Re: [PATCH] Fix PR c++/30044

[Markus Trippelsdorf <markus@trippelsdorf.de>]

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On 2015.06.23 at 19:40 -0400, Patrick Palka wrote:
> On Tue, Jun 23, 2015 at 12:38 AM, Jason Merrill <jason@redhat.com> wrote:
> > On 06/15/2015 02:32 PM, Patrick Palka wrote:
> >>
> >> On Mon, Jun 15, 2015 at 2:05 PM, Jason Merrill <jason@redhat.com> wrote:
> >>>
> >>> Any reason not to use grow_tree_vec?
> >>
> >>
> >> Doing so causes a lot of ICEs in the testsuite.  I think it's because
> >> grow_tree_vec invalidates the older parameter_vec which some trees may
> >> still be holding a reference to in their DECL_TEMPLATE_PARMS field.
> >
> >
> > Hmm, that's unfortunate, as doing it this way means we get a bunch of
> > garbage TREE_VECs in the process.  But I guess the patch is OK as is.
> 
> Yeah, though I can't think of a simple way to work around this -- any
> solution I think of seems to require a change in the representation of
> current_template_parms, something that would be quite invasive....
> Will commit the patch shortly.

Your patch causes LLVM build to hang on the attached testcase. (I killed
gcc after ~10 minutes compile time.)

perf shows:
  23.03%  cc1plus  cc1plus              [.] comp_template_parms
  19.41%  cc1plus  cc1plus              [.] structural_comptypes
  16.28%  cc1plus  cc1plus              [.] cp_type_quals
  15.89%  cc1plus  cc1plus              [.] comp_template_parms_position
  14.01%  cc1plus  cc1plus              [.] comp_type_attributes
   6.58%  cc1plus  cc1plus              [.] comptypes
...

To reproduce just run:
 g++ -c -O3 -std=c++11 gtest-all.ii

-- 
Markus

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