Change the notifyRootUpdated API to be transaction based.

This means that in-place, or root, updates need to use explicit calls to `startRootUpdate`, `finalizeRootUpdate`, and `cancelRootUpdate`. The major benefit of this change is that it enables in-place updates in DialectConversion, which simplifies the FuncOp pattern for example. The major downside to this is that the cases that *may* modify an operation in-place will need an explicit cancel on the failure branches(assuming that they started an update before attempting the transformation).

PiperOrigin-RevId: 286933674

Author: River707

include/mlir/IR/BlockSupport.h

@@ -61,6 +61,7 @@ class SuccessorRange final
 public:
   using RangeBaseT::RangeBaseT;
   SuccessorRange(Block *block);
+  SuccessorRange(Operation *term);
 
 private:
   /// See `detail::indexed_accessor_range_base` for details.

include/mlir/IR/Operation.h

@@ -385,6 +385,12 @@ class Operation final
     return {getTrailingObjects<BlockOperand>(), numSuccs};
   }
 
+  // Successor iteration.
+  using succ_iterator = SuccessorRange::iterator;
+  succ_iterator successor_begin() { return getSuccessors().begin(); }
+  succ_iterator successor_end() { return getSuccessors().end(); }
+  SuccessorRange getSuccessors() { return SuccessorRange(this); }
+
   /// Return the operands of this operation that are *not* successor arguments.
   operand_range getNonSuccessorOperands();
 

include/mlir/IR/PatternMatch.h

@@ -361,15 +361,31 @@ class PatternRewriter : public OpBuilder {
   /// block into a new block, and return it.
   virtual Block *splitBlock(Block *block, Block::iterator before);
 
-  /// This method is used as the final notification hook for patterns that end
-  /// up modifying the pattern root in place, by changing its operands.  This is
-  /// a minor efficiency win (it avoids creating a new operation and removing
-  /// the old one) but also often allows simpler code in the client.
-  ///
-  /// The valuesToRemoveIfDead list is an optional list of values that the
-  /// rewriter should remove if they are dead at this point.
-  ///
-  void updatedRootInPlace(Operation *op, ValueRange valuesToRemoveIfDead = {});
+  /// This method is used to notify the rewriter that an in-place operation
+  /// modification is about to happen. A call to this function *must* be
+  /// followed by a call to either `finalizeRootUpdate` or `cancelRootUpdate`.
+  /// This is a minor efficiency win (it avoids creating a new operation and
+  /// removing the old one) but also often allows simpler code in the client.
+  virtual void startRootUpdate(Operation *op) {}
+
+  /// This method is used to signal the end of a root update on the given
+  /// operation. This can only be called on operations that were provided to a
+  /// call to `startRootUpdate`.
+  virtual void finalizeRootUpdate(Operation *op) {}
+
+  /// This method cancels a pending root update. This can only be called on
+  /// operations that were provided to a call to `startRootUpdate`.
+  virtual void cancelRootUpdate(Operation *op) {}
+
+  /// This method is a utility wrapper around a root update of an operation. It
+  /// wraps calls to `startRootUpdate` and `finalizeRootUpdate` around the given
+  /// callable.
+  template <typename CallableT>
+  void updateRootInPlace(Operation *root, CallableT &&callable) {
+    startRootUpdate(root);
+    callable();
+    finalizeRootUpdate(root);
+  }
 
 protected:
   explicit PatternRewriter(MLIRContext *ctx) : OpBuilder(ctx) {}
@@ -378,10 +394,6 @@ class PatternRewriter : public OpBuilder {
   // These are the callback methods that subclasses can choose to implement if
   // they would like to be notified about certain types of mutations.
 
-  /// Notify the pattern rewriter that the specified operation has been mutated
-  /// in place.  This is called after the mutation is done.
-  virtual void notifyRootUpdated(Operation *op) {}
-
   /// Notify the pattern rewriter that the specified operation is about to be
   /// replaced with another set of operations.  This is called before the uses
   /// of the operation have been changed.

include/mlir/Transforms/DialectConversion.h

@@ -365,7 +365,16 @@ class ConversionPatternRewriter final : public PatternRewriter {
   Operation *insert(Operation *op) override;
 
   /// PatternRewriter hook for updating the root operation in-place.
-  void notifyRootUpdated(Operation *op) override;
+  /// Note: These methods only track updates to the top-level operation itself,
+  /// and not nested regions. Updates to regions will still require notification
+  /// through other more specific hooks above.
+  void startRootUpdate(Operation *op) override;
+
+  /// PatternRewriter hook for updating the root operation in-place.
+  void finalizeRootUpdate(Operation *op) override;
+
+  /// PatternRewriter hook for updating the root operation in-place.
+  void cancelRootUpdate(Operation *op) override;
 
   /// Return a reference to the internal implementation.
   detail::ConversionPatternRewriterImpl &getImpl();

lib/Conversion/StandardToSPIRV/ConvertStandardToSPIRVPass.cpp

@@ -54,13 +54,12 @@ FuncOpConversion::matchAndRewrite(FuncOp funcOp, ArrayRef<ValuePtr> operands,
       signatureConverter.addInputs(argType.index(), convertedType);
     }
   }
-  auto newFuncOp = rewriter.cloneWithoutRegions(funcOp);
-  rewriter.inlineRegionBefore(funcOp.getBody(), newFuncOp.getBody(),
-                              newFuncOp.end());
-  newFuncOp.setType(rewriter.getFunctionType(
-      signatureConverter.getConvertedTypes(), llvm::None));
-  rewriter.applySignatureConversion(&newFuncOp.getBody(), signatureConverter);
-  rewriter.replaceOp(funcOp.getOperation(), llvm::None);
+
+  rewriter.updateRootInPlace(funcOp, [&] {
+    funcOp.setType(rewriter.getFunctionType(
+        signatureConverter.getConvertedTypes(), llvm::None));
+    rewriter.applySignatureConversion(&funcOp.getBody(), signatureConverter);
+  });
   return matchSuccess();
 }
 

lib/Dialect/GPU/IR/GPUDialect.cpp

@@ -472,39 +472,38 @@ class PropagateConstantBounds : public OpRewritePattern<LaunchOp> {
 
   PatternMatchResult matchAndRewrite(LaunchOp launchOp,
                                      PatternRewriter &rewriter) const override {
-    auto origInsertionPoint = rewriter.saveInsertionPoint();
+    rewriter.startRootUpdate(launchOp);
+    PatternRewriter::InsertionGuard guard(rewriter);
     rewriter.setInsertionPointToStart(&launchOp.body().front());
 
     // Traverse operands passed to kernel and check if some of them are known
     // constants.  If so, clone the constant operation inside the kernel region
     // and use it instead of passing the value from the parent region.  Perform
     // the traversal in the inverse order to simplify index arithmetics when
     // dropping arguments.
-    SmallVector<ValuePtr, 8> operands(launchOp.getKernelOperandValues().begin(),
-                                      launchOp.getKernelOperandValues().end());
-    SmallVector<ValuePtr, 8> kernelArgs(launchOp.getKernelArguments().begin(),
-                                        launchOp.getKernelArguments().end());
+    auto operands = launchOp.getKernelOperandValues();
+    auto kernelArgs = launchOp.getKernelArguments();
     bool found = false;
     for (unsigned i = operands.size(); i > 0; --i) {
       unsigned index = i - 1;
-      ValuePtr operand = operands[index];
-      if (!isa_and_nonnull<ConstantOp>(operand->getDefiningOp())) {
+      Value operand = operands[index];
+      if (!isa_and_nonnull<ConstantOp>(operand->getDefiningOp()))
         continue;
-      }
 
       found = true;
-      ValuePtr internalConstant =
+      Value internalConstant =
           rewriter.clone(*operand->getDefiningOp())->getResult(0);
-      ValuePtr kernelArg = kernelArgs[index];
+      Value kernelArg = *std::next(kernelArgs.begin(), index);
       kernelArg->replaceAllUsesWith(internalConstant);
       launchOp.eraseKernelArgument(index);
     }
-    rewriter.restoreInsertionPoint(origInsertionPoint);
 
-    if (!found)
+    if (!found) {
+      rewriter.cancelRootUpdate(launchOp);
       return matchFailure();
+    }
 
-    rewriter.updatedRootInPlace(launchOp);
+    rewriter.finalizeRootUpdate(launchOp);
     return matchSuccess();
   }
 };

lib/Dialect/SPIRV/Transforms/LowerABIAttributesPass.cpp

@@ -197,13 +197,11 @@ FuncOpLowering::matchAndRewrite(FuncOp funcOp, ArrayRef<ValuePtr> operands,
   }
 
   // Creates a new function with the update signature.
-  auto newFuncOp = rewriter.cloneWithoutRegions(funcOp);
-  rewriter.inlineRegionBefore(funcOp.getBody(), newFuncOp.getBody(),
-                              newFuncOp.end());
-  newFuncOp.setType(rewriter.getFunctionType(
-      signatureConverter.getConvertedTypes(), llvm::None));
-  rewriter.applySignatureConversion(&newFuncOp.getBody(), signatureConverter);
-  rewriter.eraseOp(funcOp.getOperation());
+  rewriter.updateRootInPlace(funcOp, [&] {
+    funcOp.setType(rewriter.getFunctionType(
+        signatureConverter.getConvertedTypes(), llvm::None));
+    rewriter.applySignatureConversion(&funcOp.getBody(), signatureConverter);
+  });
   return matchSuccess();
 }
 

lib/IR/Block.cpp

@@ -267,3 +267,8 @@ SuccessorRange::SuccessorRange(Block *block) : SuccessorRange(nullptr, 0) {
     if ((count = term->getNumSuccessors()))
       base = term->getBlockOperands().data();
 }
+
+SuccessorRange::SuccessorRange(Operation *term) : SuccessorRange(nullptr, 0) {
+  if ((count = term->getNumSuccessors()))
+    base = term->getBlockOperands().data();
+}

lib/IR/PatternMatch.cpp

@@ -170,23 +170,6 @@ void PatternRewriter::cloneRegionBefore(Region &region, Block *before) {
   cloneRegionBefore(region, *before->getParent(), before->getIterator());
 }
 
-/// This method is used as the final notification hook for patterns that end
-/// up modifying the pattern root in place, by changing its operands.  This is
-/// a minor efficiency win (it avoids creating a new operation and removing
-/// the old one) but also often allows simpler code in the client.
-///
-/// The opsToRemoveIfDead list is an optional list of nodes that the rewriter
-/// should remove if they are dead at this point.
-///
-void PatternRewriter::updatedRootInPlace(Operation *op,
-                                         ValueRange valuesToRemoveIfDead) {
-  // Notify the rewriter subclass that we're about to replace this root.
-  notifyRootUpdated(op);
-
-  // TODO: Process the valuesToRemoveIfDead list, removing things and calling
-  // the notifyOperationRemoved hook in the process.
-}
-
 //===----------------------------------------------------------------------===//
 // PatternMatcher implementation
 //===----------------------------------------------------------------------===//