[PATCH] D29014: [SelDag][MIR] Add FREEZE

[Juneyoung Lee via Phabricator via llvm-commits]

aqjune added a comment.

ping

If adding FREEZE to MachineIR causes maintenance cost, another possible solution is to lower SelDag's FREEZE(UNDEF) to IMPLICIT_DEF directly.
In this option, FREEZE only exist in SelDag, not in MIR.
Instead, now IMPLICIT_DEF in MIR should always yield the same value. This requires a few transformations regarding IMPLICIT_DEF in MIR to be fixed.
This may cause suboptimal codegen in a few cases, but I believe we have a solution for the cases, because a single UNDEF from SelDag can be always lowered into multiple IMPLICIT_DEFs (per each use) in MIR.


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  https://reviews.llvm.org/D29014/new/

https://reviews.llvm.org/D29014