[PATCH] D98058: [InstCombine] Simplify phis with incoming pointer-casts.

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

This indeed won't really work with `foldPHIArgOpIntoPHI()`, first because we actually don't create a new PHI,
secondly, this transform does not use-count restrictions, while `foldPHIArgOpIntoPHI()` has some.



================
Comment at: llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp:1322-1328
+    Value *Inc0 = PN.getIncomingValue(0);
+    Value *Inc0Stripped = Inc0->stripPointerCasts();
+    if (Inc0 != Inc0Stripped &&
+        all_of(PN.incoming_values(), [Inc0, Inc0Stripped](Value *Inc) {
+          return Inc0 == Inc || Inc0Stripped == Inc->stripPointerCasts();
+        })) {
+      return CastInst::CreatePointerCast(Inc0Stripped, PN.getType());
----------------
I would recommend `s/Inc/IV/`


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp:1325-1327
+        all_of(PN.incoming_values(), [Inc0, Inc0Stripped](Value *Inc) {
+          return Inc0 == Inc || Inc0Stripped == Inc->stripPointerCasts();
+        })) {
----------------
I would recommend a less brute-force approach.
Add a map<IV, stripped>, and don't redo the work if the result is known.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D98058/new/

https://reviews.llvm.org/D98058