Re: [Xen-devel] [PATCH 19/34] xen/arm: Provide eabi wrapper for __aeabi_mem* functions

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 03/26/2014 03:38 PM, Julien Grall wrote:
> On 03/26/2014 10:39 AM, Ian Campbell wrote:
>> On Tue, 2014-03-25 at 18:12 +0000, Julien Grall wrote:
>>> Hi Ian,
>>>
>>> On 03/25/2014 05:25 PM, Ian Campbell wrote:
>>>> On Tue, 2014-03-25 at 16:55 +0000, Julien Grall wrote:
>>>>> Clang doesn't provide function __aebai_mem*, implement generically as a 
>>>>> wrapper
>>>>> for mem* function provided by Xen.
>>>>
>>>> Where are the references to these functions coming from if not from the
>>>> compiler?
>>>
>>> Theses functions are called by the code generated by the compiler.
>>
>> And who normally provides them when building with clang? Some sort of
>> libclang I guess?
> 
> I've tried to compile a same compilation unit with gcc and clang. gcc is
> inlining the call to __aebi_*. See below:

I've just noticed it also calls memset/memcpy directly without the
prefix __aebi_.

> Clang assembly:
> 000002b8 <wallclock_time>:
>  2b8:   e92d4800        push    {fp, lr}
>  2bc:   e1a0b00d        mov     fp, sp
>  2c0:   e3a01024        mov     r1, #36 ; 0x24
>  2c4:   e3a02000        mov     r2, #0
>  2c8:   ebfffffe        bl      0 <__aeabi_memset>
>  2cc:   e8bd8800        pop     {fp, pc}
> 
> GCC assembly:
> 
> 00000378 <wallclock_time>:
>  378:   e52db004        push    {fp}            ; (str fp, [sp, #-4]!)
>  37c:   e28db000        add     fp, sp, #0
>  380:   e3a02000        mov     r2, #0
>  384:   e1a03000        mov     r3, r0
>  388:   e4832004        str     r2, [r3], #4
>  38c:   e5802004        str     r2, [r0, #4]
>  390:   e2833004        add     r3, r3, #4
>  394:   e4832004        str     r2, [r3], #4
>  398:   e4832004        str     r2, [r3], #4
>  39c:   e4832004        str     r2, [r3], #4
>  3a0:   e4832004        str     r2, [r3], #4
>  3a4:   e4832004        str     r2, [r3], #4
>  3a8:   e4832004        str     r2, [r3], #4
>  3ac:   e5832000        str     r2, [r3]
>  3b0:   e24bd000        sub     sp, fp, #0
>  3b4:   e49db004        pop     {fp}            ; (ldr fp, [sp], #4)
>  3b8:   e12fff1e        bx      lr
> 
> Regards,
> 


-- 
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel