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On Tue, Oct 25, 2016 at 10:44 AM, Daniel Berlin via llvm-dev <llvm-dev@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.