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

[Juneyoung Lee via Phabricator via llvm-commits]

aqjune added a comment.

To synchronize - the remaining issue was about duplicability of the freeze instruction in MIR.

In IR, a duplicated freeze may result in a different value due to the nature of undef. However, in MIR, this may be problematic in some cases.

My suggestion is to allow freeze in MIR to yield the same value when they are consecutively arranged.
This involved clarificaton of when the value of IMPLICIT_DEF could change during execution, and the updated comments of TargetOpcodes.def reflects that.

Currently, `isNotDuplicable` is still set to 1 to leave it as conservative & copiers deal with freeze specially in the future.


Repository:
  rG LLVM Github Monorepo

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

https://reviews.llvm.org/D29014