[libclc] [libclc] Add an option to build SPIR-V targets with the LLVM backend (PR #151347)

[Fraser Cormack via cfe-commits]

frasercrmck wrote:

Hi! Yeah I saw the same thing when I was playing around with this (see the PR description). At the time I remember attributing it to the GlobalISel used by SPIR-V. I didn't have any further data points to see whether it was an issue specific to the SPIR-V backend or generally a GlobalISel problem. SPIR-V does custom things with book-keeping which might account for the memory usage.

I'm no longer working on this project, but I'd suggest seeing if other GlobalISel backends see a similar degradation in performance. If not, it's probably worth filing a ticket with the SPIR-V folks.

 I don't have any good suggestions about how to work with what we've got. We could create smaller modules, or reduce parallelisation for the SPIR-V targets? Anything done would in all likelihood be a brittle workaround to the build system.

https://github.com/llvm/llvm-project/pull/151347