[mlir][tensor] fix typo in pad tiling comment
[llvm-project.git] / clang-tools-extra / clang-tidy / utils / ExprSequence.h
blob6531e1876c4fe300a340ac49d78907a7f94bcfd1
1 //===------------- ExprSequence.h - clang-tidy ----------------------------===//
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 //===----------------------------------------------------------------------===//
9 #ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_EXPRSEQUENCE_H
10 #define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_EXPRSEQUENCE_H
12 #include "clang/Analysis/CFG.h"
13 #include "clang/Lex/Lexer.h"
14 #include "llvm/ADT/DenseMap.h"
15 #include "llvm/ADT/SmallPtrSet.h"
16 #include "llvm/ADT/SmallVector.h"
18 #include "../ClangTidy.h"
20 namespace clang::tidy::utils {
22 /// Provides information about the evaluation order of (sub-)expressions within
23 /// a `CFGBlock`.
24 ///
25 /// While a `CFGBlock` does contain individual `CFGElement`s for some
26 /// sub-expressions, the order in which those `CFGElement`s appear reflects
27 /// only one possible order in which the sub-expressions may be evaluated.
28 /// However, we want to warn if any of the potential evaluation orders can lead
29 /// to a use-after-move, not just the one contained in the `CFGBlock`.
30 ///
31 /// This class implements only a simplified version of the C++ sequencing
32 /// rules. The main limitation is that we do not distinguish between value
33 /// computation and side effect -- see the "Implementation" section for more
34 /// details.
35 ///
36 /// Note: `SequenceChecker` from SemaChecking.cpp does a similar job (and much
37 /// more thoroughly), but using it would require
38 /// - Pulling `SequenceChecker` out into a header file (i.e. making it part of
39 /// the API),
40 /// - Removing the dependency of `SequenceChecker` on `Sema`, and
41 /// - (Probably) modifying `SequenceChecker` to make it suitable to be used in
42 /// this context.
43 /// For the moment, it seems preferable to re-implement our own version of
44 /// sequence checking that is special-cased to what we need here.
45 ///
46 /// Implementation
47 /// --------------
48 ///
49 /// `ExprSequence` uses two types of sequencing edges between nodes in the AST:
50 ///
51 /// - Every `Stmt` is assumed to be sequenced after its children. This is
52 /// overly optimistic because the standard only states that value computations
53 /// of operands are sequenced before the value computation of the operator,
54 /// making no guarantees about side effects (in general).
55 ///
56 /// For our purposes, this rule is sufficient, however, because this check is
57 /// interested in operations on objects, which are generally performed through
58 /// function calls (whether explicit and implicit). Function calls guarantee
59 /// that the value computations and side effects for all function arguments
60 /// are sequenced before the execution of the function.
61 ///
62 /// - In addition, some `Stmt`s are known to be sequenced before or after
63 /// their siblings. For example, the `Stmt`s that make up a `CompoundStmt`are
64 /// all sequenced relative to each other. The function
65 /// `getSequenceSuccessor()` implements these sequencing rules.
66 class ExprSequence {
67 public:
68 /// Initializes this `ExprSequence` with sequence information for the given
69 /// `CFG`. `Root` is the root statement the CFG was built from.
70 ExprSequence(const CFG *TheCFG, const Stmt *Root, ASTContext *TheContext);
72 /// Returns whether \p Before is sequenced before \p After.
73 bool inSequence(const Stmt *Before, const Stmt *After) const;
75 /// Returns whether \p After can potentially be evaluated after \p Before.
76 /// This is exactly equivalent to `!inSequence(After, Before)` but makes some
77 /// conditions read more naturally.
78 bool potentiallyAfter(const Stmt *After, const Stmt *Before) const;
80 private:
81 // Returns the sibling of \p S (if any) that is directly sequenced after \p S,
82 // or nullptr if no such sibling exists. For example, if \p S is the child of
83 // a `CompoundStmt`, this would return the Stmt that directly follows \p S in
84 // the `CompoundStmt`.
86 // As the sequencing of many constructs that change control flow is already
87 // encoded in the `CFG`, this function only implements the sequencing rules
88 // for those constructs where sequencing cannot be inferred from the `CFG`.
89 const Stmt *getSequenceSuccessor(const Stmt *S) const;
91 const Stmt *resolveSyntheticStmt(const Stmt *S) const;
93 ASTContext *Context;
94 const Stmt *Root;
96 llvm::DenseMap<const Stmt *, const Stmt *> SyntheticStmtSourceMap;
99 /// Maps `Stmt`s to the `CFGBlock` that contains them. Some `Stmt`s may be
100 /// contained in more than one `CFGBlock`; in this case, they are mapped to the
101 /// innermost block (i.e. the one that is furthest from the root of the tree).
102 class StmtToBlockMap {
103 public:
104 /// Initializes the map for the given `CFG`.
105 StmtToBlockMap(const CFG *TheCFG, ASTContext *TheContext);
107 /// Returns the block that \p S is contained in. Some `Stmt`s may be contained
108 /// in more than one `CFGBlock`; in this case, this function returns the
109 /// innermost block (i.e. the one that is furthest from the root of the tree).
110 const CFGBlock *blockContainingStmt(const Stmt *S) const;
112 private:
113 ASTContext *Context;
115 llvm::DenseMap<const Stmt *, const CFGBlock *> Map;
118 } // namespace clang::tidy::utils
120 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_EXPRSEQUENCE_H