[Bug rtl-optimization/56885] New: ICE: in assign_by_spills, at lra-assigns.c:1268 with -O -fschedule-insns -fselective-scheduling

[Bug rtl-optimization/56885] New: ICE: in assign_by_spills, at lra-assigns.c:1268 with -O -fschedule-insns -fselective-scheduling

[zsojka at seznam dot cz]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56885

             Bug #: 56885
           Summary: ICE: in assign_by_spills, at lra-assigns.c:1268 with
                    -O -fschedule-insns -fselective-scheduling
    Classification: Unclassified
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: zsojka@seznam.cz


Created attachment 29832
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29832
reduced testcase

Compiler output:
$ gcc -O -fschedule-insns -fselective-scheduling testcase.c
testcase.c: In function 'foo':
testcase.c:20:1: internal compiler error: in assign_by_spills, at
lra-assigns.c:1268
 }
 ^
0x8e1e4c assign_by_spills
        /mnt/svn/gcc-trunk/gcc/lra-assigns.c:1268
0x8e3043 lra_assign()
        /mnt/svn/gcc-trunk/gcc/lra-assigns.c:1425
0x8de8a0 lra(_IO_FILE*)
        /mnt/svn/gcc-trunk/gcc/lra.c:2299
0x8937f8 do_reload
        /mnt/svn/gcc-trunk/gcc/ira.c:4619
0x8937f8 rest_of_handle_reload
        /mnt/svn/gcc-trunk/gcc/ira.c:4731
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.

Tested revisions:
r197604 - crash
4.8 r196898 - crash
4.7 r196898 - crash
4.6 r196898 - crash

[Bug rtl-optimization/56885] ICE: in assign_by_spills, at lra-assigns.c:1268 with -O -fschedule-insns -fselective-scheduling

[izamyatin at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56885

Igor Zamyatin <izamyatin at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |izamyatin at gmail dot com

--- Comment #3 from Igor Zamyatin <izamyatin at gmail dot com> 2013-04-09 06:58:22 UTC ---
(In reply to comment #1)
> Confirmed with trunk/4.8, but with 4.6/4.7 I see:
> 
> x.c:20:1: error: unable to find a register to spill in class ‘DIREG’
> x.c:20:1: error: this is the insn:
> (insn 33 36 35 5 (parallel [
>             (set (reg:DI 2 cx [80])
>                 (const_int 0 [0]))
>             (set (reg/f:DI 0 ax [78])
>                 (plus:DI (reg/f:DI 1 dx [77])
>                     (reg:DI 2 cx [80])))
>             (set (mem:BLK (reg/f:DI 1 dx [77]) [0 S15 A8])
>                 (const_int 0 [0]))
>             (use (reg:QI 6 bp [81]))
>             (use (reg:DI 2 cx [80]))
>         ]) x.c:16 884 {*rep_stosqi}
>      (expr_list:REG_DEAD (reg/f:DI 1 dx [77])
>         (expr_list:REG_UNUSED (reg:DI 2 cx [80])
>             (expr_list:REG_UNUSED (reg/f:DI 0 ax [78])
>                 (nil)))))
> x.c:20: confused by earlier errors, bailing out

The same error on 4.9 when IRA is turned on
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Subject: [Bug c++/56886] [4.9 regression] undesirable instantiation of class template default argument
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idV886

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-04-09 07:41:57 UTC ---
Dup of PR56838 ?

[Bug rtl-optimization/56885] [4.8/4.9 Regression] ICE: in assign_by_spills, at lra-assigns.c:1268 with -O -fschedule-insns -fselective-scheduling

[izamyatin at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56885

Igor Zamyatin <izamyatin at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ysrumyan at gmail dot com

--- Comment #4 from Igor Zamyatin <izamyatin at gmail dot com> 2013-04-09 10:53:09 UTC ---
Adding the author of the changes that fix failures of pre-alloc scheduler

[Bug rtl-optimization/56885] [4.8/4.9 Regression] ICE: in assign_by_spills, at lra-assigns.c:1268 with -O -fschedule-insns -fselective-scheduling

[ysrumyan at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56885

--- Comment #5 from Yuri Rumyantsev <ysrumyan at gmail dot com> 2013-04-09 13:33:53 UTC ---
I did simple investigation and found out that
1. Test is compiled successfully without selective scheduling, i.e. with
'-fschedule-insns' only.
2. The problem is that selective scheduler moves function argument (off) uo
through bunch of instructions correspondent to __builtin_memset() ignoring
dependency creating by ix86_dependencies_evaluation_hook() ( i tried to add
output dependency instead of anti dependency between them but it also did not
help). More precisely, we have the following sequence of insns:

(insn 30 29 31 5 (parallel [
            (set (reg:DI 77)
                (const_int 0 [0]))
            (set (reg/f:DI 75 [ D.1742 ])
                (plus:DI (reg/f:DI 74 [ D.1742 ])
                    (reg:DI 77)))
            (set (mem:BLK (reg/f:DI 74 [ D.1742 ]) [0 MEM[(void *)_17]+0 S15
A8])
                (const_int 0 [0]))
            (use (reg:QI 78))
            (use (reg:DI 77))
        ]) t.c:16 909 {*rep_stosqi}
     (expr_list:REG_DEAD (reg/f:DI 74 [ D.1742 ])
        (expr_list:REG_UNUSED (reg:DI 77)
            (expr_list:REG_UNUSED (reg/f:DI 75 [ D.1742 ])
                (nil)))))
(insn 31 30 32 5 (set (reg:SI 5 di)
        (subreg:SI (reg:DI 69 [ ivtmp.3 ]) 0)) t.c:17 85 {*movsi_internal}
     (nil))
(call_insn 32 31 33 5 (call (mem:QI (symbol_ref:DI ("bar") [flags 0x41] 
<function_decl 0x7f66061e4900 bar>) [0 bar S1 A8])
        (const_int 0 [0])) t.c:17 646 {*call}
     (expr_list:REG_DEAD (reg:SI 5 di)
        (nil))
    (expr_list:REG_BR_PRED (use (reg:SI 5 di))
        (nil)))

and there exist anti or output dependency between 30 and 31 insns created by
ix86-hook which is ignored by selective scheduler:

Moving [((31;di=r69#0;)type:set;count:2;)prio:3;orig_bb:5;] through 30:
unchanged (as RHS)

So I assume that selective scheduler needs to be tuned to be invoked before
Register Allocation phase on x86.

[Bug rtl-optimization/56885] [4.8/4.9 Regression] ICE: in assign_by_spills, at lra-assigns.c:1268 with -O -fschedule-insns -fselective-scheduling

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56885

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.8.1                       |4.8.2

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 4.8.1 has been released.

[Bug rtl-optimization/56885] [4.8/4.9 Regression] ICE: in assign_by_spills, at lra-assigns.c:1268 with -O -fschedule-insns -fselective-scheduling

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56885

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.8.2                       |4.8.3

--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 4.8.2 has been released.

[Bug rtl-optimization/56885] [4.8/4.9 Regression] ICE: in assign_by_spills, at lra-assigns.c:1268 with -O -fschedule-insns -fselective-scheduling

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56885

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2

[Bug rtl-optimization/56885] [4.8/4.9 Regression] ICE: in assign_by_spills, at lra-assigns.c:1268 with -O -fschedule-insns -fselective-scheduling

[abel at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56885

Andrey Belevantsev <abel at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |abel at gcc dot gnu.org

--- Comment #9 from Andrey Belevantsev <abel at gcc dot gnu.org> ---
Trunk does not ICE for me anymore, though the two insns Yuri mentioned are
still reordered.  I will explain what happens in more detail.

The selective scheduler supports register renaming.  So on seeing an
anti-dependence in this case for di=r69 it assumes that the RHS of this insn
can be moved up with the new register, e.g. r?? = r69 and later di = r??.  When
the new register is being chosen, there is nothing in the function that
prevents using the original register, di -- no liveness or hardware imposed
restrictions are reported by the backend so we allow to move the insn with the
original register.  The reason for this is that the dependence comes from the
implicit_set on the another insn (insn 30 in Yuri's dump), and implicit sets do
not get reflected in the dataflow information (which we get from DF_LIVE_IN
sets and df_simulate_one_insn_backwards interfaces).

Now, if the extra dependencies really come from the evaluation_hook interface
of the x86 backend, I'd note that the hook, originally implemented for ia64
only, was not intended for adding any new dependencies, but rather for
reflecting the dependencies added in the backend for its own purposes.  E.g.
for ia64 the interface allows to get the complete dependence picture before
making decisions on bundling.  So I'd claim that any dependencies created for
the scheduler should also be calculated via the general deps_analyze_insn
mechanism of sched-deps.c, with the correctly prepared deps context.  E.g. any
changes done with implicit_sets/clobbers/uses and IRA/LRA interfaces are also
visible within the selective scheduling.  The selective scheduling analyzes
dependencies between separate insns, not blocks, so the evaluation_hook
interface does not make sense for it.

To summarize, if the backend wants to stop reordering insns in question and
also forbid renaming, then this should be exposed from within a hook called
from sched-deps.c when calculating dependencies through deps_analyze_insn, not
later, and then we can judge whether the new dependence comes from
LHS/RHS/whole insn and make appropriate changes for renaming.  The current
interface does not tell us that renaming is prohibited and we cannot derive it
from the IR.  The best way would be to properly reflect all restrictions in the
IR and not end up lying to the dataflow machinery and the scheduler.

[Bug rtl-optimization/56885] [4.8/4.9 Regression] ICE: in assign_by_spills, at lra-assigns.c:1268 with -O -fschedule-insns -fselective-scheduling

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56885

--- Comment #10 from H.J. Lu <hjl.tools at gmail dot com> ---
On trunk, it was fixed by r206938.

[Bug rtl-optimization/56885] [4.8 Regression] ICE: in assign_by_spills, at lra-assigns.c:1268 with -O -fschedule-insns -fselective-scheduling

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56885

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org
      Known to work|                            |4.9.0
            Summary|[4.8/4.9 Regression] ICE:   |[4.8 Regression] ICE: in
                   |in assign_by_spills, at     |assign_by_spills, at
                   |lra-assigns.c:1268 with -O  |lra-assigns.c:1268 with -O
                   |-fschedule-insns            |-fschedule-insns
                   |-fselective-scheduling      |-fselective-scheduling
      Known to fail|4.9.0                       |

--- Comment #11 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed on the trunk then, perhaps it might be worthwhile to add the testcase
though.

[Bug rtl-optimization/56885] [4.8 Regression] ICE: in assign_by_spills, at lra-assigns.c:1268 with -O -fschedule-insns -fselective-scheduling

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56885

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.8.3                       |4.8.4

--- Comment #12 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 4.8.3 is being released, adjusting target milestone.

[Bug rtl-optimization/56885] [4.8 Regression] ICE: in assign_by_spills, at lra-assigns.c:1268 with -O -fschedule-insns -fselective-scheduling

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56885

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.8.4                       |4.8.5

--- Comment #13 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 4.8.4 has been released.

[Bug rtl-optimization/56885] [4.8 Regression] ICE: in assign_by_spills, at lra-assigns.c:1268 with -O -fschedule-insns -fselective-scheduling

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56885

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|4.8.5                       |4.9.0
      Known to fail|                            |4.8.5

--- Comment #14 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed for 4.9.0.