[llvm-dev] Representing X86 long double in Debug Info

[Keno Fischer via llvm-dev]

I'd like to revive this thread again, because the same problematic has come
up again. Originally I solved this problem by asking llvm for the AllocSize
(i.e. the size including padding), which solves the fp80 case nicely, but
e.g. also gives 32 for {i8, i8, i8}. For now I think the only thing I can
do is make the verifier accept either size, but I would like to discuss
whether we can represent the difference in IR such that we can tighten the
check.

On Tue, Nov 3, 2015 at 9:16 AM, Jonas Maebe via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

>
> Adrian Prantl via llvm-dev wrote on Mon, 02 Nov 2015:
>
> Looking at the code in clang CGDebugInfo just passes through the width of
>> the type as it is described by the TypeInfo, which in turn is defined by
>> the Target. At the moment I do not understand why an x86_fp80 is reported
>> to be 128 bits wide.
>>
>
> The x86-64 and Darwin/i386 ABI define the size of the 80 bits extended
> type in memory as 16 bytes. In all other i386 ABIs, it's defined as 12
> bytes. Delphi and, for compatibility reasons, the Free Pascal Compiler use
> 10 bytes (although FPC also has a "cextended" type that follows the
> official ABI for the platform). In FPC we use a [10 x i8] for all memory
> representations of the non-ABI 80 bits extended type.
>
> So ideally, the bitsize of the type should be specifiable separately from
> the ABI/TypeInfo, as there may be multiple in the code.
>
>
> Jonas
>
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