[Bug rtl-optimization/45652] New: [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs with -O2 -fselective-scheduling2

[Bug rtl-optimization/45652] New: [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs with -O2 -fselective-scheduling2

[zsojka at seznam dot cz]

I don't know how much is this related to PR43494. This one is failing with
-fselective-scheduling2 and with different target. Also it started failing just
few revisions ago.

Compiler output:
$ cd gcc/testsuite/gcc.dg/compat
$ gcc -O2 -fselective-scheduling2 scalar-by-value-3_main.c
scalar-by-value-3_x.c scalar-by-value-3_y.c
$ ./a.out 
Aborted

(fails with -O[23s])

Tested revisions:
r164228 - fail
r163636 - fail
r161659 - OK

Reduced testcase to follow.


-- 
           Summary: [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs
                    with -O2 -fselective-scheduling2
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: zsojka at seznam dot cz
  GCC host triplet: x86_64-pc-linux-gnu
GCC target triplet: x86_64-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45652

[Bug rtl-optimization/45652] [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs with -O2 -fselective-scheduling2

[zsojka at seznam dot cz]

------- Comment #1 from zsojka at seznam dot cz  2010-09-12 15:44 -------
Created an attachment (id=21781)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=21781&action=view)
reduced testcase

$ /mnt/svn/gcc-trunk/binary-163636-lto-fortran-checking-yes-rtl-df/bin/gcc -O2
-fselective-scheduling2 pr45652.c 
$ ./a.out 
Aborted


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45652

[Bug rtl-optimization/45652] [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs with -O2 -fselective-scheduling2

[rguenth at gcc dot gnu dot org]

-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.6.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45652

[Bug rtl-optimization/45652] [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs with -O2 -fselective-scheduling2

[amonakov at gcc dot gnu dot org]

------- Comment #2 from amonakov at gcc dot gnu dot org  2010-09-13 16:53 -------
Confirmed.  Not related to PR43949 since selective scheduling does not use
cselib.  The miscompilation seems to come from RTL aliasing: sel-sched lifts a
load that references stack via a general-purpose register above a store via
%rsp.

"bad"  cmdline: cc1 -O2 -fselective-scheduling2 -fdbg-cnt=sel_sched_insn_cnt:31
"good" cmdline: cc1 -O2 -fselective-scheduling2 -fdbg-cnt=sel_sched_insn_cnt:30

The no-aliasing decision comes from (base_alias_check):
1742      /* If one address is a stack reference there can be no alias:
1743         stack references using different base registers do not alias,
1744         a stack reference can not alias a parameter, and a stack reference
1745         can not alias a global.  */
1746      if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1747          || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1748        return 0;

Related GDB session:
Breakpoint 4, base_alias_check (x=0x7ffff6f20920, y=0x7ffff6f2d018,
x_mode=DImode, y_mode=SImode) at
/home/monoid/checkout/git/gcc-selfixes/gcc/alias.c:1687
1687      rtx x_base = find_base_term (x);
(gdb) up
#1  0x000000000076da1d in true_dependence_1 (mem=0x7ffff6f2d030,
mem_mode=SImode, mem_addr=0x7ffff6f2d018, x=0x7ffff6f30870,
x_addr=0x7ffff6f20920, 
    varies=0x14041f2 <rtx_varies_p>, mem_canonicalized=0 '\000') at
/home/monoid/checkout/git/gcc-selfixes/gcc/alias.c:2440
2440      if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
(gdb) call debug_rtx(mem)
(mem/s/c:SI (plus:DI (reg/f:DI 7 sp)
        (const_int 12 [0xc])) [5 ap.fp_offset+0 S4 A32])
(gdb) call debug_rtx(x)
(mem/s:DI (reg:DI 4 si) [0 MEM[(struct S * {ref-all})addr.0_2]+0 S8 A64])
(gdb) down
#0  base_alias_check (x=0x7ffff6f20920, y=0x7ffff6f2d018, x_mode=DImode,
y_mode=SImode) at /home/monoid/checkout/git/gcc-selfixes/gcc/alias.c:1687
1687      rtx x_base = find_base_term (x);
(gdb) n
...
(gdb) list
1741    
1742      /* If one address is a stack reference there can be no alias:
1743         stack references using different base registers do not alias,
1744         a stack reference can not alias a parameter, and a stack reference
1745         can not alias a global.  */
1746      if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1747          || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1748        return 0;
1749    
1750      return 1;
(gdb) call debug_rtx(x_base)
(address (reg:DI 4 si))
(gdb) call debug_rtx(y_base)
(address:DI (reg/f:DI 7 sp))
(gdb) fin
Run till exit from #0  base_alias_check (x=0x7ffff6f20920, y=0x7ffff6f2d018,
x_mode=DImode, y_mode=SImode)
    at /home/monoid/checkout/git/gcc-selfixes/gcc/alias.c:1746
0x000000000076da1d in true_dependence_1 (mem=0x7ffff6f2d030, mem_mode=SImode,
mem_addr=0x7ffff6f2d018, x=0x7ffff6f30870, x_addr=0x7ffff6f20920, 
    varies=0x14041f2 <rtx_varies_p>, mem_canonicalized=0 '\000') at
/home/monoid/checkout/git/gcc-selfixes/gcc/alias.c:2440
2440      if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
Value returned is $58 = 0


-- 

amonakov at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |amonakov at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2010-09-13 16:53:59
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45652

[Bug rtl-optimization/45652] [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs with -O2 -fselective-scheduling2

[abel at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45652

--- Comment #12 from Andrey Belevantsev <abel at gcc dot gnu.org> 2011-04-07 06:53:48 UTC ---
Author: abel
Date: Thu Apr  7 06:53:44 2011
New Revision: 172080

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=172080
Log:
        Backport from mainline
        2010-11-22  Alexander Monakov  <amonakov@ispras.ru>

        PR rtl-optimization/45652
        * alias.c (get_reg_base_value): New.
        * rtl.h (get_reg_base_value): Add prototype.
        * sel-sched.c (init_regs_for_mode): Use it.  Don't use registers with
        non-null REG_BASE_VALUE for renaming.


Added:
    branches/gcc-4_5-branch/gcc/testsuite/gcc.dg/pr45652.c
Modified:
    branches/gcc-4_5-branch/gcc/ChangeLog
    branches/gcc-4_5-branch/gcc/alias.c
    branches/gcc-4_5-branch/gcc/rtl.h
    branches/gcc-4_5-branch/gcc/sel-sched.c
    branches/gcc-4_5-branch/gcc/testsuite/ChangeLog

[Bug rtl-optimization/45652] [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs with -O2 -fselective-scheduling2

[amonakov at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45652

Alexander Monakov <amonakov at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #11 from Alexander Monakov <amonakov at gcc dot gnu.org> 2010-11-22 10:36:42 UTC ---
Fixed on the trunk.

[Bug rtl-optimization/45652] [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs with -O2 -fselective-scheduling2

[amonakov at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45652

--- Comment #10 from Alexander Monakov <amonakov at gcc dot gnu.org> 2010-11-22 10:35:10 UTC ---
Author: amonakov
Date: Mon Nov 22 10:35:06 2010
New Revision: 167025

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=167025
Log:
    PR rtl-optimization/45652
    * alias.c (get_reg_base_value): New.
    * rtl.h (get_reg_base_value): Add prototype.
    * sel-sched.c (init_regs_for_mode): Use it.  Don't use registers with
    non-null REG_BASE_VALUE for renaming.

testsuite:
    * gcc.dg/pr45652.c: New.


Added:
    trunk/gcc/testsuite/gcc.dg/pr45652.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/alias.c
    trunk/gcc/rtl.h
    trunk/gcc/sel-sched.c
    trunk/gcc/testsuite/ChangeLog

[Bug rtl-optimization/45652] [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs with -O2 -fselective-scheduling2

[amonakov at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45652

Alexander Monakov <amonakov at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |amonakov at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #9 from Alexander Monakov <amonakov at gcc dot gnu.org> 2010-11-17 15:39:57 UTC ---
(In reply to comment #8)
> > Btw, the scheduler guys have a fix in the works already.
> 
> Then they should assign the PR to someone to avoid duplicating efforts.

Sorry.  I'm testing the following patch.  There's no way to update
REG_BASE_VALUE from sel-sched on the fly, because it affects aliasing for
multiple MEMs (even off the code motion paths), making computed availability
sets inconsistent with new dependencies.

diff --git a/gcc/alias.c b/gcc/alias.c
index 2e0ac06..e79a780 100644
--- a/gcc/alias.c
+++ b/gcc/alias.c
@@ -1291,6 +1291,12 @@ record_set (rtx dest, const_rtx set, void *data
ATTRIBUTE_UNUSED)
   reg_seen[regno] = 1;
 }

+rtx
+get_reg_base_value (unsigned int regno)
+{
+  return VEC_index (rtx, reg_base_value, regno);
+}
+
 /* If a value is known for REGNO, return it.  */

 rtx
diff --git a/gcc/rtl.h b/gcc/rtl.h
index 3e1df2c..22721a2 100644
--- a/gcc/rtl.h
+++ b/gcc/rtl.h
@@ -2508,6 +2508,7 @@ extern rtx find_base_term (rtx);
 extern rtx gen_hard_reg_clobber (enum machine_mode, unsigned int);
 extern rtx get_reg_known_value (unsigned int);
 extern bool get_reg_known_equiv_p (unsigned int);
+extern rtx get_reg_base_value (unsigned int);

 #ifdef STACK_REGS
 extern int stack_regs_mentioned (const_rtx insn);
diff --git a/gcc/sel-sched.c b/gcc/sel-sched.c
index 70e831d..544348c 100644
--- a/gcc/sel-sched.c
+++ b/gcc/sel-sched.c
@@ -1139,6 +1139,8 @@ init_regs_for_mode (enum machine_mode mode)
             /* Can't use regs which aren't saved by
                the prologue.  */
             || !TEST_HARD_REG_BIT (sel_hrd.regs_ever_used, cur_reg + i)
+        || get_reg_base_value (cur_reg + i)
 #ifdef LEAF_REGISTERS
             /* We can't use a non-leaf register if we're in a
                leaf function.  */

[Bug rtl-optimization/45652] [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs with -O2 -fselective-scheduling2

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45652

--- Comment #8 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2010-11-17 15:31:36 UTC ---
> Btw, the scheduler guys have a fix in the works already.

Then they should assign the PR to someone to avoid duplicating efforts.

[Bug rtl-optimization/45652] [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs with -O2 -fselective-scheduling2

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45652

--- Comment #7 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-11-17 14:08:35 UTC ---
Btw, the scheduler guys have a fix in the works already.

[Bug rtl-optimization/45652] [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs with -O2 -fselective-scheduling2

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45652

--- Comment #6 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-11-17 14:08:01 UTC ---
(In reply to comment #5)
> P1 sounds a little overrated, it's a specialized option and an artificial test.
> Only IA-64 really uses this thing, right?

All regressions towards the last release on primary or secondary targets
are P1 if they do not involve invalid source or checking-only problems.

[Bug rtl-optimization/45652] [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs with -O2 -fselective-scheduling2

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45652

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

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

--- Comment #5 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2010-11-17 14:05:45 UTC ---
P1 sounds a little overrated, it's a specialized option and an artificial test.
Only IA-64 really uses this thing, right?

[Bug rtl-optimization/45652] [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs with -O2 -fselective-scheduling2

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45652

--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-11-04 16:48:49 UTC ---
And indeed --param selsched-insns-to-rename=0 fixes the testcase.

[Bug rtl-optimization/45652] [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs with -O2 -fselective-scheduling2

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45652

--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-11-04 16:35:55 UTC ---
It looks like scheduling itself adds the instruction that references
(mem/s:DI (reg:DI 4 si) [0 MEM[(struct S * {ref-all})addr.0_2]+0 S8 A64])
making use of 'si' where it was formerly not used but fails to record its
set and thus invalidate the base alias info.

Thus, register renaming needs to properly fixup alias info or refrain
from touching registers which have reg_base_value set.

[Bug rtl-optimization/45652] [4.6 Regression] gcc.dg/compat/scalar-by-value-3 FAILs with -O2 -fselective-scheduling2

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45652

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

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