[llvm-dev] InstCombine, graph rewriting, Equality saturation (original) (raw)

Siddharth Bhat via llvm-dev llvm-dev at lists.llvm.org
Thu Sep 7 10:52:39 PDT 2017

Thanks for the response.

Should I create a small prototype of equality saturation as an LLVM pass so that there can be some concrete discussion on this? I'd love pointers.

Thanks, Siddharth

On Wed 6 Sep, 2017, 23:35 John Regehr via llvm-dev <llvm-dev at lists.llvm.org> wrote:

Equality saturation is very cool work and Ross Tate mentioned to me that he'd be happy to chat with you about this. > But also, you might take a look at some existing projects in this general space that are already integrated with LLVM, such as Souper and Alive. > InstCombine is pretty cool but developing techniques to build these things automatically is awesome and on my wish list. There's potential for improvements in all of: speed, code quality, and correctness. > While we're on the subject: Are the canonicalization rules for LLVM IR documented anywhere? > Thanks, > John >> https://github.com/google/souper https://github.com/nunoplopes/alive >>> On 9/5/17 4:57 PM, (IIIT) Siddharth Bhat via llvm-dev wrote: > Hello all, > > I've seen some discussion that InstCombine is "too general" and that > llvm should implement a proper graph rewrite mechanism: > > Link to llvm-dev discussion about > this: http://lists.llvm.org/pipermail/llvm-dev/2017-May/113219.html, > Link to review where this came up (and I first heard about > it): https://reviews.llvm.org/D37195. > > I wanted to understand what the current issues with InstCombine are, and > if a graph rewriter prototype is something people are interested in. I > find the idea appealing, from what little I know it, so I'd be > interested in hacking something up. > > What would such a framework look like? Is there past literature on the > subject? From what I know, many functional compilers using combinator > based compilation were graph rewriting. Is there other prior art? > > Also, there is the idea of Equality Saturation > (http://www.cs.cornell.edu/~ross/publications/eqsat/) that I found out > about recently. Could this be used to augment the InstCombine > infrastructure? > > Thanks, > ~Siddharth > > -- > Sending this from my phone, please excuse any typos! > > _> ________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev > _________________________ LLVM Developers mailing list llvm-dev at lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

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