[PATCH] D52707: Switch optimization in IR for known maximum switch values

[Hans Wennborg via Phabricator via llvm-commits]

hans added inline comments.


================
Comment at: lib/Transforms/Utils/SimplifyCFG.cpp:4884
+                         DefaultResultsList, DL, TTI))
+      return false;
+
----------------
ayonam wrote:
> hans wrote:
> > What's happening here? Why do we need to find a constant value on the phi node?
> > 
> > We'll need to update any phi node in the default block when adding the new case, but there's no need for it to be constant.
> It should just be a Value and not a Constant.  I had a test case that had a constant on the PHI node and hence I had coded thus.
> 
> I tried changing this to a Value and realized that there isn't a method that gives me all the Values that are created in a given Case block.  There is a method that returns all constants that are created in a Case block.  Would you know of any other method that would return me the Values?  Or else I will have to write one of my own.
> 
> 
What I'm saying is there should be no need to compute the resulting value at phi nodes at all. That stuff is used when replacing switches with a table of constant values, it does not apply here.


https://reviews.llvm.org/D52707