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

[Nikita Popov via cfe-commits]

nikic wrote:

> Note that the option is off by default as using the SPIR-V backend, at least on my machine, uses a lot of memory and the process is often killed in a parallelized build. It does complete, however.

I see the same behavior, goes up to something like 30GB. The input is not particularly large (just 300k lines of IR).

>From a quick run through massif, it looks like MachineInstrs in SPIRVGlobalRegistry are the memory hog?

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