address comments

Author: matthias-springer

mlir/include/mlir/IR/PatternMatch.h

@@ -504,6 +504,11 @@ class RewriterBase : public OpBuilder {
   }
 
   /// This method erases an operation that is known to have no uses.
+  ///
+  /// If the current insertion point is before the erased operation, it is
+  /// adjusted to the following operation (or the end of the block). If the
+  /// current insertion point is within the erased operation, the insertion
+  /// point is left in an invalid state.
   virtual void eraseOp(Operation *op);
 
   /// This method erases all operations in a block.

mlir/lib/IR/PatternMatch.cpp

@@ -152,44 +152,17 @@ void RewriterBase::replaceOp(Operation *op, Operation *newOp) {
   eraseOp(op);
 }
 
-/// Returns the given block iterator if it lies within the block `b`.
-/// Otherwise, otherwise finds the ancestor of the given block iterator that
-/// lies within `b`. Returns and "empty" iterator if the latter fails.
-///
-/// Note: This is a variant of Block::findAncestorOpInBlock that operates on
-/// block iterators instead of ops.
-static std::pair<Block *, Block::iterator>
-findAncestorIteratorInBlock(Block *b, Block *itBlock, Block::iterator it) {
-  // Case 1: The iterator lies within the block.
-  if (itBlock == b)
-    return std::make_pair(itBlock, it);
-
-  // Otherwise: Find ancestor iterator. Bail if we run out of parent ops.
-  Operation *parentOp = itBlock->getParentOp();
-  if (!parentOp)
-    return std::make_pair(static_cast<Block *>(nullptr), Block::iterator());
-  Operation *op = b->findAncestorOpInBlock(*parentOp);
-  if (!op)
-    return std::make_pair(static_cast<Block *>(nullptr), Block::iterator());
-  return std::make_pair(op->getBlock(), op->getIterator());
-}
-
 /// This method erases an operation that is known to have no uses. The uses of
 /// the given operation *must* be known to be dead.
 void RewriterBase::eraseOp(Operation *op) {
   assert(op->use_empty() && "expected 'op' to have no uses");
   auto *rewriteListener = dyn_cast_if_present<Listener>(listener);
 
-  // If the current insertion point is before/within the erased operation, we
-  // need to adjust the insertion point to be after the operation.
-  if (getInsertionBlock()) {
-    Block *insertionBlock;
-    Block::iterator insertionPoint;
-    std::tie(insertionBlock, insertionPoint) = findAncestorIteratorInBlock(
-        op->getBlock(), getInsertionBlock(), getInsertionPoint());
-    if (insertionBlock && insertionPoint == op->getIterator())
-      setInsertionPointAfter(op);
-  }
+  // If the current insertion point is before the erased operation, we adjust
+  // the insertion point to be after the operation.
+  if (getInsertionBlock() == op->getBlock() &&
+      getInsertionPoint() == op->getIterator())
+    setInsertionPointAfter(op);
 
   // Fast path: If no listener is attached, the op can be dropped in one go.
   if (!rewriteListener) {