[MLIR][Transform] Consolidate result of structured.split into one list (#111171)

Follow-up a review comment from
#82792 (comment)
as a separate PR:

	E.g.:
	```
	%0:2 = transform.structured.split
	```
	is changed to
	```
	%t = transform.structured.split
	%0:2 = transform.split_handle %t
	```

Author: joeyye-work

mlir/include/mlir/Dialect/Linalg/TransformOps/LinalgTransformOps.td

@@ -703,8 +703,10 @@ def MultiTileSizesOp : Op<Transform_Dialect, "structured.multitile_sizes",
                          { target_size = 10, dimension = 1 }
                        : !transform.any_op, !transform.param<i64>,
                          !transform.param<i64>, !transform.param<i64>
-    %low, %high = structured.split %target after %split { dimension = 1 }
+    %handles = structured.split %target after %split { dimension = 1 }
                 : !transform.any_op, !transform.param<i64>
+    %low, %high = transform.split_handle %handles : (!transform.any_op)
+                      -> (!transform.any_op, !transform.any_op)
     %tiled_low, %loop1 = structured.tile_using_for %low [0, %sz1]
                        : (!transform.any_op, !transform.param<i64>)
                       -> (!transform.any_op, !transform.any_op)
@@ -1452,30 +1454,32 @@ def SplitOp : Op<Transform_Dialect, "structured.split",
     operations pointed to by the target handle.
 
     The operation consumes the target handle, but preserves the chunk size
-    handle if provided. Without the `multiway` attribute, it produces two
-    new handles pointing to the two parts of the structured op after splitting,
-    in the same order as the target operand, with the first handle
-    corresponding to the part with lower iteration space indices.
+    handle if provided. Without the `multiway` attribute, it produces a
+    new handle that is a list of the two parts of the structured op after
+    splitting, whose lower index part corresponding to the part with lower
+    iteration space indices.
 
     Multiway split mode is enabled by specifying the `multiway` attribute.
     In this mode a single `target` op is split into multiple parts covering
     the iteration space of the specified dimension. `static_chunk_sizes` and
     `dynamic_chunk_sizes` in this case is a list of chunk sizes that the given
-    dimension should be split into. With `multiway` it produces two handles;
-    the first handle is a list of the multiple parts of the structured op
+    dimension should be split into. With `multiway` it also produces a handle;
+    The result handle is a list of the multiple parts of the structured op
     after splitting, where the target dimensions for each linalg op in the
     list corresponds to the chunk sizes specfied in the input split list.
     If the chunk sizes do not cover the entire iteration space, the leftover
-    chunk is the last payload in the first handle. The second handle is empty.
+    chunk is the last payload in the result handle.
+
+    As the result handle is most of time a list, an `transform.split_handle`
+    is needed to access individual handle.
   }];
 
   let arguments = (ins TransformHandleTypeInterface:$target,
                        I64Attr:$dimension,
                        Optional<TransformAnyParamTypeOrAnyHandle>:$dynamic_chunk_sizes,
                        I64Attr:$static_chunk_sizes,
                        UnitAttr:$multiway);
-  let results = (outs TransformHandleTypeInterface:$first,
-                      TransformHandleTypeInterface:$second);
+  let results = (outs TransformHandleTypeInterface:$split_list);
   let hasCustomAssemblyFormat = 1;
   let hasVerifier = 1;
 }

mlir/lib/Dialect/Linalg/TransformOps/LinalgTransformOps.cpp

@@ -2363,10 +2363,10 @@ SplitOp::apply(transform::TransformRewriter &rewriter,
     return DiagnosedSilenceableFailure::success();
   };
 
+  SmallVector<Operation *> opList;
   if (isMultiwaySplit) {
 
     // Split a single target operation at multiple points.
-    SmallVector<Operation *> opList;
     TilingInterface head, tail;
     Operation *target = payload.front();
 
@@ -2406,8 +2406,6 @@ SplitOp::apply(transform::TransformRewriter &rewriter,
     // Append any leftover parts to the end of the result list.
     if (tail)
       opList.push_back(tail.getOperation());
-    results.set(cast<OpResult>(getFirst()), opList);
-    results.set(cast<OpResult>(getSecond()), {});
 
   } else {
     // Split each target operation.
@@ -2453,9 +2451,11 @@ SplitOp::apply(transform::TransformRewriter &rewriter,
       return diag;
     }
 
-    results.set(cast<OpResult>(getFirst()), first);
-    results.set(cast<OpResult>(getSecond()), second);
+    opList.append(first);
+    if (second.size())
+      opList.append(second);
   }
+  results.set(cast<OpResult>(getSplitList()), opList);
   return DiagnosedSilenceableFailure::success();
 }
 
@@ -2507,7 +2507,7 @@ ParseResult SplitOp::parse(OpAsmParser &parser, OperationState &result) {
   result.addAttribute(
       SplitOp::getStaticChunkSizesAttrName(result.name).getValue(),
       staticChunkSizes);
-  result.addTypes({targetType, targetType});
+  result.addTypes(targetType);
   return success();
 }
 

mlir/python/mlir/dialects/transform/structured.py

@@ -445,7 +445,6 @@ def __init__(
             dynamic_chunk_sizes = chunk_sizes
 
         super().__init__(
-            target.type,
             target.type,
             target,
             dimension=dimension,

mlir/test/Dialect/Linalg/continuous-tiling-full.mlir

@@ -4,7 +4,7 @@ module attributes {transform.with_named_sequence} {
   transform.named_sequence @__transform_main(%arg1: !transform.any_op {transform.readonly}) {
     %0 = transform.structured.match ops{["linalg.matmul"]} in %arg1 : (!transform.any_op) -> !transform.any_op
     %tile_sizes, %chunk_sizes = transform.structured.continuous_tile_sizes %0 { dimension = 0, target_size = 9 } : (!transform.any_op) -> !transform.any_op
-    %linalg_splits, %empty = transform.structured.split %0 after %chunk_sizes { dimension = 0, multiway } : !transform.any_op, !transform.any_op
+    %linalg_splits = transform.structured.split %0 after %chunk_sizes { dimension = 0, multiway } : !transform.any_op, !transform.any_op
     transform.foreach %linalg_splits, %tile_sizes : !transform.any_op, !transform.any_op {
     ^bb1(%linalg_split: !transform.any_op, %tile_size: !transform.any_op):
       %tiled_linalg_split, %dim0_loop = transform.structured.tile_using_for %linalg_split tile_sizes [%tile_size] : (!transform.any_op, !transform.any_op) -> (!transform.any_op, !transform.any_op)
@@ -65,7 +65,7 @@ module attributes {transform.with_named_sequence} {
   transform.named_sequence @__transform_main(%arg1: !transform.any_op {transform.readonly}) {
     %0 = transform.structured.match ops{["linalg.matmul"]} in %arg1 : (!transform.any_op) -> !transform.any_op
     %tile_sizes, %chunk_sizes = transform.structured.continuous_tile_sizes %0 { dimension = 0, target_size = 9 } : (!transform.any_op) -> !transform.param<i64>
-    %linalg_splits, %empty = transform.structured.split %0 after %chunk_sizes { dimension = 0, multiway } : !transform.any_op, !transform.param<i64>
+    %linalg_splits = transform.structured.split %0 after %chunk_sizes { dimension = 0, multiway } : !transform.any_op, !transform.param<i64>
     transform.foreach %linalg_splits, %tile_sizes : !transform.any_op, !transform.param<i64> {
     ^bb1(%linalg_split: !transform.any_op, %tile_size: !transform.param<i64>):
       %tiled_linalg_split, %dim0_loop = transform.structured.tile_using_for %linalg_split tile_sizes [%tile_size] : (!transform.any_op, !transform.param<i64>) -> (!transform.any_op, !transform.any_op)
@@ -126,7 +126,7 @@ module attributes {transform.with_named_sequence} {
   transform.named_sequence @__transform_main(%arg1: !transform.any_op {transform.readonly}) {
     %0 = transform.structured.match ops{["linalg.matmul"]} in %arg1 : (!transform.any_op) -> !transform.any_op
     %tile_sizes, %chunk_sizes = transform.structured.continuous_tile_sizes %0 { dimension = 0, target_size = 9 } : (!transform.any_op) -> !transform.any_op
-    %linalg_splits, %empty = transform.structured.split %0 after %chunk_sizes { dimension = 0, multiway } : !transform.any_op, !transform.any_op
+    %linalg_splits = transform.structured.split %0 after %chunk_sizes { dimension = 0, multiway } : !transform.any_op, !transform.any_op
     transform.foreach %linalg_splits, %tile_sizes with_zip_shortest : !transform.any_op, !transform.any_op {
     ^bb1(%linalg_split: !transform.any_op, %tile_size: !transform.any_op):
       %tiled_linalg_split, %dim0_loop = transform.structured.tile_using_for %linalg_split tile_sizes [%tile_size] : (!transform.any_op, !transform.any_op) -> (!transform.any_op, !transform.any_op)
@@ -177,4 +177,4 @@ func.func @continuous_tile_dynamic_linalg_matmul(
 // CHECK:     %[[AM16:.*]] = affine.min #[[$MAP12]]()[%{{.*}}, %{{.*}}, %[[AM0]], %[[AM4]], %[[AM8]], %[[AM12]]]
 // CHECK:     %{{.*}} = scf.for %[[IDX:.+]] = %[[C0]] to %[[AM16]] step %[[C1]] iter_args(%[[OUT:.+]] = %{{.*}}) -> (tensor<?x?xf32>) {
 // CHECK:       %[[MM:.+]] = linalg.matmul ins(%{{.*}}, %{{.*}} : tensor<1x?xf32>, tensor<?x?xf32>) outs(%{{.*}} : tensor<1x?xf32>) -> tensor<1x?xf32>
-// CHECK:       %{{.*}} = tensor.insert_slice %[[MM]] into %[[OUT]][%[[IDX]], 0] [1, %{{.*}}] [1, 1] : tensor<1x?xf32> into tensor<?x?xf32>
+// CHECK:       %{{.*}} = tensor.insert_slice %[[MM]] into %[[OUT]][%[[IDX]], 0] [1, %{{.*}}] [1, 1] : tensor<1x?xf32> into tensor<?x?xf32>

mlir/test/Dialect/Linalg/continuous-tiling-multiway-split.mlir

@@ -8,7 +8,7 @@ module attributes {transform.with_named_sequence} {
   transform.named_sequence @__transform_main(%arg1: !transform.any_op {transform.readonly}) {
     %0 = transform.structured.match ops{["linalg.matmul"]} in %arg1 : (!transform.any_op) -> !transform.any_op
     %tiles, %splits = transform.structured.continuous_tile_sizes %0 { dimension = 1, target_size = 9} : (!transform.any_op) -> !transform.any_op
-    %low, %high = transform.structured.split %0 after %splits { dimension = 1, multiway } : !transform.any_op, !transform.any_op
+    %splits2 = transform.structured.split %0 after %splits { dimension = 1, multiway } : !transform.any_op, !transform.any_op
     transform.yield
   }
 }
@@ -58,7 +58,7 @@ module attributes {transform.with_named_sequence} {
   transform.named_sequence @__transform_main(%arg1: !transform.any_op {transform.readonly}) {
     %0 = transform.structured.match ops{["linalg.matmul"]} in %arg1 : (!transform.any_op) -> !transform.any_op
     %tiles, %splits = transform.structured.continuous_tile_sizes %0 { dimension = 1, target_size = 9} : (!transform.any_op) -> !transform.param<i64>
-    %low, %high = transform.structured.split %0 after %splits { dimension = 1, multiway } : !transform.any_op, !transform.param<i64>
+    %splits2 = transform.structured.split %0 after %splits { dimension = 1, multiway } : !transform.any_op, !transform.param<i64>
     transform.yield
   }
 }

mlir/test/Dialect/Linalg/multisize-tiling-full.mlir

@@ -6,14 +6,16 @@ module attributes {transform.with_named_sequence} {
   transform.named_sequence @__transform_main(%arg1: !transform.any_op {transform.readonly}) {
     %0 = transform.structured.match ops{["linalg.generic"]} in %arg1 : (!transform.any_op) -> !transform.any_op
     %1:3 = transform.structured.multitile_sizes %0 { dimension = 0, target_size = 3} : (!transform.any_op) -> !transform.any_op
-    %2:2 = transform.structured.split %0 after %1#2 { dimension = 0 } : !transform.any_op, !transform.any_op
+    %split = transform.structured.split %0 after %1#2 { dimension = 0 } : !transform.any_op, !transform.any_op
+    %2:2 = transform.split_handle %split : (!transform.any_op) -> (!transform.any_op, !transform.any_op)
     %3:2 = transform.structured.tile_using_for %2#0 tile_sizes [%1#0] : (!transform.any_op, !transform.any_op) -> (!transform.any_op, !transform.any_op)
     %4:2 = transform.structured.tile_using_for %2#1 tile_sizes [%1#1] : (!transform.any_op, !transform.any_op) -> (!transform.any_op, !transform.any_op)
     %5 = transform.merge_handles %3#0, %4#0 : !transform.any_op
     transform.foreach %5 : !transform.any_op {
     ^bb0(%inner_linalg: !transform.any_op):
       %low, %high, %split_point = transform.structured.multitile_sizes %inner_linalg { dimension = 1, target_size = 10} : (!transform.any_op) -> !transform.any_op
-      %inner_linalg_low, %inner_linalg_high = transform.structured.split %inner_linalg after %split_point { dimension = 1 } : !transform.any_op, !transform.any_op
+      %split2 = transform.structured.split %inner_linalg after %split_point { dimension = 1 } : !transform.any_op, !transform.any_op
+      %inner_linalg_low, %inner_linalg_high = transform.split_handle %split2 : (!transform.any_op) -> (!transform.any_op, !transform.any_op)
       transform.structured.tile_using_for %inner_linalg_low tile_sizes [0, %low] : (!transform.any_op, !transform.any_op) -> (!transform.any_op, !transform.any_op)
       transform.structured.tile_using_for %inner_linalg_high tile_sizes [0, %high] : (!transform.any_op, !transform.any_op) -> (!transform.any_op, !transform.any_op)
     }
@@ -111,14 +113,16 @@ module attributes {transform.with_named_sequence} {
     %0 = transform.structured.match ops{["linalg.generic"]} in %arg1 : (!transform.any_op) -> !transform.any_op
     %1:3 = transform.structured.multitile_sizes %0 { dimension = 0, target_size = 3} : (!transform.any_op) -> !transform.param<i64>
     %t:3 = transform.structured.multitile_sizes %0 { dimension = 1, target_size = 10} : (!transform.any_op) -> !transform.param<i64>
-    %2:2 = transform.structured.split %0 after %1#2 { dimension = 0 } : !transform.any_op, !transform.param<i64>
+    %split = transform.structured.split %0 after %1#2 { dimension = 0 } : !transform.any_op, !transform.param<i64>
+    %2:2 = transform.split_handle %split : (!transform.any_op) -> (!transform.any_op, !transform.any_op)
     %3:2 = transform.structured.tile_using_for %2#0 tile_sizes [%1#0] : (!transform.any_op, !transform.param<i64>) -> (!transform.any_op, !transform.any_op)
     %4:2 = transform.structured.tile_using_for %2#1 tile_sizes [%1#1] : (!transform.any_op, !transform.param<i64>) -> (!transform.any_op, !transform.any_op)
     %5 = transform.merge_handles %3#0, %4#0 : !transform.any_op
     %tt:3 = transform.replicate num(%5) %t#0, %t#1, %t#2 : !transform.any_op, !transform.param<i64>, !transform.param<i64>, !transform.param<i64>
     transform.foreach %5, %tt#0, %tt#1, %tt#2 : !transform.any_op, !transform.param<i64>, !transform.param<i64>, !transform.param<i64> {
     ^bb0(%inner_linalg: !transform.any_op, %low: !transform.param<i64>, %high: !transform.param<i64>, %split_point: !transform.param<i64>):
-      %inner_linalg_low, %inner_linalg_high = transform.structured.split %inner_linalg after %split_point { dimension = 1 } : !transform.any_op, !transform.param<i64>
+      %split2 = transform.structured.split %inner_linalg after %split_point { dimension = 1 } : !transform.any_op, !transform.param<i64>
+      %inner_linalg_low, %inner_linalg_high = transform.split_handle %split2 : (!transform.any_op) -> (!transform.any_op, !transform.any_op)
       transform.structured.tile_using_for %inner_linalg_low tile_sizes [0, %low] : (!transform.any_op, !transform.param<i64>) -> (!transform.any_op, !transform.any_op)
       transform.structured.tile_using_for %inner_linalg_high tile_sizes [0, %high] : (!transform.any_op, !transform.param<i64>) -> (!transform.any_op, !transform.any_op)
     }

mlir/test/Dialect/Linalg/transform-op-split.mlir

@@ -3,7 +3,7 @@
 module attributes {transform.with_named_sequence} {
   transform.named_sequence @__transform_main(%arg1: !transform.any_op {transform.readonly}) {
     %0 = transform.structured.match ops{["linalg.generic"]} in %arg1 : (!transform.any_op) -> !transform.any_op
-    %1:2 = transform.structured.split %0 after 42 { dimension = 0 } : !transform.any_op
+    %1 = transform.structured.split %0 after 42 { dimension = 0 } : !transform.any_op
     transform.yield
   }
 }
@@ -53,7 +53,7 @@ func.func @one_d_static(%arg0: tensor<100xf32>, %arg1: tensor<100xf32>) -> tenso
 module attributes {transform.with_named_sequence} {
   transform.named_sequence @__transform_main(%arg1: !transform.any_op {transform.readonly}) {
     %0 = transform.structured.match ops{["linalg.generic"]} in %arg1 : (!transform.any_op) -> !transform.any_op
-    %1:2 = transform.structured.split %0 after 42 { dimension = 0 } : !transform.any_op
+    %1 = transform.structured.split %0 after 42 { dimension = 0 } : !transform.any_op
     transform.yield
   }
 }
@@ -138,8 +138,9 @@ func.func @dynamic(%arg0: tensor<100xf32>, %arg1: tensor<100xf32>) -> tensor<100
 module attributes {transform.with_named_sequence} {
   transform.named_sequence @__transform_main(%arg1: !transform.any_op {transform.readonly}) {
     %0 = transform.structured.match ops{["linalg.generic"]} in %arg1 : (!transform.any_op) -> !transform.any_op
-    %1:2 = transform.structured.split %0 after 4 { dimension = 0 } : !transform.any_op
-    %2:2 = transform.structured.split %1#1 after 16 { dimension = 1 } : !transform.any_op
+    %t = transform.structured.split %0 after 4 { dimension = 0 } : !transform.any_op
+    %1:2 = transform.split_handle %t : (!transform.any_op) -> (!transform.any_op, !transform.any_op)
+    %2 = transform.structured.split %1#1 after 16 { dimension = 1 } : !transform.any_op
     transform.yield
   }
 }
@@ -197,7 +198,7 @@ func.func @two_d(%arg0: tensor<10x34xf32>,
 module attributes {transform.with_named_sequence} {
   transform.named_sequence @__transform_main(%arg1: !transform.any_op {transform.consumed}) {
     // expected-error @below {{expects either a dynamic or a static split point to be provided}}
-    %0:2 = "transform.structured.split"(%arg1) { dimension = 1, static_chunk_sizes = -9223372036854775808 } : (!transform.any_op) -> (!transform.any_op, !transform.any_op)
+    %0 = "transform.structured.split"(%arg1) { dimension = 1, static_chunk_sizes = -9223372036854775808 } : (!transform.any_op) -> (!transform.any_op)
     transform.yield
   }
 }
@@ -303,7 +304,7 @@ module attributes {transform.with_named_sequence} {
     %0 = transform.structured.match ops{["linalg.generic"]} in %arg1 : (!transform.any_op) -> !transform.any_op
     // expected-error @below {{splitting does not produce the second part for a subset of targets}}
     // expected-note @below {{expected splitting to produce the second part of all or none of the targets}}
-    %1:2 = transform.structured.split %0 after 142 { dimension = 0 } : !transform.any_op
+    %1 = transform.structured.split %0 after 142 { dimension = 0 } : !transform.any_op
     transform.yield
   }
 }

mlir/test/Dialect/Linalg/transform-ops.mlir

@@ -18,7 +18,8 @@ transform.sequence failures(propagate) {
 
 transform.sequence failures(propagate) {
 ^bb1(%arg0: !transform.any_op):
-  %0:2 = transform.structured.split %arg0 after 42 { dimension = 0 } : !transform.any_op
+  %t = transform.structured.split %arg0 after 42 { dimension = 0 } : !transform.any_op
+  %0:2 = transform.split_handle %t : (!transform.any_op) -> (!transform.any_op, !transform.any_op)
   transform.structured.split %0#0 after %0#1 { dimension = 1 } : !transform.any_op, !transform.any_op
 }
 

mlir/test/python/dialects/transform_structured_ext.py

@@ -361,11 +361,15 @@ def testScalarize(target):
 @run
 @create_sequence
 def testSplit(target):
-    split = structured.SplitOp(target, dimension=1, chunk_sizes=42)
+    handle = structured.SplitOp(target, dimension=1, chunk_sizes=42)
+    split = transform.SplitHandleOp(
+        [transform.AnyOpType.get(), transform.AnyOpType.get()], handle
+    )
     structured.SplitOp(split.results[0], dimension=3, chunk_sizes=split.results[1])
     # CHECK-LABEL: TEST: testSplit
-    # CHECK: %[[F:.+]], %[[S:.+]] = transform.structured.split %{{.*}} after 42 {dimension = 1
-    # CHECK: transform.structured.split %[[F]] after %[[S]] {dimension = 3
+    # CHECK: %[[G:.+]] = transform.structured.split %{{.*}} after 42 {dimension = 1
+    # CHECK: %[[F:.+]]:2 = split_handle %[[G]]
+    # CHECK: transform.structured.split %[[F]]#0 after %[[F]]#1 {dimension = 3
 
 
 @run