[OpenMP][RISCV] Add riscv32 support

[wangpc-pp]

CMake flags and some core changes are added to support riscv32
platform basically.

Fix #99427

[asb]

Tagging my colleague @mikhailramalho who's been doing some RV32 stuff recently so can at least provide additional testing if not a full code review.

[mikhailramalho]

@wangpc-pp could you provide instructions on how to test this patch?

I can use the setup I have to test libc to test your patch.

[wangpc-pp]

@wangpc-pp could you provide instructions on how to test this patch?

I can use the setup I have to test libc to test your patch.

Thanks!
The process can be:

1. Build a rv32 Clang/LLVM toolchian.
2. Build openmp and install it to the above toolchain:

cmake -DCMAKE_INSTALL_PREFIX=${TOOLCHAIN_PATH} \
    -DCMAKE_C_COMPILER=${TOOLCHAIN_PATH}/bin/clang \
    -DCMAKE_CXX_COMPILER=${TOOLCHAIN_PATH}/bin/clang++ \
    -DOPENMP_ENABLE_LIBOMPTARGET=Off \
    -DCMAKE_C_FLAGS="-march=rv32gc" \
    -DCMAKE_CXX_FLAGS="-march=rv32gc" \
    -DCMAKE_BUILD_TYPE=Release \
    -DLIBOMP_ARCH=riscv32 \
    -DLIBOMP_HAVE_WARN_SHARED_TEXTREL_FLAG=On \
    -DLIBOMP_HAVE_AS_NEEDED_FLAG=On \
    -DLIBOMP_HAVE_VERSION_SCRIPT_FLAG=On \
    -DLIBOMP_HAVE_STATIC_LIBGCC_FLAG=On \
    -DLIBOMP_HAVE_Z_NOEXECSTACK_FLAG=On \
    -DDISABLE_OMPD_GDB_PLUGIN=On \
    -DLIBOMP_OMPD_GDB_SUPPORT=Off \
    -DLIBOMP_ENABLE_SHARED=ON \
    ../openmp

You may set LIBOMP_ENABLE_SHARED to OFF to build static libraries.
3. Compile and run tests under openmp/runtime/src.

[shiltian]

You may also need changes in OMPT and OMPD. They are arch dependent I think.

[wangpc-pp]

You may also need changes in OMPT and OMPD. They are arch dependent I think.

I just searched "riscv64" and made riscv32 changes around riscv64 codes. We may not need to change OMPT/OMPD, or they are lack of riscv64 support?

[shiltian]

The structure of the code change looks good to me, but I'm not familiar with RISC-V arch so I'm not sure the technical soundness of the asm changes. I suppose it has been tested.

[dtcxzyw]

Reverse ping.

[wangpc-pp]

Reverse ping.

I can't guarantee the correctness of this implementation... It's hard to test.

[shiltian]

We need to test it to ensure that most of it works as expected.

[jprotze]

For ompt, only the tests use some arch/isa specific assumptions. If the tests succeed, no changes are necessary. Otherwise, some tweaks might be necessary in runtime/test/ompt/callback.h look for ARCH specific code.

Ompd is usually only activated for selected supported architectures. If you want to support OpenMP debugging for the architecture, you would need to check whether it works out of the box, or whether changes are necessary.

[joshua-arch1]

Can you run the suite https://github.com/OpenMP-Validation-and-Verification/OpenMP_VV? Actually there are several tests failed for riscv64. I think what we need to do now is to improve the riscv64 implementation first and then riscv32.