[PING][PATCH][4.9]Backport "Fix register corruption bug in ree"

[Richard Biener]

On Fri, 6 Nov 2015, Renlin Li wrote:

> Hi Richard,
> 
> I am trying to come up with a simple test case, but failed to do so.
> 
> I have isolated the function where bug is triggered. However, in order to make
> it a useful test case, the silently corrupted register should be used
> somewhere, and should affect the correctness of the program. I cannot create
> such an context.
> 
> 
> libstdc++-v3/testsuite/tr1/8_c_compatibility/complex/50880.cc is a concreted
> example which will trigger this bug.

Well, if that testcase exposes the bug you already have a testcase.

Richard.

> Here is a short description about why the test case failed:
> 
> wrong code-gen in ree pass:
> 
> (insn 279 278 531 2 (set (reg:TF 32 v0)
>         (zero_extend:TF (reg:DI 19 x19 [orig:150 __x+8 ] [150])))
> /libstdc++-v3/include/complex:861 691 {aarch64_movtflow_di}
>      (nil))
> (insn 531 279 275 2 (set (reg:TF 3 x3)
>         (reg:TF 32 v0)) /libstdc++-v3/include/complex:861 -1
>      (nil))
> (insn 275 531 510 2 (set (reg:DI 23 x23 [orig:151 __y ] [151])
>         (mem:DI (plus:DI (reg/v/f:DI 0 x0 [orig:104 __z ] [104])
>                 (const_int 16 [0x10])) [9 MEM[(const long double &)__z_4(D) +
> 16]+0 S8 A128])) /libstdc++-v3/include/complex:859 34 {*movdi_aarch64}
>      (nil))
> (insn 510 275 19 2 (set (zero_extract:TF (reg:TF 32 v0)
>             (const_int 64 [0x40])
>             (const_int 64 [0x40]))
>         (zero_extend:TF (reg:DI 2 x2 [ __x+-8 ])))
> /libstdc++-v3/include/complex:861 689 {aarch64_movtfhigh_di}
>      (nil))
> 
> 
> insn 531 clobbers x4 as well. That's exactly the same problem described in
> Wilco's email. The following is what the correct code should look like. It's
> generated after applying Wilco's fix.
> 
> 
> (insn 279 278 275 2 (set (reg:DI 3 x3 [orig:185 __x ] [185])
>         (reg:DI 19 x19 [orig:150 __x+8 ] [150]))
> /libstdc++-v3/include/complex:861 34 {*movdi_aarch64}
>      (nil))
> (insn 275 279 509 2 (set (reg:DI 23 x23 [orig:151 __y ] [151])
>         (mem:DI (plus:DI (reg/v/f:DI 0 x0 [orig:104 __z ] [104])
>                 (const_int 16 [0x10])) [9 MEM[(const long double &)__z_4(D) +
> 16]+0 S8 A128])) /libstdc++-v3/include/complex:859 34 {*movdi_aarch64}
>      (nil))
> (insn 509 275 510 2 (set (reg:TF 32 v0)
>         (zero_extend:TF (reg:DI 3 x3 [orig:185 __x ] [185])))
> /libstdc++-v3/include/complex:861 691 {aarch64_movtflow_di}
>      (nil))
> (insn 510 509 19 2 (set (zero_extract:TF (reg:TF 32 v0)
>             (const_int 64 [0x40])
>             (const_int 64 [0x40]))
>         (zero_extend:TF (reg:DI 2 x2 [ __x+-8 ])))
> /libstdc++-v3/include/complex:861 689 {aarch64_movtfhigh_di}
>      (nil))
> 
> 
> 
> Regards,
> Renlin Li
> 
> On 29/10/15 16:33, Richard Biener wrote:
> > On October 29, 2015 4:37:08 PM GMT+01:00, Ramana Radhakrishnan
> > <ramana.gcc@googlemail.com> wrote:
> > > On Thu, Jun 4, 2015 at 2:16 PM, Renlin Li <renlin.li@arm.com> wrote:
> > > > Ping ~
> > > > 
> > > > Can somebody review it? Thank you!
> > > > 
> > > > Regards,
> > > > Renlin Li
> > > > 
> > > > 
> > > > On 16/04/15 10:32, Renlin Li wrote:
> > > > > Ping~
> > > > > 
> > > > > Regards,
> > > > > Renlin Li
> > > > > 
> > > > > On 16/04/15 10:09, wrote:
> > > > > > Ping~
> > > > > > Anybody has time to review it?
> > > > > > 
> > > > > > 
> > > > > > Regards,
> > > > > > Renlin Li
> > > > > > 
> > > > > > On 06/02/15 17:48, Renlin Li wrote:
> > > > > > > Hi all,
> > > > > > > 
> > > > > > > This is a backport patch for branch 4.9. You can find the
> > > original=20
> > > > > > > patch
> > > here:https://gcc.gnu.org/ml/gcc-patches/2014-09/msg00356.html
> > > > > > > And it has been commit on the trunk as r215205.
> > > > > > > 
> > > > > > > This fixes a few libstdc++-v3 test suite failures.
> > > > > > > x86_64 bootstraps Okay, aarch64_be-none-elf libstdc++-v3 tested
> > > Okay.
> > > > > > > Okay to commit on branch 4.9?
> > > > > > > 
> > > > > > > Regards,
> > > > > > > Renlin Li
> > > > > > > 
> > > > > > > 2015-02-06  Renlin Li<renlin.li@arm.com>
> > > > > > > 
> > > > > > >       Backport from mainline
> > > > > > >       2014-09-12  Wilco Dijkstra<wilco.dijkstra@arm.com>
> > > > > > > 
> > > > > > >       * gcc/ree.c (combine_reaching_defs): Ensure inserted copy
> > > don't=20
> > > > > > > change
> > > > > > >       the number of hard registers.
> > > > > > > 
> > > richi - an RM question -
> > > 
> > > Is this something that can be pulled back to GCC 4.9 branch assuming
> > > testing still shows no regressions  - it breaks aarch64 be on GCC 4.9
> > If it is a regression or wrong-code fix its OK with a test case.
> > 
> > Richard.
> > 
> > > ...
> > > 
> > > 
> > > regards
> > > Ramana
> > 
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)