[llvm] [InstCombinePHI] Enhance PHI CSE to remove redundant phis (PR #163453)

[Yingwei Zheng via llvm-commits]

================
@@ -4866,6 +4866,89 @@ static Value *simplifySelectWithFCmp(Value *Cond, Value *T, Value *F,
   return nullptr;
 }
 
+/// Look for the following pattern and simplify %1 to %identicalPhi.
+/// Here %phi, %1 and %phi.next perform the same functionality as
----------------
dtcxzyw wrote:

It would be better to give `%1` a meaningful name.


https://github.com/llvm/llvm-project/pull/163453