Reapply "[DispatchCreation] Extend multi-use producer fusion" (#19032)

Since the upstream changes to `getBackwardSlice` have been integrated
(llvm/llvm-project#114452), its now possible to
reland #18855.

The first commit relands the reverted changes. The second commit uses
`BackwardSliceOptions::omitUsesFromAbove` to track all transitive
definitions of the possibly fusible op preventing ops being moved before
uses. Also, added two tests that check for this issue.



Closes #18879

---------

Signed-off-by: Ian Wood <[email protected]>

Author: IanWood1

.github/workflows/pkgci_regression_test.yml

@@ -220,7 +220,7 @@ jobs:
             --goldentime-rocm-unet-ms 419.0 \
             --goldentime-rocm-clip-ms 18.5 \
             --goldentime-rocm-vae-ms 337.0 \
-            --goldendispatch-rocm-unet 1531 \
+            --goldendispatch-rocm-unet 1527 \
             --goldendispatch-rocm-clip 1141 \
             --goldendispatch-rocm-vae 246 \
             --goldensize-rocm-unet-bytes 2280000  \
@@ -241,7 +241,7 @@ jobs:
             --goldentime-rocm-unet-ms 95.0 \
             --goldentime-rocm-clip-ms 15.5 \
             --goldentime-rocm-vae-ms 80.0 \
-            --goldendispatch-rocm-unet 1531 \
+            --goldendispatch-rocm-unet 1527 \
             --goldendispatch-rocm-clip 1141 \
             --goldendispatch-rocm-vae 246 \
             --goldensize-rocm-unet-bytes 2270000 \

compiler/src/iree/compiler/DispatchCreation/FuseHorizontalContractions.cpp

@@ -7,6 +7,7 @@
 #include "iree/compiler/Dialect/Flow/IR/FlowOps.h"
 #include "iree/compiler/Dialect/Flow/Transforms/RegionOpUtils.h"
 #include "iree/compiler/Dialect/LinalgExt/Utils/Utils.h"
+#include "iree/compiler/DispatchCreation/FusionUtils.h"
 #include "iree/compiler/DispatchCreation/Passes.h"
 #include "mlir/Analysis/SliceAnalysis.h"
 #include "mlir/Analysis/TopologicalSortUtils.h"
@@ -107,25 +108,6 @@ static bool isEmptyFillContractionDAGRootOp(
   return true;
 }
 
-/// Check that a given operation is "horizontal" to the group. The operation
-/// is horizontal if the `slice` of the operation does not contain any op
-/// from the group.
-static bool isHorizontalToGroup(Operation *op,
-                                const llvm::SetVector<Operation *> &currGroup,
-                                const DominanceInfo &dominanceInfo,
-                                Operation *seedOp) {
-  BackwardSliceOptions options;
-  // Limit the slice to the seed to make sure the slice is small.
-  options.filter = [&](Operation *op) {
-    return !dominanceInfo.properlyDominates(op, seedOp);
-  };
-  llvm::SetVector<Operation *> slice;
-  getBackwardSlice(op, &slice, options);
-  return !llvm::any_of(currGroup, [&](Operation *groupedOp) {
-    return slice.contains(groupedOp);
-  });
-}
-
 /// Get user of operation that is a truncate operation.
 static std::optional<linalg::GenericOp>
 getTruncateOp(Operation *op,
@@ -149,8 +131,8 @@ getTruncateOp(Operation *op,
     if (!checkOperationEquivalence(genericOp, seedTruncateOp.value())) {
       return std::nullopt;
     }
-    if (!isHorizontalToGroup(genericOp, groupedOperations, dominanceInfo,
-                             seedTruncateOp.value())) {
+    if (!isHorizontalToGroup(genericOp, groupedOperations.getArrayRef(),
+                             dominanceInfo, seedTruncateOp.value())) {
       return std::nullopt;
     }
   }
@@ -226,7 +208,8 @@ static std::optional<HorizontalFusionGroup> getHorizontalFusionGroupMembers(
     if (!dominanceInfo.properlyDominates(seedOp, linalgOp)) {
       return false;
     }
-    if (!isHorizontalToGroup(linalgOp, allOps, dominanceInfo, seedOp)) {
+    if (!isHorizontalToGroup(linalgOp, allOps.getArrayRef(), dominanceInfo,
+                             seedOp)) {
       return false;
     }
     return true;
@@ -346,40 +329,6 @@ static AffineMap getConcatenatedIndexingMap(RewriterBase &rewriter,
   return newIndexingMap.insertResult(rewriter.getAffineDimExpr(0), 0);
 }
 
-/// During horizontal fusion, there might be operands of the fused operations
-/// whose definitions are interspersed between the fused operations. For groups
-/// chosen to fuse horizontally, such operations can be moved before the
-/// seed contraction operation (where the fused operation is generated).
-template <typename T>
-static LogicalResult
-moveOperandDefs(RewriterBase &rewriter, ArrayRef<T> operations,
-                Operation *insertionPoint, DominanceInfo &dominanceInfo,
-                ArrayRef<linalg::LinalgOp> ignoreOperations = {}) {
-  BackwardSliceOptions options;
-  llvm::DenseSet<Operation *> ignoreOperationsSet;
-  ignoreOperationsSet.insert(ignoreOperations.begin(), ignoreOperations.end());
-  options.filter = [&](Operation *op) {
-    return !dominanceInfo.properlyDominates(op, insertionPoint) &&
-           !ignoreOperationsSet.contains(op);
-  };
-  // Set inclusive to true cause the slice is computed from the operand, and
-  // we want to include the defining op (which is the point here)
-  options.inclusive = true;
-
-  llvm::SetVector<Operation *> slice;
-  for (auto op : operations) {
-    for (auto operand : op->getOperands()) {
-      getBackwardSlice(operand, &slice, options);
-    }
-  }
-
-  mlir::topologicalSort(slice);
-  for (auto op : slice) {
-    rewriter.moveOpBefore(op, insertionPoint);
-  }
-  return success();
-}
-
 /// On finding this pattern
 /// ```
 /// %0 = linalg.matmul ins(%arg0, %arg1)

compiler/src/iree/compiler/DispatchCreation/FuseMultiUseElementwiseProducer.cpp

@@ -16,9 +16,13 @@
 #include "iree/compiler/Dialect/LinalgExt/IR/LinalgExtInterfaces.h"
 #include "iree/compiler/Dialect/LinalgExt/IR/LinalgExtOps.h"
 #include "iree/compiler/Dialect/LinalgExt/Utils/Utils.h"
+#include "iree/compiler/DispatchCreation/FusionUtils.h"
 #include "iree/compiler/DispatchCreation/Passes.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
+#include "mlir/Analysis/SliceAnalysis.h"
 #include "mlir/Analysis/TopologicalSortUtils.h"
 #include "mlir/Dialect/Affine/IR/AffineOps.h"
 #include "mlir/Dialect/Linalg/IR/Linalg.h"
@@ -45,25 +49,55 @@ static llvm::cl::opt<int64_t> clLinalgMaxConstantFoldElements(
     llvm::cl::desc("Maximum number of elements to try to constant fold."),
     llvm::cl::init(0));
 
+static Operation *getMostDominantUse(Operation *op,
+                                     const DominanceInfo &dominanceInfo) {
+  auto uses = op->getUses();
+  auto it = llvm::find_if(uses, [&](OpOperand &source) {
+    Operation *sourceOp = source.getOwner();
+
+    return llvm::all_of(uses, [&](OpOperand &target) {
+      Operation *targetOp = target.getOwner();
+      return dominanceInfo.dominates(sourceOp, targetOp);
+    });
+  });
+  if (it != uses.end()) {
+    return it->getOwner();
+  }
+  return nullptr;
+}
+
 /// Check if any of the use dominates all other uses of the operation.
-static std::optional<OpOperand *> getFusableUse(Operation *op,
-                                                DominanceInfo &dominanceInfo) {
+static Operation *getFusableUse(Operation *op,
+                                const DominanceInfo &dominanceInfo) {
   auto uses = op->getUses();
+  Operation *fusableUse = nullptr;
   for (OpOperand &source : uses) {
     Operation *sourceOp = source.getOwner();
-    bool dominatesAllUsers = true;
-    for (OpOperand &target : uses) {
+
+    bool dominatesAllFusableOps = llvm::all_of(uses, [&](OpOperand &target) {
       Operation *targetOp = target.getOwner();
-      if (!dominanceInfo.dominates(sourceOp, targetOp)) {
-        dominatesAllUsers = false;
-        break;
-      }
-    }
-    if (dominatesAllUsers) {
-      return &source;
+      return !isa<linalg::GenericOp>(targetOp) ||
+             dominanceInfo.dominates(sourceOp, targetOp);
+    });
+    if (dominatesAllFusableOps) {
+      fusableUse = sourceOp;
+      break;
     }
   }
-  return std::nullopt;
+  Operation *mostDominantOp = getMostDominantUse(op, dominanceInfo);
+  if (!fusableUse || !mostDominantOp) {
+    return nullptr;
+  }
+
+  // If `fusableUse` dominates all other users, there's nothing else to do.
+  if (fusableUse == mostDominantOp) {
+    return fusableUse;
+  }
+
+  SmallVector<Operation *> users(op->getUsers().begin(), op->getUsers().end());
+  return isHorizontalToGroup(fusableUse, users, dominanceInfo, mostDominantOp)
+             ? fusableUse
+             : nullptr;
 }
 
 static OpOperand *getFirstUseInConsumer(Operation *producer,
@@ -91,6 +125,7 @@ static SmallVector<OpOperand *> getAllUsesInConsumer(Operation *producer,
 /// using elementwise fusion.
 static LogicalResult doMultiUseFusion(Operation *rootOp,
                                       llvm::SetVector<Operation *> &fusableOps,
+                                      const DominanceInfo &dominanceInfo,
                                       RewriterBase &rewriter) {
   assert(rootOp && "root op cant be null");
 
@@ -112,11 +147,20 @@ static LogicalResult doMultiUseFusion(Operation *rootOp,
   Operation *consumerOp = rootOp;
   OpBuilder::InsertionGuard g(rewriter);
   for (Operation *producerOp : llvm::reverse(fusedOpsVec)) {
+    Operation *mostDominantUser = getMostDominantUse(producerOp, dominanceInfo);
     // Fuse all uses from producer -> consumer. It has been checked
     // before that all uses are fusable.
     while (OpOperand *fusedOperand =
                getFirstUseInConsumer(producerOp, consumerOp)) {
       rewriter.setInsertionPoint(consumerOp);
+
+      if (consumerOp != mostDominantUser &&
+          failed(moveOperandDefs(rewriter, ArrayRef<Operation *>{consumerOp},
+                                 mostDominantUser, dominanceInfo))) {
+        return rewriter.notifyMatchFailure(consumerOp,
+                                           "failed to move operand defs");
+      }
+      rewriter.moveOpBefore(consumerOp, mostDominantUser);
       FailureOr<linalg::ElementwiseOpFusionResult> fusionResult =
           linalg::fuseElementwiseOps(rewriter, fusedOperand);
       if (failed(fusionResult)) {
@@ -190,9 +234,8 @@ static FailureOr<unsigned> fuseMultiUseProducers(Operation *funcOp,
           }
 
           // 6. Check that the `genericOp` dominates all uses of `producer`.
-          std::optional<OpOperand *> fusableUse =
-              getFusableUse(producer, dominanceInfo);
-          if (!fusableUse || fusableUse.value()->getOwner() != genericOp) {
+          Operation *fusableUse = getFusableUse(producer, dominanceInfo);
+          if (!fusableUse || fusableUse != genericOp) {
             continue;
           }
 
@@ -232,7 +275,8 @@ static FailureOr<unsigned> fuseMultiUseProducers(Operation *funcOp,
 
   IRRewriter rewriter(context);
   for (auto it = fusedOps.rbegin(), ie = fusedOps.rend(); it != ie; ++it) {
-    if (failed(doMultiUseFusion(it->first, it->second, rewriter))) {
+    if (failed(
+            doMultiUseFusion(it->first, it->second, dominanceInfo, rewriter))) {
       return funcOp->emitOpError("failed multi use fusion");
     }
   }

compiler/src/iree/compiler/DispatchCreation/FusionUtils.cpp

@@ -10,7 +10,11 @@
 #include "compiler/src/iree/compiler/DispatchCreation/FusionUtils.h"
 #include "compiler/src/iree/compiler/Dialect/Flow/Transforms/RegionOpUtils.h"
 #include "iree/compiler/Dialect/LinalgExt/Utils/Utils.h"
+#include "mlir/Analysis/SliceAnalysis.h"
 #include "mlir/Dialect/Linalg/IR/Linalg.h"
+#include "mlir/IR/Dominance.h"
+#include "mlir/IR/OpDefinition.h"
+#include "mlir/Transforms/RegionUtils.h"
 
 namespace mlir::iree_compiler::DispatchCreation {
 
@@ -97,4 +101,22 @@ bool areFusableAsElementwiseOps(MLIRContext *context, OpOperand *fusedOperand,
   return true;
 }
 
+bool isHorizontalToGroup(Operation *op, ArrayRef<Operation *> currGroup,
+                         const DominanceInfo &dominanceInfo,
+                         Operation *seedOp) {
+  assert(dominanceInfo.properlyDominates(seedOp, op) &&
+         op->getParentRegion() == seedOp->getParentRegion());
+  BackwardSliceOptions options;
+  options.omitUsesFromAbove = false;
+  // Limit the slice to the seed to make sure the slice is small.
+  options.filter = [&](Operation *op) {
+    return !dominanceInfo.properlyDominates(op, seedOp);
+  };
+  llvm::SetVector<Operation *> slice;
+  getBackwardSlice(op, &slice, options);
+  return !llvm::any_of(currGroup, [&](Operation *groupedOp) {
+    return slice.contains(groupedOp);
+  });
+}
+
 } // namespace mlir::iree_compiler::DispatchCreation

compiler/src/iree/compiler/DispatchCreation/FusionUtils.h

@@ -10,6 +10,10 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "mlir/Analysis/SliceAnalysis.h"
+#include "mlir/Analysis/TopologicalSortUtils.h"
+#include "mlir/Dialect/Linalg/IR/Linalg.h"
+#include "mlir/IR/Dominance.h"
 #include "mlir/IR/Operation.h"
 
 namespace mlir::iree_compiler::DispatchCreation {
@@ -19,4 +23,45 @@ namespace mlir::iree_compiler::DispatchCreation {
 bool areFusableAsElementwiseOps(MLIRContext *context, OpOperand *operand,
                                 bool fuseMultiReduction);
 
+/// Check that a given operation is "horizontal" to the group. The operation
+/// is horizontal if the program slice of the operation (from op back to seedOp)
+/// does not contain any op from the group.
+bool isHorizontalToGroup(Operation *op, ArrayRef<Operation *> currGroup,
+                         const DominanceInfo &dominanceInfo, Operation *seedOp);
+
+/// Moves the operands and transitive defs for each op in `operations` directly
+/// after `insertionPoint`. Note: this does not check if it is legal to move the
+/// operands.
+template <typename T>
+static LogicalResult
+moveOperandDefs(RewriterBase &rewriter, ArrayRef<T> operations,
+                Operation *insertionPoint, const DominanceInfo &dominanceInfo,
+                ArrayRef<linalg::LinalgOp> ignoreOperations = {}) {
+  BackwardSliceOptions options;
+  options.omitUsesFromAbove = false;
+  llvm::DenseSet<Operation *> ignoreOperationsSet;
+  ignoreOperationsSet.insert(ignoreOperations.begin(), ignoreOperations.end());
+  options.filter = [&](Operation *op) {
+    return !dominanceInfo.properlyDominates(op, insertionPoint) &&
+           !ignoreOperationsSet.contains(op);
+  };
+  // Set inclusive to true cause the slice is computed from the operand, and
+  // we want to include the defining op (which is the point here)
+  options.inclusive = true;
+
+  llvm::SetVector<Operation *> slice;
+  for (auto op : operations) {
+    assert(insertionPoint->getBlock() == op->getBlock());
+    for (auto operand : op->getOperands()) {
+      getBackwardSlice(operand, &slice, options);
+    }
+  }
+
+  mlir::topologicalSort(slice);
+  for (auto op : slice) {
+    rewriter.moveOpBefore(op, insertionPoint);
+  }
+  return success();
+}
+
 } // namespace mlir::iree_compiler::DispatchCreation