llvm-project

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//===--- IncorrectRoundingsCheck.cpp - clang-tidy ------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "IncorrectRoundingsCheck.h"
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#include "clang/AST/DeclBase.h"
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#include "clang/AST/Type.h"
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#include "clang/ASTMatchers/ASTMatchFinder.h"
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#include "clang/ASTMatchers/ASTMatchers.h"
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#include "clang/Lex/Lexer.h"
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using namespace clang::ast_matchers;
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namespace clang::tidy::bugprone {
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static llvm::APFloat getHalf(const llvm::fltSemantics &Semantics) {
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  return llvm::APFloat(Semantics, 1U) / llvm::APFloat(Semantics, 2U);
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}
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namespace {
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AST_MATCHER(FloatingLiteral, floatHalf) {
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  return Node.getValue() == getHalf(Node.getSemantics());
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}
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} // namespace
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void IncorrectRoundingsCheck::registerMatchers(MatchFinder *MatchFinder) {
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  // Match a floating literal with value 0.5.
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  auto FloatHalf = floatLiteral(floatHalf());
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  // Match a floating point expression.
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  auto FloatType = expr(hasType(realFloatingPointType()));
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  // Find expressions of cast to int of the sum of a floating point expression
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  // and 0.5.
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  MatchFinder->addMatcher(
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      traverse(TK_AsIs,
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               implicitCastExpr(
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                   hasImplicitDestinationType(isInteger()),
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                   ignoringParenCasts(binaryOperator(
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                       hasOperatorName("+"), hasOperands(FloatType, FloatType),
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                       hasEitherOperand(ignoringParenImpCasts(FloatHalf)))))
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                   .bind("CastExpr")),
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      this);
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}
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void IncorrectRoundingsCheck::check(const MatchFinder::MatchResult &Result) {
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  const auto *CastExpr = Result.Nodes.getNodeAs<ImplicitCastExpr>("CastExpr");
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  diag(CastExpr->getBeginLoc(),
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       "casting (double + 0.5) to integer leads to incorrect rounding; "
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       "consider using lround (#include <cmath>) instead");
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}
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} // namespace clang::tidy::bugprone
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