1 //===--- UseStdNumbersCheck.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 "UseStdNumbersCheck.h"
10 #include "../ClangTidyDiagnosticConsumer.h"
11 #include "clang/AST/ASTContext.h"
12 #include "clang/AST/Decl.h"
13 #include "clang/AST/Expr.h"
14 #include "clang/AST/Stmt.h"
15 #include "clang/AST/Type.h"
16 #include "clang/ASTMatchers/ASTMatchFinder.h"
17 #include "clang/ASTMatchers/ASTMatchers.h"
18 #include "clang/ASTMatchers/ASTMatchersInternal.h"
19 #include "clang/ASTMatchers/ASTMatchersMacros.h"
20 #include "clang/Basic/Diagnostic.h"
21 #include "clang/Basic/LLVM.h"
22 #include "clang/Basic/LangOptions.h"
23 #include "clang/Basic/SourceLocation.h"
24 #include "clang/Basic/SourceManager.h"
25 #include "clang/Lex/Lexer.h"
26 #include "llvm/ADT/STLExtras.h"
27 #include "llvm/ADT/SmallVector.h"
28 #include "llvm/ADT/StringRef.h"
29 #include "llvm/Support/FormatVariadic.h"
30 #include "llvm/Support/MathExtras.h"
31 #include <array>
32 #include <cmath>
33 #include <cstdint>
34 #include <cstdlib>
35 #include <initializer_list>
36 #include <string>
37 #include <tuple>
38 #include <utility>
39
40 namespace {
41 using namespace clang::ast_matchers;
42 using clang::ast_matchers::internal::Matcher;
43 using llvm::StringRef;
44
AST_MATCHER_P2(clang::FloatingLiteral,near,double,Value,double,DiffThreshold)45 AST_MATCHER_P2(clang::FloatingLiteral, near, double, Value, double,
46 DiffThreshold) {
47 return std::abs(Node.getValueAsApproximateDouble() - Value) < DiffThreshold;
48 }
49
AST_MATCHER_P(clang::QualType,hasCanonicalTypeUnqualified,Matcher<clang::QualType>,InnerMatcher)50 AST_MATCHER_P(clang::QualType, hasCanonicalTypeUnqualified,
51 Matcher<clang::QualType>, InnerMatcher) {
52 return !Node.isNull() &&
53 InnerMatcher.matches(Node->getCanonicalTypeUnqualified(), Finder,
54 Builder);
55 }
56
AST_MATCHER(clang::QualType,isArithmetic)57 AST_MATCHER(clang::QualType, isArithmetic) {
58 return !Node.isNull() && Node->isArithmeticType();
59 }
AST_MATCHER(clang::QualType,isFloating)60 AST_MATCHER(clang::QualType, isFloating) {
61 return !Node.isNull() && Node->isFloatingType();
62 }
63
AST_MATCHER_P(clang::Expr,anyOfExhaustive,std::vector<Matcher<clang::Stmt>>,Exprs)64 AST_MATCHER_P(clang::Expr, anyOfExhaustive, std::vector<Matcher<clang::Stmt>>,
65 Exprs) {
66 bool FoundMatch = false;
67 for (const auto &InnerMatcher : Exprs) {
68 clang::ast_matchers::internal::BoundNodesTreeBuilder Result = *Builder;
69 if (InnerMatcher.matches(Node, Finder, &Result)) {
70 *Builder = std::move(Result);
71 FoundMatch = true;
72 }
73 }
74 return FoundMatch;
75 }
76
77 // Using this struct to store the 'DiffThreshold' config value to create the
78 // matchers without the need to pass 'DiffThreshold' into every matcher.
79 // 'DiffThreshold' is needed in the 'near' matcher, which is used for matching
80 // the literal of every constant and for formulas' subexpressions that look at
81 // literals.
82 struct MatchBuilder {
83 auto
ignoreParenAndArithmeticCasting__anon60bcb47f0111::MatchBuilder84 ignoreParenAndArithmeticCasting(const Matcher<clang::Expr> Matcher) const {
85 return expr(hasType(qualType(isArithmetic())), ignoringParenCasts(Matcher));
86 }
87
ignoreParenAndFloatingCasting__anon60bcb47f0111::MatchBuilder88 auto ignoreParenAndFloatingCasting(const Matcher<clang::Expr> Matcher) const {
89 return expr(hasType(qualType(isFloating())), ignoringParenCasts(Matcher));
90 }
91
matchMathCall__anon60bcb47f0111::MatchBuilder92 auto matchMathCall(const StringRef FunctionName,
93 const Matcher<clang::Expr> ArgumentMatcher) const {
94 return expr(ignoreParenAndFloatingCasting(
95 callExpr(callee(functionDecl(hasName(FunctionName),
96 hasParameter(0, hasType(isArithmetic())))),
97 hasArgument(0, ArgumentMatcher))));
98 }
99
matchSqrt__anon60bcb47f0111::MatchBuilder100 auto matchSqrt(const Matcher<clang::Expr> ArgumentMatcher) const {
101 return matchMathCall("sqrt", ArgumentMatcher);
102 }
103
104 // Used for top-level matchers (i.e. the match that replaces Val with its
105 // constant).
106 //
107 // E.g. The matcher of `std::numbers::pi` uses this matcher to look for
108 // floatLiterals that have the value of pi.
109 //
110 // If the match is for a top-level match, we only care about the literal.
matchFloatLiteralNear__anon60bcb47f0111::MatchBuilder111 auto matchFloatLiteralNear(const StringRef Constant, const double Val) const {
112 return expr(ignoreParenAndFloatingCasting(
113 floatLiteral(near(Val, DiffThreshold)).bind(Constant)));
114 }
115
116 // Used for non-top-level matchers (i.e. matchers that are used as inner
117 // matchers for top-level matchers).
118 //
119 // E.g.: The matcher of `std::numbers::log2e` uses this matcher to check if
120 // `e` of `log2(e)` is declared constant and initialized with the value for
121 // eulers number.
122 //
123 // Here, we do care about literals and about DeclRefExprs to variable
124 // declarations that are constant and initialized with `Val`. This allows
125 // top-level matchers to see through declared constants for their inner
126 // matches like the `std::numbers::log2e` matcher.
matchFloatValueNear__anon60bcb47f0111::MatchBuilder127 auto matchFloatValueNear(const double Val) const {
128 const auto Float = floatLiteral(near(Val, DiffThreshold));
129
130 const auto Dref = declRefExpr(
131 to(varDecl(hasType(qualType(isConstQualified(), isFloating())),
132 hasInitializer(ignoreParenAndFloatingCasting(Float)))));
133 return expr(ignoreParenAndFloatingCasting(anyOf(Float, Dref)));
134 }
135
matchValue__anon60bcb47f0111::MatchBuilder136 auto matchValue(const int64_t ValInt) const {
137 const auto Int =
138 expr(ignoreParenAndArithmeticCasting(integerLiteral(equals(ValInt))));
139 const auto Float = expr(ignoreParenAndFloatingCasting(
140 matchFloatValueNear(static_cast<double>(ValInt))));
141 const auto Dref = declRefExpr(to(varDecl(
142 hasType(qualType(isConstQualified(), isArithmetic())),
143 hasInitializer(expr(anyOf(ignoringImplicit(Int),
144 ignoreParenAndFloatingCasting(Float)))))));
145 return expr(anyOf(Int, Float, Dref));
146 }
147
match1Div__anon60bcb47f0111::MatchBuilder148 auto match1Div(const Matcher<clang::Expr> Match) const {
149 return binaryOperator(hasOperatorName("/"), hasLHS(matchValue(1)),
150 hasRHS(Match));
151 }
152
matchEuler__anon60bcb47f0111::MatchBuilder153 auto matchEuler() const {
154 return expr(anyOf(matchFloatValueNear(llvm::numbers::e),
155 matchMathCall("exp", matchValue(1))));
156 }
matchEulerTopLevel__anon60bcb47f0111::MatchBuilder157 auto matchEulerTopLevel() const {
158 return expr(anyOf(matchFloatLiteralNear("e_literal", llvm::numbers::e),
159 matchMathCall("exp", matchValue(1)).bind("e_pattern")))
160 .bind("e");
161 }
162
matchLog2Euler__anon60bcb47f0111::MatchBuilder163 auto matchLog2Euler() const {
164 return expr(
165 anyOf(
166 matchFloatLiteralNear("log2e_literal", llvm::numbers::log2e),
167 matchMathCall("log2", matchEuler()).bind("log2e_pattern")))
168 .bind("log2e");
169 }
170
matchLog10Euler__anon60bcb47f0111::MatchBuilder171 auto matchLog10Euler() const {
172 return expr(
173 anyOf(
174 matchFloatLiteralNear("log10e_literal",
175 llvm::numbers::log10e),
176 matchMathCall("log10", matchEuler()).bind("log10e_pattern")))
177 .bind("log10e");
178 }
179
matchPi__anon60bcb47f0111::MatchBuilder180 auto matchPi() const { return matchFloatValueNear(llvm::numbers::pi); }
matchPiTopLevel__anon60bcb47f0111::MatchBuilder181 auto matchPiTopLevel() const {
182 return matchFloatLiteralNear("pi_literal", llvm::numbers::pi).bind("pi");
183 }
184
matchEgamma__anon60bcb47f0111::MatchBuilder185 auto matchEgamma() const {
186 return matchFloatLiteralNear("egamma_literal", llvm::numbers::egamma)
187 .bind("egamma");
188 }
189
matchInvPi__anon60bcb47f0111::MatchBuilder190 auto matchInvPi() const {
191 return expr(anyOf(matchFloatLiteralNear("inv_pi_literal",
192 llvm::numbers::inv_pi),
193 match1Div(matchPi()).bind("inv_pi_pattern")))
194 .bind("inv_pi");
195 }
196
matchInvSqrtPi__anon60bcb47f0111::MatchBuilder197 auto matchInvSqrtPi() const {
198 return expr(anyOf(
199 matchFloatLiteralNear("inv_sqrtpi_literal",
200 llvm::numbers::inv_sqrtpi),
201 match1Div(matchSqrt(matchPi())).bind("inv_sqrtpi_pattern")))
202 .bind("inv_sqrtpi");
203 }
204
matchLn2__anon60bcb47f0111::MatchBuilder205 auto matchLn2() const {
206 return expr(anyOf(matchFloatLiteralNear("ln2_literal", llvm::numbers::ln2),
207 matchMathCall("log", matchValue(2)).bind("ln2_pattern")))
208 .bind("ln2");
209 }
210
machterLn10__anon60bcb47f0111::MatchBuilder211 auto machterLn10() const {
212 return expr(
213 anyOf(matchFloatLiteralNear("ln10_literal", llvm::numbers::ln10),
214 matchMathCall("log", matchValue(10)).bind("ln10_pattern")))
215 .bind("ln10");
216 }
217
matchSqrt2__anon60bcb47f0111::MatchBuilder218 auto matchSqrt2() const {
219 return expr(anyOf(matchFloatLiteralNear("sqrt2_literal",
220 llvm::numbers::sqrt2),
221 matchSqrt(matchValue(2)).bind("sqrt2_pattern")))
222 .bind("sqrt2");
223 }
224
matchSqrt3__anon60bcb47f0111::MatchBuilder225 auto matchSqrt3() const {
226 return expr(anyOf(matchFloatLiteralNear("sqrt3_literal",
227 llvm::numbers::sqrt3),
228 matchSqrt(matchValue(3)).bind("sqrt3_pattern")))
229 .bind("sqrt3");
230 }
231
matchInvSqrt3__anon60bcb47f0111::MatchBuilder232 auto matchInvSqrt3() const {
233 return expr(anyOf(matchFloatLiteralNear("inv_sqrt3_literal",
234 llvm::numbers::inv_sqrt3),
235 match1Div(matchSqrt(matchValue(3)))
236 .bind("inv_sqrt3_pattern")))
237 .bind("inv_sqrt3");
238 }
239
matchPhi__anon60bcb47f0111::MatchBuilder240 auto matchPhi() const {
241 const auto PhiFormula = binaryOperator(
242 hasOperatorName("/"),
243 hasLHS(binaryOperator(
244 hasOperatorName("+"), hasEitherOperand(matchValue(1)),
245 hasEitherOperand(matchMathCall("sqrt", matchValue(5))))),
246 hasRHS(matchValue(2)));
247 return expr(anyOf(PhiFormula.bind("phi_pattern"),
248 matchFloatLiteralNear("phi_literal", llvm::numbers::phi)))
249 .bind("phi");
250 }
251
252 double DiffThreshold;
253 };
254
getCode(const StringRef Constant,const bool IsFloat,const bool IsLongDouble)255 std::string getCode(const StringRef Constant, const bool IsFloat,
256 const bool IsLongDouble) {
257 if (IsFloat) {
258 return ("std::numbers::" + Constant + "_v<float>").str();
259 }
260 if (IsLongDouble) {
261 return ("std::numbers::" + Constant + "_v<long double>").str();
262 }
263 return ("std::numbers::" + Constant).str();
264 }
265
isRangeOfCompleteMacro(const clang::SourceRange & Range,const clang::SourceManager & SM,const clang::LangOptions & LO)266 bool isRangeOfCompleteMacro(const clang::SourceRange &Range,
267 const clang::SourceManager &SM,
268 const clang::LangOptions &LO) {
269 if (!Range.getBegin().isMacroID()) {
270 return false;
271 }
272 if (!clang::Lexer::isAtStartOfMacroExpansion(Range.getBegin(), SM, LO)) {
273 return false;
274 }
275
276 if (!Range.getEnd().isMacroID()) {
277 return false;
278 }
279
280 if (!clang::Lexer::isAtEndOfMacroExpansion(Range.getEnd(), SM, LO)) {
281 return false;
282 }
283
284 return true;
285 }
286
287 } // namespace
288
289 namespace clang::tidy::modernize {
UseStdNumbersCheck(const StringRef Name,ClangTidyContext * const Context)290 UseStdNumbersCheck::UseStdNumbersCheck(const StringRef Name,
291 ClangTidyContext *const Context)
292 : ClangTidyCheck(Name, Context),
293 IncludeInserter(Options.getLocalOrGlobal("IncludeStyle",
294 utils::IncludeSorter::IS_LLVM),
295 areDiagsSelfContained()),
296 DiffThresholdString{Options.get("DiffThreshold", "0.001")} {
297 if (DiffThresholdString.getAsDouble(DiffThreshold)) {
298 configurationDiag(
299 "Invalid DiffThreshold config value: '%0', expected a double")
300 << DiffThresholdString;
301 DiffThreshold = 0.001;
302 }
303 }
304
registerMatchers(MatchFinder * const Finder)305 void UseStdNumbersCheck::registerMatchers(MatchFinder *const Finder) {
306 const auto Matches = MatchBuilder{DiffThreshold};
307 std::vector<Matcher<clang::Stmt>> ConstantMatchers = {
308 Matches.matchLog2Euler(), Matches.matchLog10Euler(),
309 Matches.matchEulerTopLevel(), Matches.matchEgamma(),
310 Matches.matchInvSqrtPi(), Matches.matchInvPi(),
311 Matches.matchPiTopLevel(), Matches.matchLn2(),
312 Matches.machterLn10(), Matches.matchSqrt2(),
313 Matches.matchInvSqrt3(), Matches.matchSqrt3(),
314 Matches.matchPhi(),
315 };
316
317 Finder->addMatcher(
318 expr(
319 anyOfExhaustive(std::move(ConstantMatchers)),
320 unless(hasParent(explicitCastExpr(hasDestinationType(isFloating())))),
321 hasType(qualType(hasCanonicalTypeUnqualified(
322 anyOf(qualType(asString("float")).bind("float"),
323 qualType(asString("double")),
324 qualType(asString("long double")).bind("long double")))))),
325 this);
326 }
327
check(const MatchFinder::MatchResult & Result)328 void UseStdNumbersCheck::check(const MatchFinder::MatchResult &Result) {
329 /*
330 List of all math constants in the `<numbers>` header
331 + e
332 + log2e
333 + log10e
334 + pi
335 + inv_pi
336 + inv_sqrtpi
337 + ln2
338 + ln10
339 + sqrt2
340 + sqrt3
341 + inv_sqrt3
342 + egamma
343 + phi
344 */
345
346 // The ordering determines what constants are looked at first.
347 // E.g. look at 'inv_sqrt3' before 'sqrt3' to be able to replace the larger
348 // expression
349 constexpr auto Constants = std::array<std::pair<StringRef, double>, 13>{
350 std::pair{StringRef{"log2e"}, llvm::numbers::log2e},
351 std::pair{StringRef{"log10e"}, llvm::numbers::log10e},
352 std::pair{StringRef{"e"}, llvm::numbers::e},
353 std::pair{StringRef{"egamma"}, llvm::numbers::egamma},
354 std::pair{StringRef{"inv_sqrtpi"}, llvm::numbers::inv_sqrtpi},
355 std::pair{StringRef{"inv_pi"}, llvm::numbers::inv_pi},
356 std::pair{StringRef{"pi"}, llvm::numbers::pi},
357 std::pair{StringRef{"ln2"}, llvm::numbers::ln2},
358 std::pair{StringRef{"ln10"}, llvm::numbers::ln10},
359 std::pair{StringRef{"sqrt2"}, llvm::numbers::sqrt2},
360 std::pair{StringRef{"inv_sqrt3"}, llvm::numbers::inv_sqrt3},
361 std::pair{StringRef{"sqrt3"}, llvm::numbers::sqrt3},
362 std::pair{StringRef{"phi"}, llvm::numbers::phi},
363 };
364
365 auto MatchedLiterals =
366 llvm::SmallVector<std::tuple<std::string, double, const Expr *>>{};
367
368 const auto &SM = *Result.SourceManager;
369 const auto &LO = Result.Context->getLangOpts();
370
371 const auto IsFloat = Result.Nodes.getNodeAs<QualType>("float") != nullptr;
372 const auto IsLongDouble =
373 Result.Nodes.getNodeAs<QualType>("long double") != nullptr;
374
375 for (const auto &[ConstantName, ConstantValue] : Constants) {
376 const auto *const Match = Result.Nodes.getNodeAs<Expr>(ConstantName);
377 if (Match == nullptr) {
378 continue;
379 }
380
381 const auto Range = Match->getSourceRange();
382
383 const auto IsMacro = Range.getBegin().isMacroID();
384
385 // We do not want to emit a diagnostic when we are matching a macro, but the
386 // match inside of the macro does not cover the whole macro.
387 if (IsMacro && !isRangeOfCompleteMacro(Range, SM, LO)) {
388 continue;
389 }
390
391 if (const auto PatternBindString = (ConstantName + "_pattern").str();
392 Result.Nodes.getNodeAs<Expr>(PatternBindString) != nullptr) {
393 const auto Code = getCode(ConstantName, IsFloat, IsLongDouble);
394 diag(Range.getBegin(), "prefer '%0' to this %select{formula|macro}1")
395 << Code << IsMacro << FixItHint::CreateReplacement(Range, Code);
396 return;
397 }
398
399 const auto LiteralBindString = (ConstantName + "_literal").str();
400 if (const auto *const Literal =
401 Result.Nodes.getNodeAs<FloatingLiteral>(LiteralBindString)) {
402 MatchedLiterals.emplace_back(
403 ConstantName,
404 std::abs(Literal->getValueAsApproximateDouble() - ConstantValue),
405 Match);
406 }
407 }
408
409 // We may have had no matches with literals, but a match with a pattern that
410 // was a part of a macro which was therefore skipped.
411 if (MatchedLiterals.empty()) {
412 return;
413 }
414
415 llvm::sort(MatchedLiterals, [](const auto &LHS, const auto &RHS) {
416 return std::get<1>(LHS) < std::get<1>(RHS);
417 });
418
419 const auto &[Constant, Diff, Node] = MatchedLiterals.front();
420
421 const auto Range = Node->getSourceRange();
422 const auto IsMacro = Range.getBegin().isMacroID();
423
424 // We do not want to emit a diagnostic when we are matching a macro, but the
425 // match inside of the macro does not cover the whole macro.
426 if (IsMacro && !isRangeOfCompleteMacro(Range, SM, LO)) {
427 return;
428 }
429
430 const auto Code = getCode(Constant, IsFloat, IsLongDouble);
431 diag(Range.getBegin(),
432 "prefer '%0' to this %select{literal|macro}1, differs by '%2'")
433 << Code << IsMacro << llvm::formatv("{0:e2}", Diff).str()
434 << FixItHint::CreateReplacement(Range, Code)
435 << IncludeInserter.createIncludeInsertion(
436 Result.SourceManager->getFileID(Range.getBegin()), "<numbers>");
437 }
438
registerPPCallbacks(const SourceManager & SM,Preprocessor * const PP,Preprocessor * const ModuleExpanderPP)439 void UseStdNumbersCheck::registerPPCallbacks(
440 const SourceManager &SM, Preprocessor *const PP,
441 Preprocessor *const ModuleExpanderPP) {
442 IncludeInserter.registerPreprocessor(PP);
443 }
444
storeOptions(ClangTidyOptions::OptionMap & Opts)445 void UseStdNumbersCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
446 Options.store(Opts, "IncludeStyle", IncludeInserter.getStyle());
447 Options.store(Opts, "DiffThreshold", DiffThresholdString);
448 }
449 } // namespace clang::tidy::modernize
450