[MetaSchedule][M4a] Schedule Rule: Random-Compute-Location

include/tvm/tir/schedule/schedule.h

@@ -210,6 +210,14 @@ class ScheduleNode : public runtime::Object {
    */
   virtual Array<ExprRV> SamplePerfectTile(const LoopRV& loop_rv, int n, int max_innermost_factor,
                                           Optional<Array<Integer>> decision = NullOpt) = 0;
+  /*!
+   * \brief Sample a compute-at location of the given block
+   * \param block_rv The block whose compute-at location is to be sampled
+   * \param decision The sampling decision
+   * \return The sampled loop where the input block is to be computed at
+   */
+  virtual LoopRV SampleComputeLocation(const BlockRV& block_rv,
+                                       Optional<Integer> decision = NullOpt) = 0;
 
   /******** Schedule: Get blocks & loops ********/
   /*!

include/tvm/tir/stmt.h

@@ -1361,6 +1361,13 @@ constexpr const char* script_parsing_detect_access = "tir.script_parsing_detect_
  */
 constexpr const char* pragma_loop_partition_hint = "pragma_loop_partition_hint";
 
+/*! \brief Mark the tiling structure of blocks that are applied by rule Multi-Level-Tiling */
+constexpr const char* meta_schedule_tiling_structure = "meta_schedule.tiling_structure";
+
+/*! \brief Mark the block whose producer needs to be applied by rule Random-Compute-Location */
+constexpr const char* meta_schedule_random_compute_producer =
+    "meta_schedule.random_compute_producer";
+
 /*!
  * \brief Check if attr_key is a pragma key extension
  * \param attr_key The attr key to be compared

python/tvm/meta_schedule/schedule_rule/__init__.py

@@ -17,3 +17,4 @@
 blocks in a schedule. See also PostOrderApply.
 """
 from .schedule_rule import PyScheduleRule, ScheduleRule
+from .random_compute_location import RandomComputeLocation

python/tvm/meta_schedule/schedule_rule/random_compute_location.py

@@ -0,0 +1,31 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+"""Rule that randomly select a compute-at location for a free block"""
+from tvm._ffi import register_object
+
+from .. import _ffi_api
+from .schedule_rule import ScheduleRule
+
+
+@register_object("meta_schedule.RandomComputeLocation")
+class RandomComputeLocation(ScheduleRule):
+    """A rule that randomly select a compute-at location for a free block"""
+
+    def __init__(self) -> None:
+        self.__init_handle_by_constructor__(
+            _ffi_api.ScheduleRuleRandomComputeLocation,  # type: ignore # pylint: disable=no-member
+        )

python/tvm/meta_schedule/testing/space_generation.py

@@ -0,0 +1,33 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+# pylint: disable=missing-module-docstring,missing-function-docstring,missing-class-docstring
+from typing import List
+
+from tvm.tir import Schedule
+from tvm.tir.schedule import Trace
+
+
+def check_trace(spaces: List[Schedule], expected: List[List[str]]):
+    expected_traces = {"\n".join(t) for t in expected}
+    actual_traces = set()
+    for space in spaces:
+        trace = Trace(space.trace.insts, {})
+        trace = trace.simplified(remove_postproc=True)
+        str_trace = "\n".join(str(trace).strip().splitlines())
+        actual_traces.add(str_trace)
+        assert str_trace in expected_traces, "\n" + str_trace
+    assert len(expected_traces) == len(actual_traces)

python/tvm/tir/schedule/schedule.py

@@ -369,6 +369,32 @@ def sample_perfect_tile(
             )
         )
 
+    @type_checked
+    def sample_compute_location(
+        self,
+        block: BlockRV,
+        decision: Optional[int] = None,
+    ) -> LoopRV:
+        """Sample a compute-at location of the given block
+
+        Parameters
+        ----------
+        block : BlockRV
+            The block whose compute-at location is to be sampled
+        decision : Optional[int]
+            The sampling decision
+
+        Returns
+        -------
+        result : LoopRV
+            The sampled loop where the input block is to be computed at
+        """
+        return _ffi_api.ScheduleSampleComputeLocation(  # type: ignore  # pylint: disable=no-member
+            self,
+            block,
+            decision,
+        )
+
     ########## Schedule: Get blocks & loops ##########
     @type_checked
     def get_block(

src/meta_schedule/schedule_rule/random_compute_location.cc

@@ -0,0 +1,123 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+#include "../utils.h"
+
+namespace tvm {
+namespace meta_schedule {
+
+class RandomComputeLocationNode : public ScheduleRuleNode {
+ public:
+  // Inherited from ScheduleRuleNode
+  void InitializeWithTuneContext(const TuneContext& context) final {}
+
+  // Inherited from ScheduleRuleNode
+  Array<tir::Schedule> Apply(const tir::Schedule& sch, const tir::BlockRV& block_rv) final {
+    if (!CheckConditions(sch, block_rv)) {
+      return {sch};
+    }
+
+    // Step 1. If the producer of the input block needs a random compute-at location (specified by
+    // the annotation), we collect the producer first, and transform the producer block later.
+    // - The reason we collect the producer before transforming the input block is that, if the
+    // decision of Sample-Compute-Location is "compute-inline" for the input block, we can no longer
+    // access the input block. Hence we collect its producer ahead of time.
+    // - Note that only single producer is allowed in this case.
+    Array<tir::BlockRV> producers{nullptr};
+    if (tir::HasAnn(sch->GetSRef(block_rv), tir::attr::meta_schedule_random_compute_producer,
+                    true)) {
+      producers = sch->GetProducers(block_rv);
+      sch->Unannotate(block_rv, tir::attr::meta_schedule_random_compute_producer);
+      ICHECK_EQ(producers.size(), 1);
+    }
+
+    // Step 2. Transform the input block.
+    tir::Schedule res = RandomlyComputeAt(sch, block_rv);
+
+    // Step 3. Transform the producer block if compute-location sampling is needed.
+    if (producers.defined()) {
+      res = RandomlyComputeAt(res, producers[0]);
+    }
+
+    return {res};
+  }
+
+ private:
+  bool CheckConditions(const tir::Schedule sch, const tir::BlockRV& block_rv) const {
+    tir::StmtSRef block_sref = sch->GetSRef(block_rv);
+    const tir::BlockNode* block = TVM_SREF_TO_BLOCK(block, block_sref);
+
+    // Cond 1. The block is not the root block.
+    if (block_sref->parent == nullptr) {
+      return false;
+    }
+    // Cond 2. The block should be the direct child block of the root block.
+    if (GetScopeRoot(sch->state(), block_sref,          //
+                     /*require_stage_pipeline=*/false,  //
+                     /*require_subtree_compact_dataflow=*/false)
+            ->parent != nullptr) {
+      return false;
+    }
+    // Cond 3 & 4. The block has at least one outer loop, and the outermost loop has only one child
+    // block.
+    Array<tir::StmtSRef> loop_srefs = tir::GetLoops(block_sref);
+    if (loop_srefs.empty()) {
+      return false;
+    }
+    if (tir::GetChildBlockSRefOnSRefTree(sch->state(), loop_srefs[0]).size() > 1) {
+      return false;
+    }
+    // Cond 5. The block is not tiled. We check this condition by examine the block's annotation.
+    if (tir::HasBeenMultiLevelTiled(block_sref)) {
+      return false;
+    }
+    // Cond 6. The block has at lease one consumer.
+    if (tir::GetConsumers(sch->state(), sch->GetSRef(block_rv)).empty()) {
+      return false;
+    }
+    return true;
+  }
+
+  /*!
+   * \brief Keep sampling a compute-at location for the input block until success.
+   * \param sch The TIR schedule
+   * \param block_rv The block whose compute-at location is to be sampled
+   * \return The TIR schedule after transformation
+   */
+  tir::Schedule RandomlyComputeAt(const tir::Schedule& sch, const tir::BlockRV& block_rv) {
+    tir::LoopRV compute_at_loc = sch->SampleComputeLocation(block_rv);
+    sch->ComputeAt(block_rv, compute_at_loc, true);
+    return sch;
+  }
+
+ public:
+  void VisitAttrs(tvm::AttrVisitor* v) {}
+
+  static constexpr const char* _type_key = "meta_schedule.RandomComputeLocation";
+  TVM_DECLARE_FINAL_OBJECT_INFO(RandomComputeLocationNode, ScheduleRuleNode);
+};
+
+ScheduleRule ScheduleRule::RandomComputeLocation() {
+  return ScheduleRule(make_object<RandomComputeLocationNode>());
+}
+
+TVM_REGISTER_NODE_TYPE(RandomComputeLocationNode);
+TVM_REGISTER_GLOBAL("meta_schedule.ScheduleRuleRandomComputeLocation")
+    .set_body_typed(ScheduleRule::RandomComputeLocation);
+}  // namespace meta_schedule
+}  // namespace tvm

src/tir/schedule/analysis.h

@@ -266,6 +266,39 @@ BlockRealize CheckGetSingleChildBlockRealizeOnSRefTree(const ScheduleState& self
  */
 BlockRealize GetBlockRealize(const ScheduleState& self, const StmtSRef& block_sref);
 
+/*!
+ * \brief Get the IterVarType of the specific loop, according to the blocks it's bound to
+ * \param loop_sref The loop to be checked
+ * \return The IterVarType of the specific loop
+ */
+IterVarType GetLoopIterType(const StmtSRef& loop_sref);
+
+/*!
+ * \brief Get the lowest common ancestor of an array of blocks or loops on the sref tree
+ * \param srefs The block srefs or loop srefs whose lowest common ancestor is to be queried
+ * \return The lowest common ancestor of the input block srefs or loop srefs
+ * \note The input array is required to have at least one sref
+ */
+StmtSRef GetSRefLowestCommonAncestor(const Array<StmtSRef>& srefs);
+
+/*!
+ * \brief Checks if the given block has been applied by multi-level tiling. We check this by
+ *        examine the block's annotation.
+ * \param block_sref The block to be checked
+ * \return A boolean indicating whether the block has been multi-level tiled.
+ */
+bool HasBeenMultiLevelTiled(const StmtSRef& block_sref);
+
+/*!
+ * \brief Collect all the feasible compute-at locations of the input block
+ * \param self The schedule state
+ * \param block_sref The block whose compute-at locations are to be collected
+ * \return All the feasible compute-at locations of the input block, given as an array of loop srefs
+ *         and an array of their indices among the outer loops of the input block
+ */
+std::pair<Array<StmtSRef>, std::vector<int>> CollectComputeLocation(const ScheduleState& self,
+                                                                    const StmtSRef& block_sref);
+
 /******** Producer-consumer relation ********/
 
 /*!