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| 1 | +/* |
| 2 | + * Licensed to the Apache Software Foundation (ASF) under one |
| 3 | + * or more contributor license agreements. See the NOTICE file |
| 4 | + * distributed with this work for additional information |
| 5 | + * regarding copyright ownership. The ASF licenses this file |
| 6 | + * to you under the Apache License, Version 2.0 (the |
| 7 | + * "License"); you may not use this file except in compliance |
| 8 | + * with the License. You may obtain a copy of the License at |
| 9 | + * |
| 10 | + * http://www.apache.org/licenses/LICENSE-2.0 |
| 11 | + * |
| 12 | + * Unless required by applicable law or agreed to in writing, |
| 13 | + * software distributed under the License is distributed on an |
| 14 | + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| 15 | + * KIND, either express or implied. See the License for the |
| 16 | + * specific language governing permissions and limitations |
| 17 | + * under the License. |
| 18 | + */ |
| 19 | +#include "../utils.h" |
| 20 | + |
| 21 | +namespace tvm { |
| 22 | +namespace tir { |
| 23 | + |
| 24 | +/*! |
| 25 | + * \brief Calculate the strides of the buffer |
| 26 | + * \param buffer The buffer |
| 27 | + * \return The strides |
| 28 | + */ |
| 29 | +Array<PrimExpr> GetStrides(const Buffer& buffer) { |
| 30 | + if (!buffer->strides.empty()) { |
| 31 | + ICHECK_EQ(buffer->strides.size(), buffer->shape.size()); |
| 32 | + return buffer->strides; |
| 33 | + } |
| 34 | + int ndim = buffer->shape.size(); |
| 35 | + if (ndim == 0) { |
| 36 | + return {}; |
| 37 | + } |
| 38 | + Array<PrimExpr> strides(ndim, PrimExpr{nullptr}); |
| 39 | + PrimExpr stride = make_const(buffer->DefaultIndexType(), 1); |
| 40 | + for (int i = ndim - 1; i >= 0; --i) { |
| 41 | + strides.Set(i, stride); |
| 42 | + stride = stride * buffer->shape[i]; |
| 43 | + } |
| 44 | + return strides; |
| 45 | +} |
| 46 | + |
| 47 | +/*! |
| 48 | + * \brief Auxiliary class that collects the IterSplitExpr in the indexing pattern |
| 49 | + * to help decision making in layout transformation |
| 50 | + */ |
| 51 | +class SplitExprCollector { |
| 52 | + public: |
| 53 | + /*! |
| 54 | + * \brief The corresponding IterSplitExpr, simplified for our case |
| 55 | + * The pattern is `source // lower_factor % extent * scale` |
| 56 | + */ |
| 57 | + struct SplitExpr { |
| 58 | + /*! \brief The source variable */ |
| 59 | + Var source; |
| 60 | + /*! \brief The lower factor of the split expression */ |
| 61 | + int64_t lower_factor; |
| 62 | + /*! \brief The extent of the split expression */ |
| 63 | + int64_t extent; |
| 64 | + }; |
| 65 | + |
| 66 | + /*! |
| 67 | + * \brief Collect the split expressions in the indexing pattern |
| 68 | + * \param index The indexing pattern |
| 69 | + * \param input_iters The input iterators' domain |
| 70 | + * \param predicate The predicate of the affine map |
| 71 | + * \param require_bijective Whether the affine map is required to be bijective |
| 72 | + * \param analyzer The analyzer |
| 73 | + * \return The collected split expressions |
| 74 | + */ |
| 75 | + static std::vector<SplitExpr> Collect(const PrimExpr& index, |
| 76 | + const Map<Var, Range>& input_iters, // |
| 77 | + const PrimExpr& predicate, // |
| 78 | + bool require_bijective, // |
| 79 | + arith::Analyzer* analyzer) { |
| 80 | + DiagnosticContext diag_ctx(DiagnosticContext::Default(IRModule())); |
| 81 | + Array<arith::IterSumExpr> iter_sum_exprs = arith::DetectIterMap( |
| 82 | + {analyzer->Simplify(index)}, input_iters, predicate, require_bijective, analyzer, diag_ctx); |
| 83 | + if (iter_sum_exprs.empty()) { |
| 84 | + return {}; |
| 85 | + } |
| 86 | + ICHECK_EQ(iter_sum_exprs.size(), 1); |
| 87 | + if (iter_sum_exprs[0]->args.size() == 0) { |
| 88 | + return {}; |
| 89 | + } |
| 90 | + SplitExprCollector collector; |
| 91 | + collector.Visit(iter_sum_exprs[0]); |
| 92 | + if (collector.failed_) { |
| 93 | + return {}; |
| 94 | + } |
| 95 | + return std::move(collector.exprs_); |
| 96 | + } |
| 97 | + |
| 98 | + private: |
| 99 | + void Visit(const arith::IterSplitExpr& expr) { |
| 100 | + if (const auto* var = expr->source->source.as<tir::VarNode>()) { |
| 101 | + const int64_t* lower_factor = as_const_int(expr->lower_factor); |
| 102 | + const int64_t* extent = as_const_int(expr->extent); |
| 103 | + if (lower_factor == nullptr || extent == nullptr) { |
| 104 | + failed_ = true; |
| 105 | + return; |
| 106 | + } |
| 107 | + exprs_.push_back(SplitExpr{GetRef<Var>(var), *lower_factor, *extent}); |
| 108 | + } else if ( const auto* iter_sum_expr = expr-> source-> source. as<arith::IterSumExprNode>()) { |
| 109 | + Visit(GetRef<arith::IterSumExpr>(iter_sum_expr)); |
| 110 | + } else { |
| 111 | + ICHECK(false) << "Unexpected type: " << expr->source->source->GetTypeKey(); |
| 112 | + } |
| 113 | + } |
| 114 | + |
| 115 | + void Visit(const arith::IterSumExpr& expr) { |
| 116 | + for (const arith::IterSplitExpr& arg : expr->args) { |
| 117 | + Visit(arg); |
| 118 | + } |
| 119 | + } |
| 120 | + |
| 121 | + /*! \brief Whether the analysis failed */ |
| 122 | + bool failed_ = false; |
| 123 | + /*! \brief The collected split expressions */ |
| 124 | + std::vector<SplitExpr> exprs_; |
| 125 | +}; |
| 126 | + |
| 127 | +Optional<IndexMap> SuggestIndexMap( const Buffer& buffer, const Array<PrimExpr>& indices, |
| 128 | + const Array<For>& loops, const PrimExpr& predicate, |
| 129 | + arith::Analyzer* analyzer) { |
| 130 | + int ndim = buffer->shape.size(); |
| 131 | + int n_loops = loops.size(); |
| 132 | + // Step 1. Collect the domains and indices of loop variables |
| 133 | + Map<Var, Range> input_iters; |
| 134 | + std::unordered_map<const VarNode*, int> var2id; |
| 135 | + var2id.reserve(n_loops); |
| 136 | + for (int i = 0; i < n_loops; ++i) { |
| 137 | + const For& loop = loops[i]; |
| 138 | + input_iters.Set(loop->loop_var, Range::FromMinExtent(loop->min, loop->extent)); |
| 139 | + var2id.emplace(loop->loop_var.get(), i); |
| 140 | + } |
| 141 | + // Step 2. Calculate a functor that flattens a multi-dimensional index |
| 142 | + auto f_flatten_index = [ndim, strides = GetStrides(buffer), dtype = buffer->DefaultIndexType()]( |
| 143 | + const Array<PrimExpr>& indices) -> PrimExpr { |
| 144 | + PrimExpr flatten_index = make_const(dtype, 0); |
| 145 | + for (int i = 0; i < ndim; ++i) { |
| 146 | + flatten_index = flatten_index + strides[i] * indices[i]; |
| 147 | + } |
| 148 | + return flatten_index; |
| 149 | + }; |
| 150 | + // Step 3. Detect the IterSplitExpr of the indexing pattern |
| 151 | + std::vector<SplitExprCollector::SplitExpr> split_exprs = SplitExprCollector::Collect( |
| 152 | + /*index=*/f_flatten_index(indices), input_iters, predicate, |
| 153 | + /*require_bijective=*/false, analyzer); |
| 154 | + if (split_exprs.empty()) { |
| 155 | + return NullOpt; |
| 156 | + } |
| 157 | + // Step 4. Sort the order of the split expressions |
| 158 | + std::vector<int> order(split_exprs.size(), 0); |
| 159 | + std::generate(order.begin(), order.end(), [n = 0]() mutable { return n++; }); |
| 160 | + std::sort(order.begin(), order.end(), [&split_exprs, &var2id](int _a, int _b) -> bool { |
| 161 | + const SplitExprCollector::SplitExpr& a = split_exprs[_a]; |
| 162 | + const SplitExprCollector::SplitExpr& b = split_exprs[_b]; |
| 163 | + int a_var_id = var2id.at(a.source.get()); |
| 164 | + int b_var_id = var2id.at(b.source.get()); |
| 165 | + if (a_var_id != b_var_id) { |
| 166 | + return a_var_id < b_var_id; |
| 167 | + } |
| 168 | + return a.lower_factor > b.lower_factor; |
| 169 | + }); |
| 170 | + // Step 5. Create the indexing mapping |
| 171 | + auto f_alter_layout = [f_flatten_index = std::move(f_flatten_index), // |
| 172 | + split_exprs = std::move(split_exprs), // |
| 173 | + order = std::move(order), // |
| 174 | + shape = buffer->shape, // |
| 175 | + analyzer // |
| 176 | + ](Array<Var> indices) -> Array<PrimExpr> { |
| 177 | + ICHECK_EQ(indices.size(), shape.size()); |
| 178 | + for (int i = 0, n = indices.size(); i < n; ++i) { |
| 179 | + analyzer->Bind(indices[i], Range::FromMinExtent(0, shape[i])); |
| 180 | + } |
| 181 | + PrimExpr index = f_flatten_index({indices.begin(), indices.end()}); |
| 182 | + int ndim = split_exprs.size(); |
| 183 | + // Step 5.1. Split the flattened index according to `split_exprs` |
| 184 | + std::vector<PrimExpr> split; |
| 185 | + split.reserve(ndim); |
| 186 | + for (int i = ndim - 1; i >= 0; --i) { |
| 187 | + index = analyzer->Simplify(index); |
| 188 | + int64_t extent = split_exprs[i].extent; |
| 189 | + split.push_back(analyzer->Simplify(floormod(index, extent))); |
| 190 | + index = floordiv(index, extent); |
| 191 | + } |
| 192 | + std::reverse(split.begin(), split.end()); |
| 193 | + // Step 5.2. Reorder the indexing pattern according to `order` |
| 194 | + Array<PrimExpr> results; |
| 195 | + results.reserve(ndim); |
| 196 | + for (int i = 0; i < ndim; ++i) { |
| 197 | + results.push_back(split[order[i]]); |
| 198 | + } |
| 199 | + return results; |
| 200 | + }; |
| 201 | + return IndexMap::FromFunc(ndim, f_alter_layout); |
| 202 | +} |
| 203 | + |
| 204 | +TVM_REGISTER_GLOBAL("tir.schedule.SuggestIndexMap") |
| 205 | + .set_body_typed([](Buffer buffer, Array<PrimExpr> indices, Array<For> loops, |
| 206 | + PrimExpr predicate) { |
| 207 | + arith::Analyzer analyzer; |
| 208 | + return SuggestIndexMap(buffer, indices, loops, predicate, &analyzer); |
| 209 | + }); |
| 210 | + |
| 211 | +} // namespace tir |
| 212 | +} // namespace tvm |
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