Re: [PATCH] MIPS: Fix PR target/98491 (ChangeLog)

[Jeff Law <law@redhat.com>]

On 2/12/21 7:17 AM, Xi Ruoyao wrote:
> On 2021-01-11 01:01 +0800, Xi Ruoyao wrote:
>> Hi Jeff and Jakub,
>>
>> On 2021-01-04 14:19 -0700, Jeff Law wrote:
>>> On 1/4/21 2:00 PM, Jakub Jelinek wrote:
>>>> On Mon, Jan 04, 2021 at 01:51:59PM -0700, Jeff Law via Gcc-patches wrote:
>>>>>> Sorry, I forgot to include the ChangeLog:
>>>>>>
>>>>>>     gcc/ChangeLog:
>>>>>>     
>>>>>>     2020-12-31  Xi Ruoyao <xry111@mengyan1223.wang>
>>>>>>     
>>>>>>             PR target/98491
>>>>>>             * config/mips/mips.c (mips_symbol_insns): Do not use
>>>>>>               MSA_SUPPORTED_MODE_P if mode is MAX_MACHINE_MODE.
>>>>> So I absolutely agree the current code is wrong as it does an out of
>>>>> bounds array access.
>>>>>
>>>>>
>>>>> Would it be better to instead to change MSA_SUPPORTED_MODE_P to evaluate
>>>>> to zero if MODE is MAX_MACHINE_MODE?  That would protect all the uses of
>>>>> MSA_SUPPORTED_MODE_P.    Something like this perhaps?
>>>> But MAX_MACHINE_MODE is the one past last valid mode, I'm not aware of
>>>> any target that would protect all macros that deal with modes that way.
>>>>
>>>> So, perhaps best would be stop using the MAX_MACHINE_MODE as magic value
>>>> for that function and instead use say VOIDmode that shouldn't normally
>>>> appear either?
>>> I think we have to allow VOIDmode because constants don't necessarily
>>> have modes.   And I certainly agree that using MAX_MACHINE_MODE like
>>> this is ugly and error prone (as we can see from the BZ).
>>>
>>> I also couldn't convince myself that the code and comments were actually
>>> consistent, particularly for MSA targets which the comment claims can
>>> never handle constants for ld/st (and thus should be returning 0 for
>>> MAX_MACHINE_MODE).  Though maybe mips_symbol_insns_1 ultimately handles
>>> that correctly.
>>>
>>>
>>>> But I don't really see anything wrong on the mips_symbol_insns above
>>>> change either.
>>> Me neither.  I'm just questioning if bullet-proofing in the
>>> MSA_SUPPORTED_MODE_P would be a better option.  While I've worked in the
>>> MIPS port in the past, I don't really have any significannt experience
>>> with the MSA support.
>> I can't understand the comment either.  To me it looks like it's possible to
>> remove this "if (MSA_SUPPORTED_P (mode)) return 0;"
>>
>> CC Robert to get some help.
> Happy new lunar year folks.
>
> I found a newer email address of Robert.  Hope it is still being used.
>
> Could someone update MAINTAINERS file by the way?
If you have an updated email address, I can reach out to Robert and see
if he wants his entry updated or removed.

Thanks,
jeff