[GitHub] [tvm] Hzfengsy commented on a change in pull request #9360: [TensorIR] Cross-Thread Reduction

[GitBox <gi...@apache.org>]

Hzfengsy commented on a change in pull request #9360:
URL: https://github.com/apache/tvm/pull/9360#discussion_r747369463



##########
File path: src/tir/transforms/lower_cross_thread_reduction.cc
##########
@@ -0,0 +1,590 @@
+/*
+ * 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.
+ */
+
+/*!
+ * \file lower_cross_thread_reduction.cc
+ */
+#include <tvm/arith/analyzer.h>
+#include <tvm/tir/analysis.h>
+#include <tvm/tir/stmt_functor.h>
+#include <tvm/tir/transform.h>
+
+#include "../schedule/analysis.h"
+#include "ir_utils.h"
+
+namespace tvm {
+namespace tir {
+
+/*!
+ * \brief Check the dominant property of a block:
+ * the block is the only writer of its output, dominating the reader of its output buffers
+ * \param scope_block The scope block of the block to be checked
+ * \param block The block whose dominant property is to be checked
+ * \return A boolean indicating if the block is a dominant block
+ */
+bool IsDominantBlock(const Block& scope_block, const Block& block) {
+  // Step 1. Count the number of writers for each buffer written by the scope block.
+  std::unordered_map<const BufferNode*, int> buffer_writer_cnt;
+  PreOrderVisit(scope_block->body, [&buffer_writer_cnt](const ObjectRef& obj) {
+    if (const auto* block = obj.as<BlockNode>()) {
+      for (const BufferRegion& buffer_region : block->writes) {
+        ++buffer_writer_cnt[buffer_region->buffer.get()];
+      }
+      return false;
+    }
+    return true;
+  });
+  // Step 2. Check whether `block` is the only writer of its outputs.
+  for (const BufferRegion& buffer_region : block->writes) {
+    ICHECK(buffer_writer_cnt.count(buffer_region->buffer.get()));
+    if (buffer_writer_cnt[buffer_region->buffer.get()] != 1) {
+      return false;
+    }
+  }
+  return true;
+}
+
+/*!
+ * \brief Check whether the input block is a reduction block.
+ * \param block_realize The block to be checked
+ * \param loop_range_map The mapping from the loop variables outside the input block to their ranges
+ * \param scope_block The scope block of the input block
+ * \param analyzer The analyzer
+ * \return A boolean indicating whether the input block is a reduction block.
+ * \note A similar check has been implemented in "src/tir/schedule/analysis.h", but that check is
+ * based on `tir.Schedule`. Here we have no schedule information, and thus we must implement the
+ * check again.
+ */
+bool IsReductionBlock(const BlockRealize& block_realize, const Map<Var, Range>& loop_range_map,

Review comment:
       Can we reuse the current API?

##########
File path: src/tir/transforms/lower_cross_thread_reduction.cc
##########
@@ -0,0 +1,590 @@
+/*
+ * 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.
+ */
+
+/*!
+ * \file lower_cross_thread_reduction.cc
+ */
+#include <tvm/arith/analyzer.h>
+#include <tvm/tir/analysis.h>
+#include <tvm/tir/stmt_functor.h>
+#include <tvm/tir/transform.h>
+
+#include "../schedule/analysis.h"
+#include "ir_utils.h"
+
+namespace tvm {
+namespace tir {
+
+/*!
+ * \brief Check the dominant property of a block:
+ * the block is the only writer of its output, dominating the reader of its output buffers
+ * \param scope_block The scope block of the block to be checked
+ * \param block The block whose dominant property is to be checked
+ * \return A boolean indicating if the block is a dominant block
+ */
+bool IsDominantBlock(const Block& scope_block, const Block& block) {
+  // Step 1. Count the number of writers for each buffer written by the scope block.
+  std::unordered_map<const BufferNode*, int> buffer_writer_cnt;
+  PreOrderVisit(scope_block->body, [&buffer_writer_cnt](const ObjectRef& obj) {
+    if (const auto* block = obj.as<BlockNode>()) {
+      for (const BufferRegion& buffer_region : block->writes) {
+        ++buffer_writer_cnt[buffer_region->buffer.get()];
+      }
+      return false;
+    }
+    return true;
+  });
+  // Step 2. Check whether `block` is the only writer of its outputs.
+  for (const BufferRegion& buffer_region : block->writes) {
+    ICHECK(buffer_writer_cnt.count(buffer_region->buffer.get()));
+    if (buffer_writer_cnt[buffer_region->buffer.get()] != 1) {
+      return false;
+    }
+  }
+  return true;
+}
+
+/*!
+ * \brief Check whether the input block is a reduction block.
+ * \param block_realize The block to be checked
+ * \param loop_range_map The mapping from the loop variables outside the input block to their ranges
+ * \param scope_block The scope block of the input block
+ * \param analyzer The analyzer
+ * \return A boolean indicating whether the input block is a reduction block.
+ * \note A similar check has been implemented in "src/tir/schedule/analysis.h", but that check is
+ * based on `tir.Schedule`. Here we have no schedule information, and thus we must implement the
+ * check again.
+ */
+bool IsReductionBlock(const BlockRealize& block_realize, const Map<Var, Range>& loop_range_map,
+                      const Block& scope_block, arith::Analyzer* analyzer) {
+  const auto* block = block_realize->block.as<BlockNode>();
+  // Cond 1. The block has the `init` statement.
+  if (!block->init.defined()) {
+    return false;
+  }
+  // Cond 2. All the block bindings are quasi-affine expressions.
+  if (!IsAffineBinding(block_realize, loop_range_map, analyzer)) {
+    return false;
+  }
+  // Cond 3. All block vars are either data parallel block vars or reduction block vars. Meanwhile,
+  // we collect all the reduction block vars.
+  if (!ContainsOnlyDataParAndReductionBlockIter(block->iter_vars)) {
+    return false;
+  }
+  // Cond 4. Dominant: the block is the only writer of its output, dominating the reader of its
+  // output buffers.
+  if (!IsDominantBlock(scope_block, GetRef<Block>(block))) {
+    return false;
+  }
+  // Cond 5. The reduction block vars are not used to index the output buffers.
+  return ReductionIterNotIndexOutputBuffer(GetRef<Block>(block));
+}
+
+/*!
+ * \brief Create an intermediate buffer with specified name and data type
+ * \param name The specified name
+ * \param dtype The specified data type
+ * \return The created buffer
+ */
+Buffer CreateReductionBuffer(String name, const DataType& dtype) {
+  Var var(name, PointerType(PrimType(dtype), "local"));
+  return Buffer(var, dtype, {1}, {1}, PrimExpr(), std::move(name), 0, 0, kDefault);

Review comment:
       It seems that the shape and other attrs are incorrect




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