[PATCH] [SROA] Simplify PHI nodes before promoting the alloca

[Mark Heffernan]

Just a couple suggestions which might simplify the code.

================
Comment at: lib/Transforms/Scalar/SROA.cpp:3106
@@ +3105,3 @@
+                           SmallPtrSetImpl<PHINode *> &OriginatesFromOther,
+                           Value *Source) {
+  if (Visited.count(PN))
----------------
Couple bike-shed suggestions:

Maybe name the function PHINodeEquivalentToSource?

You could also replace both ptr sets with a map<PHINode *, bool> where membership indicates it's been visited and the value indicates equivalence.

================
Comment at: lib/Transforms/Scalar/SROA.cpp:3141
@@ +3140,3 @@
+    if (!PHINodeOriginatesFromOther(PN, Visited, OriginatesFromOther, NewAI))
+      ToDelete.insert(PN);
+  }
----------------
If you use a map<PHINode *, bool> for equivalence as mentioned above, you can cleanly do away with ToDelete.  Just iterate through the map and replace the nodes with a true value.  I, think, necessarily those will all be in PHIUsers.

http://reviews.llvm.org/D4659