[Bug target/27883] New: [4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[Bug target/27883] New: [4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[tbm at cyrius dot com]

I get the following ICE with current gcc 4.2 on mips.  It appeared some time
between 20051124 and 20060419.  Unfortunately I don't have any compiler
versions inbetween these dates around so I cannot narrow it down further.

(sid)tbm@swarm:~/delta/bin$ /usr/lib/gcc-snapshot/bin/g++ -c -O2 mini.c
mini.c: In member function 'void std::Radau15::Step(const std::Frame&,
std::Frame&, std::Interaction*)':
mini.c:96: internal compiler error: in schedule_insns, at sched-rgn.c:3038
Please submit a full bug report,
with preprocessed source if appropriate.
See <URL:http://gcc.gnu.org/bugs.html> for instructions.


-- 
           Summary: [4.2 regression] in schedule_insns, at sched-rgn.c:3038
                    on mips
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tbm at cyrius dot com
 GCC build triplet: mipsel-linux-gnu
  GCC host triplet: mipsel-linux-gnu
GCC target triplet: mipsel-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug target/27883] [4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[tbm at cyrius dot com]

------- Comment #1 from tbm at cyrius dot com  2006-06-03 14:43 -------
Created an attachment (id=11589)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11589&action=view)
test case


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug target/27883] [4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2006-06-03 16:01 -------
I bet a beer that this was caused by:
2006-03-16  Maxim Kuvyrkov <mkuvyrkov@ispras.ru>

        * target.h (struct spec_info_def): New opaque declaration.
....


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice-on-valid-code
   Target Milestone|---                         |4.2.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug target/27883] [4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[mmitchel at gcc dot gnu dot org]

-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug target/27883] [4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[mkuvyrkov at gcc dot gnu dot org]

------- Comment #3 from mkuvyrkov at gcc dot gnu dot org  2006-06-07 15:29 -------
(In reply to comment #2)
> I bet a beer that this was caused by:
> 2006-03-16  Maxim Kuvyrkov <mkuvyrkov@ispras.ru>
> 
>         * target.h (struct spec_info_def): New opaque declaration.
> ....
> 

Nope.  This one is caused by combine.c .

1. Combine generates a REG_DEAD note of the register that don't even appear in
the code.
2. This note survives life2 but gets deleted in sched-rgn.c: check_dead_notes1
().
3. After scheduler is finished, it recalculates life info, not attaching a
REG_DEAD note for that register (which is, I think, correct).
4. Scheduler fails on the assert.

So, the major problem is that combiner emits a strange REG_DEAD note (see
combine.c: distribute_notes ()) and the minor problem is that life2 doesn't fix
this (though, it would not generate such note by itself).


-- 

mkuvyrkov at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mkuvyrkov at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug target/27883] [4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[wilson at gcc dot gnu dot org]

------- Comment #4 from wilson at gcc dot gnu dot org  2006-06-27 03:02 -------
This only fails for --enable-checking builds, which is the default for
mainline, but not release branches.  I was able to reproduce this with gcc-4.0,
but not gcc-3.4.  The difference between the two is that gcc-4.0 has the
__builtin_copysign support, which emits the RTL that triggers the error.  The
error has probably been latent for a while.

The insn that causes the problem is
(jump_insn 99 98 113 15 (set (pc)
        (if_then_else (ge:SI (subreg:SI (reg:DF 32 $f0) 4)
                (const_int 0 [0x0]))
            (label_ref 101)
            (pc))) 261 {*branch_zerosi} (insn_list:REG_DEP_TRUE 94 (nil))
    (expr_list:REG_DEAD (reg:SI 33 $f1)
        (expr_list:REG_BR_PROB (const_int 5000 [0x1388])
            (nil))))
On a 32-bit mips target, DFmode $f0 is a register pair $f0/$f1, so technically
this is correct.  There is a corresponding REG_UNUSED for $f0 on the insn that
sets (reg:DF 32 $f0).

However, flow doesn't track individual regs in subregs, it only tracks the
whole subreg.  Note that mark_used_reg ignores subregs.  So when we execute the
second life pass, we end up with
(jump_insn 98 97 112 17 (set (pc)
        (if_then_else (ge (subreg:SI (reg:DF 32 $f0) 4)
                (const_int 0 [0x0]))
            (label_ref 100)
            (pc))) 271 {*branch_ordersi} (insn_list:REG_DEP_TRUE 93 (nil))
    (expr_list:REG_DEAD (reg:DF 32 $f0)
        (expr_list:REG_DEAD (reg:SI 33 $f1)
            (expr_list:REG_BR_PROB (const_int 5000 [0x1388])
                (nil)))))
Note that we now have two overlapping REG_DEAD notes plus an overlapping
REG_UNUSED note on a previous insn.  When sched runs, it deletes both REG_DEAD
notes, but only readds one, resulting in the abort for a REG_DEAD note
consistency problem.

A subreg of a hard register is normally not allowed, but it is created in this
case because CANNOT_CHANGE_CLASS_MODE is defined, and HARD_REGNO_MODE_OK says
that an SImode $f1 is not OK.  The result is that simplify_subreg doesn't
simplify this.  The other part is that register_operand says it is OK. 
Eventually, this gets fixed by reload.

Fixing combine to get this right looks complicated.  Combine has to know that
the register was used inside a subreg, and then figure out that the subreg
wasn't simplified because of CANNOT_CHANGE_CLASS_MODE, etc.

I think a simpler solution here is to note that the life2 pass would have
worked correctly if it deleted all prior REG_UNUSED/REG_DEAD notes before it
started.  Incidentally, the comments for the life2 pass say it was explicitly
added to fix REG_UNUSED/REG_DEAD problems with distribute_notes in combine, so
it was apparently added to fix a related problem.  It just isn't working the
way it was originally intended.

It is curious that life2 is running immediately before sched, instead of
immediately after combine.  If we ran it immediately after combine, we could
get rid of the REG_DEAD/REG_UNUSED support in distribute_notes, which is
probably the most complicated, and most buggy, part of combine.  This would
also speed up the compiler a little bit.


-- 

wilson at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |wilson at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2006-06-27 03:02:40
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug target/27883] [4.0/4.1/4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice-checking
      Known to fail|                            |4.0.0 4.1.0 4.2.0
      Known to work|                            |3.4.0
            Summary|[4.2 regression] in         |[4.0/4.1/4.2 regression] in
                   |schedule_insns, at sched-   |schedule_insns, at sched-
                   |rgn.c:3038 on mips          |rgn.c:3038 on mips
   Target Milestone|4.2.0                       |4.1.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug target/27883] [4.0/4.1/4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[wilson at gcc dot gnu dot org]

------- Comment #5 from wilson at gcc dot gnu dot org  2006-07-11 01:32 -------
This is already fixed on dataflow-branch.  At the end of combine_instructions,
it runs a global dataflow pass that removes all REG_DEAD and REG_UNUSED notes
before creating new ones.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug target/27883] [4.0/4.1/4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[wilson at gcc dot gnu dot org]

------- Comment #6 from wilson at gcc dot gnu dot org  2006-07-11 01:41 -------
Created an attachment (id=11857)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11857&action=view)
Delete old REG_DEAD notes before creating new ones.

This works for the testcase, but is otherwise untested.  This just deletes the
old REG_DEAD notes for a local life update before creating new ones.  I believe
this could be made simpler by eliminating UPDATE_LIFE_GLOBAL_RM_NOTES, and then
calling count_or_remove_death_notes if PROP_DEATH_NOTES is set for both global
and local updates.  However, assuming we want what is on dataflow-branch, it
seems better to go with a safer non-conflicting patch for now, and let
dataflow-branch be the long term fix.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug target/27883] [4.0/4.1/4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[echristo at apple dot com]

------- Comment #7 from echristo at apple dot com  2006-07-22 21:14 -------
Jim, were you going to check this in or did you need some more testing on it?


-- 

echristo at apple dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug target/27883] [4.0/4.1/4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[pinskia at gcc dot gnu dot org]

------- Comment #8 from pinskia at gcc dot gnu dot org  2006-07-22 22:07 -------
This bug does not belong in waiting as it is not waiting on the user input but
a developer input.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW
   Last reconfirmed|2006-06-27 03:02:40         |2006-07-22 22:07:25
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug target/27883] [4.0/4.1/4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[wilson at tuliptree dot org]

------- Comment #9 from wilson at tuliptree dot org  2006-07-24 19:34 -------
Subject: Re:  [4.0/4.1/4.2 regression] in schedule_insns,
        at sched-rgn.c:3038 on mips

On Sat, 2006-07-22 at 14:14, echristo at apple dot com wrote:
> ------- Comment #7 from echristo at apple dot com  2006-07-22 21:14 -------
> Jim, were you going to check this in or did you need some more testing on it?

I haven't had time to test it yet.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug target/27883] [4.0/4.1/4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[tbm at gcc dot gnu dot org]

------- Comment #10 from tbm at gcc dot gnu dot org  2006-08-23 18:56 -------
(In reply to comment #9)
> > Jim, were you going to check this in or did you need some more testing on it?
> 
> I haven't had time to test it yet.

Any update on this, Jim?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug target/27883] [4.0/4.1/4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[wilson at specifix dot com]

------- Comment #11 from wilson at specifix dot com  2006-08-23 21:25 -------
Subject: Re:  [4.0/4.1/4.2 regression] in schedule_insns,
 at sched-rgn.c:3038 on mips

tbm at gcc dot gnu dot org wrote:
> Any update on this, Jim?

No.  My life continues to be busy and complicated, making it difficult 
to do much gcc work.

However, I did put a patch in the PR.  If anyone else has time, they 
could try testing it.  It needs a bootstrap and regression test.

I think the problem is best fixed on mainline by merging in the dataflow 
branch, but for currently supported releases, and for the pending 4.2 
release, I think the simple fix in the PR is best.  So if we add this 
fix to the mainline now, then we need to remember to remove it when the 
dataflow branch goes in, or else prevent it from migrating to the 
dataflow branch.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug target/27883] [4.0/4.1/4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[tbm at cyrius dot com]

------- Comment #12 from tbm at cyrius dot com  2006-08-25 19:05 -------
Update: mzero6.c fails because of this ICE too.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug target/27883] [4.0/4.1/4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[tbm at cyrius dot com]

------- Comment #13 from tbm at cyrius dot com  2006-08-25 20:09 -------
Reduced testcase:

double copysign (double x, double y);
double GetDouble();
double a = copysign (1.0, GetDouble());


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug target/27883] [4.0/4.1/4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[tbm at cyrius dot com]

------- Comment #14 from tbm at cyrius dot com  2006-08-27 13:20 -------
Bootstrapped and regtested successfully on mipsel-linux-gnu and
x86_64-linux-gnu


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug rtl-optimization/27883] [4.0/4.1/4.2 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[pinskia at gcc dot gnu dot org]

------- Comment #15 from pinskia at gcc dot gnu dot org  2006-09-07 04:24 -------
Subject: Bug 27883

Author: pinskia
Date: Thu Sep  7 04:24:24 2006
New Revision: 116739

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=116739
Log:
2006-09-06  James E Wilson  <wilson@specifix.com>

        PR rtl-opt/27883
        * flow.c (update_life_info): If UPDATE_LIFE_LOCAL and PROP_DEATH_NOTES
        then call count_or_remove_death_notes.

2006-09-06  Andrew Pinski  <pinskia@physics.uc.edu>

        PR rtl-opt/27883
        * g++.dg/opt/copysign-1.C: New test.


Added:
    trunk/gcc/testsuite/g++.dg/opt/copysign-1.C
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/flow.c
    trunk/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug rtl-optimization/27883] [4.0/4.1 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[pinskia at gcc dot gnu dot org]

------- Comment #16 from pinskia at gcc dot gnu dot org  2006-09-07 04:24 -------
Fixed at least on the mainline now.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|4.0.0 4.1.0 4.2.0           |4.0.0 4.1.0
      Known to work|3.4.0                       |3.4.0 4.2.0
            Summary|[4.0/4.1/4.2 regression] in |[4.0/4.1 regression] in
                   |schedule_insns, at sched-   |schedule_insns, at sched-
                   |rgn.c:3038 on mips          |rgn.c:3038 on mips


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug rtl-optimization/27883] [4.0/4.1 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[amylaar at gcc dot gnu dot org]

------- Comment #17 from amylaar at gcc dot gnu dot org  2006-10-31 14:34 -------
(In reply to comment #4)
> It is curious that life2 is running immediately before sched, instead of
> immediately after combine.  If we ran it immediately after combine, we could
> get rid of the REG_DEAD/REG_UNUSED support in distribute_notes, which is
> probably the most complicated, and most buggy, part of combine.  This would
> also speed up the compiler a little bit.

The combiner itself relies on REG_DEAD notes to find out what it can combine.
If you leave an invalid REG_DEAD note, it can lead to wrong code being emitted.
If you don't leave in valid REG_DEAD notes in their proper place, multi-step
instruction combinations will stop working - and with the three insn limit on
any single combination, this is likely to stop quite a lot of combinations.
Most combiner bridge patterns will become useless.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug rtl-optimization/27883] [4.0/4.1 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[ebotcazou at gcc dot gnu dot org]

------- Comment #18 from ebotcazou at gcc dot gnu dot org  2007-01-24 11:30 -------
Given that this is not user-visible in released compilers and won't very
likely lead to wrong code, I propose to mark it WONTFIX for 4.0 and 4.1.


-- 

ebotcazou at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ebotcazou at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug rtl-optimization/27883] [4.0/4.1 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[tbm at gcc dot gnu dot org]

------- Comment #19 from tbm at gcc dot gnu dot org  2007-01-24 12:01 -------
(In reply to comment #18)
> Given that this is not user-visible in released compilers and won't very
> likely lead to wrong code, I propose to mark it WONTFIX for 4.0 and 4.1.

Speaking as the submitter, I don't mind if this is done.

BTW, we should not forget Jim's Comment #11: the patch should be backed out
from 4.3 when the dataflow branch is merged.  Which I believe is going to
happen soon?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883

[Bug rtl-optimization/27883] [4.0/4.1 regression] in schedule_insns, at sched-rgn.c:3038 on mips

[ebotcazou at gcc dot gnu dot org]

------- Comment #20 from ebotcazou at gcc dot gnu dot org  2007-02-10 15:17 -------
Not user-visible in 4.1.x.


-- 

ebotcazou at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |WONTFIX


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27883