position;
 }
 
-reverse_iterator rbegin(StringRef Path) {
+reverse_iterator rbegin(StringRef Path, Style style) {
   reverse_iterator I;
   I.Path = Path;
   I.Position = Path.size();
+  I.S = style;
   return ++I;
 }
 
@@ -324,10 +322,9 @@ reverse_iterator rend(StringRef Path) {
 reverse_iterator &reverse_iterator::operator++() {
   // If we're at the end and the previous char was a '/', return '.' unless
   // we are the root path.
-  size_t root_dir_pos = root_dir_start(Path);
-  if (Position == Path.size() &&
-      Path.size() > root_dir_pos + 1 &&
-      is_separator(Path[Position - 1])) {
+  size_t root_dir_pos = root_dir_start(Path, S);
+  if (Position == Path.size() && Path.size() > root_dir_pos + 1 &&
+      is_separator(Path[Position - 1], S)) {
     --Position;
     Component = ".";
     return *this;
@@ -336,13 +333,12 @@ reverse_iterator &reverse_iterator::operator++() {
   // Skip separators unless it's the root directory.
   size_t end_pos = Position;
 
-  while(end_pos > 0 &&
-        (end_pos - 1) != root_dir_pos &&
-        is_separator(Path[end_pos - 1]))
+  while (end_pos > 0 && (end_pos - 1) != root_dir_pos &&
+         is_separator(Path[end_pos - 1], S))
     --end_pos;
 
   // Find next separator.
-  size_t start_pos = filename_pos(Path.substr(0, end_pos));
+  size_t start_pos = filename_pos(Path.substr(0, end_pos), S);
   Component = Path.slice(start_pos, end_pos);
   Position = start_pos;
   return *this;
@@ -357,21 +353,15 @@ ptrdiff_t reverse_iterator::operator-(const reverse_iterator &RHS) const {
   return Position - RHS.Position;
 }
 
-StringRef root_path(StringRef path) {
-  const_iterator b = begin(path),
-                 pos = b,
-                 e = end(path);
+StringRef root_path(StringRef path, Style style) {
+  const_iterator b = begin(path, style), pos = b, e = end(path);
   if (b != e) {
-    bool has_net = b->size() > 2 && is_separator((*b)[0]) && (*b)[1] == (*b)[0];
-    bool has_drive =
-#ifdef LLVM_ON_WIN32
-      b->endswith(":");
-#else
-      false;
-#endif
+    bool has_net =
+        b->size() > 2 && is_separator((*b)[0], style) && (*b)[1] == (*b)[0];
+    bool has_drive = (real_style(style) == Style::windows) && b->endswith(":");
 
     if (has_net || has_drive) {
-      if ((++pos != e) && is_separator((*pos)[0])) {
+      if ((++pos != e) && is_separator((*pos)[0], style)) {
         // {C:/,//net/}, so get the first two components.
         return path.substr(0, b->size() + pos->size());
       } else {
@@ -381,7 +371,7 @@ StringRef root_path(StringRef path) {
     }
 
     // POSIX style root directory.
-    if (is_separator((*b)[0])) {
+    if (is_separator((*b)[0], style)) {
       return *b;
     }
   }
@@ -389,17 +379,12 @@ StringRef root_path(StringRef path) {
   return StringRef();
 }
 
-StringRef root_name(StringRef path) {
-  const_iterator b = begin(path),
-                 e = end(path);
+StringRef root_name(StringRef path, Style style) {
+  const_iterator b = begin(path, style), e = end(path);
   if (b != e) {
-    bool has_net = b->size() > 2 && is_separator((*b)[0]) && (*b)[1] == (*b)[0];
-    bool has_drive =
-#ifdef LLVM_ON_WIN32
-      b->endswith(":");
-#else
-      false;
-#endif
+    bool has_net =
+        b->size() > 2 && is_separator((*b)[0], style) && (*b)[1] == (*b)[0];
+    bool has_drive = (real_style(style) == Style::windows) && b->endswith(":");
 
     if (has_net || has_drive) {
       // just {C:,//net}, return the first component.
@@ -411,27 +396,21 @@ StringRef root_name(StringRef path) {
   return StringRef();
 }
 
-StringRef root_directory(StringRef path) {
-  const_iterator b = begin(path),
-                 pos = b,
-                 e = end(path);
+StringRef root_directory(StringRef path, Style style) {
+  const_iterator b = begin(path, style), pos = b, e = end(path);
   if (b != e) {
-    bool has_net = b->size() > 2 && is_separator((*b)[0]) && (*b)[1] == (*b)[0];
-    bool has_drive =
-#ifdef LLVM_ON_WIN32
-      b->endswith(":");
-#else
-      false;
-#endif
+    bool has_net =
+        b->size() > 2 && is_separator((*b)[0], style) && (*b)[1] == (*b)[0];
+    bool has_drive = (real_style(style) == Style::windows) && b->endswith(":");
 
     if ((has_net || has_drive) &&
         // {C:,//net}, skip to the next component.
-        (++pos != e) && is_separator((*pos)[0])) {
+        (++pos != e) && is_separator((*pos)[0], style)) {
       return *pos;
     }
 
     // POSIX style root directory.
-    if (!has_net && is_separator((*b)[0])) {
+    if (!has_net && is_separator((*b)[0], style)) {
       return *b;
     }
   }
@@ -440,15 +419,13 @@ StringRef root_directory(StringRef path) {
   return StringRef();
 }
 
-StringRef relative_path(StringRef path) {
-  StringRef root = root_path(path);
+StringRef relative_path(StringRef path, Style style) {
+  StringRef root = root_path(path, style);
   return path.substr(root.size());
 }
 
-void append(SmallVectorImpl<char> &path, const Twine &a,
-                                         const Twine &b,
-                                         const Twine &c,
-                                         const Twine &d) {
+void append(SmallVectorImpl<char> &path, Style style, const Twine &a,
+            const Twine &b, const Twine &c, const Twine &d) {
   SmallString<32> a_storage;
   SmallString<32> b_storage;
   SmallString<32> c_storage;
@@ -461,13 +438,15 @@ void append(SmallVectorImpl<char> &path, const Twine &a,
   if (!d.isTriviallyEmpty()) components.push_back(d.toStringRef(d_storage));
 
   for (auto &component : components) {
-    bool path_has_sep = !path.empty() && is_separator(path[path.size() - 1]);
-    bool component_has_sep = !component.empty() && is_separator(component[0]);
-    bool is_root_name = has_root_name(component);
+    bool path_has_sep =
+        !path.empty() && is_separator(path[path.size() - 1], style);
+    bool component_has_sep =
+        !component.empty() && is_separator(component[0], style);
+    bool is_root_name = has_root_name(component, style);
 
     if (path_has_sep) {
       // Strip separators from beginning of component.
-      size_t loc = component.find_first_not_of(separators);
+      size_t loc = component.find_first_not_of(separators(style));
       StringRef c = component.substr(loc);
 
       // Append it.
@@ -477,41 +456,47 @@ void append(SmallVectorImpl<char> &path, const Twine &a,
 
     if (!component_has_sep && !(path.empty() || is_root_name)) {
       // Add a separator.
-      path.push_back(preferred_separator);
+      path.push_back(preferred_separator(style));
     }
 
     path.append(component.begin(), component.end());
   }
 }
 
-void append(SmallVectorImpl<char> &path,
-            const_iterator begin, const_iterator end) {
+void append(SmallVectorImpl<char> &path, const Twine &a, const Twine &b,
+            const Twine &c, const Twine &d) {
+  append(path, Style::native, a, b, c, d);
+}
+
+void append(SmallVectorImpl<char> &path, const_iterator begin,
+            const_iterator end, Style style) {
   for (; begin != end; ++begin)
-    path::append(path, *begin);
+    path::append(path, style, *begin);
 }
 
-StringRef parent_path(StringRef path) {
-  size_t end_pos = parent_path_end(path);
+StringRef parent_path(StringRef path, Style style) {
+  size_t end_pos = parent_path_end(path, style);
   if (end_pos == StringRef::npos)
     return StringRef();
   else
     return path.substr(0, end_pos);
 }
 
-void remove_filename(SmallVectorImpl<char> &path) {
-  size_t end_pos = parent_path_end(StringRef(path.begin(), path.size()));
+void remove_filename(SmallVectorImpl<char> &path, Style style) {
+  size_t end_pos = parent_path_end(StringRef(path.begin(), path.size()), style);
   if (end_pos != StringRef::npos)
     path.set_size(end_pos);
 }
 
-void replace_extension(SmallVectorImpl<char> &path, const Twine &extension) {
+void replace_extension(SmallVectorImpl<char> &path, const Twine &extension,
+                       Style style) {
   StringRef p(path.begin(), path.size());
   SmallString<32> ext_storage;
   StringRef ext = extension.toStringRef(ext_storage);
 
   // Erase existing extension.
   size_t pos = p.find_last_of('.');
-  if (pos != StringRef::npos && pos >= filename_pos(p))
+  if (pos != StringRef::npos && pos >= filename_pos(p, style))
     path.set_size(pos);
 
   // Append '.' if needed.
@@ -523,8 +508,8 @@ void replace_extension(SmallVectorImpl<char> &path, const Twine &extension) {
 }
 
 void replace_path_prefix(SmallVectorImpl<char> &Path,
-                         const StringRef &OldPrefix,
-                         const StringRef &NewPrefix) {
+                         const StringRef &OldPrefix, const StringRef &NewPrefix,
+                         Style style) {
   if (OldPrefix.empty() && NewPrefix.empty())
     return;
 
@@ -540,61 +525,58 @@ void replace_path_prefix(SmallVectorImpl<char> &Path,
 
   StringRef RelPath = OrigPath.substr(OldPrefix.size());
   SmallString<256> NewPath;
-  path::append(NewPath, NewPrefix);
-  path::append(NewPath, RelPath);
+  path::append(NewPath, style, NewPrefix);
+  path::append(NewPath, style, RelPath);
   Path.swap(NewPath);
 }
 
-void native(const Twine &path, SmallVectorImpl<char> &result) {
+void native(const Twine &path, SmallVectorImpl<char> &result, Style style) {
   assert((!path.isSingleStringRef() ||
           path.getSingleStringRef().data() != result.data()) &&
          "path and result are not allowed to overlap!");
   // Clear result.
   result.clear();
   path.toVector(result);
-  native(result);
+  native(result, style);
 }
 
-void native(SmallVectorImpl<char> &Path) {
+void native(SmallVectorImpl<char> &Path, Style style) {
   if (Path.empty())
     return;
-#ifdef LLVM_ON_WIN32
-  std::replace(Path.begin(), Path.end(), '/', '\\');
-  if (Path[0] == '~' && (Path.size() == 1 || is_separator(Path[1]))) {
-    SmallString<128> PathHome;
-    home_directory(PathHome);
-    PathHome.append(Path.begin() + 1, Path.end());
-    Path = PathHome;
-  }
-#else
-  for (auto PI = Path.begin(), PE = Path.end(); PI < PE; ++PI) {
-    if (*PI == '\\') {
-      auto PN = PI + 1;
-      if (PN < PE && *PN == '\\')
-        ++PI; // increment once, the for loop will move over the escaped slash
-      else
-        *PI = '/';
+  if (real_style(style) == Style::windows) {
+    std::replace(Path.begin(), Path.end(), '/', '\\');
+    if (Path[0] == '~' && (Path.size() == 1 || is_separator(Path[1], style))) {
+      SmallString<128> PathHome;
+      home_directory(PathHome);
+      PathHome.append(Path.begin() + 1, Path.end());
+      Path = PathHome;
+    }
+  } else {
+    for (auto PI = Path.begin(), PE = Path.end(); PI < PE; ++PI) {
+      if (*PI == '\\') {
+        auto PN = PI + 1;
+        if (PN < PE && *PN == '\\')
+          ++PI; // increment once, the for loop will move over the escaped slash
+        else
+          *PI = '/';
+      }
     }
   }
-#endif
 }
 
-std::string convert_to_slash(StringRef path) {
-#ifdef LLVM_ON_WIN32
+std::string convert_to_slash(StringRef path, Style style) {
+  if (real_style(style) != Style::windows)
+    return path;
+
   std::string s = path.str();
   std::replace(s.begin(), s.end(), '\\', '/');
   return s;
-#else
-  return path;
-#endif
 }
 
-StringRef filename(StringRef path) {
-  return *rbegin(path);
-}
+StringRef filename(StringRef path, Style style) { return *rbegin(path, style); }
 
-StringRef stem(StringRef path) {
-  StringRef fname = filename(path);
+StringRef stem(StringRef path, Style style) {
+  StringRef fname = filename(path, style);
   size_t pos = fname.find_last_of('.');
   if (pos == StringRef::npos)
     return fname;
@@ -606,8 +588,8 @@ StringRef stem(StringRef path) {
       return fname.substr(0, pos);
 }
 
-StringRef extension(StringRef path) {
-  StringRef fname = filename(path);
+StringRef extension(StringRef path, Style style) {
+  StringRef fname = filename(path, style);
   size_t pos = fname.find_last_of('.');
   if (pos == StringRef::npos)
     return StringRef();
@@ -619,110 +601,109 @@ StringRef extension(StringRef path) {
       return fname.substr(pos);
 }
 
-bool is_separator(char value) {
-  switch(value) {
-#ifdef LLVM_ON_WIN32
-    case '\\': // fall through
-#endif
-    case '/': return true;
-    default: return false;
-  }
+bool is_separator(char value, Style style) {
+  if (value == '/')
+    return true;
+  if (real_style(style) == Style::windows)
+    return value == '\\';
+  return false;
 }
 
-static const char preferred_separator_string[] = { preferred_separator, '\0' };
-
-StringRef get_separator() {
-  return preferred_separator_string;
+StringRef get_separator(Style style) {
+  if (real_style(style) == Style::windows)
+    return "\\";
+  return "/";
 }
 
-bool has_root_name(const Twine &path) {
+bool has_root_name(const Twine &path, Style style) {
   SmallString<128> path_storage;
   StringRef p = path.toStringRef(path_storage);
 
-  return !root_name(p).empty();
+  return !root_name(p, style).empty();
 }
 
-bool has_root_directory(const Twine &path) {
+bool has_root_directory(const Twine &path, Style style) {
   SmallString<128> path_storage;
   StringRef p = path.toStringRef(path_storage);
 
-  return !root_directory(p).empty();
+  return !root_directory(p, style).empty();
 }
 
-bool has_root_path(const Twine &path) {
+bool has_root_path(const Twine &path, Style style) {
   SmallString<128> path_storage;
   StringRef p = path.toStringRef(path_storage);
 
-  return !root_path(p).empty();
+  return !root_path(p, style).empty();
 }
 
-bool has_relative_path(const Twine &path) {
+bool has_relative_path(const Twine &path, Style style) {
   SmallString<128> path_storage;
   StringRef p = path.toStringRef(path_storage);
 
-  return !relative_path(p).empty();
+  return !relative_path(p, style).empty();
 }
 
-bool has_filename(const Twine &path) {
+bool has_filename(const Twine &path, Style style) {
   SmallString<128> path_storage;
   StringRef p = path.toStringRef(path_storage);
 
-  return !filename(p).empty();
+  return !filename(p, style).empty();
 }
 
-bool has_parent_path(const Twine &path) {
+bool has_parent_path(const Twine &path, Style style) {
   SmallString<128> path_storage;
   StringRef p = path.toStringRef(path_storage);
 
-  return !parent_path(p).empty();
+  return !parent_path(p, style).empty();
 }
 
-bool has_stem(const Twine &path) {
+bool has_stem(const Twine &path, Style style) {
   SmallString<128> path_storage;
   StringRef p = path.toStringRef(path_storage);
 
-  return !stem(p).empty();
+  return !stem(p, style).empty();
 }
 
-bool has_extension(const Twine &path) {
+bool has_extension(const Twine &path, Style style) {
   SmallString<128> path_storage;
   StringRef p = path.toStringRef(path_storage);
 
-  return !extension(p).empty();
+  return !extension(p, style).empty();
 }
 
-bool is_absolute(const Twine &path) {
+bool is_absolute(const Twine &path, Style style) {
   SmallString<128> path_storage;
   StringRef p = path.toStringRef(path_storage);
 
-  bool rootDir = has_root_directory(p),
-#ifdef LLVM_ON_WIN32
-       rootName = has_root_name(p);
-#else
-       rootName = true;
-#endif
+  bool rootDir = has_root_directory(p, style);
+  bool rootName =
+      (real_style(style) != Style::windows) || has_root_name(p, style);
 
   return rootDir && rootName;
 }
 
-bool is_relative(const Twine &path) { return !is_absolute(path); }
+bool is_relative(const Twine &path, Style style) {
+  return !is_absolute(path, style);
+}
 
-StringRef remove_leading_dotslash(StringRef Path) {
+StringRef remove_leading_dotslash(StringRef Path, Style style) {
   // Remove leading "./" (or ".//" or "././" etc.)
-  while (Path.size() > 2 && Path[0] == '.' && is_separator(Path[1])) {
+  while (Path.size() > 2 && Path[0] == '.' && is_separator(Path[1], style)) {
     Path = Path.substr(2);
-    while (Path.size() > 0 && is_separator(Path[0]))
+    while (Path.size() > 0 && is_separator(Path[0], style))
       Path = Path.substr(1);
   }
   return Path;
 }
 
-static SmallString<256> remove_dots(StringRef path, bool remove_dot_dot) {
+static SmallString<256> remove_dots(StringRef path, bool remove_dot_dot,
+                                    Style style) {
   SmallVector<StringRef, 16> components;
 
   // Skip the root path, then look for traversal in the components.
-  StringRef rel = path::relative_path(path);
-  for (StringRef C : llvm::make_range(path::begin(rel), path::end(rel))) {
+  StringRef rel = path::relative_path(path, style);
+  for (StringRef C :
+       llvm::make_range(path::begin(rel, style), path::end(rel))) {
     if (C == ".")
       continue;
     // Leading ".." will remain in the path unless it's at the root.
@@ -731,22 +712,23 @@ static SmallString<256> remove_dots(StringRef path, bool remove_dot_dot) {
         components.pop_back();
         continue;
       }
-      if (path::is_absolute(path))
+      if (path::is_absolute(path, style))
         continue;
     }
     components.push_back(C);
   }
 
-  SmallString<256> buffer = path::root_path(path);
+  SmallString<256> buffer = path::root_path(path, style);
   for (StringRef C : components)
-    path::append(buffer, C);
+    path::append(buffer, style, C);
   return buffer;
 }
 
-bool remove_dots(SmallVectorImpl<char> &path, bool remove_dot_dot) {
+bool remove_dots(SmallVectorImpl<char> &path, bool remove_dot_dot,
+                 Style style) {
   StringRef p(path.data(), path.size());
 
-  SmallString<256> result = remove_dots(p, remove_dot_dot);
+  SmallString<256> result = remove_dots(p, remove_dot_dot, style);
   if (result == path)
     return false;
 
@@ -784,7 +766,7 @@ createTemporaryFile(const Twine &Model, int &ResultFD,
                     llvm::SmallVectorImpl<char> &ResultPath, FSEntity Type) {
   SmallString<128> Storage;
   StringRef P = Model.toNullTerminatedStringRef(Storage);
-  assert(P.find_first_of(separators) == StringRef::npos &&
+  assert(P.find_first_of(separators(Style::native)) == StringRef::npos &&
          "Model must be a simple filename.");
   // Use P.begin() so that createUniqueEntity doesn't need to recreate Storage.
   return createUniqueEntity(P.begin(), ResultFD, ResultPath,
@@ -826,12 +808,9 @@ static std::error_code make_absolute(const Twine &current_directory,
                                      bool use_current_directory) {
   StringRef p(path.data(), path.size());
 
-  bool rootDirectory = path::has_root_directory(p),
-#ifdef LLVM_ON_WIN32
-       rootName = path::has_root_name(p);
-#else
-       rootName = true;
-#endif
+  bool rootDirectory = path::has_root_directory(p);
+  bool rootName =
+      (real_style(Style::native) != Style::windows) || path::has_root_name(p);
 
   // Already absolute.
   if (rootName && rootDirectory)