[PATCH] D153351: [RISCV] Fold vmv.v.v into vops

[Philip Reames via Phabricator via llvm-commits]

reames added inline comments.


================
Comment at: llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp:3517
+
+    // Make sure there's a corresponding MaskedPseudo otherwise it's not safe to
+    // change VL.
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reames wrote:
> Please rebase this over D154620, and then use the exact same code structure as the vmerge transform.  Having them different makes it very hard to follow.  
> 
> Hm, this is just a thought.  But could we take the existing vmerge transform, and split it into two steps?  If a vmv.v.v is like a vmerge with a all ones mask, could the vmerge transform become "first form vmv.v.v" and "then fold vmv.v.v into true"?  We in fact already have both of these pieces, can we simply reorder and restructure?
Ignore the just a thought bit.  That handles the sub-case where the mask is all ones, but does not handle the arbitrary mask case.  I got myself confused with thinking about the unmasking peephole, but that's a different bit of logic.


Repository:
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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D153351/new/

https://reviews.llvm.org/D153351