[Clang] Fix the new driver crashing when using '-fsyntax-only'

The new driver currently crashses when attempting to use the
'-fsyntax-only' option. This is because the option causes all output to
be given the `TY_Nothing' type which should signal the end of the
pipeline. The new driver was not treating this correctly and attempting
to use empty input. This patch fixes the handling so we do not attempt
to continue when the input is nothing.

One concession is that we must now check when generating the arguments
for Clang if the input is of 'TY_Nothing'. This is because the new
driver will only create code if the device code is a dependency on the
host, creating the output without the dependency would require a
complete rewrite of the logic as we do not maintain any state between
calls to 'BuildOffloadingActions' so I believe this is the most
straightforward method.

Reviewed By: tra

Differential Revision: https://reviews.llvm.org/D133161

1 files changed, 11 insertions, 3 deletions

diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 36fba5d..9517331a 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -4309,10 +4309,14 @@ Action *Driver::BuildOffloadingActions(Compilation &C,
 
       auto TCAndArch = TCAndArchs.begin();
       for (Action *&A : DeviceActions) {
+        if (A->getType() == types::TY_Nothing)
+          continue;
+
         A = ConstructPhaseAction(C, Args, Phase, A, Kind);
 
         if (isa<CompileJobAction>(A) && isa<CompileJobAction>(HostAction) &&
-            Kind == Action::OFK_OpenMP) {
+            Kind == Action::OFK_OpenMP &&
+            HostAction->getType() != types::TY_Nothing) {
           // OpenMP offloading has a dependency on the host compile action to
           // identify which declarations need to be emitted. This shouldn't be
           // collapsed with any other actions so we can use it in the device.
@@ -4380,11 +4384,15 @@ Action *Driver::BuildOffloadingActions(Compilation &C,
              nullptr, Action::OFK_None);
   }
 
+  // If we are unable to embed a single device output into the host, we need to
+  // add each device output as a host dependency to ensure they are still built.
+  bool SingleDeviceOutput = !llvm::any_of(OffloadActions, [](Action *A) {
+    return A->getType() == types::TY_Nothing;
+  }) && isa<CompileJobAction>(HostAction);
   OffloadAction::HostDependence HDep(
       *HostAction, *C.getSingleOffloadToolChain<Action::OFK_Host>(),
       /*BoundArch=*/nullptr, isa<CompileJobAction>(HostAction) ? DDep : DDeps);
-  return C.MakeAction<OffloadAction>(
-      HDep, isa<CompileJobAction>(HostAction) ? DDep : DDeps);
+  return C.MakeAction<OffloadAction>(HDep, SingleDeviceOutput ? DDep : DDeps);
 }
 
 Action *Driver::ConstructPhaseAction(