1 //===--- UnrollLoopsCheck.h - clang-tidy ------------------------*- C++ -*-===//
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 #ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ALTERA_UNROLLLOOPSCHECK_H
10 #define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ALTERA_UNROLLLOOPSCHECK_H
11 
12 #include "../ClangTidyCheck.h"
13 
14 namespace clang::tidy::altera {
15 
16 /// Finds inner loops that have not been unrolled, as well as fully unrolled
17 /// loops with unknown loop bounds or a large number of iterations.
18 ///
19 /// Unrolling inner loops could improve the performance of OpenCL kernels.
20 /// However, if they have unknown loop bounds or a large number of iterations,
21 /// they cannot be fully unrolled, and should be partially unrolled.
22 ///
23 /// For the user-facing documentation see:
24 /// http://clang.llvm.org/extra/clang-tidy/checks/altera/unroll-loops.html
25 class UnrollLoopsCheck : public ClangTidyCheck {
26 public:
27   UnrollLoopsCheck(StringRef Name, ClangTidyContext *Context);
28   void registerMatchers(ast_matchers::MatchFinder *Finder) override;
29   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
30 
31 private:
32   /// Recommend partial unrolling if number of loop iterations is greater than
33   /// MaxLoopIterations.
34   const unsigned MaxLoopIterations;
35   /// The kind of unrolling, if any, applied to a given loop.
36   enum UnrollType {
37     // This loop has no #pragma unroll directive associated with it.
38     NotUnrolled,
39     // This loop has a #pragma unroll directive associated with it.
40     FullyUnrolled,
41     // This loop has a #pragma unroll <num> directive associated with it.
42     PartiallyUnrolled
43   };
44   /// Attempts to extract an integer value from either side of the
45   /// BinaryOperator. Returns true and saves the result to &value if successful,
46   /// returns false otherwise.
47   bool extractValue(int &Value, const BinaryOperator *Op,
48                     const ASTContext *Context);
49   /// Returns true if the given loop statement has a large number of iterations,
50   /// as determined by the integer value in the loop's condition expression,
51   /// if one exists.
52   bool hasLargeNumIterations(const Stmt *Statement,
53                              const IntegerLiteral *CXXLoopBound,
54                              const ASTContext *Context);
55   /// Checks one hand side of the binary operator to ascertain if the upper
56   /// bound on the number of loops is greater than max_loop_iterations or not.
57   /// If the expression is not evaluatable or not an integer, returns false.
58   bool exprHasLargeNumIterations(const Expr *Expression,
59                                  const ASTContext *Context) const;
60   /// Returns the type of unrolling, if any, associated with the given
61   /// statement.
62   enum UnrollType unrollType(const Stmt *Statement, ASTContext *Context);
63   /// Returns the condition expression within a given for statement. If there is
64   /// none, or if the Statement is not a loop, then returns a NULL pointer.
65   const Expr *getCondExpr(const Stmt *Statement);
66   /// Returns True if the loop statement has known bounds.
67   bool hasKnownBounds(const Stmt *Statement, const IntegerLiteral *CXXLoopBound,
68                       const ASTContext *Context);
69   void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
70 };
71 
72 } // namespace clang::tidy::altera
73 
74 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ALTERA_UNROLLLOOPSCHECK_H
75