Re: [PATCH v2] rs6000: Rework option -mpowerpc64 handling [PR106680]

["Kewen.Lin" <linkw@linux.ibm.com>]

Hi Sebastian,

on 2024/2/5 18:38, Sebastian Huber wrote:
> Hello,
> 
> On 27.12.22 11:16, Kewen.Lin via Gcc-patches wrote:
>> Hi Segher,
>>
>> on 2022/12/24 04:26, Segher Boessenkool wrote:
>>> Hi!
>>>
>>> On Wed, Oct 12, 2022 at 04:12:21PM +0800, Kewen.Lin wrote:
>>>> PR106680 shows that -m32 -mpowerpc64 is different from
>>>> -mpowerpc64 -m32, this is determined by the way how we
>>>> handle option powerpc64 in rs6000_handle_option.
>>>>
>>>> Segher pointed out this difference should be taken as
>>>> a bug and we should ensure that option powerpc64 is
>>>> independent of -m32/-m64.  So this patch removes the
>>>> handlings in rs6000_handle_option and add some necessary
>>>> supports in rs6000_option_override_internal instead.
>>>
>>> Sorry for the late review.
>>>
>>>> +  /* Don't expect powerpc64 enabled on those OSes with OS_MISSING_POWERPC64,
>>>> +     since they don't support saving the high part of 64-bit registers on
>>>> +     context switch.  If the user explicitly specifies it, we won't interfere
>>>> +     with the user's specification.  */
>>>
>>> It depends on the OS, and what you call "context switch".  For example
>>> on Linux the context switches done by the kernel are fine, only things
>>> done by setjmp/longjmp and getcontext/setcontext are not.  So just be a
>>> bit more vague here?  "Since they do not save and restore the high half
>>> of the GPRs correctly in all cases", something like that?
>>>
>>> Okay for trunk like that.  Thanks!
>>>
>>
>> Thanks!  Adjusted as you suggested and committed in r13-4894-gacc727cf02a144.
> 
> I am a bit late, however, this broke the 32-bit support for -mcpu=e6500. For RTEMS, I have the following multilibs:
> 
> MULTILIB_REQUIRED += mcpu=e6500/m32
> MULTILIB_REQUIRED += mcpu=e6500/m32/mvrsave
> MULTILIB_REQUIRED += mcpu=e6500/m32/msoft-float/mno-altivec
> MULTILIB_REQUIRED += mcpu=e6500/m64
> MULTILIB_REQUIRED += mcpu=e6500/m64/mvrsave
> 
> I configured GCC as a bi-arch compiler (32-bit and 64-bit). It seems you removed the -m32 handling, so I am not sure how to approach this issue. I added a test case to the PR:
> 
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106680

Thanks for reporting, I'll have a look at it (but I'm starting to be on vacation, so there may be slow response).

I'm not sure what's happened in bugzilla recently, but I didn't receive any mail notifications on your comments
#c5 and #c6 (sorry for the late response), since PR106680 is in state resolved maybe it's good to file a new
one for further tracking. :)

BR,
Kewen