Re: PATCH: PR target/59363: [4.9 Regression] r203886 miscompiles git

[Michael Zolotukhin <michael dot v dot zolotukhin at gmail dot com>]

Hi Uros, HJ,

I checked expand_movmem_epilogue - it seemingly doesn't have such a
problem, so the patch is ok.

We might want to add similar adjust_automodify_address_nv call to here as well:
    if (TARGET_64BIT)
        {
          dest = change_address (destmem, DImode, destptr);
          emit_insn (gen_strset (destptr, dest, value));
          emit_insn (gen_strset (destptr, dest, value));
        }
      else
        {
          dest = change_address (destmem, SImode, destptr);
          emit_insn (gen_strset (destptr, dest, value));
          emit_insn (gen_strset (destptr, dest, value));
          emit_insn (gen_strset (destptr, dest, value));
          emit_insn (gen_strset (destptr, dest, value));
        }
(code snippet from previous HJ's comment in bugzilla).
I think it's needed here, but I didn't manage to exploit the bug in
this code. Maybe Uros or Jan can comment whether it's needed in such
code or not.

Thanks,
Michael


On 3 December 2013 12:11, Uros Bizjak <ubizjak@gmail.com> wrote:
> On Tue, Dec 3, 2013 at 2:05 AM, H.J. Lu <hongjiu.lu@intel.com> wrote:
>
>> emit_memset fails to adjust destination address after gen_strset, which
>> leads to the wrong address in aliasing info.  This patch fixes it.
>> Tested on Linux/x86-64.  OK to install?
>>
>> 2013-12-03   H.J. Lu  <hongjiu.lu@intel.com>
>>
>>         PR target/59363
>>         * config/i386/i386.c (emit_memset): Adjust destination address
>>         after gen_strset.
>>
>> gcc/testsuite/
>>
>> 2013-12-03   H.J. Lu  <hongjiu.lu@intel.com>
>>
>>         PR target/59363
>>         * gcc.target/i386/pr59363.c: New file.
>
> OK, but according to [1], there are other places where similar issues
> should be fixed. I propose to wait for Michael's analysis and eventual
> patch, and fix them all together.
>
> [1] http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59363#c21
>
> Thanks,
> Uros.



-- 
---
Best regards,
Michael V. Zolotukhin,
Software Engineer
Intel Corporation.