1 //===- Interchange.cpp - Linalg interchange transformation ----------------===//
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 interchange transformation.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "mlir/Dialect/Linalg/Analysis/DependenceAnalysis.h"
14 #include "mlir/Dialect/Linalg/IR/Linalg.h"
15 #include "mlir/Dialect/Linalg/Transforms/Transforms.h"
16 #include "mlir/Dialect/Linalg/Utils/Utils.h"
17 #include "mlir/Dialect/Utils/IndexingUtils.h"
18 #include "mlir/Dialect/Utils/StructuredOpsUtils.h"
19 #include "mlir/Dialect/Vector/IR/VectorOps.h"
20 #include "mlir/IR/AffineExpr.h"
21 #include "mlir/IR/Matchers.h"
22 #include "mlir/IR/PatternMatch.h"
23 #include "mlir/Pass/Pass.h"
24 #include "mlir/Support/LLVM.h"
25 #include "llvm/ADT/ScopeExit.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/raw_ostream.h"
28 #include <type_traits>
29 
30 #define DEBUG_TYPE "linalg-interchange"
31 
32 using namespace mlir;
33 using namespace mlir::linalg;
34 
35 static LogicalResult
36 interchangeGenericOpPrecondition(GenericOp genericOp,
37                                  ArrayRef<unsigned> interchangeVector) {
38   // Interchange vector must be non-empty and match the number of loops.
39   if (interchangeVector.empty() ||
40       genericOp.getNumLoops() != interchangeVector.size())
41     return failure();
42   // Permutation map must be invertible.
43   if (!inversePermutation(AffineMap::getPermutationMap(interchangeVector,
44                                                        genericOp.getContext())))
45     return failure();
46   return success();
47 }
48 
49 FailureOr<GenericOp>
50 mlir::linalg::interchangeGenericOp(RewriterBase &rewriter, GenericOp genericOp,
51                                    ArrayRef<unsigned> interchangeVector) {
52   if (failed(interchangeGenericOpPrecondition(genericOp, interchangeVector)))
53     return rewriter.notifyMatchFailure(genericOp, "preconditions not met");
54 
55   // 1. Compute the inverse permutation map, it must be non-null since the
56   // preconditions are satisfied.
57   MLIRContext *context = genericOp.getContext();
58   AffineMap permutationMap = inversePermutation(
59       AffineMap::getPermutationMap(interchangeVector, context));
60   assert(permutationMap && "unexpected null map");
61 
62   // Start a guarded inplace update.
63   rewriter.startRootUpdate(genericOp);
64   auto guard =
65       llvm::make_scope_exit([&]() { rewriter.finalizeRootUpdate(genericOp); });
66 
67   // 2. Compute the interchanged indexing maps.
68   SmallVector<AffineMap> newIndexingMaps;
69   for (OpOperand *opOperand : genericOp.getInputAndOutputOperands()) {
70     AffineMap m = genericOp.getTiedIndexingMap(opOperand);
71     if (!permutationMap.isEmpty())
72       m = m.compose(permutationMap);
73     newIndexingMaps.push_back(m);
74   }
75   genericOp->setAttr(getIndexingMapsAttrName(),
76                      rewriter.getAffineMapArrayAttr(newIndexingMaps));
77 
78   // 3. Compute the interchanged iterator types.
79   ArrayRef<Attribute> itTypes = genericOp.iterator_types().getValue();
80   SmallVector<Attribute> itTypesVector;
81   llvm::append_range(itTypesVector, itTypes);
82   SmallVector<int64_t> permutation(interchangeVector.begin(),
83                                    interchangeVector.end());
84   applyPermutationToVector(itTypesVector, permutation);
85   genericOp->setAttr(getIteratorTypesAttrName(),
86                      ArrayAttr::get(context, itTypesVector));
87 
88   // 4. Transform the index operations by applying the permutation map.
89   if (genericOp.hasIndexSemantics()) {
90     OpBuilder::InsertionGuard guard(rewriter);
91     for (IndexOp indexOp :
92          llvm::make_early_inc_range(genericOp.getBody()->getOps<IndexOp>())) {
93       rewriter.setInsertionPoint(indexOp);
94       SmallVector<Value> allIndices;
95       allIndices.reserve(genericOp.getNumLoops());
96       llvm::transform(llvm::seq<uint64_t>(0, genericOp.getNumLoops()),
97                       std::back_inserter(allIndices), [&](uint64_t dim) {
98                         return rewriter.create<IndexOp>(indexOp->getLoc(), dim);
99                       });
100       rewriter.replaceOpWithNewOp<AffineApplyOp>(
101           indexOp, permutationMap.getSubMap(indexOp.dim()), allIndices);
102     }
103   }
104 
105   return genericOp;
106 }
107