[libcxx-commits] [PATCH] D74163: [demangler] Fix the parsing of long double literals for PowerPC and S390

[Ulrich Weigand via Phabricator via libcxx-commits]

uweigand added a comment.

In D74163#1891378 <https://reviews.llvm.org/D74163#1891378>, @xingxue wrote:

> > I'm still wondering about Intel.  Can there ever be a literal encoded using 'g' on Intel?  If yes, then treating it as "long double" would still be wrong, because 'g' encodes IEEE128 (__float128), while "long double" is the Intel extended (80-bit) format, right?
> > 
> > On the other hand, if 'g' encoded literals can never happen on Intel (or other platforms), maybe it would be better to have the code handling 'g' within a #ifdef section only active on powerpc and s390?
>
> For X86, 'e' is used for 80-bit `long double` and 'g' is used for 128-bit `long double`.  The following is the code in Clang.
>
>   clang/lib/Basic/Targets/X86.h
>   ....
>   const char *getLongDoubleMangling() const override {
>     return LongDoubleFormat == &llvm::APFloat::IEEEquad() ? "g" : "e";
>   }
>   ...
>    


But then this patch must be incorrect, given that it does

  return getDerived().template parseFloatingLiteral<long double>();

for **both** the 'e' and 'g' cases on Intel.    Now I guess it depends on how the file is compiled (with -mlong-double-80 or -mlong-double-128), but either way, one of the cases will be handled incorrectly.


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https://reviews.llvm.org/D74163