[PR67891] drop is_gimple_reg test from set_parm_rtl

[Alexandre Oliva]

On Oct 14, 2015, Richard Biener <richard.guenther@gmail.com> wrote:

> On Wed, Oct 14, 2015 at 5:25 AM, Alexandre Oliva <aoliva@redhat.com> wrote:
>> On Oct 12, 2015, Richard Biener <richard.guenther@gmail.com> wrote:
>> 
>>> On Sat, Oct 10, 2015 at 3:16 PM, Alexandre Oliva <aoliva@redhat.com> wrote:
>>>> On Oct  9, 2015, Richard Biener <richard.guenther@gmail.com> wrote:
>>>> 
>>>>> Ok.  Note that I think emit_block_move shouldn't mess with the addressable flag.
>>>> 
>>>> I have successfully tested a patch that stops it from doing so,
>>>> reverting https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49429#c11 but
>>>> according to bugs 49429 and 49454, it looks like removing it would mess
>>>> with escape analysis introduced in r175063 for bug 44194.  The thread
>>>> that introduces the mark_addressable calls suggests some discomfort with
>>>> this solution, and even a suggestion that the markings should be
>>>> deferred past the end of expand, but in the end there was agreement to
>>>> go with it.  https://gcc.gnu.org/ml/gcc-patches/2011-06/msg01746.html
>> 
>>> Aww, indeed.  Of course the issue is that we don't track pointers to the
>>> stack introduced during RTL properly.
>> 
>>> Thanks for checking.  Might want to add a comment before that
>>> addressable setting now that you've done the archeology.
>> 
>> I decided to give the following approach a try instead.  The following
>> patch was regstrapped on x86_64-linux-gnu and i686-linux-gnu.
>> Ok to install?

> It looks ok to me but lacks a comment in mark_addressable_1 why we
> do this queueing when currently expanding to RTL.

>> +/* Mark X as addressable or queue it up if called during expand.  */
>> +
>> +static void
>> +mark_addressable_1 (tree x)

How about this:

/* Mark X as addressable or queue it up if called during expand.  We
   don't want to apply it immediately during expand because decls are
   made addressable at that point due to RTL-only concerns, such as
   uses of memcpy for block moves, and TREE_ADDRESSABLE changes
   is_gimple_reg, which might make it seem like a variable that used
   to be a gimple_reg shouldn't have been an SSA name.  So we queue up
   this flag setting and only apply it when we're done with GIMPLE and
   only RTL issues matter.  */

-- 
Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
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Free Software Evangelist|Red Hat Brasil GNU Toolchain Engineer