1 | /* |
2 | * Licensed to the Apache Software Foundation (ASF) under one |
3 | * or more contributor license agreements. See the NOTICE file |
4 | * distributed with this work for additional information |
5 | * regarding copyright ownership. The ASF licenses this file |
6 | * to you under the Apache License, Version 2.0 (the |
7 | * "License"); you may not use this file except in compliance |
8 | * with the License. You may obtain a copy of the License at |
9 | * |
10 | * http://www.apache.org/licenses/LICENSE-2.0 |
11 | * |
12 | * Unless required by applicable law or agreed to in writing, |
13 | * software distributed under the License is distributed on an |
14 | * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
15 | * KIND, either express or implied. See the License for the |
16 | * specific language governing permissions and limitations |
17 | * under the License. |
18 | */ |
19 | |
20 | /*! |
21 | * Out of bounds array access static analyzer. |
22 | */ |
23 | |
24 | #include <tvm/tir/transform.h> |
25 | |
26 | #include "../../arith/ir_visitor_with_analyzer.h" |
27 | #include "../schedule/error.h" |
28 | |
29 | namespace tvm { |
30 | namespace tir { |
31 | namespace transform { |
32 | struct OOBLocation { |
33 | Buffer buf; |
34 | size_t dimension; |
35 | ObjectRef index; |
36 | arith::IntSet index_bounds; |
37 | arith::IntSet shape_bounds; |
38 | }; |
39 | |
40 | class OOBError : public ScheduleError { |
41 | public: |
42 | OOBError(IRModule mod, std::vector<OOBLocation> locations) : mod_(mod), locations_(locations) {} |
43 | String FastErrorString() const final { return "Out of bound memory access" ; } |
44 | |
45 | String DetailRenderTemplate() const final { |
46 | std::stringstream s; |
47 | for (const auto& oob : locations_) { |
48 | s << "Out of bounds memory access on buffer " << oob.buf->name << " dimension " |
49 | << oob.dimension << "." ; |
50 | s << " index " << oob.index << " with bounds [" << oob.index_bounds.min() << ", " |
51 | << oob.index_bounds.max() << "] is outside the range [0, " << oob.shape_bounds.min() |
52 | << "]." ; |
53 | s << "\n" ; |
54 | } |
55 | return s.str(); |
56 | } |
57 | IRModule mod() const final { return mod_; } |
58 | Array<ObjectRef> LocationsOfInterest() const final { |
59 | std::vector<ObjectRef> locs; |
60 | for (auto loc : locations_) { |
61 | locs.push_back(loc.index); |
62 | } |
63 | return locs; |
64 | } |
65 | |
66 | private: |
67 | IRModule mod_; |
68 | std::vector<OOBLocation> locations_; |
69 | }; |
70 | class OOBCheckerVisitor final : public arith::IRVisitorWithAnalyzer { |
71 | using IRVisitorWithAnalyzer::VisitExpr_; |
72 | using IRVisitorWithAnalyzer::VisitStmt_; |
73 | |
74 | public: |
75 | void VisitStmt_(const BufferStoreNode* node) final { |
76 | for (size_t i = 0; i < node->buffer->shape.size(); i++) { |
77 | CheckBounds(node, i); |
78 | } |
79 | IRVisitorWithAnalyzer::VisitStmt_(node); |
80 | } |
81 | void VisitExpr_(const BufferLoadNode* node) final { |
82 | for (size_t i = 0; i < node->buffer->shape.size(); i++) { |
83 | CheckBounds(node, i); |
84 | } |
85 | IRVisitorWithAnalyzer::VisitExpr_(node); |
86 | } |
87 | |
88 | template <class T> |
89 | void CheckBounds(const T* node, size_t i) { |
90 | auto ind_bounds = analyzer_.int_set(node->indices[i]); |
91 | auto shape_bounds = analyzer_.int_set(node->buffer->shape[i]); |
92 | // We would expect that |
93 | // `analyzer_.CanProve(node->indices[i] < 0 || node->indices[i] >= node->buffer->shape[i])` |
94 | // would be the way to check if any out of bounds access occurs here, but `CanProve` checks if |
95 | // the statement is true for all possible values (universal quantification). For a mix of in |
96 | // bounds and out of bounds access, no out of bounds access would be reported. We instead want |
97 | // to check if there is any value for which the access is out of bounds (existential |
98 | // quantification). |
99 | // An solution would be to check that the index is in bounds for every possible value. This |
100 | // has the problem that some valid access patterns maybe be valid but not provably valid. We |
101 | // prefer that this analysis is conservative and only shows errors that are provable. This leads |
102 | // us to the following check: are the bounds of the index outside the bounds of the shape. |
103 | if (analyzer_.CanProve(ind_bounds.max() >= shape_bounds.min()) || |
104 | analyzer_.CanProve(ind_bounds.min() < 0)) { |
105 | errors.push_back({node->buffer, i, node->indices[i], ind_bounds, shape_bounds}); |
106 | } |
107 | } |
108 | |
109 | std::vector<OOBLocation> errors; |
110 | }; |
111 | |
112 | transform::Pass OOBChecker() { |
113 | auto pass_func = [=](tir::PrimFunc func, IRModule mod, transform::PassContext ctx) { |
114 | OOBCheckerVisitor checker; |
115 | checker(func->body); |
116 | if (checker.errors.size() > 0) { |
117 | // mod doesn't contain our function, so we construct a new mod with out function |
118 | IRModule func_mod({{GlobalVar("main" ), func}}); |
119 | LOG(FATAL) << OOBError(func_mod, checker.errors).RenderReport("Out of bounds checker" ); |
120 | } |
121 | return func; |
122 | }; |
123 | return transform::CreatePrimFuncPass(pass_func, 0, "tir.analysis.OOBChecker" , {}); |
124 | } |
125 | |
126 | TVM_REGISTER_GLOBAL("tir.analysis.OOBChecker" ).set_body_typed(OOBChecker); |
127 | } // namespace transform |
128 | } // namespace tir |
129 | } // namespace tvm |
130 | |