Re: PING: [PATCH] PR target/67215: -fno-plt needs improvements for x86

["H.J. Lu" <hjl.tools@gmail.com>]

On Tue, Oct 27, 2015 at 5:52 AM, Jiong Wang <jiong.wang@foss.arm.com> wrote:
>
>
> On 27/10/15 11:37, H.J. Lu wrote:
>>
>> On Tue, Oct 27, 2015 at 4:20 AM, Bernd Schmidt <bschmidt@redhat.com>
>> wrote:
>>>
>>> On 10/19/2015 09:55 PM, H.J. Lu wrote:
>>>>
>>>>           * calls.c (prepare_call_address): Don't handle -fno-plt here.
>>>
>>>
>>> Is any other target using -fno-plt? If not, and if that's really just a
>>
>> aarch64 is the only target which checks -fno-plt from commit log below.
>> I CCed the code author.  aarch64 may suffer from the same issue.
>
>
> H.J,
>
>   Thanks for the info.
>
>   After a quick reading of the PR at
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67215,
>   I found the problem description is very x86 specific, I still don't
> understand what's
>   wrong if we do the following transformation when -fno-plt specified on
> x86-74, thus I
>   am not sure whether there is problem exist on aarch64. Can you please give
> more explanation?
>
>   call    proc2@PLT
>
>   ||
>   V
>
>   movq    proc2@GOTPCREL(%rip), %rax
>   call    *%rax

call *proc2@GOTPCREL(%rip)

doesn't use a register and saves one instruction.

-- 
H.J.