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/Complex/IR/Complex.h" 15 #include "mlir/Dialect/Linalg/IR/LinalgOps.h" 16 #include "mlir/Dialect/Linalg/IR/LinalgTypes.h" 17 #include "mlir/Dialect/Linalg/Passes.h" 18 #include "mlir/Dialect/Linalg/Transforms/Transforms.h" 19 #include "mlir/Dialect/Linalg/Utils/Utils.h" 20 #include "mlir/Dialect/SCF/SCF.h" 21 #include "mlir/IR/AffineExpr.h" 22 #include "mlir/IR/AffineExprVisitor.h" 23 #include "mlir/IR/AffineMap.h" 24 #include "mlir/IR/ImplicitLocOpBuilder.h" 25 #include "mlir/Support/LLVM.h" 26 #include "mlir/Transforms/FoldUtils.h" 27 #include "llvm/ADT/MapVector.h" 28 #include "llvm/ADT/TypeSwitch.h" 29 #include "llvm/Support/CommandLine.h" 30 31 using namespace mlir; 32 using namespace mlir::linalg; 33 using namespace mlir::scf; 34 35 using llvm::MapVector; 36 37 #define DEBUG_TYPE "linalg-promotion" 38 39 /// Alloc a new buffer of `size` * `width` i8; where `width` is given by the 40 /// data `layout` for `elementType`. 41 /// Use AllocOp or AllocaOp depending on `options`. 42 /// Take an optional alignment. 43 static Value allocBuffer(ImplicitLocOpBuilder &b, 44 const LinalgPromotionOptions &options, 45 Type elementType, Value allocSize, DataLayout &layout, 46 Optional<unsigned> alignment = None) { 47 auto width = layout.getTypeSize(elementType); 48 49 IntegerAttr alignmentAttr; 50 if (alignment.hasValue()) 51 alignmentAttr = b.getI64IntegerAttr(alignment.getValue()); 52 53 // Static buffer. 54 if (auto cst = allocSize.getDefiningOp<ConstantIndexOp>()) { 55 auto staticBufferType = 56 MemRefType::get(width * cst.getValue(), b.getIntegerType(8)); 57 if (options.useAlloca) { 58 return b.createOrFold<memref::AllocaOp>(staticBufferType, ValueRange{}, 59 alignmentAttr); 60 } 61 return b.createOrFold<memref::AllocOp>(staticBufferType, ValueRange{}, 62 alignmentAttr); 63 } 64 65 // Fallback dynamic buffer. 66 auto dynamicBufferType = MemRefType::get(-1, b.getIntegerType(8)); 67 Value mul = 68 b.createOrFold<MulIOp>(b.create<ConstantIndexOp>(width), allocSize); 69 if (options.useAlloca) 70 return b.create<memref::AllocaOp>(dynamicBufferType, mul, alignmentAttr); 71 return b.create<memref::AllocOp>(dynamicBufferType, mul, alignmentAttr); 72 } 73 74 /// Default allocation callback function. This allocates a promoted buffer when 75 /// no call back to do so is provided. The default is to allocate a 76 /// memref<..xi8> and return a view to get a memref type of shape 77 /// boundingSubViewSize. 78 static Optional<Value> 79 defaultAllocBufferCallBack(const LinalgPromotionOptions &options, 80 OpBuilder &builder, memref::SubViewOp subView, 81 ArrayRef<Value> boundingSubViewSize, 82 Optional<unsigned> alignment, DataLayout &layout) { 83 ShapedType viewType = subView.getType(); 84 ImplicitLocOpBuilder b(subView.getLoc(), builder); 85 auto zero = b.createOrFold<ConstantIndexOp>(0); 86 auto one = b.createOrFold<ConstantIndexOp>(1); 87 88 Value allocSize = one; 89 for (auto size : llvm::enumerate(boundingSubViewSize)) 90 allocSize = b.createOrFold<MulIOp>(allocSize, size.value()); 91 Value buffer = allocBuffer(b, options, viewType.getElementType(), allocSize, 92 layout, alignment); 93 SmallVector<int64_t, 4> dynSizes(boundingSubViewSize.size(), 94 ShapedType::kDynamicSize); 95 Value view = b.createOrFold<memref::ViewOp>( 96 MemRefType::get(dynSizes, viewType.getElementType()), buffer, zero, 97 boundingSubViewSize); 98 return view; 99 } 100 101 /// Default implementation of deallocation of the buffer use for promotion. It 102 /// expects to get the same value that the default allocation method returned, 103 /// i.e. result of a ViewOp. 104 static LogicalResult 105 defaultDeallocBufferCallBack(const LinalgPromotionOptions &options, 106 OpBuilder &b, Value fullLocalView) { 107 if (!options.useAlloca) { 108 auto viewOp = cast<memref::ViewOp>(fullLocalView.getDefiningOp()); 109 b.create<memref::DeallocOp>(viewOp.source().getLoc(), viewOp.source()); 110 } 111 return success(); 112 } 113 114 namespace { 115 116 /// Helper struct that captures the information required to apply the 117 /// transformation on each op. This bridges the abstraction gap with the 118 /// user-facing API which exposes positional arguments to control which operands 119 /// are promoted. 120 struct LinalgOpInstancePromotionOptions { 121 LinalgOpInstancePromotionOptions(LinalgOp op, 122 const LinalgPromotionOptions &options); 123 /// SubViews to promote. 124 MapVector<int64_t, Value> subViews; 125 /// True if the full view should be used for the promoted buffer. 126 DenseMap<Value, bool> useFullTileBuffers; 127 128 /// Callback functions for allocation and deallocation of promoted buffers, as 129 /// well as to copy the data into and out of these buffers. 130 AllocBufferCallbackFn allocationFn; 131 DeallocBufferCallbackFn deallocationFn; 132 CopyCallbackFn copyInFn; 133 CopyCallbackFn copyOutFn; 134 135 /// Allow the use of dynamically-sized buffers. 136 bool dynamicBuffers; 137 138 /// Alignment of promoted buffer. 139 Optional<unsigned> alignment; 140 }; 141 } // namespace 142 143 LinalgOpInstancePromotionOptions::LinalgOpInstancePromotionOptions( 144 LinalgOp linalgOp, const LinalgPromotionOptions &options) 145 : subViews(), dynamicBuffers(options.dynamicBuffers), 146 alignment(options.alignment) { 147 assert(linalgOp.hasBufferSemantics() && "revisit usage of shaped operand"); 148 int64_t nBuffers = linalgOp.getNumShapedOperands(); 149 auto vUseFullTileBuffers = 150 options.useFullTileBuffers.getValueOr(llvm::SmallBitVector()); 151 vUseFullTileBuffers.resize(nBuffers, options.useFullTileBuffersDefault); 152 153 for (int64_t idx = 0; idx != nBuffers; ++idx) { 154 if (options.operandsToPromote && !options.operandsToPromote->count(idx)) 155 continue; 156 auto *op = linalgOp.getShapedOperand(idx).getDefiningOp(); 157 if (auto sv = dyn_cast_or_null<memref::SubViewOp>(op)) { 158 subViews[idx] = sv; 159 useFullTileBuffers[sv] = vUseFullTileBuffers[idx]; 160 } 161 } 162 163 if (options.allocationFn) { 164 allocationFn = *options.allocationFn; 165 } else { 166 allocationFn = [&](OpBuilder &b, memref::SubViewOp subViewOp, 167 ArrayRef<Value> boundingSubViewSize, 168 DataLayout &layout) -> Optional<Value> { 169 return defaultAllocBufferCallBack(options, b, subViewOp, 170 boundingSubViewSize, alignment, layout); 171 }; 172 } 173 174 if (options.deallocationFn) { 175 deallocationFn = *options.deallocationFn; 176 } else { 177 deallocationFn = [&](OpBuilder &b, Value buffer) { 178 return defaultDeallocBufferCallBack(options, b, buffer); 179 }; 180 } 181 182 // Save the loc because `linalgOp` goes out of scope. 183 Location loc = linalgOp.getLoc(); 184 auto defaultCopyCallBack = [loc](OpBuilder &b, Value src, 185 Value dst) -> LogicalResult { 186 b.create<linalg::CopyOp>(loc, src, dst); 187 return success(); 188 }; 189 copyInFn = (options.copyInFn ? *(options.copyInFn) : defaultCopyCallBack); 190 copyOutFn = (options.copyOutFn ? *(options.copyOutFn) : defaultCopyCallBack); 191 } 192 193 // Performs promotion of a `subView` into a local buffer of the size of the 194 // *ranges* of the `subView`. This produces a buffer whose size may be bigger 195 // than the actual size of the `subView` at the boundaries. 196 // This is related to the full/partial tile problem. 197 // Returns a PromotionInfo containing a `buffer`, `fullLocalView` and 198 // `partialLocalView` such that: 199 // * `buffer` is always the size of the full tile. 200 // * `fullLocalView` is a dense contiguous view into that buffer. 201 // * `partialLocalView` is a dense non-contiguous slice of `fullLocalView` 202 // that corresponds to the size of `subView` and accounting for boundary 203 // effects. 204 // The point of the full tile buffer is that constant static tile sizes are 205 // folded and result in a buffer type with statically known size and alignment 206 // properties. 207 // To account for general boundary effects, padding must be performed on the 208 // boundary tiles. For now this is done with an unconditional `fill` op followed 209 // by a partial `copy` op. 210 Optional<PromotionInfo> mlir::linalg::promoteSubviewAsNewBuffer( 211 OpBuilder &b, Location loc, memref::SubViewOp subView, 212 AllocBufferCallbackFn allocationFn, DataLayout &layout) { 213 auto viewType = subView.getType(); 214 auto rank = viewType.getRank(); 215 SmallVector<Value, 4> fullSizes; 216 SmallVector<OpFoldResult> partialSizes; 217 fullSizes.reserve(rank); 218 partialSizes.reserve(rank); 219 for (auto en : llvm::enumerate(subView.getOrCreateRanges(b, loc))) { 220 auto rangeValue = en.value(); 221 // Try to extract a tight constant. 222 LLVM_DEBUG(llvm::dbgs() << "Extract tightest: " << rangeValue.size << "\n"); 223 IntegerAttr sizeAttr = getSmallestBoundingIndex(rangeValue.size); 224 Value size = 225 (!sizeAttr) ? rangeValue.size : b.create<ConstantOp>(loc, sizeAttr); 226 LLVM_DEBUG(llvm::dbgs() << "Extracted tightest: " << size << "\n"); 227 fullSizes.push_back(size); 228 partialSizes.push_back( 229 b.createOrFold<memref::DimOp>(loc, subView, en.index())); 230 } 231 SmallVector<int64_t, 4> dynSizes(fullSizes.size(), -1); 232 // If a callback is not specified, then use the default implementation for 233 // allocating the promoted buffer. 234 Optional<Value> fullLocalView = allocationFn(b, subView, fullSizes, layout); 235 if (!fullLocalView) 236 return {}; 237 SmallVector<OpFoldResult, 4> zeros(fullSizes.size(), b.getIndexAttr(0)); 238 SmallVector<OpFoldResult, 4> ones(fullSizes.size(), b.getIndexAttr(1)); 239 auto partialLocalView = b.createOrFold<memref::SubViewOp>( 240 loc, *fullLocalView, zeros, partialSizes, ones); 241 return PromotionInfo{*fullLocalView, partialLocalView}; 242 } 243 244 static Optional<MapVector<int64_t, PromotionInfo>> 245 promoteSubViews(ImplicitLocOpBuilder &b, 246 LinalgOpInstancePromotionOptions options, DataLayout &layout) { 247 if (options.subViews.empty()) 248 return {}; 249 250 MapVector<int64_t, PromotionInfo> promotionInfoMap; 251 252 for (auto v : options.subViews) { 253 memref::SubViewOp subView = 254 cast<memref::SubViewOp>(v.second.getDefiningOp()); 255 Optional<PromotionInfo> promotionInfo = promoteSubviewAsNewBuffer( 256 b, b.getLoc(), subView, options.allocationFn, layout); 257 if (!promotionInfo) 258 return {}; 259 promotionInfoMap[v.first] = *promotionInfo; 260 261 // Only fill the buffer if the full local view is used 262 if (!options.useFullTileBuffers[v.second]) 263 continue; 264 Type subviewEltType = subView.getType().getElementType(); 265 Value fillVal = 266 llvm::TypeSwitch<Type, Value>(subviewEltType) 267 .Case([&](FloatType t) { 268 return b.create<ConstantOp>(FloatAttr::get(t, 0.0)); 269 }) 270 .Case([&](IntegerType t) { 271 return b.create<ConstantOp>(IntegerAttr::get(t, 0)); 272 }) 273 .Case([&](ComplexType t) { 274 Value tmp; 275 if (auto et = t.getElementType().dyn_cast<FloatType>()) 276 tmp = b.create<ConstantOp>(FloatAttr::get(et, 0.0)); 277 else if (auto et = t.getElementType().cast<IntegerType>()) 278 tmp = b.create<ConstantOp>(IntegerAttr::get(et, 0)); 279 return b.create<complex::CreateOp>(t, tmp, tmp); 280 }) 281 .Default([](auto) { return Value(); }); 282 if (!fillVal) 283 return {}; 284 b.create<linalg::FillOp>(promotionInfo->fullLocalView, fillVal); 285 } 286 287 // Copy data into the promoted buffers. Use callback if provided. 288 for (auto v : options.subViews) { 289 auto info = promotionInfoMap.find(v.first); 290 if (info == promotionInfoMap.end()) 291 continue; 292 if (failed(options.copyInFn( 293 b, cast<memref::SubViewOp>(v.second.getDefiningOp()), 294 info->second.partialLocalView))) 295 return {}; 296 } 297 return promotionInfoMap; 298 } 299 300 static Optional<LinalgOp> 301 promoteSubViews(ImplicitLocOpBuilder &b, LinalgOp op, 302 LinalgOpInstancePromotionOptions options, DataLayout &layout) { 303 assert(op.hasBufferSemantics() && "expected linalg op with buffer semantics"); 304 305 if (auto convOp = dyn_cast<linalg::ConvOp>(op.getOperation())) { 306 // TODO: add a level of indirection to linalg.generic. 307 if (convOp.padding()) 308 return {}; 309 } 310 311 // 1. Promote the specified views and use them in the new op. 312 auto promotedBuffersAndViews = promoteSubViews(b, options, layout); 313 if (!promotedBuffersAndViews || 314 promotedBuffersAndViews->size() != options.subViews.size()) 315 return {}; 316 317 // 2. Append all other operands as they appear, this enforces that such 318 // operands are not views. This is to support cases such as FillOp taking 319 // extra scalars etc. Keep a reference to output buffers; 320 SmallVector<Value, 8> opViews; 321 opViews.reserve(op.getNumShapedOperands()); 322 SmallVector<std::pair<Value, Value>, 8> writebackViews; 323 writebackViews.reserve(promotedBuffersAndViews->size()); 324 for (auto view : llvm::enumerate(op.getShapedOperands())) { 325 if (options.subViews.count(view.index()) != 0) { 326 if (options.useFullTileBuffers[view.value()]) 327 opViews.push_back( 328 (*promotedBuffersAndViews)[view.index()].fullLocalView); 329 else 330 opViews.push_back( 331 (*promotedBuffersAndViews)[view.index()].partialLocalView); 332 if (static_cast<int64_t>(view.index()) >= op.getNumInputs()) 333 writebackViews.emplace_back(std::make_pair( 334 view.value(), 335 (*promotedBuffersAndViews)[view.index()].partialLocalView)); 336 } else { 337 opViews.push_back(view.value()); 338 } 339 } 340 op->setOperands(0, opViews.size(), opViews); 341 342 OpBuilder::InsertionGuard guard(b); 343 b.setInsertionPointAfter(op); 344 // 3. Emit write-back for the promoted output views: copy the partial view. 345 for (auto viewAndPartialLocalView : writebackViews) { 346 if (failed(options.copyOutFn(b, viewAndPartialLocalView.second, 347 viewAndPartialLocalView.first))) 348 return {}; 349 } 350 351 // 4. Dealloc all local buffers. 352 for (const auto &pi : *promotedBuffersAndViews) 353 (void)options.deallocationFn(b, pi.second.fullLocalView); 354 return op; 355 } 356 357 LogicalResult 358 mlir::linalg::promoteSubviewsPrecondition(Operation *op, 359 LinalgPromotionOptions options) { 360 LinalgOp linOp = dyn_cast<LinalgOp>(op); 361 // Transformation applies to buffers only. 362 if (!linOp || !linOp.hasBufferSemantics()) 363 return failure(); 364 // Check that at least one of the requested operands is indeed a subview. 365 for (auto en : llvm::enumerate(linOp.getShapedOperands())) { 366 auto sv = isa_and_nonnull<memref::SubViewOp>(en.value().getDefiningOp()); 367 if (sv) { 368 if (!options.operandsToPromote.hasValue() || 369 options.operandsToPromote->count(en.index())) 370 return success(); 371 } 372 } 373 // TODO: Check all subviews requested are bound by a static constant. 374 // TODO: Check that the total footprint fits within a given size. 375 return failure(); 376 } 377 378 Optional<LinalgOp> 379 mlir::linalg::promoteSubViews(OpBuilder &builder, LinalgOp linalgOp, 380 LinalgPromotionOptions options) { 381 LinalgOpInstancePromotionOptions linalgOptions(linalgOp, options); 382 auto layout = DataLayout::closest(linalgOp); 383 ImplicitLocOpBuilder b(linalgOp.getLoc(), builder); 384 return ::promoteSubViews(b, linalgOp, linalgOptions, layout); 385 } 386 387 namespace { 388 struct LinalgPromotionPass : public LinalgPromotionBase<LinalgPromotionPass> { 389 LinalgPromotionPass() = default; 390 LinalgPromotionPass(bool dynamicBuffers, bool useAlloca) { 391 this->dynamicBuffers = dynamicBuffers; 392 this->useAlloca = useAlloca; 393 } 394 395 void runOnFunction() override { 396 getFunction().walk([&](LinalgOp op) { 397 auto options = LinalgPromotionOptions() 398 .setDynamicBuffers(dynamicBuffers) 399 .setUseAlloca(useAlloca); 400 if (failed(promoteSubviewsPrecondition(op, options))) 401 return; 402 LLVM_DEBUG(llvm::dbgs() << "Promote: " << *(op.getOperation()) << "\n"); 403 ImplicitLocOpBuilder b(op.getLoc(), op); 404 promoteSubViews(b, op, options); 405 }); 406 } 407 }; 408 } // namespace 409 410 // TODO: support more transformation options in the pass. 411 std::unique_ptr<OperationPass<FuncOp>> 412 mlir::createLinalgPromotionPass(bool dynamicBuffers, bool useAlloca) { 413 return std::make_unique<LinalgPromotionPass>(dynamicBuffers, useAlloca); 414 } 415 std::unique_ptr<OperationPass<FuncOp>> mlir::createLinalgPromotionPass() { 416 return std::make_unique<LinalgPromotionPass>(); 417 } 418