[llvm-dev] Questions about jump threading optimization and what we can do

Nicolai Hähnle via llvm-dev
Sun, 02 Feb 2020 08:53:44 -0000

On Fri, Jan 31, 2020 at 12:47 AM Karl Rehm via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Since the bug report here: https://bugs.llvm.org/show_bug.cgi?id=44679
I've been thinking about cases like it, such as:
https://godbolt.org/z/Fwq8mn
>
> I wonder what we can do about this in a general sense. As far as I can
tell, the jump threading algorithm is *really* conservative, which is one reason
this isn't working as well as I'd hope; however, we don't want to
produce irreducible control flow that the other passes would work less
effectively on. Thoughts?

Just brainstorming, really, but what about running a less conservative
version of JumpThreading later, _after_ loop passes have run?

Cheers,
Nicolai



>
> - Karl
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