Calling convention for "Routines for floating point emulation"

Yichao Yu
Wed Sep 28 23:54:00 GMT 2016

On Wed, Sep 28, 2016 at 7:45 PM, Yichao Yu <> wrote:
> On Wed, Sep 28, 2016 at 7:39 PM, Joseph Myers <> wrote:
>> On Wed, 28 Sep 2016, Yichao Yu wrote:
>>> In particular, it seems that on all the platforms with a
>>> arm*-*-gnueabihf triple I've checked (alarm armv7h, alarm armv6h,
>>> debian armhf, fedora armv7hl) the __powidf2 function (and possibly
>>> many others) are compiled with the AAPCS VFP calling convention, which
>>> is also how it is used by gcc. However, LLVM dev (CC'd) claims that
>>> these routines are meant to be always using soft floating point
>>> calling convention even on platforms using hard floating point ABI.
>> The RTABI functions should use the base AAPCS calling conventions.  That
>> was something I dealt with when working on the implementation of the VFP
>> ABI variant <>.
>> Except where an external ABI defines things like that, the normal
>> expectation for libgcc functions is that they have the same ABI as for an
>> ordinary C function with the same prototype.  That is, since libgcc.texi
>> gives a prototype for __powidf2 without saying anything special about its
>> ABI, and since it is not a function defined in RTABI, it can be taken to
> I guess other ppl on the list probably know this but what's the list
> of function in RTABI?

Is it

> Thanks.
>> use the VFP ABI when compiling for that ABI.
>> --
>> Joseph S. Myers

More information about the Gcc mailing list