[Driver][SYCL][New offload] Support external host compiler (#19505)

Use of -fsycl-host-compiler allows for users to use an external compiler
to perform the host compilation when performing offload builds. The new
model has the expectation for the device 'object' to be embedded within
the host object via the `clang-offload-packager`. These fat objects are
consumed by the `clang-linker-wrapper`.

External host compilers do not have the ability to embed the device
binary when creating the host object. Fortunately, the
`clang-linker-wrapper` allows for consumption of bundled fat objects.

Update the driver when using -fsycl-host-compiler and the new offloading
model to generate bundled files instead of embedded objects. This
support is for object generation only at this time. Preprocessing and
assembly file intermediates are not yet supported.

Author: mdtoguchi

clang/lib/Driver/Driver.cpp

@@ -7748,9 +7748,17 @@ Action *Driver::BuildOffloadingActions(Compilation &C,
     return HostAction;
   }
 
+  // For SYCL offloading with -fsycl-host-compiler enabled, we do not have the
+  // ability to embed the packaged file.
+  bool SYCLBundleFile = C.isOffloadingHostKind(Action::OFK_SYCL) &&
+                        Args.hasArg(options::OPT_fsycl_host_compiler_EQ) &&
+                        isa<AssembleJobAction>(HostAction);
+
   // Don't build offloading actions if we do not have a compile action. If
-  // preprocessing only ignore embedding.
-  if (!(isa<CompileJobAction>(HostAction) ||
+  // preprocessing only ignore embedding.  When needing to do bundling for
+  // SYCL, allow the building of offloading actions to add the device side to
+  // the bundle.
+  if (!(isa<CompileJobAction>(HostAction) || SYCLBundleFile ||
         getFinalPhase(Args) == phases::Preprocess))
     return HostAction;
 
@@ -7888,6 +7896,17 @@ Action *Driver::BuildOffloadingActions(Compilation &C,
       tools::SYCL::populateSYCLDeviceTraitsMacrosArgs(C, Args, TCAndArchs);
   }
 
+  // Now that we have all of the offload actions populated, we special case
+  // SYCL -fsycl-host-compiler to perform a bundling action instead of a
+  // packaging action.
+  if (SYCLBundleFile) {
+    ActionList BundlingActions(OffloadActions);
+    BundlingActions.push_back(HostAction);
+    Action *BundlingAction =
+        C.MakeAction<OffloadBundlingJobAction>(BundlingActions);
+    return BundlingAction;
+  }
+
   // HIP code in device-only non-RDC mode will bundle the output if it invoked
   // the linker.
   bool ShouldBundleHIP =
@@ -7933,6 +7952,11 @@ Action *Driver::BuildOffloadingActions(Compilation &C,
     DDep.add(*LinkAction, *C.getSingleOffloadToolChain<Action::OFK_Host>(),
              nullptr, C.getActiveOffloadKinds());
     return C.MakeAction<OffloadAction>(DDep, types::TY_Nothing);
+  } else if (C.isOffloadingHostKind(Action::OFK_SYCL) &&
+             Args.hasArg(options::OPT_fsycl_host_compiler_EQ)) {
+    // -fsycl-host-compiler will create a bundled object instead of an
+    // embedded packaged object.  Effectively avoid doing the packaging.
+    return HostAction;
   } else {
     // Package all the offloading actions into a single output that can be
     // embedded in the host and linked.

clang/test/Driver/sycl-host-compiler.cpp

@@ -0,0 +1,106 @@
+// Tests the abilities involved with using an external host compiler
+// with the new offload model.
+
+/// Enabling with -fsycl-host-compiler
+// RUN: %clangxx -fsycl --offload-new-driver -fsycl-host-compiler=/some/dir/g++ %s -### 2>&1 \
+// RUN:  | FileCheck -check-prefix=HOST_COMPILER %s
+// HOST_COMPILER: clang{{.*}} "-fsycl-is-device"
+// HOST_COMPILER-SAME: "-fsycl-int-header=[[INTHEADER:.+\.h]]" "-fsycl-int-footer=[[INTFOOTER:.+\.h]]"
+// HOST_COMPILER-SAME: "-o" "[[DEVICEBC:.+\.bc]]"
+// HOST_COMPILER: append-file{{.*}} "--append=[[INTFOOTER]]"
+// HOST_COMPILER-SAME: "--output=[[APPENDFILESRC:.+\.cpp]]" "--use-include"
+// HOST_COMPILER: g++{{.*}} "[[APPENDFILESRC]]"
+// HOST_COMPILER-SAME: "-c" "-include" "[[INTHEADER]]"
+// HOST_COMPILER-SAME: "-iquote"
+// HOST_COMPILER-SAME: "-isystem" "{{.*}}bin{{[/\\]+}}..{{[/\\]+}}include{{[/\\]+}}sycl"
+// HOST_COMPILER-SAME: "-isystem" "{{.*}}bin{{[/\\]+}}..{{[/\\]+}}include{{[/\\]+}}sycl{{[/\\]+}}stl_wrappers"
+// HOST_COMPILER-SAME: "-isystem" "{{.*}}bin{{[/\\]+}}..{{[/\\]+}}include"
+// HOST_COMPILER-SAME: "-o" "[[HOSTOBJ:.+\.o]]"
+// HOST_COMPILER: clang-offload-bundler{{.*}} "-output=[[BUNDLEOBJ:.+\.o]]" "-input=[[DEVICEBC]]" "-input=[[HOSTOBJ]]"
+// HOST_COMPILER: clang-linker-wrapper{{.*}} "[[BUNDLEOBJ]]"
+
+// RUN: %clang_cl -fsycl --offload-new-driver -fsycl-host-compiler=/some/dir/cl %s -### 2>&1 \
+// RUN:  | FileCheck -check-prefix=HOST_COMPILER_CL %s
+// HOST_COMPILER_CL: clang{{.*}} "-fsycl-is-device"
+// HOST_COMPILER_CL-SAME: "-fsycl-int-header=[[INTHEADER:.+\.h]]" "-fsycl-int-footer=[[INTFOOTER:.+\.h]]"
+// HOST_COMPILER_CL-SAME: "-o" "[[DEVICEBC:.+\.bc]]"
+// HOST_COMPILER_CL: append-file{{.*}} "--append=[[INTFOOTER]]"
+// HOST_COMPILER_CL-SAME: "--output=[[APPENDFILESRC:.+\.cpp]]" "--use-include"
+// HOST_COMPILER_CL: cl{{.*}} "[[APPENDFILESRC]]"
+// HOST_COMPILER_CL-SAME: "-c" "-Fo[[HOSTOBJ:.+\.obj]]" "-FI" "[[INTHEADER]]"
+// HOST_COMPILER_CL-SAME: "/external:W0"
+// HOST_COMPILER_CL-SAME: "/external:I" "{{.*}}bin{{[/\\]+}}..{{[/\\]+}}include{{[/\\]+}}sycl"
+// HOST_COMPILER_CL-SAME: "/external:I" "{{.*}}bin{{[/\\]+}}..{{[/\\]+}}include{{[/\\]+}}sycl{{[/\\]+}}stl_wrappers"
+// HOST_COMPILER_CL-SAME: "/external:I" "{{.*}}bin{{[/\\]+}}..{{[/\\]+}}include"
+// HOST_COMPILER_CL: clang-offload-bundler{{.*}} "-output=[[BUNDLEOBJ:.+\.obj]]" "-input=[[DEVICEBC]]" "-input=[[HOSTOBJ]]"
+// HOST_COMPILER_CL: clang-linker-wrapper{{.*}} "[[BUNDLEOBJ]]"
+
+/// Check for additional host options.
+// RUN: %clangxx -fsycl --offload-new-driver -fsycl-host-compiler=g++ -fsycl-host-compiler-options="-DFOO -DBAR" %s -### 2>&1 \
+// RUN:  | FileCheck -check-prefix=HOST_OPTIONS %s
+// HOST_OPTIONS: g++{{.*}} "-o" "[[HOSTOBJ:.+\.o]]"{{.*}} "-DFOO" "-DBAR"
+
+// RUN: %clang_cl -fsycl --offload-new-driver -fsycl-host-compiler=cl -fsycl-host-compiler-options="/DFOO /DBAR /O2" %s -### 2>&1 \
+// RUN:  | FileCheck -check-prefix=HOST_OPTIONS_CL %s
+// HOST_OPTIONS_CL: cl{{.*}} "-Fo[[HOSTOBJ:.+\.obj]]"{{.*}} "/DFOO" "/DBAR" "/O2"
+
+/// Object output check.
+// RUN: %clangxx -fsycl --offload-new-driver -fsycl-host-compiler=g++ -c %s -### 2>&1 \
+// RUN:  | FileCheck -check-prefix=HOST_OBJECT %s
+// HOST_OBJECT: g++{{.*}} "-c"{{.*}} "-o" "[[OBJOUT:.+\.o]]"
+// HOST_OBJECT: clang-offload-bundler{{.*}} "-input={{.*}}.bc" "-input=[[OBJOUT]]"
+
+// RUN: %clang_cl -fsycl --offload-new-driver -fsycl-host-compiler=cl -c %s -### 2>&1 \
+// RUN:  | FileCheck -check-prefix=HOST_OBJECT_CL %s
+// HOST_OBJECT_CL: cl{{.*}} "-c"{{.*}} "-Fo[[OBJOUT:.+\.obj]]"
+// HOST_OBJECT_CL: clang-offload-bundler{{.*}} "-input={{.*}}.bc" "-input=[[OBJOUT]]"
+
+/// Missing argument error -fsycl-host-compiler=.
+// RUN: not %clangxx -fsycl --offload-new-driver -fsycl-host-compiler= -c -### %s 2>&1 \
+// RUN:  | FileCheck -check-prefix=HOST_COMPILER_NOARG %s
+// HOST_COMPILER_NOARG: missing argument to '-fsycl-host-compiler='
+
+/// Error for -fsycl-host-compiler and -fsycl-unnamed-lambda combination.
+// RUN: not %clangxx -fsycl --offload-new-driver -fsycl-host-compiler=g++ -fsycl-unnamed-lambda -c -### %s 2>&1 \
+// RUN:  | FileCheck -check-prefix=HOST_COMPILER_AND_UNNAMED_LAMBDA %s
+// HOST_COMPILER_AND_UNNAMED_LAMBDA: error: cannot specify '-fsycl-unnamed-lambda' along with '-fsycl-host-compiler'
+
+// -fsycl-host-compiler implies -fno-sycl-unnamed-lambda.
+// RUN: %clangxx -### -fsycl --offload-new-driver -fsycl-host-compiler=g++ -c -### %s 2>&1 \
+// RUN:  | FileCheck -check-prefix=IMPLY-NO-SYCL-UNNAMED-LAMBDA %s
+// IMPLY-NO-SYCL-UNNAMED-LAMBDA: clang{{.*}} "-fno-sycl-unnamed-lambda"
+
+// Zc:__cplusplus, Zc:__cplusplus- check.
+// RUN: %clang_cl -### -fsycl-host-compiler=cl -fsycl --offload-new-driver %s 2>&1 | FileCheck -check-prefix=CHECK-ZC-CPLUSPLUS %s
+// RUN: %clang_cl -### -fsycl-host-compiler=cl -fsycl --offload-new-driver -fsycl-host-compiler-options=/Zc:__cplusplus- %s 2>&1 | FileCheck -check-prefix=CHECK-ZC-CPLUSPLUS-MINUS %s
+// RUN: %clang_cl -### %s 2>&1 | FileCheck -check-prefix=CHECK-NO-ZC-CPLUSPLUS %s
+// RUN: %clang_cl -### -fsycl-host-compiler=g++ -fsycl --offload-new-driver %s 2>&1 | FileCheck -check-prefix=CHECK-NO-ZC-CPLUSPLUS %s
+// CHECK-ZC-CPLUSPLUS: "/Zc:__cplusplus"
+// CHECK-ZC-CPLUSPLUS-MINUS: "/Zc:__cplusplus-"
+// CHECK-NO-ZC-CPLUSPLUS-NOT: "/Zc:__cplusplus"
+
+/// -fsycl-host-compiler -save-temps behavior
+// RUN: %clangxx -### -fsycl-host-compiler=g++ -fsycl --offload-new-driver \
+// RUN:          -save-temps -c %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK_SAVE_TEMPS %s
+// CHECK_SAVE_TEMPS-NOT: error: unsupported output type when using external host compiler
+// CHECK_SAVE_TEMPS: clang{{.*}} "-fsycl-is-device"
+// CHECK_SAVE_TEMPS-SAME: "-E" {{.*}} "-o" "[[PREPROC_OUT:.+sycl-spir64-unknown-unknown.ii]]"
+// CHECK_SAVE_TEMPS-NEXT: clang{{.*}} "-fsycl-is-device"
+// CHECK_SAVE_TEMPS-SAME: "-emit-llvm-bc"{{.*}} "-o" "[[DEVICE_BC1:.+\.bc]]"{{.*}} "[[PREPROC_OUT]]"
+// CHECK_SAVE_TEMPS-NEXT: clang{{.*}} "-fsycl-is-device"
+// CHECK_SAVE_TEMPS-SAME: "-emit-llvm-bc"{{.*}} "-o" "[[DEVICE_BC2:.+\.bc]]"{{.*}} "[[DEVICE_BC1]]"
+// CHECK_SAVE_TEMPS-NEXT: append-file{{.*}} "--output=[[APPEND_CPP:.+\.cpp]]
+// CHECK_SAVE_TEMPS-NEXT: g++{{.*}} "[[APPEND_CPP]]" "-c"
+// CHECK_SAVE_TEMPS-SAME: "-o" "[[HOST_OBJ:.+\.o]]"
+// CHECK_SAVE_TEMPS-NEXT: clang-offload-bundler{{.*}} "-input=[[DEVICE_BC2]]" "-input=[[HOST_OBJ]]"
+
+/// Test to verify binary from PATH is used
+// RUN: rm -rf %t && mkdir -p %t/test_path
+// RUN: touch %t/test_path/clang++ && chmod +x %t/test_path/clang++
+// RUN: env "PATH=%t/test_path%{pathsep}%PATH%" \
+// RUN: %clangxx -### -fsycl -fsycl-host-compiler=clang++ \
+// RUN:   -fsycl-host-compiler-options=-DDUMMY_OPT --offload-new-driver \
+// RUN:   %s 2>&1 \
+// RUN: | FileCheck -check-prefix=PATH_CHECK %s
+// PATH_CHECK: {{(/|\\\\)}}test_path{{(/|\\\\)}}clang++{{.*}} "-DDUMMY_OPT"