1 //===- Promotion.cpp - Implementation of linalg Promotion -----------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file implements the linalg dialect Promotion pass. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "PassDetail.h" 14 #include "mlir/Dialect/Affine/EDSC/Intrinsics.h" 15 #include "mlir/Dialect/Linalg/EDSC/Intrinsics.h" 16 #include "mlir/Dialect/Linalg/IR/LinalgOps.h" 17 #include "mlir/Dialect/Linalg/IR/LinalgTypes.h" 18 #include "mlir/Dialect/Linalg/Passes.h" 19 #include "mlir/Dialect/Linalg/Utils/Utils.h" 20 #include "mlir/Dialect/LoopOps/LoopOps.h" 21 #include "mlir/Dialect/StandardOps/EDSC/Intrinsics.h" 22 #include "mlir/IR/AffineExpr.h" 23 #include "mlir/IR/AffineExprVisitor.h" 24 #include "mlir/IR/AffineMap.h" 25 #include "mlir/Support/LLVM.h" 26 #include "mlir/Support/STLExtras.h" 27 #include "mlir/Transforms/FoldUtils.h" 28 29 #include "llvm/ADT/SetVector.h" 30 #include "llvm/Support/CommandLine.h" 31 32 using namespace mlir; 33 using namespace mlir::edsc; 34 using namespace mlir::edsc::intrinsics; 35 using namespace mlir::linalg; 36 using namespace mlir::loop; 37 38 using llvm::SetVector; 39 40 using folded_affine_min = folded::ValueBuilder<AffineMinOp>; 41 using folded_linalg_range = folded::ValueBuilder<linalg::RangeOp>; 42 using folded_std_dim = folded::ValueBuilder<DimOp>; 43 using folded_std_subview = folded::ValueBuilder<SubViewOp>; 44 using folded_std_view = folded::ValueBuilder<ViewOp>; 45 46 #define DEBUG_TYPE "linalg-promotion" 47 48 /// If `size` comes from an AffineMinOp and one of the dimensions of AffineMin 49 /// is a constant then return a new value set to the smallest such constant. 50 /// Otherwise return size. 51 static Value extractSmallestConstantBoundingSize(OpBuilder &b, Location loc, 52 Value size) { 53 auto affineMinOp = dyn_cast_or_null<AffineMinOp>(size.getDefiningOp()); 54 if (!affineMinOp) 55 return size; 56 if (!llvm::any_of(affineMinOp.getAffineMap().getResults(), [](AffineExpr e) { 57 return e.dyn_cast<AffineConstantExpr>(); 58 })) 59 return size; 60 int64_t minConst = std::numeric_limits<int64_t>::max(); 61 for (auto e : affineMinOp.getAffineMap().getResults()) 62 if (auto cst = e.dyn_cast<AffineConstantExpr>()) 63 minConst = std::min(minConst, cst.getValue()); 64 assert(minConst != std::numeric_limits<int64_t>::max()); 65 return b.create<ConstantIndexOp>(loc, minConst); 66 } 67 68 static Value allocBuffer(Type elementType, Value size, bool dynamicBuffers, 69 OperationFolder *folder) { 70 auto *ctx = size.getContext(); 71 auto width = llvm::divideCeil(elementType.getIntOrFloatBitWidth(), 8); 72 if (!dynamicBuffers) 73 if (auto cst = dyn_cast_or_null<ConstantIndexOp>(size.getDefiningOp())) 74 return std_alloc( 75 MemRefType::get(width * cst.getValue(), IntegerType::get(8, ctx))); 76 Value mul = 77 folded_std_muli(folder, folded_std_constant_index(folder, width), size); 78 return std_alloc(MemRefType::get(-1, IntegerType::get(8, ctx)), mul); 79 } 80 81 // Performs promotion of a `subView` into a local buffer of the size of the 82 // *ranges* of the `subView`. This produces a buffer whose size may be bigger 83 // than the actual size of the `subView` at the boundaries. 84 // This is related to the full/partial tile problem. 85 // Returns a PromotionInfo containing a `buffer`, `fullLocalView` and 86 // `partialLocalView` such that: 87 // * `buffer` is always the size of the full tile. 88 // * `fullLocalView` is a dense contiguous view into that buffer. 89 // * `partialLocalView` is a dense non-contiguous slice of `fullLocalView` 90 // that corresponds to the size of `subView` and accounting for boundary 91 // effects. 92 // The point of the full tile buffer is that constant static tile sizes are 93 // folded and result in a buffer type with statically known size and alignment 94 // properties. 95 // To account for general boundary effects, padding must be performed on the 96 // boundary tiles. For now this is done with an unconditional `fill` op followed 97 // by a partial `copy` op. 98 static PromotionInfo promoteFullTileBuffer(OpBuilder &b, Location loc, 99 SubViewOp subView, 100 bool dynamicBuffers, 101 OperationFolder *folder) { 102 auto zero = folded_std_constant_index(folder, 0); 103 auto one = folded_std_constant_index(folder, 1); 104 105 auto viewType = subView.getType(); 106 auto rank = viewType.getRank(); 107 Value allocSize = one; 108 SmallVector<Value, 8> fullSizes, partialSizes; 109 fullSizes.reserve(rank); 110 partialSizes.reserve(rank); 111 for (auto en : llvm::enumerate(subView.getRanges())) { 112 auto rank = en.index(); 113 auto rangeValue = en.value(); 114 // Try to extract a tight constant 115 Value size = extractSmallestConstantBoundingSize(b, loc, rangeValue.size); 116 allocSize = folded_std_muli(folder, allocSize, size).getValue(); 117 fullSizes.push_back(size); 118 partialSizes.push_back(folded_std_dim(folder, subView, rank)); 119 } 120 SmallVector<int64_t, 4> dynSizes(fullSizes.size(), -1); 121 auto buffer = 122 allocBuffer(viewType.getElementType(), allocSize, dynamicBuffers, folder); 123 auto fullLocalView = folded_std_view( 124 folder, MemRefType::get(dynSizes, viewType.getElementType()), buffer, 125 fullSizes); 126 SmallVector<Value, 4> zeros(fullSizes.size(), zero); 127 SmallVector<Value, 4> ones(fullSizes.size(), one); 128 auto partialLocalView = 129 folded_std_subview(folder, fullLocalView, zeros, partialSizes, ones); 130 return PromotionInfo{buffer, fullLocalView, partialLocalView}; 131 } 132 133 SmallVector<PromotionInfo, 8> 134 mlir::linalg::promoteSubViews(OpBuilder &b, Location loc, 135 ArrayRef<Value> subViews, bool dynamicBuffers, 136 OperationFolder *folder) { 137 if (subViews.empty()) 138 return {}; 139 140 ScopedContext scope(b, loc); 141 SmallVector<PromotionInfo, 8> res; 142 res.reserve(subViews.size()); 143 DenseMap<Value, PromotionInfo> promotionInfoMap; 144 for (auto v : subViews) { 145 SubViewOp subView = cast<SubViewOp>(v.getDefiningOp()); 146 auto promotionInfo = 147 promoteFullTileBuffer(b, loc, subView, dynamicBuffers, folder); 148 promotionInfoMap.insert(std::make_pair(subView.getResult(), promotionInfo)); 149 res.push_back(promotionInfo); 150 } 151 152 for (auto v : subViews) { 153 SubViewOp subView = cast<SubViewOp>(v.getDefiningOp()); 154 auto info = promotionInfoMap.find(v); 155 if (info == promotionInfoMap.end()) 156 continue; 157 Value fillVal; 158 if (auto t = subView.getType().getElementType().dyn_cast<FloatType>()) 159 fillVal = folded_std_constant(folder, FloatAttr::get(t, 0.0)); 160 else if (auto t = 161 subView.getType().getElementType().dyn_cast<IntegerType>()) 162 fillVal = folded_std_constant_int(folder, 0, t); 163 // TODO(ntv): fill is only necessary if `promotionInfo` has a full local 164 // view that is different from the partial local view and we are on the 165 // boundary. 166 linalg_fill(info->second.fullLocalView, fillVal); 167 } 168 169 for (auto v : subViews) { 170 auto info = promotionInfoMap.find(v); 171 if (info == promotionInfoMap.end()) 172 continue; 173 linalg_copy(cast<SubViewOp>(v.getDefiningOp()), 174 info->second.partialLocalView); 175 } 176 return res; 177 } 178 179 LinalgOp mlir::linalg::promoteSubViewOperands(OpBuilder &b, LinalgOp op, 180 SetVector<Value> subViews, 181 bool dynamicBuffers, 182 OperationFolder *folder) { 183 assert(op.hasBufferSemantics() && "expected linalg op with buffer semantics"); 184 185 if (auto convOp = dyn_cast<linalg::ConvOp>(op.getOperation())) { 186 // TODO(ntv): add a level of indirection to linalg.generic. 187 if (convOp.padding()) 188 llvm_unreachable("Unexpected conv with padding"); 189 } 190 191 // 1. Promote the specified views and use them in the new op. 192 ScopedContext scope(b, op.getLoc()); 193 auto promotedBufferAndViews = promoteSubViews( 194 b, op.getLoc(), subViews.getArrayRef(), dynamicBuffers, folder); 195 SmallVector<Value, 8> opViews; 196 opViews.reserve(op.getNumInputsAndOutputs()); 197 SmallVector<std::pair<Value, Value>, 8> writebackViews; 198 writebackViews.reserve(subViews.size()); 199 unsigned promotedIdx = 0; 200 for (auto view : op.getInputsAndOutputBuffers()) { 201 if (subViews.count(view) != 0) { 202 opViews.push_back(promotedBufferAndViews[promotedIdx].fullLocalView); 203 writebackViews.emplace_back(std::make_pair( 204 view, promotedBufferAndViews[promotedIdx].partialLocalView)); 205 promotedIdx++; 206 } else { 207 opViews.push_back(view); 208 } 209 } 210 211 // 2. Append all other operands as they appear, this enforces that such 212 // operands are not views. This is to support cases such as FillOp taking 213 // extra scalars etc. 214 auto operands = getAssumedNonViewOperands(op); 215 opViews.append(operands.begin(), operands.end()); 216 LinalgOp res = op.clone(b, op.getLoc(), opViews); 217 218 // 3. Emit write-back for the promoted output views: copy the partial view. 219 for (auto viewAndPartialLocalView : writebackViews) { 220 // WARNING: MUST use the old op to determine whether the operand view is an 221 // output. 222 bool isOutput = 223 op.getIndexOfOutputBuffer(viewAndPartialLocalView.first).hasValue(); 224 if (isOutput) 225 linalg_copy(viewAndPartialLocalView.second, 226 viewAndPartialLocalView.first); 227 } 228 229 // 4. Dealloc local buffers. 230 for (const auto &pi : promotedBufferAndViews) 231 std_dealloc(pi.buffer); 232 233 return res; 234 } 235 236 static void promoteSubViews(FuncOp f, bool dynamicBuffers) { 237 SmallVector<LinalgOp, 8> toErase; 238 OperationFolder folder(f.getContext()); 239 f.walk([dynamicBuffers, &folder, &toErase](LinalgOp op) { 240 if (!op.hasBufferSemantics()) 241 return; 242 243 // TODO(ntv) some heuristic here to decide what to promote. Atm only float 244 // and integer buffers can be promoted. 245 SetVector<Value> subViews; 246 OpBuilder b(op); 247 for (auto it : op.getInputsAndOutputBuffers()) 248 if (auto sv = dyn_cast_or_null<SubViewOp>(it.getDefiningOp())) 249 if (sv.getType().getElementType().isSignlessIntOrFloat()) 250 subViews.insert(sv); 251 if (!subViews.empty()) { 252 promoteSubViewOperands(b, op, subViews, dynamicBuffers, &folder); 253 toErase.push_back(op); 254 } 255 }); 256 for (auto op : toErase) 257 op.erase(); 258 } 259 260 namespace { 261 struct LinalgPromotionPass : public LinalgPromotionBase<LinalgPromotionPass> { 262 LinalgPromotionPass() = default; 263 LinalgPromotionPass(bool dynamicBuffers) { 264 this->dynamicBuffers = dynamicBuffers; 265 } 266 267 void runOnFunction() override { 268 promoteSubViews(getFunction(), dynamicBuffers); 269 } 270 }; 271 } // namespace 272 273 std::unique_ptr<OperationPass<FuncOp>> 274 mlir::createLinalgPromotionPass(bool dynamicBuffers) { 275 return std::make_unique<LinalgPromotionPass>(dynamicBuffers); 276 } 277 std::unique_ptr<OperationPass<FuncOp>> mlir::createLinalgPromotionPass() { 278 return std::make_unique<LinalgPromotionPass>(); 279 } 280