[llvm-dev] RFC: Killing undef and spreading poison (original) (raw)

Reid Kleckner via llvm-dev llvm-dev at lists.llvm.org
Tue Oct 25 11:16:28 PDT 2016

On Tue, Oct 25, 2016 at 10:44 AM, Daniel Berlin via llvm-dev < llvm-dev at lists.llvm.org> wrote:

Easier is a relative term. I expect optimally choosing which freezes to eliminate where, etc, reduces to a covering problem variant (or just straight ILP) :)

I think it's fine for GVN to fold them all to the same thing. The only difference between freeze(poison) and zero is that you can use a pre-existing register like RBP or RSP that says constant across the lifetime of the function so you don't need to materialize a zero if you don't have one already. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20161025/5f16b112/attachment.html>

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