1 files changed, 25 insertions, 6 deletions
diff --git a/include/llvm/Option/Arg.h b/include/llvm/Option/Arg.h
index d0086bb6d611..22e2bcf06a6e 100644
--- a/include/llvm/Option/Arg.h
+++ b/include/llvm/Option/Arg.h
@@ -1,9 +1,8 @@
 //===- Arg.h - Parsed Argument Classes --------------------------*- C++ -*-===//
 //
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 ///
@@ -59,6 +58,11 @@ private:
   /// The argument values, as C strings.
   SmallVector<const char *, 2> Values;
 
+  /// If this arg was created through an alias, this is the original alias arg.
+  /// For example, *this might be "-finput-charset=utf-8" and Alias might
+  /// point to an arg representing "/source-charset:utf-8".
+  std::unique_ptr<Arg> Alias;
+
 public:
   Arg(const Option Opt, StringRef Spelling, unsigned Index,
       const Arg *BaseArg = nullptr);
@@ -71,7 +75,15 @@ public:
   ~Arg();
 
   const Option &getOption() const { return Opt; }
+
+  /// Returns the used prefix and name of the option:
+  /// For `--foo=bar`, returns `--foo=`.
+  /// This is often the wrong function to call:
+  /// * Use `getValue()` to get `bar`.
+  /// * Use `getAsString()` to get a string suitable for printing an Arg in
+  ///   a diagnostic.
   StringRef getSpelling() const { return Spelling; }
+
   unsigned getIndex() const { return Index; }
 
   /// Return the base argument which generated this arg.
@@ -83,6 +95,11 @@ public:
   }
   void setBaseArg(const Arg *BaseArg) { this->BaseArg = BaseArg; }
 
+  /// Args are converted to their unaliased form.  For args that originally
+  /// came from an alias, this returns the alias the arg was produced from.
+  const Arg* getAlias() const { return Alias.get(); }
+  void setAlias(std::unique_ptr<Arg> Alias) { this->Alias = std::move(Alias); }
+
   bool getOwnsValues() const { return OwnsValues; }
   void setOwnsValues(bool Value) const { OwnsValues = Value; }
 
@@ -120,8 +137,10 @@ public:
   void print(raw_ostream &O) const;
   void dump() const;
 
-  /// Return a formatted version of the argument and
-  /// its values, for debugging and diagnostics.
+  /// Return a formatted version of the argument and its values, for
+  /// diagnostics. Since this is for diagnostics, if this Arg was produced
+  /// through an alias, this returns the string representation of the alias
+  /// that the user wrote.
   std::string getAsString(const ArgList &Args) const;
 };