[Tooling] Infer driver mode and target for FixedCompilationDatabase

[de1acr0ix]

Summary

When creating FixedCompilationDatabase from command line, compiler
command is often provided. This commit tries to infer driver mode and
target from that so that clang tools does not need to specify them
explicitly.

[de1acr0ix]

I realized an obvious problem: if the first argument is "-cc" or something compiler option ends with a possible driver mode suffix it would be treated as compiler binary name.

[de1acr0ix]

Check if argv[0] is an option before inferring - anything starting with dash or slash (but without a second slash) will be treated as compiler option.

[de1acr0ix]

It is impossible to handle the case that positional argument starts with a source file with a driver mode suffix in file name stem, such as "somecpp.cpp".

clang/lib/Tooling/CompilationDatabase.cpp

static bool stripPositionalArgs(std::vector<const char *> Args,
 
   // The clang executable path isn't required since the jobs the driver builds
   // will not be executed.
   std::unique_ptr<driver::Driver> NewDriver(new driver::Driver(
       /* ClangExecutable= */ "", llvm::sys::getDefaultTargetTriple(),
       Diagnostics));
   NewDriver->setCheckInputsExist(false);
 
+  // Try to infer driver mode and target from the original argv[0].
+  driver::ParsedClangName NameParts;
+  if (!Args.empty()) {
+    NameParts = driver::ToolChain::getTargetAndModeFromProgramName(Args[0]);
+    if (NameParts.DriverMode) {
+      Args.insert(Args.begin(), NameParts.DriverMode);
+    }
+
+    if (NameParts.TargetIsValid) {
+      const char *arr[] = {"-target", NameParts.TargetPrefix.c_str()};
+      Args.insert(Args.begin(), std::begin(arr), std::end(arr));
+    }
+  }
+
   // This becomes the new argv[0]. The value is used to detect libc++ include
   // dirs on Mac, it isn't used for other platforms.
   std::string Argv0 = GetClangToolCommand();
   Args.insert(Args.begin(), Argv0.c_str());
 
   // By adding -c, we force the driver to treat compilation as the last phase.
   // It will then issue warnings via Diagnostics about un-used options that
   // would have been used for linking. If the user provided a compiler name as

clang/unittests/Tooling/CompilationDatabaseTest.cpp

TEST(ParseFixedCompilationDatabase, HandlesArgv0) {
   ASSERT_EQ(1ul, Result.size());
   ASSERT_EQ(".", Result[0].Directory);
   std::vector<std::string> Expected;
   ASSERT_THAT(Result[0].CommandLine,
               ElementsAre(EndsWith("clang-tool"), "source"));
   EXPECT_EQ(2, Argc);
 }
 
+TEST(ParseFixedCompilationDatabase, InferDriverMode) {
+  const char *Argv[] = {"1", "2", "--", "cl.exe", "-nologo", "somefile.cpp"};
+  int Argc = sizeof(Argv) / sizeof(char *);
+  std::string ErrorMsg;
+  std::unique_ptr<FixedCompilationDatabase> Database =
+      FixedCompilationDatabase::loadFromCommandLine(Argc, Argv, ErrorMsg);
+  ASSERT_TRUE((bool)Database);
+  ASSERT_TRUE(ErrorMsg.empty());
+  std::vector<CompileCommand> Result = Database->getCompileCommands("source");
+  ASSERT_EQ(1ul, Result.size());
+  ASSERT_EQ(".", Result[0].Directory);
+  std::vector<std::string> Expected;
+  ASSERT_THAT(Result[0].CommandLine,
+              ElementsAre(EndsWith("clang-tool"), "--driver-mode=cl", "-nologo",
+                          "source"));
+  EXPECT_EQ(2, Argc);
+}
+
+TEST(ParseFixedCompilationDatabase, InferTarget) {
+  const char *Argv[] = {"1", "2", "--", "x86_64-linux-gnu-gcc", "somefile.cpp"};
+  int Argc = sizeof(Argv) / sizeof(char *);
+  std::string ErrorMsg;
+  LLVMInitializeX86TargetInfo();
+  std::unique_ptr<FixedCompilationDatabase> Database =
+      FixedCompilationDatabase::loadFromCommandLine(Argc, Argv, ErrorMsg);
+  ASSERT_TRUE((bool)Database);
+  ASSERT_TRUE(ErrorMsg.empty());
+  std::vector<CompileCommand> Result = Database->getCompileCommands("source");
+  ASSERT_EQ(1ul, Result.size());
+  ASSERT_EQ(".", Result[0].Directory);
+  std::vector<std::string> Expected;
+  ASSERT_THAT(Result[0].CommandLine,
+              ElementsAre(EndsWith("clang-tool"), "-target", "x86_64-linux-gnu",
+                          "source"));
+  EXPECT_EQ(2, Argc);
+}
+
 struct MemCDB : public CompilationDatabase {
   using EntryMap = llvm::StringMap<SmallVector<CompileCommand, 1>>;
   EntryMap Entries;
   MemCDB(const EntryMap &E) : Entries(E) {}
 
   std::vector<CompileCommand> getCompileCommands(StringRef F) const override {
     auto Ret = Entries.lookup(F);
     return {Ret.begin(), Ret.end()};