[PATCH] D57033: [SSAUpdater] Handle case with single available value faster.

[Florian Hahn via Phabricator via llvm-commits]

fhahn added a comment.

In D57033#1365676 <https://reviews.llvm.org/D57033#1365676>, @efriedma wrote:

> SSAUpdater has code to insert undef in certain cases.  Can you prove those cases don't apply to all callers of GetValueAtEndOfBlock?




In D57033#1365676 <https://reviews.llvm.org/D57033#1365676>, @efriedma wrote:

> SSAUpdater has code to insert undef in certain cases.  Can you prove those cases don't apply to all callers of GetValueAtEndOfBlock?


IIUC, SSAUpdater insert undefs for uses in unreachable blocks. As it is, this patch would rename uses in unreachable block to use the lcssa PHI node instead of undef. It should be straight forward to do such checks in LCSSA (DT is available), so I think it is easier to move the code to LCSSA. What do you think?


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https://reviews.llvm.org/D57033