[Transform][Fusion] yield fused producer if necessary (#289)

Author: Yun-Fly

lib/gc/Transforms/TilingUsingInterfaceX.cpp

@@ -21,6 +21,7 @@
 #include "mlir/IR/PatternMatch.h"
 #include "mlir/Interfaces/DestinationStyleOpInterface.h"
 #include "mlir/Interfaces/TilingInterface.h"
+#include "mlir/Transforms/RegionUtils.h"
 #include "llvm/ADT/TypeSwitch.h"
 #include "llvm/Support/Debug.h"
 #include <optional>
@@ -255,6 +256,28 @@ SmallVector<LoopLikeOpInterface> mlir::scfX::getOuterNestLoopsWhile(
   return {nestLoops.rbegin(), nestLoops.rend()};
 }
 
+/// A listener that watches which ops were erased.
+struct ErasedOpListener : public RewriterBase::Listener {
+private:
+  /// Pointers to all erased operations and blocks.
+  DenseSet<void *> erased;
+  // Hook old listener.
+  OpBuilder::Listener *oldListenerHook = nullptr;
+
+public:
+  ErasedOpListener() = default;
+  ErasedOpListener(OpBuilder::Listener *oldListener)
+      : oldListenerHook(oldListener) {}
+  void notifyOperationErased(Operation *op) override {
+    // Call old listener hook.
+    if (auto *oldListener =
+            dyn_cast_if_present<RewriterBase::Listener>(oldListenerHook))
+      oldListener->notifyOperationErased(op);
+    erased.insert(op);
+  }
+  bool isErased(Operation *op) { return erased.count(op); }
+};
+
 /// Enhanced version of `tileAndFuseProducerOfSliceImpl`, which can deal with
 /// multi-level `extractSliceOp`. E.g.
 ///
@@ -296,6 +319,55 @@ mlir::scfX::tileAndFuseProducerOfSlice(RewriterBase &rewriter,
         tileAndFuseProducerOfSliceImpl(rewriter, sliceOp, outerLoops);
     if (!fuseProducerResult)
       return std::nullopt;
+
+    // Cache old listener.
+    OpBuilder::Listener *oldListener = rewriter.getListener();
+    // Set new listener.
+    ErasedOpListener newListener = ErasedOpListener(oldListener);
+    rewriter.setListener(&newListener);
+
+    auto producerOp =
+        cast<TilingInterface>(fuseProducerResult->origProducer.getDefiningOp());
+    unsigned resultNumber = fuseProducerResult->origProducer.getResultNumber();
+    // cache candidate slice
+    auto extractSliceOp = cast<tensor::ExtractSliceOp>(candidateSliceOp);
+    SmallVector<OpFoldResult> offsets = extractSliceOp.getMixedOffsets(),
+                              sizes = extractSliceOp.getMixedSizes(),
+                              strides = extractSliceOp.getMixedStrides();
+    // Explicitly execute DCE.
+    (void)mlir::simplifyRegions(rewriter, {*producerOp->getParentRegion()});
+    // If fused producer has multiple users.
+    bool yieldReplacement = !newListener.isErased(producerOp);
+    // Reset to old listener.
+    rewriter.setListener(oldListener);
+
+    if (yieldReplacement) {
+      OpBuilder::InsertionGuard g(rewriter);
+      // Set insertPoint right before tiled op.
+      rewriter.setInsertionPoint(fuseProducerResult->tiledOps[0]);
+      // Manually clone new candidate slice.
+      auto clonedExtractSliceOp = rewriter.create<tensor::ExtractSliceOp>(
+          producerOp->getLoc(), producerOp->getResult(resultNumber), offsets,
+          sizes, strides);
+      // Yield replacement for fused producer in avoid of repeated computation.
+      if (failed(scf::yieldReplacementForFusedProducer(
+              rewriter, clonedExtractSliceOp, fuseProducerResult.value(),
+              outerLoops)))
+        return std::nullopt;
+      // Erase cloned candidate slice.
+      rewriter.eraseOp(clonedExtractSliceOp);
+
+      unsigned loopNumResults = outerLoops.front()->getNumResults(),
+               producerNumResults = producerOp->getNumResults();
+      // Replace other users of fused producer with new loop results.
+      for (auto &&[index, result] : llvm::enumerate(producerOp->getResults())) {
+        rewriter.replaceAllUsesWith(
+            result, outerLoops.front()->getResult(loopNumResults -
+                                                  producerNumResults + index));
+      }
+      // Erase fused producer op.
+      rewriter.eraseOp(producerOp);
+    }
   }
   return fuseProducerResult;
 }

test/mlir/test/gc/Transforms/iterative-tiling-and-fusion.mlir

@@ -381,11 +381,11 @@ module {
 // -----
 
 module {
-  //      CHECK: func.func @fuse_generic_matmul(
-  // CHECK-SAME:     %[[ARG0:[a-zA-Z0-9]+]]: tensor<32x32xf32>
-  // CHECK-SAME:     %[[ARG1:[a-zA-Z0-9]+]]: tensor<2x16x16xf32>
-  // CHECK-SAME:     %[[ARG2:[a-zA-Z0-9]+]]: tensor<4x16x16xf32>
-  func.func @fuse_generic_matmul(%arg0: tensor<32x32xf32>, %arg1: tensor<2x16x16xf32>, %arg2: tensor<4x16x16xf32>) -> tensor<32x64xf32> attributes {llvm.emit_c_interface} {
+  /// CHECK-LABEL:    @fuse_generic_matmul
+  /// CHECK-SAME:     %[[ARG0:[a-zA-Z0-9]+]]: tensor<32x32xf32>
+  /// CHECK-SAME:     %[[ARG1:[a-zA-Z0-9]+]]: tensor<2x16x16xf32>
+  /// CHECK-SAME:     %[[ARG2:[a-zA-Z0-9]+]]: tensor<4x16x16xf32>
+  func.func @fuse_generic_matmul(%arg0: tensor<32x32xf32>, %arg1: tensor<2x16x16xf32>, %arg2: tensor<4x16x16xf32>) -> tensor<32x64xf32> {
     /// CHECK: %[[EMPTY_OUT_0:.*]] = tensor.empty
     %0 = tensor.empty() : tensor<2x2x16x16xf32>
     %pack = tensor.pack %arg0 outer_dims_perm = [0, 1] inner_dims_pos = [0, 1] inner_tiles = [16, 16] into %0 : tensor<32x32xf32> -> tensor<2x2x16x16xf32>
@@ -429,4 +429,33 @@ module {
     /// CHECK: return %[[FINAL_RESULT]]#1
     return %unpack : tensor<32x64xf32>
   }
+}
+
+// -----
+
+module {
+  /// CHECK-LABEL: @yield_fused_producer
+  func.func @yield_fused_producer(%arg0: tensor<16x32x32xf32>) -> (tensor<16x32x32xf32>, tensor<16x32xf32>) {
+    /// CHECK: arith.constant
+    %cst_0 = arith.constant dense<2.000000e+00> : tensor<16x32x32xf32>
+    /// CHECK-NEXT: tensor.empty
+    %dest0 = tensor.empty() : tensor<16x32x32xf32>
+    %0 = linalg.powf ins(%arg0, %cst_0 : tensor<16x32x32xf32>, tensor<16x32x32xf32>) outs(%dest0 : tensor<16x32x32xf32>) -> tensor<16x32x32xf32>
+    /// CHECK-NEXT: tensor.empty
+    %dest1 = tensor.empty() : tensor<16x32xf32>
+    /// CHECK-NEXT: %[[FINAL_RESULT:.*]]:2 = scf.forall (%{{.*}}) in (16)
+    /// CHECK-NEXT: tensor.extract_slice
+    /// CHECK-NEXT: tensor.extract_slice
+    /// CHECK-NEXT: tensor.extract_slice
+    /// CHECK-NEXT: linalg.powf
+    /// CHECK-NEXT: tensor.extract_slice
+    /// CHECK-NEXT: linalg.reduce
+    %1 = linalg.reduce { arith.addf } ins(%0 : tensor<16x32x32xf32>) outs(%dest1 : tensor<16x32xf32>) dimensions = [2]
+    /// CHECK-NEXT: scf.forall.in_parallel
+    /// CHECK-NEXT: tensor.parallel_insert_slice
+    /// CHECK-NEXT: tensor.parallel_insert_slice
+    /// CHECK-NEXT: }
+    /// CHECK: return %[[FINAL_RESULT]]#1, %[[FINAL_RESULT]]#0
+    return %0, %1 : tensor<16x32x32xf32>, tensor<16x32xf32>
+  }
 }