[LLVMdev] x86_fp80, f80, and -m96bit-long-double

[Jonas Maebe]

On 01 Nov 2010, at 18:37, Duncan Sands wrote:

> I think the "fact" that x86 long double is 16 byte aligned on x86-64 is
> hard-wired in.

Note that it's not just about alignment, but mainly about the reserved storage size.

> I'm not sure how hard this would be to control via a
> command line option (i.e. -m96bit-long-double).

Is there no different way to go about this? Our compiler currently supports the x87 long double type as
a) 10 bytes, for Turbo Pascal and Delphi-compatibility
b) 12 bytes, for non-Darwin ABI/C x86 compatibility
c) 16 bytes, for Darwin x86 ABI/C and x86_64 ABI/C compatibility

long doubles of type a) and c), or of type b) and c), can occur in the same compilation unit. A command line switch does not offer sufficient flexibility in this case.


Jonas