[clang-tidy] Avoid float compare in bugprone-incorrect-roundings

[PiotrZSL]

Summary

Using APFloat to compare floating numbers instead of float/double.

Fixes: 46424

[carlosgalvezp]

Looks good, small suggestions! I appreciate having this small patch prior to the next one fixing the actual issue.

clang-tools-extra/clang-tidy/bugprone/IncorrectRoundingsCheck.cpp

28

Remove static

28

I think you can just combine those lines into one to get rid of the variable.

return Literal == getHalf(llvm::APFloat::IEEEsingle());

[PiotrZSL]

D147908 fixes comments from this on, it's just split into 2 reviews, this as fixing issue, and other as introducing improvment.

clang-tools-extra/clang-tidy/bugprone/IncorrectRoundingsCheck.cpp

28

This get re-worked in D147908, that depend on this change.

28

This get reworked in D147908.

[PiotrZSL]

Fix review comments

clang-tools-extra/clang-tidy/bugprone/IncorrectRoundingsCheck.cpp

 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/ASTMatchers/ASTMatchers.h"
 #include "clang/Lex/Lexer.h"
 
 using namespace clang::ast_matchers;
 
 namespace clang::tidy::bugprone {
 
+static llvm::APFloat getHalf(const llvm::fltSemantics &Semantics) {
+  return llvm::APFloat(Semantics, 1U) / llvm::APFloat(Semantics, 2U);
+}
+
 namespace {
 AST_MATCHER(FloatingLiteral, floatHalf) {
   const auto &Literal = Node.getValue();
-  if ((&Node.getSemantics()) == &llvm::APFloat::IEEEsingle())
-    return Literal.convertToFloat() == 0.5f;
-  if ((&Node.getSemantics()) == &llvm::APFloat::IEEEdouble())
-    return Literal.convertToDouble() == 0.5;
+  if ((&Node.getSemantics()) == &llvm::APFloat::IEEEsingle()) {
+    static llvm::APFloat Half = getHalf(llvm::APFloat::IEEEsingle());
+    return Literal == Half;
+  }
+  if ((&Node.getSemantics()) == &llvm::APFloat::IEEEdouble()) {
+    static llvm::APFloat Half = getHalf(llvm::APFloat::IEEEdouble());
+    return Literal == Half;
+  }
   return false;
 }
 } // namespace
 
 void IncorrectRoundingsCheck::registerMatchers(MatchFinder *MatchFinder) {
   // Match a floating literal with value 0.5.
   auto FloatHalf = floatLiteral(floatHalf());