[Support/Path] sys::path::replace_path_prefix fix and simplifications

Added unit tests for 2 scenarios that were failing.
Made replace_path_prefix back to 3 parameters instead of 5, simplifying the implementation. The other 2 were always used with the default value.

This commit is intended to be the first of 3:
1) simplify/fix replace_path_prefix.
2) use it in the context of -fdebug-prefix-map and -fmacro-prefix-map (see D76869).
3) Make Windows version of replace_path_prefix insensitive to both case and separators (slash vs backslash).

Differential Revision: https://reviews.llvm.org/D77223

include/llvm/Support/Path.h

@@ -153,32 +153,23 @@ void replace_extension(SmallVectorImpl<char> &path, const Twine &extension,
 /// @code
 ///   /foo, /old, /new => /foo
 ///   /old, /old, /new => /new
-///   /old, /old/, /new, false => /old
-///   /old, /old/, /new, true => /new
+///   /old, /old/, /new => /old
 ///   /old/foo, /old, /new => /new/foo
 ///   /old/foo, /old/, /new => /new/foo
 ///   /old/foo, /old/, /new/ => /new/foo
 ///   /oldfoo, /old, /new => /oldfoo
 ///   /foo, <empty>, /new => /new/foo
 ///   /foo, <empty>, new => new/foo
-///   /old/foo, /old, <empty>, false => /foo
-///   /old/foo, /old, <empty>, true => foo
+///   /old/foo, /old, <empty> => /foo
 /// @endcode
 ///
 /// @param Path If \a Path starts with \a OldPrefix modify to instead
 ///        start with \a NewPrefix.
-/// @param OldPrefix The path prefix to strip from \a Path. Any trailing
-///        path separator is ignored if strict is true.
+/// @param OldPrefix The path prefix to strip from \a Path.
 /// @param NewPrefix The path prefix to replace \a NewPrefix with.
-/// @param style The path separator style
-/// @param strict If strict is true, a directory separator following
-///        \a OldPrefix will also be stripped. Otherwise, directory
-///        separators will only be matched and stripped when present
-///        in \a OldPrefix.
 /// @result true if \a Path begins with OldPrefix
-bool replace_path_prefix(SmallVectorImpl<char> &Path,
-                         const StringRef &OldPrefix, const StringRef &NewPrefix,
-                         Style style = Style::native, bool strict = false);
+bool replace_path_prefix(SmallVectorImpl<char> &Path, StringRef OldPrefix,
+                         StringRef NewPrefix);
 
 /// Append to path.
 ///

lib/Support/Path.cpp

@@ -496,49 +496,25 @@ void replace_extension(SmallVectorImpl<char> &path, const Twine &extension,
   path.append(ext.begin(), ext.end());
 }
 
-bool replace_path_prefix(SmallVectorImpl<char> &Path,
-                         const StringRef &OldPrefix, const StringRef &NewPrefix,
-                         Style style, bool strict) {
+bool replace_path_prefix(SmallVectorImpl<char> &Path, StringRef OldPrefix,
+                         StringRef NewPrefix) {
   if (OldPrefix.empty() && NewPrefix.empty())
     return false;
 
   StringRef OrigPath(Path.begin(), Path.size());
-  StringRef OldPrefixDir;
-
-  if (!strict && OldPrefix.size() > OrigPath.size())
+  if (!OrigPath.startswith(OldPrefix))
     return false;
 
-  // Ensure OldPrefixDir does not have a trailing separator.
-  if (!OldPrefix.empty() && is_separator(OldPrefix.back()))
-    OldPrefixDir = parent_path(OldPrefix, style);
-  else
-    OldPrefixDir = OldPrefix;
-
-  if (!OrigPath.startswith(OldPrefixDir))
-    return false;
-
-  if (OrigPath.size() > OldPrefixDir.size())
-    if (!is_separator(OrigPath[OldPrefixDir.size()], style) && strict)
-      return false;
-
   // If prefixes have the same size we can simply copy the new one over.
-  if (OldPrefixDir.size() == NewPrefix.size() && !strict) {
+  if (OldPrefix.size() == NewPrefix.size()) {
     llvm::copy(NewPrefix, Path.begin());
     return true;
   }
 
-  StringRef RelPath = OrigPath.substr(OldPrefixDir.size());
+  StringRef RelPath = OrigPath.substr(OldPrefix.size());
   SmallString<256> NewPath;
-  path::append(NewPath, style, NewPrefix);
-  if (!RelPath.empty()) {
-    if (!is_separator(RelPath[0], style) || !strict)
-      path::append(NewPath, style, RelPath);
-    else
-      path::append(NewPath, style, relative_path(RelPath, style));
-  }
-
+  (Twine(NewPrefix) + RelPath).toVector(NewPath);
   Path.swap(NewPath);
-
   return true;
 }
 

unittests/Support/Path.cpp

@@ -1254,21 +1254,14 @@ TEST(Support, ReplacePathPrefix) {
   path::replace_path_prefix(Path, OldPrefix, EmptyPrefix);
   EXPECT_EQ(Path, "/foo");
   Path = Path2;
-  path::replace_path_prefix(Path, OldPrefix, EmptyPrefix, path::Style::native,
-                            true);
+  path::replace_path_prefix(Path, OldPrefixSep, EmptyPrefix);
   EXPECT_EQ(Path, "foo");
   Path = Path3;
-  path::replace_path_prefix(Path, OldPrefix, NewPrefix, path::Style::native,
-                            false);
+  path::replace_path_prefix(Path, OldPrefix, NewPrefix);
   EXPECT_EQ(Path, "/newnew/foo");
   Path = Path3;
-  path::replace_path_prefix(Path, OldPrefix, NewPrefix, path::Style::native,
-                            true);
-  EXPECT_EQ(Path, "/oldnew/foo");
-  Path = Path3;
-  path::replace_path_prefix(Path, OldPrefixSep, NewPrefix, path::Style::native,
-                            true);
-  EXPECT_EQ(Path, "/oldnew/foo");
+  path::replace_path_prefix(Path, OldPrefix, NewPrefix2);
+  EXPECT_EQ(Path, "/longernewnew/foo");
   Path = Path1;
   path::replace_path_prefix(Path, EmptyPrefix, NewPrefix);
   EXPECT_EQ(Path, "/new/foo");
@@ -1279,13 +1272,8 @@ TEST(Support, ReplacePathPrefix) {
   path::replace_path_prefix(Path, OldPrefix, NewPrefix);
   EXPECT_EQ(Path, "/new/");
   Path = OldPrefix;
-  path::replace_path_prefix(Path, OldPrefixSep, NewPrefix, path::Style::native,
-                            false);
+  path::replace_path_prefix(Path, OldPrefixSep, NewPrefix);
   EXPECT_EQ(Path, "/old");
-  Path = OldPrefix;
-  path::replace_path_prefix(Path, OldPrefixSep, NewPrefix, path::Style::native,
-                            true);
-  EXPECT_EQ(Path, "/new");
 }
 
 TEST_F(FileSystemTest, OpenFileForRead) {