[llvm] [Offload] Add support for riscv64 to host plugin (PR #115773)

[via llvm-commits]

joshua-arch1 wrote:

> Some debug information would help, I don't know if you built with `-DLIBOMPTARGET_ENABLE_DEBUG=ON`

clang -I./ompvv -lm -fopenmp=libomp -fopenmp-targets=riscv64-unknown-linux-gnu  -march=rv64gc  -DVERBOSE_MODE=1  -DOMPTARGET_DEBUG=1  tests/4.5/target/test_target_defaultmap.c -o clang_test_target_defaultmap.c.o
error: OpenMP target is invalid: 'riscv64-unknown-linux-gnu'

Do we need -fopenmp-targets to enable target offloading on riscv? 

>From the error in https://github.com/OpenMP-Validation-and-Verification/OpenMP_VV/blob/master/tests/4.5/target/test_target_defaultmap.c, I think the #pragma omp target cannot work.

[OMPVV_ERROR: test_target_defaultmap.c:81]  Condition scalar_char != 'a' failed 
[OMPVV_ERROR: test_target_defaultmap.c:82]  Condition scalar_short != 10 failed 
[OMPVV_ERROR: test_target_defaultmap.c:83]  Condition scalar_int != 11 failed 
[OMPVV_ERROR: test_target_defaultmap.c:84]  Condition scalar_float != 5.5f failed 
[OMPVV_ERROR: test_target_defaultmap.c:85]  Condition scalar_double != 10.45 failed 
[OMPVV_ERROR: test_target_defaultmap.c:86]  Condition scalar_enum != VAL1 failed 
[OMPVV_ERROR: test_target_defaultmap.c:94]  Condition test_defaultmap_off() failed 
[OMPVV_INFO: test_target_defaultmap.c:96] The value of errors is 6.
[OMPVV_RESULT: test_target_defaultmap.c] Test failed on the host.

https://github.com/llvm/llvm-project/pull/115773