Revert " [clang] Refactor to remove clangDriver dependency from clangFrontend and flangFrontend (#165277)" (#169397)

This reverts commit 3773bbe and relands the last revert attempt 40334b8.
3773bbe broke the build for the build configuration described in here:
#165277 (comment)

Author: naveen-seth

clang-tools-extra/clangd/CompileCommands.cpp

@@ -132,7 +132,8 @@ std::optional<std::string> detectSysroot() {
 
 std::string detectStandardResourceDir() {
   static int StaticForMainAddr; // Just an address in this process.
-  return GetResourcesPath("clangd", (void *)&StaticForMainAddr);
+  return CompilerInvocation::GetResourcesPath("clangd",
+                                              (void *)&StaticForMainAddr);
 }
 
 // The path passed to argv[0] is important:

clang-tools-extra/clangd/Compiler.cpp

@@ -9,7 +9,6 @@
 #include "Compiler.h"
 #include "support/Logger.h"
 #include "clang/Basic/TargetInfo.h"
-#include "clang/Driver/CreateInvocationFromArgs.h"
 #include "clang/Frontend/CompilerInvocation.h"
 #include "clang/Lex/PreprocessorOptions.h"
 #include "clang/Serialization/PCHContainerOperations.h"

clang/docs/ReleaseNotes.rst

@@ -84,8 +84,6 @@ Potentially Breaking Changes
 - Downstream projects that previously linked only against ``clangDriver`` may
   now (also) need to link against the new ``clangOptions`` library, since
   options-related code has been moved out of the Driver into a separate library.
-- The ``clangFrontend`` library no longer depends on ``clangDriver``, which may
-  break downstream projects that relied on this transitive dependency.
 
 C/C++ Language Potentially Breaking Changes
 -------------------------------------------

clang/include/clang/Driver/CommonArgs.h

@@ -291,6 +291,16 @@ void handleVectorizeLoopsArgs(const llvm::opt::ArgList &Args,
 void handleVectorizeSLPArgs(const llvm::opt::ArgList &Args,
                             llvm::opt::ArgStringList &CmdArgs);
 
+// Parse -mprefer-vector-width=. Return the Value string if well-formed.
+// Otherwise, return an empty string and issue a diagnosic message if needed.
+StringRef parseMPreferVectorWidthOption(clang::DiagnosticsEngine &Diags,
+                                        const llvm::opt::ArgList &Args);
+
+// Parse -mrecip. Return the Value string if well-formed.
+// Otherwise, return an empty string and issue a diagnosic message if needed.
+StringRef parseMRecipOption(clang::DiagnosticsEngine &Diags,
+                            const llvm::opt::ArgList &Args);
+
 // Convert ComplexRangeKind to a string that can be passed as a frontend option.
 std::string complexRangeKindToStr(LangOptions::ComplexRangeKind Range);
 

clang/include/clang/Driver/CreateASTUnitFromArgs.h

@@ -406,6 +406,10 @@ class Driver {
                               SmallString<128> &CrashDiagDir);
 
 public:
+  /// Takes the path to a binary that's either in bin/ or lib/ and returns
+  /// the path to clang's resource directory.
+  static std::string GetResourcesPath(StringRef BinaryPath);
+
   Driver(StringRef ClangExecutable, StringRef TargetTriple,
          DiagnosticsEngine &Diags, std::string Title = "clang LLVM compiler",
          IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS = nullptr);