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Re: [PATCH] powerpc: fix PR 39254 in rs6000.c


Joern,

I successfully bootstrapped on AIX with the patch.  It also has been
bootstrapped on Linux for POWER.  The hidden LABEL_REFs are causing
more problems, so I agree that the patch should be committed and if
the historical problem for the original problem of deleted constant
pool variables reappears, we can solve it some other way.

Please commit the patch.

Thanks, David

On Wed, May 27, 2009 at 6:52 PM, Joern Rennecke<joernr@arc.com> wrote:
> On Wed, May 27, 2009 at 03:03:57PM -0400, David Edelsohn wrote:
>> ? ? ? * config/rs6000/rs6000.c (rs6000_emit_move): Don't emit a USE
>> ? ? ? for the symbol ref of a constant that is the source of a move.
>>
>> I doubt this patch is completely correct. ?The email and the Bugzilla
>> thread provide no justification for the change, other than it works.
>> I suspect the USE may be specific to the AIX ABI and may not longer be
>> necessary when section anchors is enabled. ?It still may be needed for
>> free-standing constants placed in the TOC.
>
> This is why ?I said I thought the patch should be tested on a power or
> powerpc AIX target.
>
> Could you perform such a bootstrap and/or regression test?
>
> Considering the age of the code, there is a possibility that it addressed
> a problem that no longer exists; but if it still exists, I think the
> USE belongs to an actual instruction that the USE semantically belongs to;
> I would first like to see the a case where the USE is needed to get a
> better idea of this.
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