donat.nagy marked 2 inline comments as done. donat.nagy added inline comments.
================ Comment at: lib/StaticAnalyzer/Checkers/ConversionChecker.cpp:164 + // double and possibly long double on some systems + RepresentsUntilExp = 53; break; + case 32: ---------------- donat.nagy wrote: > xazax.hun wrote: > > A link to the source of these number would be useful. How are these > > calculated. Also, as far as I know the current C++ standard does not > > require anything about how floating points are represented in an > > implementation. So it would be great to somehow refer to the representation > > used by clang rather than hardcoding these values. (Note that I am > > perfectly fine with warning for implementation defined behavior as the > > original version also warn for such in case of integers.) > I took these magic numbers from the IEEE 754 standard; I completely agree > that their introduction is far from being elegant. > > Unfortunately it seems that referring to the representation used by clang > seems to be somewhat difficult, see e.g. this old [[ > https://stackoverflow.com/questions/13780931/how-do-i-get-llvm-types-from-clang > | stackoverflow answer ]]. In the Z3 solver a similar problem was solved by > defining a static function ([[ > https://clang.llvm.org/doxygen/Z3ConstraintManager_8cpp_source.html#l00269 | > getFloatSemantics() ]]) which uses a switch to translate the bit width of a > floating point type into an llvm::fltSemantics value (which contains the > precision value as a field). > > I could imagine three solutions: > > - reimplementing the logic getFloatSemantics, > - moving getFloatSemantics to some utility library and using it from there, > - keeping the current code, with comments describing my assumptions and > referencing the IEEE standard. > > Which of these is the best? > > Note: According to the documentation [[ > https://releases.llvm.org/2.5/docs/LangRef.html#t_floating | the floating > point types ]] supported by the LLVM IR are just float, double and some high > precision extension types (which are handled by the `default:` branch of my > code). Unfortunately, I do not know what happens to the [[ > https://clang.llvm.org/docs/LanguageExtensions.html#half-precision-floating-point > | `_Float16` ]] half-width float type. I updated the patch with a comment describing my assumptions, but I will implement a different solution if that would be better. Repository: rC Clang https://reviews.llvm.org/D52730 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
