opencl-neo build fails on non-checked llvm::Expected on IGC side

[dvrogozh]

The build of scheduler.cl via ocloc:
LD_LIBRARY_PATH=/home/compute-runtime/build/bin /home/compute-runtime/build/bin/ocloc -q -file scheduler.cl -device skl -cl-intel-greater-than-4GB-buffer-required -64 -out_dir /home/compute-runtime/build/bin/scheduler/x64/gen9 -cpp_file -options -I/home/install.llvm8.igc/include/igc\ -I/home/install.llvm8.igc/include/igc/cif\ -I/home/install.llvm8.igc/include/igc/ocl_igc_shared/executable_format\ -I/home/install.llvm8.igc/include/igc/ocl_igc_shared/device_enqueue\ -I\ ../gen9\ -cl-kernel-arg-info\ -cl-std=CL2.0

May fail as follows:

Expected<T> must be checked before access or destruction.
Expected<T> value was in success state. (Note: Expected<T> values in success mode must still be checked prior to being destroyed).

#0  0x00007ffff6e05277 in raise () from /lib64/libc.so.6
#1  0x00007ffff6e06968 in abort () from /lib64/libc.so.6
#2  0x00007ffff2dfbbc3 in llvm::Expected<std::unique_ptr<llvm::Module, std::default_delete<llvm::Module> > >::fatalUncheckedExpected() const () from /lib64/libigc.so
#3  0x00007ffff2fe2035 in IGC::PreCompiledFuncImport::runOnModule(llvm::Module&) [clone .part.576] () from /lib64/libigc.so
#4  0x00007ffff3ef2972 in (anonymous namespace)::MPPassManager::runOnModule (this=0x804140, M=...) at /home/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1744
#5  0x00007ffff3ef310a in llvm::legacy::PassManagerImpl::run (this=0x7abd00, M=...) at /home/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1857
#6  0x00007ffff3ef3339 in llvm::legacy::PassManager::run (this=0x7fffffffc7a0, M=...) at /home/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1888
#7  0x00007ffff2f552fc in void IGC::CodeGen<IGC::OpenCLProgramContext>(IGC::OpenCLProgramContext*, llvm::MapVector<llvm::Function*, IGC::CShaderProgram*, llvm::DenseMap<llvm::Function*, unsigned int, llvm::DenseMapInfo<llvm::Function*>, llvm::detail::DenseMapPair<llvm::Function*, unsigned int> >, std::vector<std::pair<llvm::Function*, IGC::CShaderProgram*>, std::allocator<std::pair<llvm::Function*, IGC::CShaderProgram*> > > >&) () from /lib64/libigc.so
#8  0x00007ffff2f31024 in IGC::CodeGen(IGC::OpenCLProgramContext*) () from /lib64/libigc.so
#9  0x00007ffff2dff074 in TC::TranslateBuild(TC::STB_TranslateInputArgs const*, TC::STB_TranslateOutputArgs*, TC::TB_DATA_FORMAT, IGC::CPlatform const&, float) () from /lib64/libigc.so
#10 0x00007ffff2ecbb51 in IGC::IgcOclTranslationCtx<0ul>::Impl::Translate(unsigned long, CIF::Builtins::Buffer<1ul>*, CIF::Builtins::Buffer<1ul>*, CIF::Builtins::Buffer<1ul>*, CIF::Builtins::Buffer<1ul>*, CIF::Builtins::Buffer<1ul>*, CIF::Builtins::Buffer<1ul>*, unsigned int, void*) const () from /lib64/libigc.so
#11 0x00007ffff2ece273 in IGC::IgcOclTranslationCtx<1ul>::TranslateImpl(unsigned long, CIF::Builtins::Buffer<1ul>*, CIF::Builtins::Buffer<1ul>*, CIF::Builtins::Buffer<1ul>*, CIF::Builtins::Buffer<1ul>*, unsigned int) () from /lib64/libigc.so
#12 0x000000000041d159 in OCLRT::OfflineCompiler::buildSourceCode() ()
#13 0x0000000000420fbe in OCLRT::OfflineCompiler::build() ()
#14 0x0000000000425164 in int SafetyGuardLinux::call<int, OCLRT::OfflineCompiler, int (OCLRT::OfflineCompiler::*)()>(OCLRT::OfflineCompiler*, int (OCLRT::OfflineCompiler::*)(), int) ()
#15 0x0000000000425064 in buildWithSafetyGuard(OCLRT::OfflineCompiler*) ()
#16 0x00000000004117a2 in main ()

This happens because IGC does not check llvm::Expected here:

intel-graphics-compiler/IGC/Compiler/Optimizer/PreCompiledFuncImport.cpp

Line 406 in 952d4d1

std::unique_ptr<llvm::Module> m_pBuiltinModule = std::move(*ModuleOrErr);

while it should according to LLVM documentation and it actually does that in few other places except this one.

I was building IGC per this instruction against LLVM-8: https://github.com/dvrogozh/intel-graphics-compiler/tree/rfc_readme. Additionally the following patches were applied:

• All patches here: https://github.com/intel/opencl-clang/tree/ocl-open-80/patches
• build: use llvm_config and full symbols resolution opencl-clang#45 to fix opencl-neo driver build might fail due to non-full symbols resolution (missing -Wl,--no-undefined) opencl-clang#44
• neo patch Fix queue casts which cause spirv to die with assert compute-runtime#143 to fix spirv translator assert failure building opencl-neo targets via ocloc opencl-clang#46