[llvm-dev] Questions about jump threading optimization and what we can do (original) (raw)
Karl Rehm via llvm-dev llvm-dev at lists.llvm.org
Sun Feb 2 09:45:38 PST 2020
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Holy crap, I completely missed that. I'm sorry! That's my fault.
On Sun, Feb 2, 2020 at 12:15 PM Johannes Doerfert <jdoerfert at anl.gov> wrote:
On 01/30, Karl Rehm via llvm-dev wrote: > Since the bug report here: https://bugs.llvm.org/showbug.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?
I'm confused. In your godbold link you run it with O0 which disables almost all transformations. If we take the IR, remove the optnone attribute, run mem2reg and jump-threading we get what I think is reasonable: https://godbolt.org/z/u3fcTZ Please correct me if I misunderstand anything here. Cheers, Johannes -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20200202/34db416d/attachment.html>
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