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/Arith/Transforms/BufferizableOpInterfaceImpl.h"
10#include "mlir/Dialect/Arith/IR/Arith.h"
11#include "mlir/Dialect/Bufferization/IR/BufferizableOpInterface.h"
12#include "mlir/Dialect/Bufferization/Transforms/BufferUtils.h"
13#include "mlir/Dialect/MemRef/IR/MemRef.h"
14#include "mlir/IR/Attributes.h"
15#include "mlir/IR/Dialect.h"
16#include "mlir/IR/Operation.h"
17
18using namespace mlir;
19using namespace mlir::bufferization;
20
21namespace {
22/// Bufferization of arith.constant. Replace with memref.get_global.
23struct ConstantOpInterface
24 : public BufferizableOpInterface::ExternalModel<ConstantOpInterface,
25 arith::ConstantOp> {
26 LogicalResult bufferize(Operation *op, RewriterBase &rewriter,
27 const BufferizationOptions &options,
28 BufferizationState &state) const {
29 auto constantOp = cast<arith::ConstantOp>(op);
30 auto type = dyn_cast<RankedTensorType>(constantOp.getType());
31
32 // Only ranked tensors are supported.
33 if (!type)
34 return failure();
35
36 Attribute memorySpace;
37 if (auto memSpace = options.defaultMemorySpaceFn(type))
38 memorySpace = *memSpace;
39 else
40 return constantOp->emitError("could not infer memory space");
41
42 // Only constants inside a module are supported.
43 auto moduleOp = constantOp->getParentOfType<ModuleOp>();
44 if (!moduleOp)
45 return failure();
46
47 // Create global memory segment and replace tensor with memref pointing to
48 // that memory segment.
49 FailureOr<memref::GlobalOp> globalOp =
50 getGlobalFor(constantOp, state.getSymbolTables(),
51 options.bufferAlignment, memorySpace);
52 if (failed(globalOp))
53 return failure();
54 memref::GlobalOp globalMemref = *globalOp;
55 replaceOpWithNewBufferizedOp<memref::GetGlobalOp>(
56 rewriter, op, globalMemref.getType(), globalMemref.getName());
57
58 return success();
59 }
60
61 bool isWritable(Operation *op, Value value,
62 const AnalysisState &state) const {
63 // Memory locations returned by memref::GetGlobalOp may not be written to.
64 assert(isa<OpResult>(value));
65 return false;
66 }
67};
68
69struct IndexCastOpInterface
70 : public BufferizableOpInterface::ExternalModel<IndexCastOpInterface,
71 arith::IndexCastOp> {
72 bool bufferizesToMemoryRead(Operation *op, OpOperand &opOperand,
73 const AnalysisState &state) const {
74 return false;
75 }
76
77 bool bufferizesToMemoryWrite(Operation *op, OpOperand &opOperand,
78 const AnalysisState &state) const {
79 return false;
80 }
81
82 AliasingValueList getAliasingValues(Operation *op, OpOperand &opOperand,
83 const AnalysisState &state) const {
84 return {{op->getResult(idx: 0), BufferRelation::Equivalent}};
85 }
86
87 LogicalResult bufferize(Operation *op, RewriterBase &rewriter,
88 const BufferizationOptions &options,
89 BufferizationState &state) const {
90 auto castOp = cast<arith::IndexCastOp>(op);
91 auto resultTensorType = cast<TensorType>(castOp.getType());
92
93 FailureOr<Value> source =
94 getBuffer(rewriter, castOp.getIn(), options, state);
95 if (failed(Result: source))
96 return failure();
97 auto sourceType = cast<BaseMemRefType>(Val: source->getType());
98
99 // Result type should have same layout and address space as the source type.
100 BaseMemRefType resultType;
101 if (auto rankedMemRefType = dyn_cast<MemRefType>(sourceType)) {
102 resultType = MemRefType::get(
103 rankedMemRefType.getShape(), resultTensorType.getElementType(),
104 rankedMemRefType.getLayout(), rankedMemRefType.getMemorySpace());
105 } else {
106 auto unrankedMemrefType = cast<UnrankedMemRefType>(sourceType);
107 resultType = UnrankedMemRefType::get(resultTensorType.getElementType(),
108 unrankedMemrefType.getMemorySpace());
109 }
110
111 replaceOpWithNewBufferizedOp<arith::IndexCastOp>(rewriter, op, resultType,
112 *source);
113 return success();
114 }
115};
116
117/// Bufferization of arith.select. Just replace the operands.
118struct SelectOpInterface
119 : public BufferizableOpInterface::ExternalModel<SelectOpInterface,
120 arith::SelectOp> {
121 bool bufferizesToMemoryRead(Operation *op, OpOperand &opOperand,
122 const AnalysisState &state) const {
123 return false;
124 }
125
126 bool bufferizesToMemoryWrite(Operation *op, OpOperand &opOperand,
127 const AnalysisState &state) const {
128 return false;
129 }
130
131 AliasingValueList getAliasingValues(Operation *op, OpOperand &opOperand,
132 const AnalysisState &state) const {
133 return {{op->getOpResult(idx: 0) /*result*/, BufferRelation::Equivalent,
134 /*isDefinite=*/false}};
135 }
136
137 LogicalResult bufferize(Operation *op, RewriterBase &rewriter,
138 const BufferizationOptions &options,
139 BufferizationState &state) const {
140 auto selectOp = cast<arith::SelectOp>(op);
141 Location loc = selectOp.getLoc();
142
143 // Elementwise conditions are not supported yet. To bufferize such an op,
144 // it could be lowered to an elementwise "linalg.generic" with a new
145 // "tensor.empty" out tensor, followed by "empty tensor elimination". Such
146 // IR will bufferize.
147 if (!selectOp.getCondition().getType().isInteger(1))
148 return op->emitOpError(message: "only i1 condition values are supported");
149
150 // TODO: It would be more efficient to copy the result of the `select` op
151 // instead of its OpOperands. In the worst case, 2 copies are inserted at
152 // the moment (one for each tensor). When copying the op result, only one
153 // copy would be needed.
154 FailureOr<Value> maybeTrueBuffer =
155 getBuffer(rewriter, selectOp.getTrueValue(), options, state);
156 FailureOr<Value> maybeFalseBuffer =
157 getBuffer(rewriter, selectOp.getFalseValue(), options, state);
158 if (failed(Result: maybeTrueBuffer) || failed(Result: maybeFalseBuffer))
159 return failure();
160 Value trueBuffer = *maybeTrueBuffer;
161 Value falseBuffer = *maybeFalseBuffer;
162
163 // The "true" and the "false" operands must have the same type. If the
164 // buffers have different types, they differ only in their layout map. Cast
165 // both of them to the most dynamic MemRef type.
166 if (trueBuffer.getType() != falseBuffer.getType()) {
167 auto targetType =
168 bufferization::getBufferType(value: selectOp.getResult(), options, state);
169 if (failed(targetType))
170 return failure();
171 if (trueBuffer.getType() != *targetType)
172 trueBuffer =
173 rewriter.create<memref::CastOp>(loc, *targetType, trueBuffer);
174 if (falseBuffer.getType() != *targetType)
175 falseBuffer =
176 rewriter.create<memref::CastOp>(loc, *targetType, falseBuffer);
177 }
178
179 replaceOpWithNewBufferizedOp<arith::SelectOp>(
180 rewriter, op, selectOp.getCondition(), trueBuffer, falseBuffer);
181 return success();
182 }
183
184 FailureOr<BaseMemRefType>
185 getBufferType(Operation *op, Value value, const BufferizationOptions &options,
186 const BufferizationState &state,
187 SmallVector<Value> &invocationStack) const {
188 auto selectOp = cast<arith::SelectOp>(op);
189 assert(value == selectOp.getResult() && "invalid value");
190 auto trueType = bufferization::getBufferType(
191 value: selectOp.getTrueValue(), options, state, invocationStack);
192 auto falseType = bufferization::getBufferType(
193 value: selectOp.getFalseValue(), options, state, invocationStack);
194 if (failed(trueType) || failed(falseType))
195 return failure();
196 if (*trueType == *falseType)
197 return *trueType;
198 if (trueType->getMemorySpace() != falseType->getMemorySpace())
199 return op->emitError(message: "inconsistent memory space on true/false operands");
200
201 // If the buffers have different types, they differ only in their layout
202 // map.
203 auto memrefType = llvm::cast<MemRefType>(*trueType);
204 return getMemRefTypeWithFullyDynamicLayout(
205 RankedTensorType::get(memrefType.getShape(),
206 memrefType.getElementType()),
207 memrefType.getMemorySpace());
208 }
209};
210
211} // namespace
212
213void mlir::arith::registerBufferizableOpInterfaceExternalModels(
214 DialectRegistry &registry) {
215 registry.addExtension(extensionFn: +[](MLIRContext *ctx, ArithDialect *dialect) {
216 ConstantOp::attachInterface<ConstantOpInterface>(*ctx);
217 IndexCastOp::attachInterface<IndexCastOpInterface>(*ctx);
218 SelectOp::attachInterface<SelectOpInterface>(*ctx);
219 });
220}
221

source code of mlir/lib/Dialect/Arith/Transforms/BufferizableOpInterfaceImpl.cpp