[PATCH] D159499: [InstCombine] Fold or(phi1,phi2) into or(icmp1,icmp2)

[Noah Goldstein via Phabricator via llvm-commits]

goldstein.w.n added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp:2030
+                      m_ICmp(EqPred, m_Specific(operand->get()), m_Zero())) &&
+                EqPred == ICmpInst::ICMP_NE))))
+          return nullptr;
----------------
This seems very much so like a DAG type fold where you are basing the decision on existing expressions.
`phi` doesn't exist in backend (dagcombiner) so its a bit tricky.
@nikic, any place this can be put where it doesn't req iterating the use-list?

generally in instcombine we get our duplication by just blindly canoniclizing to a standard format.

Is there a regression if you blindly do the transform?


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  https://reviews.llvm.org/D159499/new/

https://reviews.llvm.org/D159499