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[mlir][linalg] Allow pack consumer fusion if the tile size is greater than dimension size. #149438

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@hanhanW hanhanW commented Jul 18, 2025

This happens only when you use larger tile size, which is greater than or equal to the dimension size. In this case, it is a full slice, so it is fusible.

The IR can be generated during the TileAndFuse process. It is hard to fix in such driver, so we enable the naive fusion for the case.

… than dimension size.

This only happens when you use tile size which is greater than or equal
to the dimension size. In this case, it is a full slice, so it is
fusiable.

The IR can be generated during the TileAndFuse process. It is hard to
fix in such driver, so we enable the naive fusion for the case.

Signed-off-by: hanhanW <[email protected]>
@llvmbot
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llvmbot commented Jul 18, 2025

@llvm/pr-subscribers-mlir

Author: Han-Chung Wang (hanhanW)

Changes

This happens only when you use larger tile size, which is greater than or equal to the dimension size. In this case, it is a full slice, so it is fusible.

The IR can be generated during the TileAndFuse process. It is hard to fix in such driver, so we enable the naive fusion for the case.


Full diff: https://github.com/llvm/llvm-project/pull/149438.diff

2 Files Affected:

  • (modified) mlir/lib/Dialect/Linalg/Transforms/TilingInterfaceImpl.cpp (+1-1)
  • (modified) mlir/test/Interfaces/TilingInterface/tile-and-fuse-consumer.mlir (+51)
diff --git a/mlir/lib/Dialect/Linalg/Transforms/TilingInterfaceImpl.cpp b/mlir/lib/Dialect/Linalg/Transforms/TilingInterfaceImpl.cpp
index 5a10883a6043c..eed431570452a 100644
--- a/mlir/lib/Dialect/Linalg/Transforms/TilingInterfaceImpl.cpp
+++ b/mlir/lib/Dialect/Linalg/Transforms/TilingInterfaceImpl.cpp
@@ -911,7 +911,7 @@ struct PackOpTiling
         int64_t destDimSize = packOp.getDestType().getDimSize(dim);
         bool isTiled = failed(cstTileSize) ||
                        ShapedType::isDynamic(srcDimSize) ||
-                       cstTileSize.value() != srcDimSize;
+                       cstTileSize.value() < srcDimSize;
         if (!isTiled) {
           outerDimOffsets.push_back(offsets[dim]);
           if (ShapedType::isStatic(destDimSize)) {
diff --git a/mlir/test/Interfaces/TilingInterface/tile-and-fuse-consumer.mlir b/mlir/test/Interfaces/TilingInterface/tile-and-fuse-consumer.mlir
index 7b0a8494a8acb..e9465baac7509 100644
--- a/mlir/test/Interfaces/TilingInterface/tile-and-fuse-consumer.mlir
+++ b/mlir/test/Interfaces/TilingInterface/tile-and-fuse-consumer.mlir
@@ -451,6 +451,57 @@ module attributes {transform.with_named_sequence} {
 
 // -----
 
+#map = affine_map<(d0) -> (-d0 + 4, 16)>
+func.func @fuse_pack_consumer_if_single_iteration(%arg0: tensor<4x4xf32>) -> tensor<1x4x16x1xf32> {
+  %0 = tensor.empty() : tensor<1x4x16x1xf32>
+  %1 = tensor.empty() : tensor<4x4xf32>
+  %2 = scf.forall (%arg1) = (0) to (4) step (16) shared_outs(%arg2 = %1) -> (tensor<4x4xf32>) {
+    %3 = affine.min #map(%arg1)
+    %extracted_slice = tensor.extract_slice %arg0[%arg1, 0] [%3, 4] [1, 1] : tensor<4x4xf32> to tensor<?x4xf32>
+    %extracted_slice_0 = tensor.extract_slice %arg2[%arg1, 0] [%3, 4] [1, 1] : tensor<4x4xf32> to tensor<?x4xf32>
+    %4 = linalg.exp ins(%extracted_slice : tensor<?x4xf32>) outs(%extracted_slice_0 : tensor<?x4xf32>) -> tensor<?x4xf32>
+    scf.forall.in_parallel {
+      tensor.parallel_insert_slice %4 into %arg2[%arg1, 0] [%3, 4] [1, 1] : tensor<?x4xf32> into tensor<4x4xf32>
+    }
+  }
+  %cst = arith.constant 0.000000e+00 : f32
+  %pack = linalg.pack %2 padding_value(%cst : f32) outer_dims_perm = [0, 1] inner_dims_pos = [0, 1] inner_tiles = [16, 1] into %0 : tensor<4x4xf32> -> tensor<1x4x16x1xf32>
+  return %pack : tensor<1x4x16x1xf32>
+}
+
+module attributes {transform.with_named_sequence} {
+  transform.named_sequence @__transform_main(%arg0: !transform.any_op {transform.readonly}) {
+    %0 = transform.structured.match ops{["tensor.parallel_insert_slice"]} in %arg0 : (!transform.any_op) -> !transform.any_op
+    %1 = transform.structured.match ops{["scf.forall"]} in %arg0 : (!transform.any_op) -> !transform.any_op
+    %consumer, %fused_consumer = transform.test.fuse_consumer %0 in(%1) : (!transform.any_op, !transform.any_op) -> (!transform.any_op, !transform.any_op)
+    transform.yield
+  }
+}
+//      CHECK: #[[MAP:.*]] = affine_map<(d0) -> (-d0 + 4, 16)>
+//      CHECK: func.func @fuse_pack_consumer_if_single_iteration(
+// CHECK-SAME:     %[[ARG0:[a-zA-Z0-9]+]]
+//  CHECK-DAG:   %[[PACK_INIT:.*]] = tensor.empty() : tensor<1x4x16x1xf32>
+//  CHECK-DAG:   %[[ELEM_INIT:.*]] = tensor.empty() : tensor<4x4xf32>
+//  CHECK-DAG:   %[[PAD_VAL:.*]] = arith.constant 0.000000e+00 : f32
+//      CHECK:   %{{.*}}:2 = scf.forall (%[[IV:.*]]) = (0) to (4) step (16)
+// CHECK-SAME:      shared_outs(%[[ELEM_OUT_ARG:.*]] = %[[ELEM_INIT]], %[[PACK_OUT_ARG:.*]] = %[[PACK_INIT]])
+//  CHECK-DAG:      %[[SIZE:.+]] = affine.min #[[MAP]](%[[IV]])
+//  CHECK-DAG:      %[[ELEM_SRC:.*]] = tensor.extract_slice %[[ARG0]][%[[IV]], 0] [%[[SIZE]], 4] [1, 1]
+//  CHECK-DAG:      %[[ELEM_DEST:.*]] = tensor.extract_slice %[[ELEM_OUT_ARG]][%[[IV]], 0] [%[[SIZE]], 4] [1, 1]
+//      CHECK:      %[[ELEM:.*]] = linalg.exp
+// CHECK-SAME:        ins(%[[ELEM_SRC]]
+// CHECK-SAME:        outs(%[[ELEM_DEST]]
+//  CHECK-DAG:      %[[TILED_PACK_DEST:.*]] = tensor.extract_slice %[[PACK_OUT_ARG]][%[[IV]], 0, 0, 0] [1, 4, 16, 1] [1, 1, 1, 1]
+//      CHECK:      %[[PACK:.*]] = linalg.pack %[[ELEM]]
+// CHECK-SAME:        padding_value(%[[PAD_VAL]] : f32)
+// CHECK-SAME:        outer_dims_perm = [0, 1] inner_dims_pos = [0, 1] inner_tiles = [16, 1]
+// CHECK-SAME:        into %[[TILED_PACK_DEST]]
+//      CHECK:      scf.forall.in_parallel {
+//      CHECK:          tensor.parallel_insert_slice %[[ELEM]] into %[[ELEM_OUT_ARG]][%[[IV]], 0] [%[[SIZE]], 4] [1, 1]
+//      CHECK:          tensor.parallel_insert_slice %[[PACK]] into %[[PACK_OUT_ARG]][%[[IV]], 0, 0, 0] [1, 4, 16, 1] [1, 1, 1, 1]
+
+// -----
+
 // It is valid to fuse the pack op in perfect tiling scenario when the dimension
 // is dynamic and padding is not needed.
 

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llvmbot commented Jul 18, 2025

@llvm/pr-subscribers-mlir-linalg

Author: Han-Chung Wang (hanhanW)

Changes

This happens only when you use larger tile size, which is greater than or equal to the dimension size. In this case, it is a full slice, so it is fusible.

The IR can be generated during the TileAndFuse process. It is hard to fix in such driver, so we enable the naive fusion for the case.


Full diff: https://github.com/llvm/llvm-project/pull/149438.diff

2 Files Affected:

  • (modified) mlir/lib/Dialect/Linalg/Transforms/TilingInterfaceImpl.cpp (+1-1)
  • (modified) mlir/test/Interfaces/TilingInterface/tile-and-fuse-consumer.mlir (+51)
diff --git a/mlir/lib/Dialect/Linalg/Transforms/TilingInterfaceImpl.cpp b/mlir/lib/Dialect/Linalg/Transforms/TilingInterfaceImpl.cpp
index 5a10883a6043c..eed431570452a 100644
--- a/mlir/lib/Dialect/Linalg/Transforms/TilingInterfaceImpl.cpp
+++ b/mlir/lib/Dialect/Linalg/Transforms/TilingInterfaceImpl.cpp
@@ -911,7 +911,7 @@ struct PackOpTiling
         int64_t destDimSize = packOp.getDestType().getDimSize(dim);
         bool isTiled = failed(cstTileSize) ||
                        ShapedType::isDynamic(srcDimSize) ||
-                       cstTileSize.value() != srcDimSize;
+                       cstTileSize.value() < srcDimSize;
         if (!isTiled) {
           outerDimOffsets.push_back(offsets[dim]);
           if (ShapedType::isStatic(destDimSize)) {
diff --git a/mlir/test/Interfaces/TilingInterface/tile-and-fuse-consumer.mlir b/mlir/test/Interfaces/TilingInterface/tile-and-fuse-consumer.mlir
index 7b0a8494a8acb..e9465baac7509 100644
--- a/mlir/test/Interfaces/TilingInterface/tile-and-fuse-consumer.mlir
+++ b/mlir/test/Interfaces/TilingInterface/tile-and-fuse-consumer.mlir
@@ -451,6 +451,57 @@ module attributes {transform.with_named_sequence} {
 
 // -----
 
+#map = affine_map<(d0) -> (-d0 + 4, 16)>
+func.func @fuse_pack_consumer_if_single_iteration(%arg0: tensor<4x4xf32>) -> tensor<1x4x16x1xf32> {
+  %0 = tensor.empty() : tensor<1x4x16x1xf32>
+  %1 = tensor.empty() : tensor<4x4xf32>
+  %2 = scf.forall (%arg1) = (0) to (4) step (16) shared_outs(%arg2 = %1) -> (tensor<4x4xf32>) {
+    %3 = affine.min #map(%arg1)
+    %extracted_slice = tensor.extract_slice %arg0[%arg1, 0] [%3, 4] [1, 1] : tensor<4x4xf32> to tensor<?x4xf32>
+    %extracted_slice_0 = tensor.extract_slice %arg2[%arg1, 0] [%3, 4] [1, 1] : tensor<4x4xf32> to tensor<?x4xf32>
+    %4 = linalg.exp ins(%extracted_slice : tensor<?x4xf32>) outs(%extracted_slice_0 : tensor<?x4xf32>) -> tensor<?x4xf32>
+    scf.forall.in_parallel {
+      tensor.parallel_insert_slice %4 into %arg2[%arg1, 0] [%3, 4] [1, 1] : tensor<?x4xf32> into tensor<4x4xf32>
+    }
+  }
+  %cst = arith.constant 0.000000e+00 : f32
+  %pack = linalg.pack %2 padding_value(%cst : f32) outer_dims_perm = [0, 1] inner_dims_pos = [0, 1] inner_tiles = [16, 1] into %0 : tensor<4x4xf32> -> tensor<1x4x16x1xf32>
+  return %pack : tensor<1x4x16x1xf32>
+}
+
+module attributes {transform.with_named_sequence} {
+  transform.named_sequence @__transform_main(%arg0: !transform.any_op {transform.readonly}) {
+    %0 = transform.structured.match ops{["tensor.parallel_insert_slice"]} in %arg0 : (!transform.any_op) -> !transform.any_op
+    %1 = transform.structured.match ops{["scf.forall"]} in %arg0 : (!transform.any_op) -> !transform.any_op
+    %consumer, %fused_consumer = transform.test.fuse_consumer %0 in(%1) : (!transform.any_op, !transform.any_op) -> (!transform.any_op, !transform.any_op)
+    transform.yield
+  }
+}
+//      CHECK: #[[MAP:.*]] = affine_map<(d0) -> (-d0 + 4, 16)>
+//      CHECK: func.func @fuse_pack_consumer_if_single_iteration(
+// CHECK-SAME:     %[[ARG0:[a-zA-Z0-9]+]]
+//  CHECK-DAG:   %[[PACK_INIT:.*]] = tensor.empty() : tensor<1x4x16x1xf32>
+//  CHECK-DAG:   %[[ELEM_INIT:.*]] = tensor.empty() : tensor<4x4xf32>
+//  CHECK-DAG:   %[[PAD_VAL:.*]] = arith.constant 0.000000e+00 : f32
+//      CHECK:   %{{.*}}:2 = scf.forall (%[[IV:.*]]) = (0) to (4) step (16)
+// CHECK-SAME:      shared_outs(%[[ELEM_OUT_ARG:.*]] = %[[ELEM_INIT]], %[[PACK_OUT_ARG:.*]] = %[[PACK_INIT]])
+//  CHECK-DAG:      %[[SIZE:.+]] = affine.min #[[MAP]](%[[IV]])
+//  CHECK-DAG:      %[[ELEM_SRC:.*]] = tensor.extract_slice %[[ARG0]][%[[IV]], 0] [%[[SIZE]], 4] [1, 1]
+//  CHECK-DAG:      %[[ELEM_DEST:.*]] = tensor.extract_slice %[[ELEM_OUT_ARG]][%[[IV]], 0] [%[[SIZE]], 4] [1, 1]
+//      CHECK:      %[[ELEM:.*]] = linalg.exp
+// CHECK-SAME:        ins(%[[ELEM_SRC]]
+// CHECK-SAME:        outs(%[[ELEM_DEST]]
+//  CHECK-DAG:      %[[TILED_PACK_DEST:.*]] = tensor.extract_slice %[[PACK_OUT_ARG]][%[[IV]], 0, 0, 0] [1, 4, 16, 1] [1, 1, 1, 1]
+//      CHECK:      %[[PACK:.*]] = linalg.pack %[[ELEM]]
+// CHECK-SAME:        padding_value(%[[PAD_VAL]] : f32)
+// CHECK-SAME:        outer_dims_perm = [0, 1] inner_dims_pos = [0, 1] inner_tiles = [16, 1]
+// CHECK-SAME:        into %[[TILED_PACK_DEST]]
+//      CHECK:      scf.forall.in_parallel {
+//      CHECK:          tensor.parallel_insert_slice %[[ELEM]] into %[[ELEM_OUT_ARG]][%[[IV]], 0] [%[[SIZE]], 4] [1, 1]
+//      CHECK:          tensor.parallel_insert_slice %[[PACK]] into %[[PACK_OUT_ARG]][%[[IV]], 0, 0, 0] [1, 4, 16, 1] [1, 1, 1, 1]
+
+// -----
+
 // It is valid to fuse the pack op in perfect tiling scenario when the dimension
 // is dynamic and padding is not needed.
 

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LGTM, just one comment :)

@@ -911,7 +911,7 @@ struct PackOpTiling
int64_t destDimSize = packOp.getDestType().getDimSize(dim);
bool isTiled = failed(cstTileSize) ||
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A comment here explaining the < would be nice, something like what you have in the description.

func.func @fuse_pack_consumer_if_single_iteration(%arg0: tensor<4x4xf32>) -> tensor<1x4x16x1xf32> {
%0 = tensor.empty() : tensor<1x4x16x1xf32>
%1 = tensor.empty() : tensor<4x4xf32>
%2 = scf.forall (%arg1) = (0) to (4) step (16) shared_outs(%arg2 = %1) -> (tensor<4x4xf32>) {
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Q: wouldn't/shouldn't this (and in general one-iteration loops) be folded away? Probably it should happen at a different point/place, but still just wondering :)

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