Enable configuration files in clang

Clang is inherently a cross compiler and can generate code for any target
enabled during build. It however requires to specify many parameters in the
invocation, which could be hardcoded during configuration process in the
case of single-target compiler. The purpose of configuration files is to
make specifying clang arguments easier.

A configuration file is a collection of driver options, which are inserted
into command line before other options specified in the clang invocation.
It groups related options together and allows specifying them in simpler,
more flexible and less error prone way than just listing the options
somewhere in build scripts. Configuration file may be thought as a "macro"
that names an option set and is expanded when the driver is called.

Use of configuration files is described in `UserManual.rst`.

Differential Revision: https://reviews.llvm.org/D24933


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@321621 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 260 insertions, 4 deletions

diff --git a/lib/Driver/Driver.cpp b/lib/Driver/Driver.cpp
index 9ae33b80f8..4d6cc68295 100644
--- a/lib/Driver/Driver.cpp
+++ b/lib/Driver/Driver.cpp
@@ -62,6 +62,7 @@
 #include "llvm/Option/OptSpecifier.h"
 #include "llvm/Option/OptTable.h"
 #include "llvm/Option/Option.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
@@ -70,6 +71,7 @@
 #include "llvm/Support/Program.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/StringSaver.h"
 #include <map>
 #include <memory>
 #include <utility>
@@ -92,7 +94,8 @@ Driver::Driver(StringRef ClangExecutable, StringRef DefaultTargetTriple,
       CCPrintHeadersFilename(nullptr), CCLogDiagnosticsFilename(nullptr),
       CCCPrintBindings(false), CCPrintHeaders(false), CCLogDiagnostics(false),
       CCGenDiagnostics(false), DefaultTargetTriple(DefaultTargetTriple),
-      CCCGenericGCCName(""), CheckInputsExist(true), CCCUsePCH(true),
+      CCCGenericGCCName(""), Saver(Alloc),
+      CheckInputsExist(true), CCCUsePCH(true),
       GenReproducer(false), SuppressMissingInputWarning(false) {
 
   // Provide a sane fallback if no VFS is specified.
@@ -103,6 +106,13 @@ Driver::Driver(StringRef ClangExecutable, StringRef DefaultTargetTriple,
   Dir = llvm::sys::path::parent_path(ClangExecutable);
   InstalledDir = Dir; // Provide a sensible default installed dir.
 
+#if defined(CLANG_CONFIG_FILE_SYSTEM_DIR)
+  SystemConfigDir = CLANG_CONFIG_FILE_SYSTEM_DIR;
+#endif
+#if defined(CLANG_CONFIG_FILE_USER_DIR)
+  UserConfigDir = CLANG_CONFIG_FILE_USER_DIR;
+#endif
+
   // Compute the path to the resource directory.
   StringRef ClangResourceDir(CLANG_RESOURCE_DIR);
   SmallString<128> P(Dir);
@@ -600,6 +610,216 @@ void Driver::CreateOffloadingDeviceToolChains(Compilation &C,
   //
 }
 
+/// Looks the given directories for the specified file.
+///
+/// \param[out] FilePath File path, if the file was found.
+/// \param[in]  Dirs Directories used for the search.
+/// \param[in]  FileName Name of the file to search for.
+/// \return True if file was found.
+///
+/// Looks for file specified by FileName sequentially in directories specified
+/// by Dirs.
+///
+static bool searchForFile(SmallVectorImpl<char> &FilePath,
+                          ArrayRef<std::string> Dirs,
+                          StringRef FileName) {
+  SmallString<128> WPath;
+  for (const StringRef &Dir : Dirs) {
+    if (Dir.empty())
+      continue;
+    WPath.clear();
+    llvm::sys::path::append(WPath, Dir, FileName);
+    llvm::sys::path::native(WPath);
+    if (llvm::sys::fs::is_regular_file(WPath)) {
+      FilePath = std::move(WPath);
+      return true;
+    }
+  }
+  return false;
+}
+
+bool Driver::readConfigFile(StringRef FileName) {
+  // Try reading the given file.
+  SmallVector<const char *, 32> NewCfgArgs;
+  if (!llvm::cl::readConfigFile(FileName, Saver, NewCfgArgs)) {
+    Diag(diag::err_drv_cannot_read_config_file) << FileName;
+    return true;
+  }
+
+  // Read options from config file.
+  llvm::SmallString<128> CfgFileName(FileName);
+  llvm::sys::path::native(CfgFileName);
+  ConfigFile = CfgFileName.str();
+  bool ContainErrors;
+  CfgOptions = llvm::make_unique<InputArgList>(
+      ParseArgStrings(NewCfgArgs, ContainErrors));
+  if (ContainErrors) {
+    CfgOptions.reset();
+    return true;
+  }
+
+  if (CfgOptions->hasArg(options::OPT_config)) {
+    CfgOptions.reset();
+    Diag(diag::err_drv_nested_config_file);
+    return true;
+  }
+
+  // Claim all arguments that come from a configuration file so that the driver
+  // does not warn on any that is unused.
+  for (Arg *A : *CfgOptions)
+    A->claim();
+  return false;
+}
+
+bool Driver::loadConfigFile() {
+  std::string CfgFileName;
+  bool FileSpecifiedExplicitly = false;
+
+  // Process options that change search path for config files.
+  if (CLOptions) {
+    if (CLOptions->hasArg(options::OPT_config_system_dir_EQ)) {
+      SmallString<128> CfgDir;
+      CfgDir.append(
+          CLOptions->getLastArgValue(options::OPT_config_system_dir_EQ));
+      if (!CfgDir.empty()) {
+        if (std::error_code EC = llvm::sys::fs::make_absolute(CfgDir))
+          SystemConfigDir.clear();
+        else
+          SystemConfigDir = std::string(CfgDir.begin(), CfgDir.end());
+      }
+    }
+    if (CLOptions->hasArg(options::OPT_config_user_dir_EQ)) {
+      SmallString<128> CfgDir;
+      CfgDir.append(
+          CLOptions->getLastArgValue(options::OPT_config_user_dir_EQ));
+      if (!CfgDir.empty()) {
+        if (std::error_code EC = llvm::sys::fs::make_absolute(CfgDir))
+          UserConfigDir.clear();
+        else
+          UserConfigDir = std::string(CfgDir.begin(), CfgDir.end());
+      }
+    }
+  }
+
+  // First try to find config file specified in command line.
+  if (CLOptions) {
+    std::vector<std::string> ConfigFiles =
+        CLOptions->getAllArgValues(options::OPT_config);
+    if (ConfigFiles.size() > 1) {
+      Diag(diag::err_drv_duplicate_config);
+      return true;
+    }
+
+    if (!ConfigFiles.empty()) {
+      CfgFileName = ConfigFiles.front();
+      assert(!CfgFileName.empty());
+
+      // If argument contains directory separator, treat it as a path to
+      // configuration file.
+      if (llvm::sys::path::has_parent_path(CfgFileName)) {
+        SmallString<128> CfgFilePath;
+        if (llvm::sys::path::is_relative(CfgFileName))
+          llvm::sys::fs::current_path(CfgFilePath);
+        llvm::sys::path::append(CfgFilePath, CfgFileName);
+        if (!llvm::sys::fs::is_regular_file(CfgFilePath)) {
+          Diag(diag::err_drv_config_file_not_exist) << CfgFilePath;
+          return true;
+        }
+        return readConfigFile(CfgFilePath);
+      }
+
+      FileSpecifiedExplicitly = true;
+    }
+  }
+
+  // If config file is not specified explicitly, try to deduce configuration
+  // from executable name. For instance, an executable 'armv7l-clang' will
+  // search for config file 'armv7l-clang.cfg'.
+  if (CfgFileName.empty() && !ClangNameParts.TargetPrefix.empty())
+    CfgFileName = ClangNameParts.TargetPrefix + '-' + ClangNameParts.ModeSuffix;
+
+  if (CfgFileName.empty())
+    return false;
+
+  // Determine architecture part of the file name, if it is present.
+  StringRef CfgFileArch = CfgFileName;
+  size_t ArchPrefixLen = CfgFileArch.find('-');
+  if (ArchPrefixLen == StringRef::npos)
+    ArchPrefixLen = CfgFileArch.size();
+  llvm::Triple CfgTriple;
+  CfgFileArch = CfgFileArch.take_front(ArchPrefixLen);
+  CfgTriple = llvm::Triple(llvm::Triple::normalize(CfgFileArch));
+  if (CfgTriple.getArch() == llvm::Triple::ArchType::UnknownArch)
+    ArchPrefixLen = 0;
+
+  if (!StringRef(CfgFileName).endswith(".cfg"))
+    CfgFileName += ".cfg";
+
+  // If config file starts with architecture name and command line options
+  // redefine architecture (with options like -m32 -LE etc), try finding new
+  // config file with that architecture.
+  SmallString<128> FixedConfigFile;
+  size_t FixedArchPrefixLen = 0;
+  if (ArchPrefixLen) {
+    // Get architecture name from config file name like 'i386.cfg' or
+    // 'armv7l-clang.cfg'.
+    // Check if command line options changes effective triple.
+    llvm::Triple EffectiveTriple = computeTargetTriple(*this,
+                                             CfgTriple.getTriple(), *CLOptions);
+    if (CfgTriple.getArch() != EffectiveTriple.getArch()) {
+      FixedConfigFile = EffectiveTriple.getArchName();
+      FixedArchPrefixLen = FixedConfigFile.size();
+      // Append the rest of original file name so that file name transforms
+      // like: i386-clang.cfg -> x86_64-clang.cfg.
+      if (ArchPrefixLen < CfgFileName.size())
+        FixedConfigFile += CfgFileName.substr(ArchPrefixLen);
+    }
+  }
+
+  // Prepare list of directories where config file is searched for.
+  SmallVector<std::string, 3> CfgFileSearchDirs;
+  CfgFileSearchDirs.push_back(UserConfigDir);
+  CfgFileSearchDirs.push_back(SystemConfigDir);
+  CfgFileSearchDirs.push_back(Dir);
+
+  // Try to find config file. First try file with corrected architecture.
+  llvm::SmallString<128> CfgFilePath;
+  if (!FixedConfigFile.empty()) {
+    if (searchForFile(CfgFilePath, CfgFileSearchDirs, FixedConfigFile))
+      return readConfigFile(CfgFilePath);
+    // If 'x86_64-clang.cfg' was not found, try 'x86_64.cfg'.
+    FixedConfigFile.resize(FixedArchPrefixLen);
+    FixedConfigFile.append(".cfg");
+    if (searchForFile(CfgFilePath, CfgFileSearchDirs, FixedConfigFile))
+      return readConfigFile(CfgFilePath);
+  }
+
+  // Then try original file name.
+  if (searchForFile(CfgFilePath, CfgFileSearchDirs, CfgFileName))
+    return readConfigFile(CfgFilePath);
+
+  // Finally try removing driver mode part: 'x86_64-clang.cfg' -> 'x86_64.cfg'.
+  if (!ClangNameParts.ModeSuffix.empty() &&
+      !ClangNameParts.TargetPrefix.empty()) {
+    CfgFileName.assign(ClangNameParts.TargetPrefix);
+    CfgFileName.append(".cfg");
+    if (searchForFile(CfgFilePath, CfgFileSearchDirs, CfgFileName))
+      return readConfigFile(CfgFilePath);
+  }
+
+  // Report error but only if config file was specified explicitly, by option
+  // --config. If it was deduced from executable name, it is not an error.
+  if (FileSpecifiedExplicitly) {
+    Diag(diag::err_drv_config_file_not_found) << CfgFileName;
+    for (const std::string &SearchDir : CfgFileSearchDirs)
+      if (!SearchDir.empty())
+        Diag(diag::note_drv_config_file_searched_in) << SearchDir;
+    return true;
+  }
+
+  return false;
+}
+
 Compilation *Driver::BuildCompilation(ArrayRef<const char *> ArgList) {
   llvm::PrettyStackTraceString CrashInfo("Compilation construction");
 
@@ -623,12 +843,35 @@ Compilation *Driver::BuildCompilation(ArrayRef<const char *> ArgList) {
 
   // FIXME: What are we going to do with -V and -b?
 
+  // Arguments specified in command line.
+  bool ContainsError;
+  CLOptions = llvm::make_unique<InputArgList>(
+      ParseArgStrings(ArgList.slice(1), ContainsError));
+
+  // Try parsing configuration file.
+  if (!ContainsError)
+    ContainsError = loadConfigFile();
+  bool HasConfigFile = !ContainsError && (CfgOptions.get() != nullptr);
+
+  // All arguments, from both config file and command line.
+  InputArgList Args = std::move(HasConfigFile ? std::move(*CfgOptions)
+                                              : std::move(*CLOptions));
+  if (HasConfigFile)
+    for (auto *Opt : *CLOptions) {
+      const Arg *BaseArg = &Opt->getBaseArg();
+      if (BaseArg == Opt)
+        BaseArg = nullptr;
+      Arg *Copy = new llvm::opt::Arg(Opt->getOption(), Opt->getSpelling(),
+                                     Args.size(), BaseArg);
+      Copy->getValues() = Opt->getValues();
+      if (Opt->isClaimed())
+        Copy->claim();
+      Args.append(Copy);
+    }
+
   // FIXME: This stuff needs to go into the Compilation, not the driver.
   bool CCCPrintPhases;
 
-  bool ContainsError;
-  InputArgList Args = ParseArgStrings(ArgList.slice(1), ContainsError);
-
   // Silence driver warnings if requested
   Diags.setIgnoreAllWarnings(Args.hasArg(options::OPT_w));
 
@@ -1144,6 +1387,10 @@ void Driver::PrintVersion(const Compilation &C, raw_ostream &OS) const {
 
   // Print out the install directory.
   OS << "InstalledDir: " << InstalledDir << '\n';
+
+  // If configuration file was used, print its path.
+  if (!ConfigFile.empty())
+    OS << "Configuration file: " << ConfigFile << '\n';
 }
 
 /// PrintDiagnosticCategories - Implement the --print-diagnostic-categories
@@ -1250,6 +1497,15 @@ bool Driver::HandleImmediateArgs(const Compilation &C) {
     SuppressMissingInputWarning = true;
   }
 
+  if (C.getArgs().hasArg(options::OPT_v)) {
+    if (!SystemConfigDir.empty())
+      llvm::errs() << "System configuration file directory: "
+                   << SystemConfigDir << "\n";
+    if (!UserConfigDir.empty())
+      llvm::errs() << "User configuration file directory: "
+                   << UserConfigDir << "\n";
+  }
+
   const ToolChain &TC = C.getDefaultToolChain();
 
   if (C.getArgs().hasArg(options::OPT_v))