[Mlir-commits] [mlir] [MLIR][Transforms] Fix Mem2Reg removal order to respect dominance (PR #68687)

[Tobias Gysi]

================
@@ -516,14 +518,16 @@ void MemorySlotPromoter::computeReachingDefInRegion(Region *region,
 }
 
 void MemorySlotPromoter::removeBlockingUses() {
-  llvm::SetVector<Operation *> usersToRemoveUses;
-  for (auto &user : llvm::make_first_range(info.userToBlockingUses))
-    usersToRemoveUses.insert(user);
-  SetVector<Operation *> sortedUsersToRemoveUses =
-      mlir::topologicalSort(usersToRemoveUses);
+  llvm::SmallVector<Operation *> usersToRemoveUses(
+      llvm::make_first_range(info.userToBlockingUses));
+  // The uses need to be traversed in *reverse dominance* order to ensure that
+  // transitive replacements are performed correctly.
+  llvm::sort(usersToRemoveUses, [&](Operation *a, Operation *b) {
+    return dominance.properlyDominates(b, a);
+  });
----------------
gysit wrote:

```suggestion
  llvm::sort(usersToRemoveUses, [&](Operation *lhs, Operation *rhs) {
    return dominance.properlyDominates(rhs, lhs);
  });
```
nit:

https://github.com/llvm/llvm-project/pull/68687