Lunderberg commented on a change in pull request #10538: URL: https://github.com/apache/tvm/pull/10538#discussion_r832580175
########## File path: src/tir/schedule/primitive/layout_transformation.cc ########## @@ -0,0 +1,239 @@ +/* + * 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 tir { + +class TransformLayoutRewriter : private StmtExprMutator { + public: + /*! + * \brief Rewrite the access to the buffer after the transformation + * \param scope_stmt The parent statement that contains all accesses to the target buffer + * \param old_buffer The target buffer before transformation + * \param new_buffer The new buffer after transformation + * \param index_map The transformation applied to the buffer + * \return The new AST rooting at the original parent scope and the map from the old block to the + * new block + */ + static std::pair<Stmt, Map<Block, Block>> Rewrite(const Stmt& scope_stmt, + const Buffer& old_buffer, + const Buffer& new_buffer, + const IndexMap& index_map) { + TransformLayoutRewriter rewriter(old_buffer, new_buffer, index_map); + Stmt result = rewriter(scope_stmt); + return {result, rewriter.block_sref_reuse_}; + } + + private: + TransformLayoutRewriter(const Buffer& old_buffer, const Buffer& new_buffer, + const IndexMap& index_map) + : old_buffer_(old_buffer), + new_buffer_(new_buffer), + index_map_(index_map), + buffer_data_to_buffer_{{new_buffer->data, new_buffer}} {} + + void RewriteBufferAccess(Buffer* buffer, Array<PrimExpr>* indices) { + *buffer = new_buffer_; + *indices = index_map_->MapIndices(*indices); + } + + PrimExpr VisitExpr_(const BufferLoadNode* op) final { + BufferLoad buffer_load = Downcast<BufferLoad>(StmtExprMutator::VisitExpr_(op)); + if (buffer_load->buffer.same_as(old_buffer_)) { + auto* n = buffer_load.CopyOnWrite(); + RewriteBufferAccess(&n->buffer, &n->indices); + } + return std::move(buffer_load); + } + + Stmt VisitStmt_(const BufferStoreNode* op) final { + BufferStore buffer_store = Downcast<BufferStore>(StmtExprMutator::VisitStmt_(op)); + if (buffer_store->buffer.same_as(old_buffer_)) { + auto* n = buffer_store.CopyOnWrite(); + RewriteBufferAccess(&n->buffer, &n->indices); + } + return std::move(buffer_store); + } + + void RewriteAccessRegion(Array<BufferRegion>* old_access_regions, + const Array<BufferRegion>& infered_access_regions) { + auto fmutate = [this, &infered_access_regions](const BufferRegion& buffer_region) { + if (buffer_region->buffer.same_as(old_buffer_)) { + ICHECK(infered_access_regions.size() == 1); + return infered_access_regions[0]; + } + return buffer_region; + }; + (*old_access_regions).MutateByApply(fmutate); + } + + Stmt VisitStmt_(const BlockNode* op) final { + Block block = Downcast<Block>(StmtExprMutator::VisitStmt_(op)); + auto infered_access_regions = GetBlockReadWriteRegion(block, buffer_data_to_buffer_); + auto* n = block.CopyOnWrite(); + RewriteAccessRegion(&n->reads, infered_access_regions[0]); + RewriteAccessRegion(&n->writes, infered_access_regions[1]); + block_sref_reuse_.Set(GetRef<Block>(op), block); + return std::move(block); + } + + const Buffer& old_buffer_; + const Buffer& new_buffer_; + const IndexMap& index_map_; + Map<Var, Buffer> buffer_data_to_buffer_; + Map<Block, Block> block_sref_reuse_; +}; + +class BufferIsSubregionError : public ScheduleError { + public: + explicit BufferIsSubregionError(IRModule mod, Buffer buffer) : mod_(mod), buffer_(buffer) {} + + String FastErrorString() const final { + return "ScheduleError: The input buffer is defined in `match_buffer` of a block, it is expected" + " to be a function parameter or allocated by a block"; + } + + String DetailRenderTemplate() const final { + std::ostringstream os; + os << "ScheduleError: The input buffer " << buffer_->name << " is defined in `match_buffer` of " + << "a block, it is expected to be a function parameter or allocated by a block."; + return os.str(); + } + + Array<ObjectRef> LocationsOfInterest() const final { return {}; } + IRModule mod() const final { return mod_; } + + private: + IRModule mod_; + Buffer buffer_; +}; + +void TransformLayout(ScheduleState self, const StmtSRef& block_sref, int buffer_index, + bool is_write_index, const IndexMap& index_map) { + const BlockNode* block_ptr = TVM_SREF_TO_BLOCK(block_ptr, block_sref); + Buffer old_buffer = GetNthAccessBuffer(self, GetRef<Block>(block_ptr), buffer_index, + /*is_write=*/is_write_index); + Optional<StmtSRef> defining_site_sref; + bool is_alloc; + std::tie(defining_site_sref, is_alloc) = GetBufferDefiningSite(block_sref, old_buffer); + if (defining_site_sref.defined() && !is_alloc) { + throw BufferIsSubregionError(self->mod, old_buffer); + } + + StmtSRef scope_sref = defining_site_sref.defined() + ? defining_site_sref.value() + : GetScopeRoot(self, block_sref, /*require_stage_pipeline=*/false); + const BlockNode* scope_block = TVM_SREF_TO_BLOCK(scope_block, scope_sref); + + // Step 1: Infer the shape of the new buffer + ObjectPtr<BufferNode> new_buffer_node = make_object<BufferNode>(*(old_buffer.get())); + new_buffer_node->shape = index_map->MapShape(old_buffer->shape); + Buffer new_buffer{new_buffer_node}; + + // Step 2: Rewrite access indices and regions of the buffer + Stmt new_stmt; + Map<Block, Block> block_sref_reuse; + std::tie(new_stmt, block_sref_reuse) = TransformLayoutRewriter::Rewrite( + GetRef<Block>(scope_block), old_buffer, new_buffer, index_map); + Block new_scope_block = Downcast<Block>(new_stmt); + Review comment: Got it, and that makes sense. I had been picturing it as a loopnest without any other nodes in-between, and hadn't thought on the blocks/bindings themselves. Agreed that it makes sense to have it as a separate change. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
