1 //===- Bufferize.cpp - Bufferization for std ops --------------------------===//
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 bufferization of tensor-valued std.constant ops.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "PassDetail.h"
14 #include "mlir/Dialect/StandardOps/IR/Ops.h"
15 #include "mlir/Dialect/StandardOps/Transforms/Passes.h"
16 #include "mlir/IR/BlockAndValueMapping.h"
17 #include "mlir/Transforms/Bufferize.h"
18 #include "mlir/Transforms/DialectConversion.h"
19
20 using namespace mlir;
21
22 namespace {
23 // This class creates global ops for all tensor-valued constants in the program.
24 // It creates them with pretty names and makes sure that duplicate globals
25 // aren't created.
26 class GlobalCreator {
27 public:
28 explicit GlobalCreator(ModuleOp module);
getGlobalFor(Attribute attr)29 GlobalMemrefOp getGlobalFor(Attribute attr) {
30 assert(globals.find(attr) != globals.end() && "unknown constant attr");
31 return globals[attr];
32 }
33
34 private:
35 DenseMap<Attribute, GlobalMemrefOp> globals;
36 };
37
GlobalCreator(ModuleOp module)38 GlobalCreator::GlobalCreator(ModuleOp module) {
39 BufferizeTypeConverter typeConverter;
40 // Create a builder without an insertion point. We will insert using the
41 // symbol table to guarantee unique names.
42 OpBuilder globalBuilder(module.getContext());
43 SymbolTable symbolTable(module);
44 module.walk([&](ConstantOp op) {
45 // We only want tensor constants for now.
46 auto type = op.getType().dyn_cast<RankedTensorType>();
47 if (!type)
48 return;
49 // If we already have a global for this constant value, no need to do
50 // anything else.
51 auto it = globals.find(op.getValue());
52 if (it != globals.end())
53 return;
54
55 // Create a pretty name.
56 SmallString<64> buf;
57 llvm::raw_svector_ostream os(buf);
58 interleave(type.getShape(), os, "x");
59 os << "x" << type.getElementType();
60
61 auto global = globalBuilder.create<GlobalMemrefOp>(
62 op.getLoc(), (Twine("__constant_") + os.str()).str(),
63 /*sym_visibility=*/globalBuilder.getStringAttr("private"),
64 /*type=*/
65 TypeAttr::get(typeConverter.convertType(type)), /*initial_value=*/
66 op.getValue().cast<ElementsAttr>(), /*constant=*/true);
67 symbolTable.insert(global);
68 // The symbol table inserts at the end of the module, but globals are a bit
69 // nicer if they are at the beginning.
70 global->moveBefore(&module.front());
71 globals[op.getValue()] = global;
72 });
73 }
74 } // namespace
75
76 namespace {
77 class BufferizeTensorConstantOp : public OpConversionPattern<ConstantOp> {
78 public:
BufferizeTensorConstantOp(GlobalCreator & globals,TypeConverter & typeConverter,MLIRContext * context)79 BufferizeTensorConstantOp(GlobalCreator &globals,
80 TypeConverter &typeConverter, MLIRContext *context)
81 : OpConversionPattern<ConstantOp>(typeConverter, context, /*benefit=*/1),
82 globals(globals) {}
83
84 LogicalResult
matchAndRewrite(ConstantOp op,ArrayRef<Value> operands,ConversionPatternRewriter & rewriter) const85 matchAndRewrite(ConstantOp op, ArrayRef<Value> operands,
86 ConversionPatternRewriter &rewriter) const override {
87 auto type = op.getType().dyn_cast<RankedTensorType>();
88 if (!type)
89 return failure();
90
91 auto globalMemref = globals.getGlobalFor(op.value());
92 rewriter.replaceOpWithNewOp<GetGlobalMemrefOp>(op, globalMemref.type(),
93 globalMemref.getName());
94 return success();
95 }
96 GlobalCreator &globals;
97 };
98 } // namespace
99
100 namespace {
101 struct TensorConstantBufferizePass
102 : public TensorConstantBufferizeBase<TensorConstantBufferizePass> {
runOnOperation__anonfd1905150411::TensorConstantBufferizePass103 void runOnOperation() override {
104 auto module = getOperation();
105 GlobalCreator globals(module);
106
107 auto *context = &getContext();
108 BufferizeTypeConverter typeConverter;
109 OwningRewritePatternList patterns;
110 ConversionTarget target(*context);
111
112 target.addLegalDialect<StandardOpsDialect>();
113 patterns.insert<BufferizeTensorConstantOp>(globals, typeConverter, context);
114 target.addDynamicallyLegalOp<ConstantOp>(
115 [&](ConstantOp op) { return typeConverter.isLegal(op.getType()); });
116 if (failed(applyPartialConversion(module, target, std::move(patterns))))
117 signalPassFailure();
118 }
119 };
120 } // namespace
121
createTensorConstantBufferizePass()122 std::unique_ptr<Pass> mlir::createTensorConstantBufferizePass() {
123 return std::make_unique<TensorConstantBufferizePass>();
124 }
125