Revert "[Clang] Take libstdc++ into account during GCC detection" (#154368)

Reverts #145056

Author: frederik-h

clang/docs/ReleaseNotes.rst

@@ -37,22 +37,6 @@ latest release, please see the `Clang Web Site <https://clang.llvm.org>`_ or the
 Potentially Breaking Changes
 ============================
 
-- Clang will now emit a warning if the auto-detected GCC installation
- directory (i.e. the one with the largest version number) does not
- contain libstdc++ include directories although a "complete" GCC
- installation directory containing the include directories is
- available. It is planned to change the auto-detection to prefer the
- "complete" directory in the future. The warning will disappear if
- the libstdc++ include directories are either installed or removed
- for all GCC installation directories considered by the
- auto-detection; see the output of ``clang -v`` for a list of those
- directories. If the GCC installations cannot be modified and
- maintaining the current choice of the auto-detection is desired, the
- GCC installation directory can be selected explicitly using the
- ``--gcc-install-dir`` command line argument. This will silence the
- warning. It can also be disabled using the
- ``-Wno-gcc-install-dir-libstdcxx`` command line flag.
-
 C/C++ Language Potentially Breaking Changes
 -------------------------------------------
 

clang/include/clang/Basic/DiagnosticDriverKinds.td

@@ -885,9 +885,4 @@ def warn_drv_openacc_without_cir
  : Warning<"OpenACC directives will result in no runtime behavior; use "
  "-fclangir to enable runtime effect">,
  InGroup<SourceUsesOpenACC>;
-
-def warn_drv_gcc_install_dir_libstdcxx : Warning<
- "future releases of the clang compiler will prefer GCC installations "
- "containing libstdc++ include directories; '%0' would be chosen over '%1'">,
- InGroup<DiagGroup<"gcc-install-dir-libstdcxx">>;
 }

clang/include/clang/Driver/ToolChain.h

@@ -224,6 +224,9 @@ class ToolChain {
  static void addSystemFrameworkInclude(const llvm::opt::ArgList &DriverArgs,
  llvm::opt::ArgStringList &CC1Args,
  const Twine &Path);
+ static void addSystemInclude(const llvm::opt::ArgList &DriverArgs,
+ llvm::opt::ArgStringList &CC1Args,
+ const Twine &Path);
  static void addExternCSystemInclude(const llvm::opt::ArgList &DriverArgs,
  llvm::opt::ArgStringList &CC1Args,
  const Twine &Path);
@@ -243,9 +246,6 @@ class ToolChain {
  ///@}
 
 public:
- static void addSystemInclude(const llvm::opt::ArgList &DriverArgs,
- llvm::opt::ArgStringList &CC1Args,
- const Twine &Path);
  virtual ~ToolChain();
 
  // Accessors

clang/lib/Driver/ToolChain.cpp

@@ -1409,6 +1409,13 @@ void ToolChain::addSystemFrameworkInclude(const llvm::opt::ArgList &DriverArgs,
  CC1Args.push_back(DriverArgs.MakeArgString(Path));
 }
 
+/// Utility function to add a system include directory to CC1 arguments.
+void ToolChain::addSystemInclude(const ArgList &DriverArgs,
+ ArgStringList &CC1Args, const Twine &Path) {
+ CC1Args.push_back("-internal-isystem");
+ CC1Args.push_back(DriverArgs.MakeArgString(Path));
+}
+
 /// Utility function to add a system include directory with extern "C"
 /// semantics to CC1 arguments.
 ///
@@ -1431,14 +1438,6 @@ void ToolChain::addExternCSystemIncludeIfExists(const ArgList &DriverArgs,
  addExternCSystemInclude(DriverArgs, CC1Args, Path);
 }
 
-/// Utility function to add a system include directory to CC1 arguments.
-/*static*/ void ToolChain::addSystemInclude(const ArgList &DriverArgs,
- ArgStringList &CC1Args,
- const Twine &Path) {
- CC1Args.push_back("-internal-isystem");
- CC1Args.push_back(DriverArgs.MakeArgString(Path));
-}
-
 /// Utility function to add a list of system framework directories to CC1.
 void ToolChain::addSystemFrameworkIncludes(const ArgList &DriverArgs,
  ArgStringList &CC1Args,