[clang] [llvm] [llvm][clang] Allocate a new stack instead of spawning a new thread to get more stack space (PR #133173)

[Aaron Ballman via llvm-commits]

AaronBallman wrote:

> If split stacks are negatively impacting profiling, debugging, or other compiler development tasks, I have to ask, have we considered optimizing clang stack usage?

Strong +1 to this.

> Apple platforms and tools are known to support this, so this only enables it there for now.

I'm a bit concerned about this changing behavior only for Apple platforms; that's a different folks doing triage really need to understand. Doesn't Linux also support this functionality, so we'd at least get the coverage on more than one platform? (Linux could be done in a follow-up, but I'm mostly worried we'll only ever implement this for Apple at which point I question whether the extra complexity is something the community should maintain or not.)

https://github.com/llvm/llvm-project/pull/133173