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Re: çå: [4.8 & 4.9] Backport of r211885


The issue is that I cannot reproduce it on the official released branches.
It happens on my local GCC branch (with a new port).
Let's see if the original author of the patch has an testcase.
Zhenqiang, do you have one that can reproduce this bug with the
official 4.8/4.9 branches?
Thanks.
Cheers,
Felix


On Thu, Oct 9, 2014 at 6:41 PM, Richard Biener
<richard.guenther@gmail.com> wrote:
> On Thu, Oct 9, 2014 at 11:35 AM, Yangfei (Felix) <felix.yang@huawei.com> wrote:
>>
>>> > > > On Thu, Oct 09, 2014 at 09:04:49AM +0000, Yangfei (Felix) wrote:
>>> > > > > On Wed, Oct 08, 2014 at 11:00:24PM +0800, Felix Yang wrote:
>>> > > > > The enclosed patch for 4.8 & 4.9 branch is a backport of r211885
>>> > > > > from
>>> > trunk.
>>> > > > >
>>> > > > > The only change is to use:
>>> > > > >
>>> > > > > for (def_rec = DF_INSN_INFO_DEFS (insn_info); *def_rec;
>>> > > > > def_rec++)
>>> > > > >
>>> > > > > other than the new FOR_EACH_INSN_INFO_DEF interface.
>>> > > > >
>>> > > > > Bootstrapped on x86_64-SUSE-Linux for both branches. OK to apply?
>>> > > >
>>> > > > ChangeLog entry is missing, plus description why do you want to
>>> > > > backport
>>> > it.
>>> > > > If it fixes a bug on the branches, it would be better to have a
>>> > > > bugzilla PR for that, and definitely a testcase.
>>> > > >
>>> > >
>>> > > Yeah, I will add a ChangeLog entry for this patch when it is committed.
>>> > > I encountered the same issue when working on my local customized
>>> > > 4.8/4.9
>>> > branches. Not reproduceable with the official 4.8/4.9 branches.
>>> > > I thinks it's just an enhancement for the loop invariant pass to
>>> > > make it more
>>> > versatile. It's better that 4.8/4.9 branches also inlcude this enhancement.
>>> > > OK?
>>> >
>>> > If it is just an enhancement, then those generally are not backported
>>> > to release branches (exceptions possible of course, but there needs to be a
>>> strong reason).
>>> > Each pass has some risk of breaking something, exposing previously
>>> > only latent bugs in later passes etc.
>>> >
>>> >     Jakub
>>>
>>> We can treat it as bugfix, as we got incorrect code when it triggers.
>>> It just happens so rarely. Does it worth backporting?
>>
>> And the patch fix this bug by making the loop invariant pass more conservative.
>> I didn't find a PR or testcase on trunk for this patch either.
>
> We at least want a testcase for the "we got incorrect code when it triggers".
>
> Richard.
>
>>


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