[PATCH] Do not remove labels with LABEL_PRESERVE_P

Steven Bosscher stevenb.gcc@gmail.com
Tue Sep 23 16:02:00 GMT 2014


On Fri, Sep 19, 2014 at 10:03 PM, Jeff Law <law@redhat.com> wrote:
> On 09/19/14 13:36, Ilya Enkovich wrote:
>>
>> Hi,
>>
>> During my work on enabling pseudo PIC register I've found that cfg cleaunp
>> may remove lables with LABEL_PRESERVE_P set to 1.  In my case I generated
>> SET_RIP during expand pass and cfg cleanup removed label it used as an
>> operand.  Below is a patch that fixes it.  It is not actually required for
>> our latest PIC related patch but still seems to make sense.
>>
>> Bootstrapped and tested on linux-x86_64.
>>
>> Thanks,
>> Ilya
>> --
>> 2014-09-19  Ilya Enkovich  <ilya.enkovich@intel.com>
>>
>>         * cfgcleanup.c (try_optimize_cfg): Do not remove label
>>         with LABEL_PRESERVE_P flag set.
>
> OK.  Please install.
>
> Note for those not following the x86 32 bit PIC register discussion, I asked
> Ilya to submit this separately.  It was something an earlier version of his
> patch triggered and it stood out as something that ought to be fixed
> regardless of the final form of the PIC register changes that are in
> progress.

Jeff,

Are you sure this patch is necessary, and is not just papering over
another problem? In the past, all cases I've seen where labels were
removed inadvertently were caused by incorrect reference counting or
missing REG_LABEL_* notes.

Did the label use count drop to zero? Is there a REG_LABEL_TARGET note
for the label operand?

Ciao!
Steven



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