[AMDGPU][OpenMP] Fix clang driver crash when provided -c

[pdhaliwal]

Summary

The offload action is used in four different ways as explained
in Driver.cpp:4495. When -c is present, the final phase will be
assemble (linker when -c is not present). However, this phase
is skipped according to D96769 for amdgcn. So, offload action
arrives into following situation,

compile (device) ---> offload ---> offload

without -c the chain looks like,
compile (device) ---> offload ---> linker (device)

				---> offload

The former situation creates an unhandled case which causes
problem. The solution presented in this patch delays the D96769
logic until job creation time. This keeps the offload action
in the 1 of the 4 specified situations.

[JonChesterfield]

@jdoerfert This drops the logic for save-temps that I remember being contentious.

Doing a no-op backend pass instead of skipping over it is probably more robust.

clang/lib/Driver/Driver.cpp

4600

I wonder if this would be clearer as if (isa<>() || isa<>()) followed by a ternary to pick the second argument to BuildJobs. Overall I think I prefer the separate calls, as currently written.

[jdoerfert]

Cool, this makes sense :)

clang/lib/Driver/Driver.cpp

getDeviceDependences(OffloadAction::DeviceDependences &DA,
 
         // We passed the device action as a host dependence, so we don't need to
         // do anything else with them.
         OpenMPDeviceActions.clear();
         return ABRT_Success;
       }
 
       // By default, we produce an action for each device arch.
-      for (unsigned I = 0; I < ToolChains.size(); ++I) {
-        Action *&A = OpenMPDeviceActions[I];
-        // AMDGPU does not support linking of object files, so we skip
-        // assemble and backend actions to produce LLVM IR.
-        if (ToolChains[I]->getTriple().isAMDGCN() &&
-            (CurPhase == phases::Assemble || CurPhase == phases::Backend))
-          continue;
-
+      for (Action *&A : OpenMPDeviceActions)
         A = C.getDriver().ConstructPhaseAction(C, Args, CurPhase, A);
-      }
 
       return ABRT_Success;
     }
 
     ActionBuilderReturnCode addDeviceDepences(Action *HostAction) override {
 
       // If this is an input action replicate it for each OpenMP toolchain.
       if (auto *IA = dyn_cast<InputAction>(HostAction)) {
InputInfo Driver::BuildJobsForActionNoCache(
 
   ToolSelector TS(JA, *TC, C, isSaveTempsEnabled(),
                   embedBitcodeInObject() && !isUsingLTO());
   const Tool *T = TS.getTool(Inputs, CollapsedOffloadActions);
 
   if (!T)
     return InputInfo();
 
+  if (BuildingForOffloadDevice &&
+      A->getOffloadingDeviceKind() == Action::OFK_OpenMP) {
+    if (TC->getTriple().isAMDGCN()) {
+      // AMDGCN treats backend and assemble actions as no-op because
+      // linker does not support object files.
+      if (const BackendJobAction *BA = dyn_cast<BackendJobAction>(A)) {
+        return BuildJobsForAction(C, *BA->input_begin(), TC, BoundArch,
+                                  AtTopLevel, MultipleArchs, LinkingOutput,
+                                  CachedResults, TargetDeviceOffloadKind);
+      }
+
+      if (const AssembleJobAction *AA = dyn_cast<AssembleJobAction>(A)) {
+        return BuildJobsForAction(C, *AA->input_begin(), TC, BoundArch,
+                                  AtTopLevel, MultipleArchs, LinkingOutput,
+                                  CachedResults, TargetDeviceOffloadKind);
+      }
+    }
+  }
+
   // If we've collapsed action list that contained OffloadAction we
   // need to build jobs for host/device-side inputs it may have held.
   for (const auto *OA : CollapsedOffloadActions)
     cast<OffloadAction>(OA)->doOnEachDependence(
         /*IsHostDependence=*/BuildingForOffloadDevice,
         [&](Action *DepA, const ToolChain *DepTC, const char *DepBoundArch) {
           OffloadDependencesInputInfo.push_back(BuildJobsForAction(
               C, DepA, DepTC, DepBoundArch, /* AtTopLevel */ false,

clang/test/Driver/amdgpu-openmp-toolchain.c

 // CHECK-PHASES: 1: preprocessor, {0}, cpp-output, (host-openmp)
 // CHECK-PHASES: 2: compiler, {1}, ir, (host-openmp)
 // CHECK-PHASES: 3: backend, {2}, assembler, (host-openmp)
 // CHECK-PHASES: 4: assembler, {3}, object, (host-openmp)
 // CHECK-PHASES: 5: input, "{{.*}}amdgpu-openmp-toolchain.c", c, (device-openmp)
 // CHECK-PHASES: 6: preprocessor, {5}, cpp-output, (device-openmp)
 // CHECK-PHASES: 7: compiler, {6}, ir, (device-openmp)
 // CHECK-PHASES: 8: offload, "host-openmp (x86_64-unknown-linux-gnu)" {2}, "device-openmp (amdgcn-amd-amdhsa)" {7}, ir
-// CHECK-PHASES: 9: linker, {8}, image, (device-openmp)
-// CHECK-PHASES: 10: offload, "device-openmp (amdgcn-amd-amdhsa)" {9}, image
-// CHECK-PHASES: 11: clang-offload-wrapper, {10}, ir, (host-openmp)
-// CHECK-PHASES: 12: backend, {11}, assembler, (host-openmp)
-// CHECK-PHASES: 13: assembler, {12}, object, (host-openmp)
-// CHECK-PHASES: 14: linker, {4, 13}, image, (host-openmp)
+// CHECK-PHASES: 9: backend, {8}, assembler, (device-openmp)
+// CHECK-PHASES: 10: assembler, {9}, object, (device-openmp)
+// CHECK-PHASES: 11: linker, {10}, image, (device-openmp)
+// CHECK-PHASES: 12: offload, "device-openmp (amdgcn-amd-amdhsa)" {11}, image
+// CHECK-PHASES: 13: clang-offload-wrapper, {12}, ir, (host-openmp)
+// CHECK-PHASES: 14: backend, {13}, assembler, (host-openmp)
+// CHECK-PHASES: 15: assembler, {14}, object, (host-openmp)
+// CHECK-PHASES: 16: linker, {4, 15}, image, (host-openmp)
 
 // handling of --libomptarget-amdgcn-bc-path
 // RUN:   %clang -### --target=x86_64-unknown-linux-gnu -fopenmp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx803 --libomptarget-amdgcn-bc-path=%S/Inputs/hip_dev_lib/libomptarget-amdgcn-gfx803.bc %s 2>&1 | FileCheck %s --check-prefix=CHECK-LIBOMPTARGET
 // CHECK-LIBOMPTARGET: clang{{.*}}"-cc1"{{.*}}"-triple" "amdgcn-amd-amdhsa"{{.*}}"-target-cpu" "gfx803" "-fcuda-is-device" "-mlink-builtin-bitcode"{{.*}}Inputs/hip_dev_lib/libomptarget-amdgcn-gfx803.bc"{{.*}}
 
 // RUN:   %clang -### --target=x86_64-unknown-linux-gnu -fopenmp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx803 -nogpulib %s 2>&1 | FileCheck %s --check-prefix=CHECK-NOGPULIB
 // CHECK-NOGPULIB-NOT: clang{{.*}}"-cc1"{{.*}}"-triple" "amdgcn-amd-amdhsa"{{.*}}"-target-cpu" "gfx803" "-fcuda-is-device" "-mlink-builtin-bitcode"{{.*}}libomptarget-amdgcn-gfx803.bc"{{.*}}
 

 // CHECK-PRINT-BINDINGS: "x86_64-unknown-linux-gnu" - "clang::as", inputs: ["[[OFFLOAD_S]]"], output: "[[OFFLOAD_O:.*]]"
 // CHECK-PRINT-BINDINGS: "x86_64-unknown-linux-gnu" - "GNU::Linker", inputs: ["[[HOST_O]]", "[[OFFLOAD_O]]"], output:
 
 // verify the llc is invoked for textual assembly output
 // RUN:   env LIBRARY_PATH=%S/Inputs/hip_dev_lib %clang -### --target=x86_64-unknown-linux-gnu -fopenmp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx906 -save-temps %s 2>&1 \
 // RUN:   | FileCheck %s --check-prefix=CHECK-SAVE-ASM
 // CHECK-SAVE-ASM: llc{{.*}}amdgpu-openmp-toolchain-{{.*}}-gfx906-linked.bc" "-mtriple=amdgcn-amd-amdhsa" "-mcpu=gfx906" "-filetype=asm" "-o"{{.*}}amdgpu-openmp-toolchain-{{.*}}-gfx906.s"
 // CHECK-SAVE-ASM: llc{{.*}}amdgpu-openmp-toolchain-{{.*}}-gfx906-linked.bc" "-mtriple=amdgcn-amd-amdhsa" "-mcpu=gfx906" "-filetype=obj" "-o"{{.*}}amdgpu-openmp-toolchain-{{.*}}-gfx906.o"
+
+// check the handling of -c
+// RUN:   env LIBRARY_PATH=%S/Inputs/hip_dev_lib %clang -ccc-print-bindings -c --target=x86_64-unknown-linux-gnu -fopenmp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx906 -save-temps %s 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=CHECK-C
+// CHECK-C: "x86_64-unknown-linux-gnu" - "clang",
+// CHECK-C: "x86_64-unknown-linux-gnu" - "clang",{{.*}}output: "[[HOST_BC:.*]]"
+// CHECK-C: "amdgcn-amd-amdhsa" - "clang",{{.*}}output: "[[DEVICE_I:.*]]"
+// CHECK-C: "amdgcn-amd-amdhsa" - "clang", inputs: ["[[DEVICE_I]]", "[[HOST_BC]]"]
+// CHECK-C: "x86_64-unknown-linux-gnu" - "clang"
+// CHECK-C: "x86_64-unknown-linux-gnu" - "clang::as"
+// CHECK-C: "x86_64-unknown-linux-gnu" - "offload bundler"