[Driver][SYCL] Fix integration header handling with preprocessed files (#3650)

When generating preprocessed files using -fsycl, The preprocessed
files did not contain the integration header causing the host side
of the preprocessed file to not contain that information.  Compiling
from preprocessed files are not expected to do another preprocessing
step so the addition of the integration header is lost.

Author: mdtoguchi

clang/lib/Driver/Driver.cpp

@@ -3854,24 +3854,33 @@ class OffloadingActionBuilder final {
     getDeviceDependences(OffloadAction::DeviceDependences &DA,
                          phases::ID CurPhase, phases::ID FinalPhase,
                          PhasesTy &Phases) override {
+      bool SYCLDeviceOnly = Args.hasArg(options::OPT_fsycl_device_only);
       if (CurPhase == phases::Preprocess) {
         // Do not perform the host compilation when doing preprocessing only
         // with -fsycl-device-only.
         bool IsPreprocessOnly =
             Args.getLastArg(options::OPT_E) ||
             Args.getLastArg(options::OPT__SLASH_EP, options::OPT__SLASH_P) ||
             Args.getLastArg(options::OPT_M, options::OPT_MM);
-        if (Args.hasArg(options::OPT_fsycl_device_only) && IsPreprocessOnly) {
-          for (Action *&A : SYCLDeviceActions)
+        if (IsPreprocessOnly) {
+          for (Action *&A : SYCLDeviceActions) {
             A = C.getDriver().ConstructPhaseAction(C, Args, CurPhase, A,
                                                    AssociatedOffloadKind);
-          return ABRT_Ignore_Host;
+            if (SYCLDeviceOnly)
+              continue;
+            // Add an additional compile action to generate the integration
+            // header.
+            Action *CompileAction =
+                C.MakeAction<CompileJobAction>(A, types::TY_Nothing);
+            DA.add(*CompileAction, *ToolChains.front(), nullptr,
+                   Action::OFK_SYCL);
+          }
+          return SYCLDeviceOnly ? ABRT_Ignore_Host : ABRT_Success;
         }
       }
 
       // Device compilation generates LLVM BC.
       if (CurPhase == phases::Compile) {
-        bool SYCLDeviceOnly = Args.hasArg(options::OPT_fsycl_device_only);
         for (Action *&A : SYCLDeviceActions) {
           types::ID OutputType = types::TY_LLVM_BC;
           if (SYCLDeviceOnly) {

clang/test/Driver/sycl-preprocess.cpp

@@ -0,0 +1,29 @@
+/// Test preprocessing capabilities when using -fsycl
+/// Creating a preprocessed file is expected to do an integration header
+/// creation step.
+// RUN: %clangxx -fsycl -E -o %t_output.ii %s -### 2>&1 \
+// RUN:  | FileCheck -check-prefix PREPROC_ONLY %s
+// RUN: %clang_cl -fsycl -P -Fi%t_output.ii %s -### 2>&1 \
+// RUN:  | FileCheck -check-prefix PREPROC_ONLY %s
+// PREPROC_ONLY: clang{{.*}} "-fsycl-is-device"{{.*}} "-E"{{.*}} "-o" "[[DEVICE_OUT:.+\.ii]]"
+// PREPROC_ONLY: clang{{.*}} "-fsycl-is-device"{{.*}} "-fsycl-int-header=[[INTHEADER:.+\.h]]"{{.*}} "-fsyntax-only"
+// PREPROC_ONLY: clang{{.*}} "-include" "[[INTHEADER]]"{{.*}} "-fsycl-is-host"{{.*}} "-o" "[[HOST_OUT:.+\.ii]]"
+// PREPROC_ONLY: clang-offload-bundler{{.*}} "-type=ii"{{.*}} "-outputs={{.+_output.ii}}" "-inputs=[[DEVICE_OUT]],[[HOST_OUT]]"
+
+/// When compiling from preprocessed file, no integration header is expected
+// RUN: touch %t.ii
+// RUN: %clangxx -fsycl %t.ii -### 2>&1 | FileCheck -check-prefix PREPROC_IN %s
+// PREPROC_IN: clang{{.*}} "-fsycl-is-device"
+// PREPROC_IN-NOT: "-fsycl-int-header={{.*}}"
+// PREPROC_IN: clang{{.*}} "-fsycl-is-host"
+
+// RUN: %clangxx -target x86_64-unknown-linux-gnu -fsycl -E %s -ccc-print-phases 2>&1 \
+// RUN:  | FileCheck -check-prefix PREPROC_PHASES %s
+// PREPROC_PHASES: 0: input, "[[INPUT:.+\.cpp]]", c++, (device-sycl)
+// PREPROC_PHASES: 1: preprocessor, {0}, c++-cpp-output, (device-sycl)
+// PREPROC_PHASES: 2: offload, "device-sycl (spir64-unknown-unknown-sycldevice)" {1}, c++-cpp-output
+// PREPROC_PHASES: 3: input, "[[INPUT]]", c++, (host-sycl)
+// PREPROC_PHASES: 4: compiler, {1}, none, (device-sycl)
+// PREPROC_PHASES: 5: offload, "host-sycl (x86_64-unknown-linux-gnu)" {3}, "device-sycl (spir64-unknown-unknown-sycldevice)" {4}, c++
+// PREPROC_PHASES: 6: preprocessor, {5}, c++-cpp-output, (host-sycl)
+// PREPROC_PHASES: 7: clang-offload-bundler, {2, 6}, c++-cpp-output, (host-sycl)