diff --git a/clang/include/clang/Driver/Driver.h b/clang/include/clang/Driver/Driver.h
--- a/clang/include/clang/Driver/Driver.h
+++ b/clang/include/clang/Driver/Driver.h
@@ -18,6 +18,7 @@
 #include "clang/Driver/Util.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Option/Arg.h"
 #include "llvm/Option/ArgList.h"
 #include "llvm/Support/StringSaver.h"
 
@@ -250,9 +251,18 @@
 
   // getFinalPhase - Determine which compilation mode we are in and record
   // which option we used to determine the final phase.
+  // TODO: Much of what getFinalPhase returns are not actually true compiler
+  //       modes. Fold this functionality into Types::getCompilationPhases and
+  //       handleArguments.
   phases::ID getFinalPhase(const llvm::opt::DerivedArgList &DAL,
                            llvm::opt::Arg **FinalPhaseArg = nullptr) const;
 
+  // handleArguments - All code related to claiming and printing diagnostics
+  // related to arguments to the driver are done here.
+  void handleArguments(Compilation &C, llvm::opt::DerivedArgList &Args,
+                       const InputList &Inputs, ActionList &Actions,
+                       llvm::opt::Arg *YcArg, llvm::opt::Arg *YuArg) const;
+
   // Before executing jobs, sets up response files for commands that need them.
   void setUpResponseFiles(Compilation &C, Command &Cmd);
 
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -3148,76 +3148,9 @@
 };
 } // anonymous namespace.
 
-void Driver::BuildActions(Compilation &C, DerivedArgList &Args,
-                          const InputList &Inputs, ActionList &Actions) const {
-  llvm::PrettyStackTraceString CrashInfo("Building compilation actions");
-
-  if (!SuppressMissingInputWarning && Inputs.empty()) {
-    Diag(clang::diag::err_drv_no_input_files);
-    return;
-  }
-
-  // Reject -Z* at the top level, these options should never have been exposed
-  // by gcc.
-  if (Arg *A = Args.getLastArg(options::OPT_Z_Joined))
-    Diag(clang::diag::err_drv_use_of_Z_option) << A->getAsString(Args);
-
-  // Diagnose misuse of /Fo.
-  if (Arg *A = Args.getLastArg(options::OPT__SLASH_Fo)) {
-    StringRef V = A->getValue();
-    if (Inputs.size() > 1 && !V.empty() &&
-        !llvm::sys::path::is_separator(V.back())) {
-      // Check whether /Fo tries to name an output file for multiple inputs.
-      Diag(clang::diag::err_drv_out_file_argument_with_multiple_sources)
-          << A->getSpelling() << V;
-      Args.eraseArg(options::OPT__SLASH_Fo);
-    }
-  }
-
-  // Diagnose misuse of /Fa.
-  if (Arg *A = Args.getLastArg(options::OPT__SLASH_Fa)) {
-    StringRef V = A->getValue();
-    if (Inputs.size() > 1 && !V.empty() &&
-        !llvm::sys::path::is_separator(V.back())) {
-      // Check whether /Fa tries to name an asm file for multiple inputs.
-      Diag(clang::diag::err_drv_out_file_argument_with_multiple_sources)
-          << A->getSpelling() << V;
-      Args.eraseArg(options::OPT__SLASH_Fa);
-    }
-  }
-
-  // Diagnose misuse of /o.
-  if (Arg *A = Args.getLastArg(options::OPT__SLASH_o)) {
-    if (A->getValue()[0] == '\0') {
-      // It has to have a value.
-      Diag(clang::diag::err_drv_missing_argument) << A->getSpelling() << 1;
-      Args.eraseArg(options::OPT__SLASH_o);
-    }
-  }
-
-  // Ignore /Yc/Yu if both /Yc and /Yu passed but with different filenames.
-  Arg *YcArg = Args.getLastArg(options::OPT__SLASH_Yc);
-  Arg *YuArg = Args.getLastArg(options::OPT__SLASH_Yu);
-  if (YcArg && YuArg && strcmp(YcArg->getValue(), YuArg->getValue()) != 0) {
-    Diag(clang::diag::warn_drv_ycyu_different_arg_clang_cl);
-    Args.eraseArg(options::OPT__SLASH_Yc);
-    Args.eraseArg(options::OPT__SLASH_Yu);
-    YcArg = YuArg = nullptr;
-  }
-  if (YcArg && Inputs.size() > 1) {
-    Diag(clang::diag::warn_drv_yc_multiple_inputs_clang_cl);
-    Args.eraseArg(options::OPT__SLASH_Yc);
-    YcArg = nullptr;
-  }
-
-  // Builder to be used to build offloading actions.
-  OffloadingActionBuilder OffloadBuilder(C, Args, Inputs);
-
-  // Construct the actions to perform.
-  HeaderModulePrecompileJobAction *HeaderModuleAction = nullptr;
-  ActionList LinkerInputs;
-
-  {
+void Driver::handleArguments(Compilation &C, DerivedArgList &Args,
+                             const InputList &Inputs, ActionList &Actions,
+                             Arg *YcArg, Arg *YuArg) const {
   Arg *FinalPhaseArg;
   phases::ID FinalPhase = getFinalPhase(Args, &FinalPhaseArg);
 
@@ -3229,8 +3162,7 @@
       Diag(clang::diag::err_drv_lto_without_lld);
   }
 
-    if (FinalPhase == phases::Preprocess ||
-        Args.hasArg(options::OPT__SLASH_Y_)) {
+  if (FinalPhase == phases::Preprocess || Args.hasArg(options::OPT__SLASH_Y_)) {
     // If only preprocessing or /Y- is used, all pch handling is disabled.
     // Rather than check for it everywhere, just remove clang-cl pch-related
     // flags here.
@@ -3317,6 +3249,77 @@
   }
 }
 
+void Driver::BuildActions(Compilation &C, DerivedArgList &Args,
+                          const InputList &Inputs, ActionList &Actions) const {
+  llvm::PrettyStackTraceString CrashInfo("Building compilation actions");
+
+  if (!SuppressMissingInputWarning && Inputs.empty()) {
+    Diag(clang::diag::err_drv_no_input_files);
+    return;
+  }
+
+  // Reject -Z* at the top level, these options should never have been exposed
+  // by gcc.
+  if (Arg *A = Args.getLastArg(options::OPT_Z_Joined))
+    Diag(clang::diag::err_drv_use_of_Z_option) << A->getAsString(Args);
+
+  // Diagnose misuse of /Fo.
+  if (Arg *A = Args.getLastArg(options::OPT__SLASH_Fo)) {
+    StringRef V = A->getValue();
+    if (Inputs.size() > 1 && !V.empty() &&
+        !llvm::sys::path::is_separator(V.back())) {
+      // Check whether /Fo tries to name an output file for multiple inputs.
+      Diag(clang::diag::err_drv_out_file_argument_with_multiple_sources)
+          << A->getSpelling() << V;
+      Args.eraseArg(options::OPT__SLASH_Fo);
+    }
+  }
+
+  // Diagnose misuse of /Fa.
+  if (Arg *A = Args.getLastArg(options::OPT__SLASH_Fa)) {
+    StringRef V = A->getValue();
+    if (Inputs.size() > 1 && !V.empty() &&
+        !llvm::sys::path::is_separator(V.back())) {
+      // Check whether /Fa tries to name an asm file for multiple inputs.
+      Diag(clang::diag::err_drv_out_file_argument_with_multiple_sources)
+          << A->getSpelling() << V;
+      Args.eraseArg(options::OPT__SLASH_Fa);
+    }
+  }
+
+  // Diagnose misuse of /o.
+  if (Arg *A = Args.getLastArg(options::OPT__SLASH_o)) {
+    if (A->getValue()[0] == '\0') {
+      // It has to have a value.
+      Diag(clang::diag::err_drv_missing_argument) << A->getSpelling() << 1;
+      Args.eraseArg(options::OPT__SLASH_o);
+    }
+  }
+
+  // Ignore /Yc/Yu if both /Yc and /Yu passed but with different filenames.
+  Arg *YcArg = Args.getLastArg(options::OPT__SLASH_Yc);
+  Arg *YuArg = Args.getLastArg(options::OPT__SLASH_Yu);
+  if (YcArg && YuArg && strcmp(YcArg->getValue(), YuArg->getValue()) != 0) {
+    Diag(clang::diag::warn_drv_ycyu_different_arg_clang_cl);
+    Args.eraseArg(options::OPT__SLASH_Yc);
+    Args.eraseArg(options::OPT__SLASH_Yu);
+    YcArg = YuArg = nullptr;
+  }
+  if (YcArg && Inputs.size() > 1) {
+    Diag(clang::diag::warn_drv_yc_multiple_inputs_clang_cl);
+    Args.eraseArg(options::OPT__SLASH_Yc);
+    YcArg = nullptr;
+  }
+
+  // Builder to be used to build offloading actions.
+  OffloadingActionBuilder OffloadBuilder(C, Args, Inputs);
+
+  // Construct the actions to perform.
+  HeaderModulePrecompileJobAction *HeaderModuleAction = nullptr;
+  ActionList LinkerInputs;
+
+  handleArguments(C, Args, Inputs, Actions, YcArg, YuArg);
+
   for (auto &I : Inputs) {
     types::ID InputType = I.first;
     const Arg *InputArg = I.second;