[llvm-dev] LLVM multithreading support
Zachary Turner via llvm-dev
llvm-dev at lists.llvm.org
Mon Apr 13 23:28:44 PDT 2020
On Sat, Apr 11, 2020 at 5:15 PM Chris Lattner <clattner at nondot.org> wrote:
> Historically, LLVM had a design where you could dynamically enable and
> disable multithreading support in a tool, which would be perfect for this
> use case, but it got removed by this patch
> (xref https://reviews.llvm.org/D4216). The rationale in the patch
> doesn’t make sense to me - this mode had nothing to do with the old LLVM
> global lock, this had to do with whether llvm::llvm_is_multithreaded()
> returned true or false … which all the locking stuff is guarded on.
> Would it make sense to re-enable this, or am I missing something?
It’s been a while, but also see
https://reviews.llvm.org/D4142 for more context.
This was probably one of my first patches ever to LLVM, but it sounds like
the thought process was something like:
1) Stop using llvm_start_multithreaded in two places where it wasn’t needed.
2) Realize that it’s never called anymore *anywhere*
3) Delete dead code.
Given that it’s been 6 years with nobody else needing this, I’m skeptical
that its of broad enough utility to re-introduce. On the other hand, I’m
basically inactive at this point so I have no horse in the race.
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