1 //===- BufferizableOpInterfaceImpl.cpp - Impl. of BufferizableOpInterface -===//
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 #include "mlir/Dialect/Linalg/Transforms/BufferizableOpInterfaceImpl.h"
10 #include "mlir/Dialect/Bufferization/IR/BufferizableOpInterface.h"
11 #include "mlir/Dialect/Bufferization/IR/Bufferization.h"
12 #include "mlir/Dialect/Linalg/IR/Linalg.h"
13 #include "mlir/Dialect/Tensor/IR/Tensor.h"
14 #include "mlir/IR/Dialect.h"
15 #include "mlir/IR/Operation.h"
16 
17 using namespace mlir;
18 using namespace linalg;
19 using namespace mlir::bufferization;
20 
21 namespace {
22 
23 // TODO: Ops in the linalg dialect can directly implement this interface.
24 
25 /// Generic conversion for any LinalgOp on tensors.
26 static LogicalResult bufferizeLinalgOp(RewriterBase &rewriter, LinalgOp op,
27                                        BufferizationState &state) {
28   // Take a guard before anything else.
29   OpBuilder::InsertionGuard g(rewriter);
30   rewriter.setInsertionPoint(op);
31 
32   // Nothing to do. This op is already bufferized.
33   if (op.hasBufferSemantics())
34     return success();
35 
36   // Ensure op has only tensors. Allow mixed tensor-buffer mode on a per-need
37   // basis.
38   if (!op.hasTensorSemantics())
39     return op->emitError() << "op does not have tensor semantics";
40 
41   // New input operands for the cloned op.
42   SmallVector<Value> newInputBuffers;
43   newInputBuffers.reserve(op.getNumInputs());
44   for (OpOperand *opOperand : op.getInputOperands()) {
45     if (op.isScalar(opOperand)) {
46       newInputBuffers.push_back(opOperand->get());
47       continue;
48     }
49     newInputBuffers.push_back(state.getBuffer(rewriter, opOperand->get()));
50   }
51 
52   // New output operands for the cloned op.
53   SmallVector<Value> newOutputBuffers;
54   for (OpResult opResult : op->getOpResults()) {
55     OpOperand *opOperand = op.getOutputOperand(opResult.getResultNumber());
56     Value resultBuffer = state.getBuffer(rewriter, opOperand->get());
57     newOutputBuffers.push_back(resultBuffer);
58   }
59 
60   // Merge input/output operands.
61   SmallVector<Value> newOperands = newInputBuffers;
62   newOperands.append(newOutputBuffers.begin(), newOutputBuffers.end());
63 
64   // Set insertion point now that potential alloc/dealloc are introduced.
65   rewriter.setInsertionPoint(op);
66   // Clone the op, but use the new operands. Move the existing block into the
67   // new op. Since the new op does not have any tensor results, it does not
68   // return anything.
69   assert(op->getNumRegions() == 1 && "expected that op has 1 region");
70   auto newOp = cast<LinalgOp>(op.cloneWithoutRegions(
71       rewriter, op.getLoc(), /*resultTypes=*/TypeRange{}, newOperands));
72   rewriter.inlineRegionBefore(op->getRegion(0), newOp->getRegion(0),
73                               newOp->getRegion(0).begin());
74 
75   // Replace the results of the old op with the new output buffers.
76   replaceOpWithBufferizedValues(rewriter, op, newOutputBuffers);
77 
78   return success();
79 }
80 
81 /// Bufferization of linalg.generic. Replace with a new linalg.generic that
82 /// operates entirely on memrefs.
83 template <typename OpTy>
84 struct LinalgOpInterface
85     : public BufferizableOpInterface::ExternalModel<LinalgOpInterface<OpTy>,
86                                                     OpTy> {
87   bool bufferizesToMemoryRead(Operation *op, OpOperand &opOperand,
88                               const AnalysisState &state) const {
89     // Operand is read if it is used in the computation.
90     auto genericOp = cast<linalg::LinalgOp>(op);
91     return genericOp.payloadUsesValueFromOperand(&opOperand);
92   }
93 
94   bool bufferizesToMemoryWrite(Operation *op, OpOperand &opOperand,
95                                const AnalysisState &state) const {
96     // Operand is written to if it has an aliasing OpResult.
97     auto bufferizableOp = cast<BufferizableOpInterface>(op);
98     return !bufferizableOp.getAliasingOpResult(opOperand, state).empty();
99   }
100 
101   SmallVector<OpOperand *>
102   getAliasingOpOperand(Operation *op, OpResult opResult,
103                        const AnalysisState &state) const {
104     auto genericOp = cast<linalg::LinalgOp>(op);
105 
106     // The i-th OpResult may alias with the i-th "out" tensor.
107     return {genericOp.getOutputOperand(opResult.getResultNumber())};
108   }
109 
110   SmallVector<OpResult> getAliasingOpResult(Operation *op, OpOperand &opOperand,
111                                             const AnalysisState &state) const {
112     auto genericOp = cast<linalg::LinalgOp>(op);
113 
114     // The i-th "out" tensor may alias with the i-th OpResult.
115     if (genericOp.isOutputTensor(&opOperand))
116       return {genericOp.getTiedOpResult(&opOperand)};
117     return {};
118   }
119 
120   BufferRelation bufferRelation(Operation *op, OpResult opResult,
121                                 const AnalysisState &state) const {
122     return BufferRelation::Equivalent;
123   }
124 
125   LogicalResult bufferize(Operation *op, RewriterBase &rewriter,
126                           BufferizationState &state) const {
127     return bufferizeLinalgOp(rewriter, cast<LinalgOp>(op), state);
128   }
129 };
130 
131 /// Helper structure that iterates over all LinalgOps in `OpTys` and registers
132 /// the `BufferizableOpInterface` with each of them.
133 template <typename... Ops>
134 struct LinalgOpInterfaceHelper {
135   static void registerOpInterface(MLIRContext *ctx) {
136     (void)std::initializer_list<int>{
137         0, (Ops::template attachInterface<LinalgOpInterface<Ops>>(*ctx), 0)...};
138   }
139 };
140 } // namespace
141 
142 void mlir::linalg::registerBufferizableOpInterfaceExternalModels(
143     DialectRegistry &registry) {
144   registry.addExtension(+[](MLIRContext *ctx, linalg::LinalgDialect *dialect) {
145     // Register all Linalg structured ops. `LinalgOp` is an interface and it is
146     // not possible to attach an external interface to an existing interface.
147     // Therefore, attach the `BufferizableOpInterface` to all ops one-by-one.
148     LinalgOpInterfaceHelper<
149 #define GET_OP_LIST
150 #include "mlir/Dialect/Linalg/IR/LinalgStructuredOps.cpp.inc"
151         >::registerOpInterface(ctx);
152   });
153 }
154