[mlir][IR] Add a Region::getOps method that returns a range of immediately nested operations

This allows for walking the operations nested directly within a region, without traversing nested regions.

Differential Revision: https://reviews.llvm.org/D79056

mlir/include/mlir/IR/Block.h

@@ -156,54 +156,23 @@ public:
   /// Recomputes the ordering of child operations within the block.
   void recomputeOpOrder();
 
-private:
-  /// A utility iterator that filters out operations that are not 'OpT'.
-  template <typename OpT>
-  class op_filter_iterator
-      : public llvm::filter_iterator<Block::iterator, bool (*)(Operation &)> {
-    static bool filter(Operation &op) { return llvm::isa<OpT>(op); }
-
-  public:
-    op_filter_iterator(Block::iterator it, Block::iterator end)
-        : llvm::filter_iterator<Block::iterator, bool (*)(Operation &)>(
-              it, end, &filter) {}
-
-    /// Allow implicit conversion to the underlying block iterator.
-    operator Block::iterator() const { return this->wrapped(); }
-  };
-
-public:
   /// This class provides iteration over the held operations of a block for a
   /// specific operation type.
   template <typename OpT>
-  class op_iterator : public llvm::mapped_iterator<op_filter_iterator<OpT>,
-                                                   OpT (*)(Operation &)> {
-    static OpT unwrap(Operation &op) { return cast<OpT>(op); }
-
-  public:
-    using reference = OpT;
-
-    /// Initializes the iterator to the specified filter iterator.
-    op_iterator(op_filter_iterator<OpT> it)
-        : llvm::mapped_iterator<op_filter_iterator<OpT>, OpT (*)(Operation &)>(
-              it, &unwrap) {}
-
-    /// Allow implicit conversion to the underlying block iterator.
-    operator Block::iterator() const { return this->wrapped(); }
-  };
+  using op_iterator = detail::op_iterator<OpT, iterator>;
 
   /// Return an iterator range over the operations within this block that are of
   /// 'OpT'.
   template <typename OpT> iterator_range<op_iterator<OpT>> getOps() {
     auto endIt = end();
-    return {op_filter_iterator<OpT>(begin(), endIt),
-            op_filter_iterator<OpT>(endIt, endIt)};
+    return {detail::op_filter_iterator<OpT, iterator>(begin(), endIt),
+            detail::op_filter_iterator<OpT, iterator>(endIt, endIt)};
   }
   template <typename OpT> op_iterator<OpT> op_begin() {
-    return op_filter_iterator<OpT>(begin(), end());
+    return detail::op_filter_iterator<OpT, iterator>(begin(), end());
   }
   template <typename OpT> op_iterator<OpT> op_end() {
-    return op_filter_iterator<OpT>(end(), end());
+    return detail::op_filter_iterator<OpT, iterator>(end(), end());
   }
 
   /// Return an iterator range over the operation within this block excluding

mlir/include/mlir/IR/BlockSupport.h

@@ -75,6 +75,46 @@ private:
   friend RangeBaseT;
 };
 
+//===----------------------------------------------------------------------===//
+// Operation Iterators
+//===----------------------------------------------------------------------===//
+
+namespace detail {
+/// A utility iterator that filters out operations that are not 'OpT'.
+template <typename OpT, typename IteratorT>
+class op_filter_iterator
+    : public llvm::filter_iterator<IteratorT, bool (*)(Operation &)> {
+  static bool filter(Operation &op) { return llvm::isa<OpT>(op); }
+
+public:
+  op_filter_iterator(IteratorT it, IteratorT end)
+      : llvm::filter_iterator<IteratorT, bool (*)(Operation &)>(it, end,
+                                                                &filter) {}
+
+  /// Allow implicit conversion to the underlying iterator.
+  operator IteratorT() const { return this->wrapped(); }
+};
+
+/// This class provides iteration over the held operations of a block for a
+/// specific operation type.
+template <typename OpT, typename IteratorT>
+class op_iterator
+    : public llvm::mapped_iterator<op_filter_iterator<OpT, IteratorT>,
+                                   OpT (*)(Operation &)> {
+  static OpT unwrap(Operation &op) { return cast<OpT>(op); }
+
+public:
+  using reference = OpT;
+
+  /// Initializes the iterator to the specified filter iterator.
+  op_iterator(op_filter_iterator<OpT, IteratorT> it)
+      : llvm::mapped_iterator<op_filter_iterator<OpT, IteratorT>,
+                              OpT (*)(Operation &)>(it, &unwrap) {}
+
+  /// Allow implicit conversion to the underlying block iterator.
+  operator IteratorT() const { return this->wrapped(); }
+};
+} // end namespace detail
 } // end namespace mlir
 
 namespace llvm {

mlir/include/mlir/IR/Function.h

@@ -32,9 +32,10 @@ namespace mlir {
 /// symbols referenced by name via a string attribute).
 class FuncOp
     : public Op<FuncOp, OpTrait::ZeroOperands, OpTrait::ZeroResult,
-                OpTrait::IsIsolatedFromAbove, OpTrait::FunctionLike,
-                OpTrait::AutomaticAllocationScope, OpTrait::PolyhedralScope,
-                CallableOpInterface::Trait, SymbolOpInterface::Trait> {
+                OpTrait::OneRegion, OpTrait::IsIsolatedFromAbove,
+                OpTrait::FunctionLike, OpTrait::AutomaticAllocationScope,
+                OpTrait::PolyhedralScope, CallableOpInterface::Trait,
+                SymbolOpInterface::Trait> {
 public:
   using Op::Op;
   using Op::print;

mlir/include/mlir/IR/OpDefinition.h

@@ -583,6 +583,13 @@ class OneRegion : public TraitBase<ConcreteType, OneRegion> {
 public:
   Region &getRegion() { return this->getOperation()->getRegion(0); }
 
+  /// Returns a range of operations within the region of this operation.
+  auto getOps() { return getRegion().getOps(); }
+  template <typename OpT>
+  auto getOps() {
+    return getRegion().template getOps<OpT>();
+  }
+
   static LogicalResult verifyTrait(Operation *op) {
     return impl::verifyOneRegion(op);
   }

mlir/include/mlir/IR/Region.h

@@ -34,6 +34,10 @@ public:
   /// parent container. The region must have a valid parent container.
   Location getLoc();
 
+  //===--------------------------------------------------------------------===//
+  // Block list management
+  //===--------------------------------------------------------------------===//
+
   using BlockListType = llvm::iplist<Block>;
   BlockListType &getBlocks() { return blocks; }
 
@@ -58,6 +62,72 @@ public:
     return &Region::blocks;
   }
 
+  //===--------------------------------------------------------------------===//
+  // Operation list utilities
+  //===--------------------------------------------------------------------===//
+
+  /// This class provides iteration over the held operations of blocks directly
+  /// within a region.
+  class OpIterator final
+      : public llvm::iterator_facade_base<OpIterator, std::forward_iterator_tag,
+                                          Operation> {
+  public:
+    /// Initialize OpIterator for a region, specify `end` to return the iterator
+    /// to last operation.
+    explicit OpIterator(Region *region, bool end = false);
+
+    using llvm::iterator_facade_base<OpIterator, std::forward_iterator_tag,
+                                     Operation>::operator++;
+    OpIterator &operator++();
+    Operation *operator->() const { return &*operation; }
+    Operation &operator*() const { return *operation; }
+
+    /// Compare this iterator with another.
+    bool operator==(const OpIterator &rhs) const {
+      return operation == rhs.operation;
+    }
+    bool operator!=(const OpIterator &rhs) const { return !(*this == rhs); }
+
+  private:
+    void skipOverBlocksWithNoOps();
+
+    /// The region whose operations are being iterated over.
+    Region *region;
+    /// The block of 'region' whose operations are being iterated over.
+    Region::iterator block;
+    /// The current operation within 'block'.
+    Block::iterator operation;
+  };
+
+  /// This class provides iteration over the held operations of a region for a
+  /// specific operation type.
+  template <typename OpT>
+  using op_iterator = detail::op_iterator<OpT, OpIterator>;
+
+  /// Return iterators that walk the operations nested directly within this
+  /// region.
+  OpIterator op_begin() { return OpIterator(this); }
+  OpIterator op_end() { return OpIterator(this, /*end=*/true); }
+  iterator_range<OpIterator> getOps() { return {op_begin(), op_end()}; }
+
+  /// Return iterators that walk operations of type 'T' nested directly within
+  /// this region.
+  template <typename OpT> op_iterator<OpT> op_begin() {
+    return detail::op_filter_iterator<OpT, OpIterator>(op_begin(), op_end());
+  }
+  template <typename OpT> op_iterator<OpT> op_end() {
+    return detail::op_filter_iterator<OpT, OpIterator>(op_end(), op_end());
+  }
+  template <typename OpT> iterator_range<op_iterator<OpT>> getOps() {
+    auto endIt = op_end();
+    return {detail::op_filter_iterator<OpT, OpIterator>(op_begin(), endIt),
+            detail::op_filter_iterator<OpT, OpIterator>(endIt, endIt)};
+  }
+
+  //===--------------------------------------------------------------------===//
+  // Misc. utilities
+  //===--------------------------------------------------------------------===//
+
   /// Return the region containing this region or nullptr if the region is
   /// attached to a top-level operation.
   Region *getParentRegion();
@@ -120,6 +190,10 @@ public:
   /// they are to be deleted.
   void dropAllReferences();
 
+  //===--------------------------------------------------------------------===//
+  // Operation Walkers
+  //===--------------------------------------------------------------------===//
+
   /// Walk the operations in this region in postorder, calling the callback for
   /// each operation. This method is invoked for void-returning callbacks.
   /// See Operation::walk for more details.
@@ -142,6 +216,10 @@ public:
     return WalkResult::advance();
   }
 
+  //===--------------------------------------------------------------------===//
+  // CFG view utilities
+  //===--------------------------------------------------------------------===//
+
   /// Displays the CFG in a window. This is for use from the debugger and
   /// depends on Graphviz to generate the graph.
   /// This function is defined in ViewRegionGraph and only works with that

mlir/lib/Analysis/CallGraph.cpp

@@ -87,8 +87,7 @@ static void computeCallGraph(Operation *op, CallGraph &cg,
   }
 
   for (Region &region : op->getRegions())
-    for (Block &block : region)
-      for (Operation &nested : block)
+    for (Operation &nested : region.getOps())
       computeCallGraph(&nested, cg, parentNode, resolveCalls);
 }
 

mlir/lib/Conversion/LoopsToGPU/LoopsToGPUPass.cpp

@@ -36,15 +36,14 @@ struct ForLoopMapper : public ConvertSimpleLoopsToGPUBase<ForLoopMapper> {
   }
 
   void runOnFunction() override {
-    for (Block &block : getFunction())
-      for (Operation &op : llvm::make_early_inc_range(block)) {
+    for (Operation &op : llvm::make_early_inc_range(getFunction().getOps())) {
       if (auto forOp = dyn_cast<AffineForOp>(&op)) {
         if (failed(convertAffineLoopNestToGPULaunch(forOp, numBlockDims,
                                                     numThreadDims)))
           signalPassFailure();
       } else if (auto forOp = dyn_cast<ForOp>(&op)) {
-          if (failed(convertLoopNestToGPULaunch(forOp, numBlockDims,
-                                                numThreadDims)))
+        if (failed(
+                convertLoopNestToGPULaunch(forOp, numBlockDims, numThreadDims)))
           signalPassFailure();
       }
     }
@@ -81,17 +80,13 @@ struct ImperfectlyNestedForLoopMapper
           funcOp.getLoc(), builder.getIntegerAttr(builder.getIndexType(), val));
       workGroupSizeVal.push_back(constOp);
     }
-    for (Block &block : getFunction()) {
-      for (Operation &op : llvm::make_early_inc_range(block)) {
-        if (auto forOp = dyn_cast<ForOp>(&op)) {
+    for (ForOp forOp : llvm::make_early_inc_range(funcOp.getOps<ForOp>())) {
       if (failed(convertLoopToGPULaunch(forOp, numWorkGroupsVal,
                                         workGroupSizeVal))) {
         return signalPassFailure();
       }
     }
   }
-    }
-  }
 };
 
 struct ParallelLoopToGpuPass

mlir/lib/IR/Region.cpp

@@ -146,8 +146,7 @@ static bool isIsolatedAbove(Region &region, Region &limit,
 
   // Traverse all operations in the region.
   while (!pendingRegions.empty()) {
-    for (Block &block : *pendingRegions.pop_back_val()) {
-      for (Operation &op : block) {
+    for (Operation &op : pendingRegions.pop_back_val()->getOps()) {
       for (Value operand : op.getOperands()) {
         // operand should be non-null here if the IR is well-formed. But
         // we don't assert here as this function is called from the verifier
@@ -175,7 +174,6 @@ static bool isIsolatedAbove(Region &region, Region &limit,
         pendingRegions.push_back(&subRegion);
     }
   }
-  }
   return true;
 }
 
@@ -219,6 +217,40 @@ void llvm::ilist_traits<::mlir::Block>::transferNodesFromList(
     first->parentValidOpOrderPair.setPointer(curParent);
 }
 
+//===----------------------------------------------------------------------===//
+// Region::OpIterator
+//===----------------------------------------------------------------------===//
+
+Region::OpIterator::OpIterator(Region *region, bool end)
+    : region(region), block(end ? region->end() : region->begin()) {
+  if (!region->empty())
+    skipOverBlocksWithNoOps();
+}
+
+Region::OpIterator &Region::OpIterator::operator++() {
+  // We increment over operations, if we reach the last use then move to next
+  // block.
+  if (operation != block->end())
+    ++operation;
+  if (operation == block->end()) {
+    ++block;
+    skipOverBlocksWithNoOps();
+  }
+  return *this;
+}
+
+void Region::OpIterator::skipOverBlocksWithNoOps() {
+  while (block != region->end() && block->empty())
+    ++block;
+
+  // If we are at the last block, then set the operation to first operation of
+  // next block (sentinel value used for end).
+  if (block == region->end())
+    operation = {};
+  else
+    operation = block->begin();
+}
+
 //===----------------------------------------------------------------------===//
 // RegionRange
 //===----------------------------------------------------------------------===//

mlir/lib/IR/SymbolTable.cpp

@@ -245,11 +245,9 @@ Operation *SymbolTable::lookupSymbolIn(Operation *symbolTableOp,
   assert(symbolTableOp->hasTrait<OpTrait::SymbolTable>());
 
   // Look for a symbol with the given name.
-  for (auto &block : symbolTableOp->getRegion(0)) {
-    for (auto &op : block)
+  for (auto &op : symbolTableOp->getRegion(0).front().without_terminator())
     if (getNameIfSymbol(&op) == symbol)
       return &op;
-  }
   return nullptr;
 }
 Operation *SymbolTable::lookupSymbolIn(Operation *symbolTableOp,
@@ -444,8 +442,7 @@ static Optional<WalkResult> walkSymbolUses(
     function_ref<WalkResult(SymbolTable::SymbolUse, ArrayRef<int>)> callback) {
   SmallVector<Region *, 1> worklist(llvm::make_pointer_range(regions));
   while (!worklist.empty()) {
-    for (Block &block : *worklist.pop_back_val()) {
-      for (Operation &op : block) {
+    for (Operation &op : worklist.pop_back_val()->getOps()) {
       if (walkSymbolRefs(&op, callback).wasInterrupted())
         return WalkResult::interrupt();
 
@@ -461,7 +458,6 @@ static Optional<WalkResult> walkSymbolUses(
       }
     }
   }
-  }
   return WalkResult::advance();
 }
 /// Walk all of the uses, for any symbol, that are nested within the given

mlir/lib/Transforms/Inliner.cpp

@@ -122,8 +122,7 @@ CGUseList::CGUseList(Operation *op, CallGraph &cg) {
 
   // Walk each of the symbol tables looking for discardable callgraph nodes.
   auto walkFn = [&](Operation *symbolTableOp, bool allUsesVisible) {
-    for (Block &block : symbolTableOp->getRegion(0)) {
-      for (Operation &op : block) {
+    for (Operation &op : symbolTableOp->getRegion(0).getOps()) {
       // If this is a callgraph operation, check to see if it is discardable.
       if (auto callable = dyn_cast<CallableOpInterface>(&op)) {
         if (auto *node = cg.lookupNode(callable.getCallableRegion())) {
@@ -139,7 +138,6 @@ CGUseList::CGUseList(Operation *op, CallGraph &cg) {
       walkReferencedSymbolNodes(&op, cg, alwaysLiveNodes,
                                 [](CallGraphNode *, Operation *) {});
     }
-    }
   };
   SymbolTable::walkSymbolTables(op, /*allSymUsesVisible=*/!op->getBlock(),
                                 walkFn);