Introduce an API for LLDB to compute the default module cache path

[aprantl]

Summary

LLDB creates Clang modules and had an incomplete copy of the clang Driver code that compute the -fmodule-cache-path. This patch makes the clang driver code accessible to LLDB.

[bruno]

LGTM

cfe/trunk/include/clang/Driver/Driver.h

public:
   /// Parse digits from a string \p Str and fulfill \p Digits with
   /// the parsed numbers. This method assumes that the max number of
   /// digits to look for is equal to Digits.size().
   ///
   /// \return True if the entire string was parsed and there are
   /// no extra characters remaining at the end.
   static bool GetReleaseVersion(StringRef Str,
                                 MutableArrayRef<unsigned> Digits);
+  /// Compute the default -fmodule-cache-path.
+  static void getDefaultModuleCachePath(SmallVectorImpl<char> &Result);
 };
 
 /// \return True if the last defined optimization level is -Ofast.
 /// And False otherwise.
 bool isOptimizationLevelFast(const llvm::opt::ArgList &Args);
 
 } // end namespace driver
 } // end namespace clang
 
 #endif

cfe/trunk/lib/Driver/ToolChains/Clang.cpp

static void RenderBuiltinOptions(const ToolChain &TC, const llvm::Triple &T,
 
   // le32-specific flags:
   //  -fno-math-builtin: clang should not convert math builtins to intrinsics
   //                     by default.
   if (TC.getArch() == llvm::Triple::le32)
     CmdArgs.push_back("-fno-math-builtin");
 }
 
+void Driver::getDefaultModuleCachePath(SmallVectorImpl<char> &Result) {
+  llvm::sys::path::system_temp_directory(/*erasedOnReboot=*/false, Result);
+  llvm::sys::path::append(Result, "org.llvm.clang.");
+  appendUserToPath(Result);
+  llvm::sys::path::append(Result, "ModuleCache");
+}
+
 static void RenderModulesOptions(Compilation &C, const Driver &D,
                                  const ArgList &Args, const InputInfo &Input,
                                  const InputInfo &Output,
                                  ArgStringList &CmdArgs, bool &HaveModules) {
   // -fmodules enables the use of precompiled modules (off by default).
   // Users can pass -fno-cxx-modules to turn off modules support for
   // C++/Objective-C++ programs.
   bool HaveClangModules = false;
if (!Args.hasFlag(options::OPT_fimplicit_modules,
     if (C.isForDiagnostics()) {
       // When generating crash reports, we want to emit the modules along with
       // the reproduction sources, so we ignore any provided module path.
       Path = Output.getFilename();
       llvm::sys::path::replace_extension(Path, ".cache");
       llvm::sys::path::append(Path, "modules");
     } else if (Path.empty()) {
       // No module path was provided: use the default.
-      llvm::sys::path::system_temp_directory(/*erasedOnReboot=*/false, Path);
-      llvm::sys::path::append(Path, "org.llvm.clang.");
-      appendUserToPath(Path);
-      llvm::sys::path::append(Path, "ModuleCache");
+      Driver::getDefaultModuleCachePath(Path);
     }
 
     const char Arg[] = "-fmodules-cache-path=";
     Path.insert(Path.begin(), Arg, Arg + strlen(Arg));
     CmdArgs.push_back(Args.MakeArgString(Path));
   }
 
   if (HaveModules) {