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Re: Why does __float80 depend on -mmmx/-msse?

Andrew Pinski <> writes:

> On Jun 26, 2006, at 2:09 PM, Ian Lance Taylor wrote:
> > As far as I can see, it doesn't.
> You missed:
>    if (TARGET_MMX)
>      ix86_init_mmx_sse_builtins ();
> Which HJL should have also quoted.

I didn't miss it, I was just ambiguous.  H.J. asked "Why does
__float80 have to depend on -mmmx/-msse?" and I answered "it doesn't,"
meaning that __float80 doesn't have to depend on -mmmx/-msse.

> > On the other hand, as far as I can
> > see, __float80 is undocumented and unused for the i386.  Why does it
> > exist?
> Jan added it with __float128 also:
> 2003-10-30  Jan Hubicka  <>
>          (ix86_init_mmx_sse_builtins): Add __float80, __float128.
> I think it was added for x86_64 ABI support which defines them

Are you saying that the x86_64 ABI calls for __float80 to be defined?
I can't find any reference to __float80 which is not related to gcc or

In any case that does not give any explanation for why it should only
be defined for MMX or SSE.

I don't object to defining __float80 for i386.  I agree with H.J. that
if we define it, we should define it unconditionally.  And I also say
that if we define it, we should document it, or at least find some
other document which mentions it.


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