Relax CHPL_LLVM=bundled restriction for CHPL_GPU=amd to allow bundled LLVM upgrade #28007
Description
While working on upgrading LLVM versions, I tried Chapel with ROCm 6.4 and LLVM 20. I no longer see the issues with analyzeResourceUsage which caused us to restrict ROCm compilation to the bundled LLVM (which is currently LLVM 19).
I briefly tested LLVM 21 with ROCm 6.0, which does not work. LLVM 21 requires ROCm 6.3 at minimum.
ROCm 6.3 support requires #26934 to be resolved.
Since ROCm support is tied to the bundled LLVM only, we need to make sure it works before upgrading the bundled LLVM. This is all tangled together, but I think there are a few steps we can take to resolve this
- We can't upgrade the bundled LLVM without breaking current rocm support, so deal with that first
- Test ROCm 6.2 with CHPL_LLVM 20/21, confirm it works, and relax the restriction to allow a system LLVM
- Get ROCm 6.3/6.4 working with CHPL_LLVM 20/21
- Upgrade bundled LLVM to LLVM 21
Unfortunately, this gates upgrading our bundled LLVM behind #26934, since LLVM 21 requires ROCm 6.3