1 //===--- IncorrectRoundingsCheck.cpp - 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 //===----------------------------------------------------------------------===//
8
9 #include "IncorrectRoundingsCheck.h"
10 #include "clang/AST/DeclBase.h"
11 #include "clang/AST/Type.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 #include "clang/ASTMatchers/ASTMatchers.h"
14 #include "clang/Lex/Lexer.h"
15
16 using namespace clang::ast_matchers;
17
18 namespace clang::tidy::bugprone {
19
getHalf(const llvm::fltSemantics & Semantics)20 static llvm::APFloat getHalf(const llvm::fltSemantics &Semantics) {
21 return llvm::APFloat(Semantics, 1U) / llvm::APFloat(Semantics, 2U);
22 }
23
24 namespace {
AST_MATCHER(FloatingLiteral,floatHalf)25 AST_MATCHER(FloatingLiteral, floatHalf) {
26 return Node.getValue() == getHalf(Node.getSemantics());
27 }
28 } // namespace
29
registerMatchers(MatchFinder * MatchFinder)30 void IncorrectRoundingsCheck::registerMatchers(MatchFinder *MatchFinder) {
31 // Match a floating literal with value 0.5.
32 auto FloatHalf = floatLiteral(floatHalf());
33
34 // Match a floating point expression.
35 auto FloatType = expr(hasType(realFloatingPointType()));
36
37 // Find expressions of cast to int of the sum of a floating point expression
38 // and 0.5.
39 MatchFinder->addMatcher(
40 traverse(TK_AsIs,
41 implicitCastExpr(
42 hasImplicitDestinationType(isInteger()),
43 ignoringParenCasts(binaryOperator(
44 hasOperatorName("+"), hasOperands(FloatType, FloatType),
45 hasEitherOperand(ignoringParenImpCasts(FloatHalf)))))
46 .bind("CastExpr")),
47 this);
48 }
49
check(const MatchFinder::MatchResult & Result)50 void IncorrectRoundingsCheck::check(const MatchFinder::MatchResult &Result) {
51 const auto *CastExpr = Result.Nodes.getNodeAs<ImplicitCastExpr>("CastExpr");
52 diag(CastExpr->getBeginLoc(),
53 "casting (double + 0.5) to integer leads to incorrect rounding; "
54 "consider using lround (#include <cmath>) instead");
55 }
56
57 } // namespace clang::tidy::bugprone
58