Automerge: [mlir][IR] Set insertion point when erasing an operation (#146955)

Erasing the operation to which the current insertion point is set,
leaves the insertion point in an invalid state. This commit resets the
insertion point to the following operation.

Also adjust the insertion point when inlining a block.

Author: matthias-springer

mlir/include/mlir/IR/PatternMatch.h

@@ -525,6 +525,11 @@ 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.
@@ -539,6 +544,9 @@ class RewriterBase : public OpBuilder {
   /// somewhere in the middle (or beginning) of the dest block, the source block
   /// must have no successors. Otherwise, the resulting IR would have
   /// unreachable operations.
+  ///
+  /// If the insertion point is within the source block, it is adjusted to the
+  /// destination block.
   virtual void inlineBlockBefore(Block *source, Block *dest,
                                  Block::iterator before,
                                  ValueRange argValues = {});
@@ -549,6 +557,9 @@ class RewriterBase : public OpBuilder {
   ///
   /// The source block must have no successors. Otherwise, the resulting IR
   /// would have unreachable operations.
+  ///
+  /// If the insertion point is within the source block, it is adjusted to the
+  /// destination block.
   void inlineBlockBefore(Block *source, Operation *op,
                          ValueRange argValues = {});
 
@@ -558,6 +569,9 @@ class RewriterBase : public OpBuilder {
   ///
   /// The dest block must have no successors. Otherwise, the resulting IR would
   /// have unreachable operation.
+  ///
+  /// If the insertion point is within the source block, it is adjusted to the
+  /// destination block.
   void mergeBlocks(Block *source, Block *dest, ValueRange argValues = {});
 
   /// Split the operations starting at "before" (inclusive) out of the given

mlir/lib/IR/PatternMatch.cpp

@@ -156,6 +156,11 @@ 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 the erased operation, we adjust
+  // the insertion point to be after the operation.
+  if (getInsertionPoint() == op->getIterator())
+    setInsertionPointAfter(op);
+
   // Fast path: If no listener is attached, the op can be dropped in one go.
   if (!rewriteListener) {
     op->erase();
@@ -320,6 +325,11 @@ void RewriterBase::inlineBlockBefore(Block *source, Block *dest,
       moveOpBefore(&source->front(), dest, before);
   }
 
+  // If the current insertion point is within the source block, adjust the
+  // insertion point to the destination block.
+  if (getInsertionBlock() == source)
+    setInsertionPoint(dest, getInsertionPoint());
+
   // Erase the source block.
   assert(source->empty() && "expected 'source' to be empty");
   eraseBlock(source);

mlir/lib/Transforms/Utils/DialectConversion.cpp

@@ -1759,6 +1759,12 @@ void ConversionPatternRewriter::replaceOp(Operation *op, ValueRange newValues) {
     impl->logger.startLine()
         << "** Replace : '" << op->getName() << "'(" << op << ")\n";
   });
+
+  // If the current insertion point is before the erased operation, we adjust
+  // the insertion point to be after the operation.
+  if (getInsertionPoint() == op->getIterator())
+    setInsertionPointAfter(op);
+
   SmallVector<SmallVector<Value>> newVals =
       llvm::map_to_vector(newValues, [](Value v) -> SmallVector<Value> {
         return v ? SmallVector<Value>{v} : SmallVector<Value>();
@@ -1774,6 +1780,12 @@ void ConversionPatternRewriter::replaceOpWithMultiple(
     impl->logger.startLine()
         << "** Replace : '" << op->getName() << "'(" << op << ")\n";
   });
+
+  // If the current insertion point is before the erased operation, we adjust
+  // the insertion point to be after the operation.
+  if (getInsertionPoint() == op->getIterator())
+    setInsertionPointAfter(op);
+
   impl->replaceOp(op, std::move(newValues));
 }
 
@@ -1782,6 +1794,12 @@ void ConversionPatternRewriter::eraseOp(Operation *op) {
     impl->logger.startLine()
         << "** Erase   : '" << op->getName() << "'(" << op << ")\n";
   });
+
+  // If the current insertion point is before the erased operation, we adjust
+  // the insertion point to be after the operation.
+  if (getInsertionPoint() == op->getIterator())
+    setInsertionPointAfter(op);
+
   SmallVector<SmallVector<Value>> nullRepls(op->getNumResults(), {});
   impl->replaceOp(op, std::move(nullRepls));
 }
@@ -1888,6 +1906,11 @@ void ConversionPatternRewriter::inlineBlockBefore(Block *source, Block *dest,
       moveOpBefore(&source->front(), dest, before);
   }
 
+  // If the current insertion point is within the source block, adjust the
+  // insertion point to the destination block.
+  if (getInsertionBlock() == source)
+    setInsertionPoint(dest, getInsertionPoint());
+
   // Erase the source block.
   eraseBlock(source);
 }