[mlir][NVVM|ROCDL] Explicitly construct the return type in loadBitcodeFiles in (NVVM|ROCDL)Target

[fmorac]

Summary

Fix a build failure in GCC 7 caused by the function:
std::optional<SmallVector<std::unique_ptr<llvm::Module>>> loadBitcodeFiles ,
in NVVMTarget & ROCDLTarget.
The failure is caused because GCC fails to use the move constructor in
std::optional for constructing the return value, which prompts a call to the
deleted copy constructor in std::unique_ptr, resulting in a failure.

[mehdi_amini]

mlir/lib/Target/LLVM/ROCDL/Target.cpp

163

return std::move(bcFiles); isn't enough?

[fmorac]

mlir/lib/Target/LLVM/ROCDL/Target.cpp

163

It is, I just checked, I didn't want to risk it when I submitted the revision. I'll change it.

[fmorac]

Switched to a single call of std::move

mlir/lib/Target/LLVM/NVVM/Target.cpp

 
 std::optional<SmallVector<std::unique_ptr<llvm::Module>>>
 SerializeGPUModuleBase::loadBitcodeFiles(llvm::Module &module,
                                          llvm::TargetMachine &targetMachine) {
   SmallVector<std::unique_ptr<llvm::Module>> bcFiles;
   if (failed(loadBitcodeFilesFromList(module.getContext(), targetMachine,
                                       fileList, bcFiles, true)))
     return std::nullopt;
-  return bcFiles;
+  return std::optional<SmallVector<std::unique_ptr<llvm::Module>>>(
+      std::move(bcFiles));
 }
 
 #if MLIR_CUDA_CONVERSIONS_ENABLED == 1
 namespace {
 class NVPTXSerializer : public SerializeGPUModuleBase {
 public:
   NVPTXSerializer(Operation &module, NVVMTargetAttr target,
                   const gpu::TargetOptions &targetOptions);

mlir/lib/Target/LLVM/ROCDL/Target.cpp

 
 std::optional<SmallVector<std::unique_ptr<llvm::Module>>>
 SerializeGPUModuleBase::loadBitcodeFiles(llvm::Module &module,
                                          llvm::TargetMachine &targetMachine) {
   SmallVector<std::unique_ptr<llvm::Module>> bcFiles;
   if (failed(loadBitcodeFilesFromList(module.getContext(), targetMachine,
                                       fileList, bcFiles, true)))
     return std::nullopt;
-  return bcFiles;
+  return std::optional<SmallVector<std::unique_ptr<llvm::Module>>>(
+      std::move(bcFiles));
 }
 
 LogicalResult
 SerializeGPUModuleBase::handleBitcodeFile(llvm::Module &module,
                                           llvm::TargetMachine &targetMachine) {
   // Some ROCM builds don't strip this like they should
   if (auto *openclVersion = module.getNamedMetadata("opencl.ocl.version"))
     module.eraseNamedMetadata(openclVersion);