[llvm-dev] Multi-Threading Compilers

[Florian Hahn via llvm-dev]

> On Mar 26, 2020, at 10:55, Nicolai Hähnle <nhaehnle at gmail.com> wrote:
> 
> On Thu, Mar 26, 2020 at 11:53 AM Florian Hahn <florian_hahn at apple.com> wrote:
>>> It also doesn't solve the problem of Functions themselves -- those are
>>> also GlobalValues…
>> 
>> I am not sure why not. Function passes should only rely on the information at the callsite & from the declaration IIRC. For functions, we coulkd add extra declarations and update the call sites. But I might be missing something.
> 
> Function passes can remove, duplicate, or just plain introduce call
> sites (e.g. recognize a memset pattern), which means the use lists of
> Functions can be changed during a function pass…


Sure, but a single function won’t be processed in parallel by a function pass and would just work on the 'local version' of the globals it uses, including called functions. So a function pass adding/removing calls to existing ‘local versions’ of functions should not be a problem I think. 

One problem is that function passes can add new global, e.g. new declarations if they introduce new calls. I guess that would require some locking, but should happen quite infrequently.

Cheers,
Florian