[PATCH] D75845: [ValueLattice] Add singlecrfromundef lattice value.

[Florian Hahn via Phabricator via llvm-commits]

fhahn marked 4 inline comments as done.
fhahn added inline comments.


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Comment at: llvm/include/llvm/Analysis/ValueLattice.h:47
     /// constantexprs can appear here.)
     notconstant,
 
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efriedma wrote:
> fhahn wrote:
> > efriedma wrote:
> > > Sort of a side-question while I'm here, but how are we inferring notconstant?  Is the inference safe in the presence of undef?
> > I've responded in D75120
> I guess my concern is really, does "notconstant" imply that we've proven the value isn't undef?  It would probably be worth stating that explicitly.
Right, notconstant (undef) is not allowed. I'll state that explicitly.


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Comment at: llvm/include/llvm/Analysis/ValueLattice.h:44
+    /// Transition allowed to the following states:
+    ///  constant
+    ///  singlecrfromundef
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efriedma wrote:
> Is there actually a transition from undef -> constant?
Yes it is allowed in `mergeIn()`, which also ensures going to overdefined if we merge a constant with a different constant.


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  https://reviews.llvm.org/D75845/new/

https://reviews.llvm.org/D75845