[clang][Driver] Pick the last --driver-mode in case of multiple ones

[kadircet]

Summary

This was an accidental behaviour change in D106789 and this patch
restores it back to original state.

[hans]

Thanks! I tried this locally and it fixes the issue I mentioned on D109361

[kadircet]

FYI, I've also requested cherry-pick into 13 release in https://bugs.llvm.org/show_bug.cgi?id=51779.

[hans]

In D109361#2986687, @hans wrote:

Thanks! I tried this locally and it fixes the issue I mentioned on D109361

Corection: it fixes the issue that that I mentioned on D106789 obviously.

clang/lib/Driver/Driver.cpp

llvm::StringRef clang::driver::getDriverMode(StringRef ProgName,
                                              ArrayRef<const char *> Args) {
   static const std::string OptName =
       getDriverOptTable().getOption(options::OPT_driver_mode).getPrefixedName();
   llvm::StringRef Opt;
   for (StringRef Arg : Args) {
     if (!Arg.startswith(OptName))
       continue;
     Opt = Arg;
-    break;
   }
   if (Opt.empty())
     Opt = ToolChain::getTargetAndModeFromProgramName(ProgName).DriverMode;
   return Opt.consume_front(OptName) ? Opt : "";
 }
 
 bool driver::IsClangCL(StringRef DriverMode) { return DriverMode.equals("cl"); }

clang/unittests/Driver/ToolChainTest.cpp

 //===----------------------------------------------------------------------===//
 
 #include "clang/Driver/ToolChain.h"
 #include "clang/Basic/DiagnosticIDs.h"
 #include "clang/Basic/DiagnosticOptions.h"
 #include "clang/Basic/LLVM.h"
 #include "clang/Driver/Compilation.h"
 #include "clang/Driver/Driver.h"
+#include "llvm/ADT/ArrayRef.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/TargetSelect.h"
 #include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Support/raw_ostream.h"
 #include "gtest/gtest.h"
 using namespace clang;
 using namespace clang::driver;
 
CC->setPostCallback(
       [&](const Command &C, int Ret) { CallbackHasCalled = true; });
   const JobList &Jobs = CC->getJobs();
   auto &CmdCompile = Jobs.getJobs().front();
   const Command *FailingCmd = nullptr;
   CC->ExecuteCommand(*CmdCompile, FailingCmd);
   EXPECT_TRUE(CallbackHasCalled);
 }
 
+TEST(GetDriverMode, PrefersLastDriverMode) {
+  static constexpr const char *Args[] = {"clang-cl", "--driver-mode=foo",
+                                         "--driver-mode=bar", "foo.cpp"};
+  EXPECT_EQ(getDriverMode(Args[0], llvm::makeArrayRef(Args).slice(1)), "bar");
+}
+
 } // end anonymous namespace.