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Re: [PING][AARCH64, Question] Does AARCH64 GCC support long calls?
- From: Andrew Pinski <pinskia at gmail dot com>
- To: "Yangfei (Felix)" <felix dot yang at huawei dot com>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, "marcus dot shawcroft at arm dot com" <marcus dot shawcroft at arm dot com>, "richard dot earnshaw at arm dot com" <richard dot earnshaw at arm dot com>, Suipengfei <suipengfei at huawei dot com>
- Date: Fri, 24 Oct 2014 23:34:29 -0700
- Subject: Re: [PING][AARCH64, Question] Does AARCH64 GCC support long calls?
- Authentication-results: sourceware.org; auth=none
- References: <DA41BE1DDCA941489001C7FBD7A8820E5554BF55 at szxema507-mbx dot china dot huawei dot com> <CA+=Sn1n8Bo2Q_ocMoiuuXJPm5NAjhQ=98D6WNUBaJ2eks_xGHg at mail dot gmail dot com> <DA41BE1DDCA941489001C7FBD7A8820E5554BF99 at szxema507-mbx dot china dot huawei dot com>
On Fri, Oct 24, 2014 at 11:28 PM, Yangfei (Felix) <firstname.lastname@example.org> wrote:
>> On Fri, Oct 24, 2014 at 8:35 PM, Yangfei (Felix) <email@example.com> wrote:
>> >> Hi,
>> >> I find that the -mlong-calls option is not there for AARCH64. So
>> >> can this port generate long calls?
>> >> Any plan on this option? I would like to have a try on this if it's missing :-)
>> >> Thanks.
>> > Any comments?
>> Yes you can use -mcmodel=large to this effect I think.
>> Andrew Pinski
> Thanks for the reply. It seems that -mcmodel=large is different from -mlong-calls.
> GCC still emit the BL instruction with -mcmodel=large. I thinks GCC should emit BLR instruction with -mlong-calls, right?
Oh right. Also it looks like it is not hooked up but the support is
/* Return true if calls to DECL should be treated as
long-calls (ie called via a register). */
aarch64_decl_is_long_call_p (const_tree decl ATTRIBUTE_UNUSED)
I had added the attribute in a version for this and the users of the
toolchain has not reported a bug about it so it seems like it is
I don't have time right now to add support for the option or port the
attribute to the latest version but it should be easy as returning
true from that function when the option is turned on.
> void test();
> int main()
> Assembly for this main with -mcmodel=large option:
> stp x29, x30, [sp, -16]!
> add x29, sp, 0
> bl test
> ldp x29, x30, [sp], 16