diff --git a/mlir/lib/Transforms/Utils/DialectConversion.cpp b/mlir/lib/Transforms/Utils/DialectConversion.cpp
--- a/mlir/lib/Transforms/Utils/DialectConversion.cpp
+++ b/mlir/lib/Transforms/Utils/DialectConversion.cpp
@@ -1484,7 +1484,8 @@
   auto stateHasOp = [op](const auto &it) { return it.getOperation() == op; };
   auto &rootUpdates = impl->rootUpdates;
   auto it = llvm::find_if(llvm::reverse(rootUpdates), stateHasOp);
-  rootUpdates.erase(rootUpdates.begin() + (rootUpdates.rend() - it));
+  assert(it != rootUpdates.rend() && "no root update started on op");
+  rootUpdates.erase(it.base());
 }
 
 /// PatternRewriter hook for notifying match failure reasons.
@@ -2049,7 +2050,7 @@
       orderedPatternList = anyOpLegalizerPatterns;
 
     // If the pattern is not found, then it was removed and cannot be matched.
-    auto it = llvm::find(orderedPatternList, &pattern);
+    auto *it = llvm::find(orderedPatternList, &pattern);
     if (it == orderedPatternList.end())
       return PatternBenefit::impossibleToMatch();