New clang option -MD-filter=prefix to filter files from make dependencies

[mibintc]

Summary

Intel is developing an offload compiler based on clang (that will eventually be contributed to open source). In the course of the compilation many temporary .h files are generated in /tmp. We'd like to have a way of eliding these dependencies from the -MD output. This new option -MD-filter=prefixstring is proposed.

[mibintc]

added an inline comment about the use of strncmp

lib/Frontend/DependencyFile.cpp

279

I wasn't sure about using strncmp to do the prefix comparison, but i checked around in the clang code and saw strncmp used in several places so I thought it would be acceptable.

[xbolva00]

lib/Frontend/DependencyFile.cpp

279

DependencyFilter.compare(Filename)?

[xbolva00]

lib/Frontend/DependencyFile.cpp

279

They are overloads with pos and len.

[mibintc]

respond to suggestion from @xbolva00 (thanks). Added a test case where prefix fails to match

[mibintc]

@dexonsmith Can you take a look at this patch or recommend someone who can review it? Many thanks. --Melanie

[mibintc]

@rjmccall Can you take a look at this patch or recommend someone who can review it? Many thanks. --Melanie

[mibintc]

I'll modify this to be a cc1 only option, there doesn't seem to be community interest.

docs/ClangCommandLineReference.rst

 .. option:: -MT<arg>
 
 Specify name of main file output in depfile
 
 .. option:: -MV
 
 Use NMake/Jom format for the depfile
 
+.. option:: -MD-filter=prefix
+
+Specify prefix string for dependencies which should be omitted from depfile
+
 Dumping preprocessor state
 --------------------------
 
 Flags allowing the state of the preprocessor to be dumped in various ways.
 
 .. option:: -d
 
 .. program:: clang1

include/clang/Driver/Options.td

 def MD : Flag<["-"], "MD">, Group<M_Group>,
     HelpText<"Write a depfile containing user and system headers">;
 def MMD : Flag<["-"], "MMD">, Group<M_Group>,
     HelpText<"Write a depfile containing user headers">;
 def M : Flag<["-"], "M">, Group<M_Group>,
     HelpText<"Like -MD, but also implies -E and writes to stdout by default">;
 def MM : Flag<["-"], "MM">, Group<M_Group>,
     HelpText<"Like -MMD, but also implies -E and writes to stdout by default">;
+def MD_filter : Joined<["-"], "MD-filter=">, Group<M_Group>,
+    HelpText<"Filter depfile output prefixed with string from -MMD, -MD, -MM, or -M">;
 def MF : JoinedOrSeparate<["-"], "MF">, Group<M_Group>,
     HelpText<"Write depfile output from -MMD, -MD, -MM, or -M to <file>">,
     MetaVarName<"<file>">;
 def MG : Flag<["-"], "MG">, Group<M_Group>, Flags<[CC1Option]>,
     HelpText<"Add missing headers to depfile">;
 def MJ : JoinedOrSeparate<["-"], "MJ">, Group<M_Group>,
     HelpText<"Write a compilation database entry per input">;
 def MP : Flag<["-"], "MP">, Group<M_Group>, Flags<[CC1Option]>,
def dM : Flag<["-"], "dM">, Group<d_Group>, Flags<[CC1Option]>,
   HelpText<"Print macro definitions in -E mode instead of normal output">;
 def dead__strip : Flag<["-"], "dead_strip">;
 def dependency_file : Separate<["-"], "dependency-file">, Flags<[CC1Option]>,
   HelpText<"Filename (or -) to write dependency output to">;
 def dependency_dot : Separate<["-"], "dependency-dot">, Flags<[CC1Option]>,
   HelpText<"Filename to write DOT-formatted header dependencies to">;
 def module_dependency_dir : Separate<["-"], "module-dependency-dir">,
   Flags<[CC1Option]>, HelpText<"Directory to dump module dependencies to">;
+def dependency_filter : Separate<["-"], "dependency-filter">, Flags<[CC1Option]>,
+  HelpText<"Filter dependencies with prefix from the dependency output.">;
 def dumpmachine : Flag<["-"], "dumpmachine">;
 def dumpspecs : Flag<["-"], "dumpspecs">, Flags<[Unsupported]>;
 def dumpversion : Flag<["-"], "dumpversion">;
 def dylib__file : Separate<["-"], "dylib_file">;
 def dylinker__install__name : JoinedOrSeparate<["-"], "dylinker_install_name">;
 def dylinker : Flag<["-"], "dylinker">;
 def dynamiclib : Flag<["-"], "dynamiclib">;
 def dynamic : Flag<["-"], "dynamic">, Flags<[NoArgumentUnused]>;

include/clang/Frontend/DependencyOutputOptions.h

public:
   ShowIncludesDestination ShowIncludesDest = ShowIncludesDestination::None;
 
   /// The format for the dependency file.
   DependencyOutputFormat OutputFormat = DependencyOutputFormat::Make;
 
   /// The file to write dependency output to.
   std::string OutputFile;
 
+  /// Dependency output which is prefixed with this string is filtered
+  /// from the dependency output.
+  std::string DependencyFilter;
+
   /// The file to write header include output to. This is orthogonal to
   /// ShowHeaderIncludes (-H) and will include headers mentioned in the
   /// predefines buffer. If the output file is "-", output will be sent to
   /// stderr.
   std::string HeaderIncludeOutputFile;
 
   /// A list of names to use as the targets in the dependency file; this list
   /// must contain at least one entry.

lib/Driver/ToolChains/Clang.cpp

if (A->getOption().matches(options::OPT_M) ||
         A->getOption().matches(options::OPT_MD))
       CmdArgs.push_back("-sys-header-deps");
     if ((isa<PrecompileJobAction>(JA) &&
          !Args.hasArg(options::OPT_fno_module_file_deps)) ||
         Args.hasArg(options::OPT_fmodule_file_deps))
       CmdArgs.push_back("-module-file-deps");
   }
 
+  if (Arg *MD_Filter = Args.getLastArg(options::OPT_MD_filter)) {
+    CmdArgs.push_back("-dependency-filter");
+    CmdArgs.push_back(MD_Filter->getValue());
+  }
+
   if (Args.hasArg(options::OPT_MG)) {
     if (!A || A->getOption().matches(options::OPT_MD) ||
         A->getOption().matches(options::OPT_MMD))
       D.Diag(diag::err_drv_mg_requires_m_or_mm);
     CmdArgs.push_back("-MG");
   }
 
   Args.AddLastArg(CmdArgs, options::OPT_MP);

lib/Frontend/CompilerInvocation.cpp

static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.PassPlugins = Args.getAllArgValues(OPT_fpass_plugin_EQ);
 
   return Success;
 }
 
 static void ParseDependencyOutputArgs(DependencyOutputOptions &Opts,
                                       ArgList &Args) {
   Opts.OutputFile = Args.getLastArgValue(OPT_dependency_file);
+  Opts.DependencyFilter = Args.getLastArgValue(OPT_dependency_filter);
   Opts.Targets = Args.getAllArgValues(OPT_MT);
   Opts.IncludeSystemHeaders = Args.hasArg(OPT_sys_header_deps);
   Opts.IncludeModuleFiles = Args.hasArg(OPT_module_file_deps);
   Opts.UsePhonyTargets = Args.hasArg(OPT_MP);
   Opts.ShowHeaderIncludes = Args.hasArg(OPT_H);
   Opts.HeaderIncludeOutputFile = Args.getLastArgValue(OPT_header_include_file);
   Opts.AddMissingHeaderDeps = Args.hasArg(OPT_MG);
   if (Args.hasArg(OPT_show_includes)) {

lib/Frontend/DependencyFile.cpp

 
 namespace {
 /// Private implementation for DependencyFileGenerator
 class DFGImpl : public PPCallbacks {
   std::vector<std::string> Files;
   llvm::StringSet<> FilesSet;
   const Preprocessor *PP;
   std::string OutputFile;
+  std::string DependencyFilter;
   std::vector<std::string> Targets;
   bool IncludeSystemHeaders;
   bool PhonyTarget;
   bool AddMissingHeaderDeps;
   bool SeenMissingHeader;
   bool IncludeModuleFiles;
   DependencyOutputFormat OutputFormat;
   unsigned InputFileIndex;
 
 private:
   bool FileMatchesDepCriteria(const char *Filename,
                               SrcMgr::CharacteristicKind FileType);
   void OutputDependencyFile();
 
 public:
   DFGImpl(const Preprocessor *_PP, const DependencyOutputOptions &Opts)
-    : PP(_PP), OutputFile(Opts.OutputFile), Targets(Opts.Targets),
+    : PP(_PP), OutputFile(Opts.OutputFile),
+      DependencyFilter(Opts.DependencyFilter), Targets(Opts.Targets),
       IncludeSystemHeaders(Opts.IncludeSystemHeaders),
       PhonyTarget(Opts.UsePhonyTargets),
       AddMissingHeaderDeps(Opts.AddMissingHeaderDeps),
       SeenMissingHeader(false),
       IncludeModuleFiles(Opts.IncludeModuleFiles),
       OutputFormat(Opts.OutputFormat),
       InputFileIndex(0) {
     for (const auto &ExtraDep : Opts.ExtraDeps) {

 
 /// FileMatchesDepCriteria - Determine whether the given Filename should be
 /// considered as a dependency.
 bool DFGImpl::FileMatchesDepCriteria(const char *Filename,
                                      SrcMgr::CharacteristicKind FileType) {
   if (isSpecialFilename(Filename))
     return false;
 
+  if (DependencyFilter.size() &&
+      strncmp(Filename, DependencyFilter.c_str(), DependencyFilter.size()) == 0)
+    // Remove dependencies that are prefixed by the Filter string.
+    return false;
+
   if (IncludeSystemHeaders)
     return true;
 
   return !isSystem(FileType);
 }
 
 void DFGImpl::FileChanged(SourceLocation Loc,
                           FileChangeReason Reason,

test/Frontend/dependency-gen.c

 // Basic test
 // RUN: rm -rf %t.dir
 // RUN: mkdir -p %t.dir/a/b
 // RUN: echo > %t.dir/a/b/x.h
 // RUN: cd %t.dir
 // RUN: %clang -MD -MF - %s -fsyntax-only -I a/b | FileCheck -check-prefix=CHECK-ONE %s
 // CHECK-ONE: {{ }}a{{[/\\]}}b{{[/\\]}}x.h
+// RUN: %clang -MD -MF - %s -fsyntax-only -I a/b -MD-filter="a/b" | FileCheck -check-prefix=CHECK-FILTER %s
+// CHECK-FILTER-NOT: {{ }}a{{[/\\]}}b{{[/\\]}}x.h
+// RUN: %clang -MD -MF - %s -fsyntax-only -I a/b -MD-filter="a/b" | FileCheck -check-prefix=CHECK-WS %s
+// CHECK-WS: {{^ *$}}
 
 // PR8974 (-include flag)
 // RUN: %clang -MD -MF - %s -fsyntax-only -include a/b/x.h -DINCLUDE_FLAG_TEST | FileCheck -check-prefix=CHECK-TWO %s
 // CHECK-TWO: {{ }}a{{[/\\]}}b{{[/\\]}}x.h
 
 // rdar://problem/9734352 (paths involving ".")
 // RUN: %clang -MD -MF - %s -fsyntax-only -I ./a/b | FileCheck -check-prefix=CHECK-THREE %s
 // CHECK-THREE: {{ }}a{{[/\\]}}b{{[/\\]}}x.h