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

[Xi Ruoyao <xry111@mengyan1223.wang>]

Resend the mail.  I had to fill in a form to send mail to Robert.

On 2021-02-12 22:17 +0800, 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?

-- 
Xi Ruoyao <xry111@mengyan1223.wang>
School of Aerospace Science and Technology, Xidian University