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/Affine/IR/AffineOps.h"
14 #include "mlir/Dialect/Linalg/Analysis/DependenceAnalysis.h"
15 #include "mlir/Dialect/Linalg/IR/Linalg.h"
16 #include "mlir/Dialect/Linalg/Transforms/Transforms.h"
17 #include "mlir/Dialect/Linalg/Utils/Utils.h"
18 #include "mlir/Dialect/Utils/IndexingUtils.h"
19 #include "mlir/Dialect/Utils/StructuredOpsUtils.h"
20 #include "mlir/Dialect/Vector/IR/VectorOps.h"
21 #include "mlir/IR/AffineExpr.h"
22 #include "mlir/IR/Matchers.h"
23 #include "mlir/IR/PatternMatch.h"
24 #include "mlir/Pass/Pass.h"
25 #include "mlir/Support/LLVM.h"
26 #include "llvm/ADT/ScopeExit.h"
27 #include "llvm/Support/Debug.h"
28 #include "llvm/Support/raw_ostream.h"
29 #include <type_traits>
30 
31 #define DEBUG_TYPE "linalg-interchange"
32 
33 using namespace mlir;
34 using namespace mlir::linalg;
35 
36 static LogicalResult
37 interchangeGenericOpPrecondition(GenericOp genericOp,
38                                  ArrayRef<unsigned> interchangeVector) {
39   // Interchange vector must be non-empty and match the number of loops.
40   if (interchangeVector.empty() ||
41       genericOp.getNumLoops() != interchangeVector.size())
42     return failure();
43   // Permutation map must be invertible.
44   if (!inversePermutation(AffineMap::getPermutationMap(interchangeVector,
45                                                        genericOp.getContext())))
46     return failure();
47   return success();
48 }
49 
50 FailureOr<GenericOp>
51 mlir::linalg::interchangeGenericOp(RewriterBase &rewriter, GenericOp genericOp,
52                                    ArrayRef<unsigned> interchangeVector) {
53   if (failed(interchangeGenericOpPrecondition(genericOp, interchangeVector)))
54     return rewriter.notifyMatchFailure(genericOp, "preconditions not met");
55 
56   // 1. Compute the inverse permutation map, it must be non-null since the
57   // preconditions are satisfied.
58   MLIRContext *context = genericOp.getContext();
59   AffineMap permutationMap = inversePermutation(
60       AffineMap::getPermutationMap(interchangeVector, context));
61   assert(permutationMap && "unexpected null map");
62 
63   // Start a guarded inplace update.
64   rewriter.startRootUpdate(genericOp);
65   auto guard =
66       llvm::make_scope_exit([&]() { rewriter.finalizeRootUpdate(genericOp); });
67 
68   // 2. Compute the interchanged indexing maps.
69   SmallVector<AffineMap> newIndexingMaps;
70   for (OpOperand *opOperand : genericOp.getInputAndOutputOperands()) {
71     AffineMap m = genericOp.getTiedIndexingMap(opOperand);
72     if (!permutationMap.isEmpty())
73       m = m.compose(permutationMap);
74     newIndexingMaps.push_back(m);
75   }
76   genericOp->setAttr(getIndexingMapsAttrName(),
77                      rewriter.getAffineMapArrayAttr(newIndexingMaps));
78 
79   // 3. Compute the interchanged iterator types.
80   ArrayRef<Attribute> itTypes = genericOp.iterator_types().getValue();
81   SmallVector<Attribute> itTypesVector;
82   llvm::append_range(itTypesVector, itTypes);
83   SmallVector<int64_t> permutation(interchangeVector.begin(),
84                                    interchangeVector.end());
85   applyPermutationToVector(itTypesVector, permutation);
86   genericOp->setAttr(getIteratorTypesAttrName(),
87                      ArrayAttr::get(context, itTypesVector));
88 
89   // 4. Transform the index operations by applying the permutation map.
90   if (genericOp.hasIndexSemantics()) {
91     OpBuilder::InsertionGuard guard(rewriter);
92     for (IndexOp indexOp :
93          llvm::make_early_inc_range(genericOp.getBody()->getOps<IndexOp>())) {
94       rewriter.setInsertionPoint(indexOp);
95       SmallVector<Value> allIndices;
96       allIndices.reserve(genericOp.getNumLoops());
97       llvm::transform(llvm::seq<uint64_t>(0, genericOp.getNumLoops()),
98                       std::back_inserter(allIndices), [&](uint64_t dim) {
99                         return rewriter.create<IndexOp>(indexOp->getLoc(), dim);
100                       });
101       rewriter.replaceOpWithNewOp<AffineApplyOp>(
102           indexOp, permutationMap.getSubMap(indexOp.dim()), allIndices);
103     }
104   }
105 
106   return genericOp;
107 }
108