[Bug other/54814] New: [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[Bug other/54814] New: [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

             Bug #: 54814
           Summary: [4.8 Regression] ICE: unable to find a register to
                    spill in class 'R0_REG'
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code, ra
          Severity: normal
          Priority: P3
         Component: other
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: gjl@gcc.gnu.org
                CC: eric.weddington@atmel.com
            Target: avr


Created attachment 28358
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28358
spills.txt: Hundreds of Spill Fails

The testsuit throws hundreds of spill fails when running against the avr cross
compiler.

The testsuite used to produce about ~5 spill fails with avr-gcc.

The strange with these spill fails is that they report register class RO_REG
which contains just one fixed register.

./gcc/testsuite/gcc.c-torture/compile/20010426-1.c:19:1: error: unable to find
a register to spill in class 'R0_REG'

./gcc/testsuite/gcc.c-torture/compile/20040121-1.c:41:1: error: unable to find
a register to spill in class 'R0_REG'

...

For a complete list see attachment.



== configure ==

SVN trunk r192090 from today (2012-10-04)

$ ../../gcc.gnu.org/trunk/configure --target=avr
--prefix=/local/gnu/install/gcc-4.8 --disable-nls --with-dwarf2
--enable-target-optspace=yes --enable-languages=c,c++

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-10-14
     Ever Confirmed|0                           |1

--- Comment #1 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-10-14 11:15:36 UTC ---
Setting to NEW.  There is enough evidence from the test cases in the test
suite.

Moreover, I am getting this ICE with real-world code so this is not just a
purely academic problem.

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.8.0

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P4

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

--- Comment #2 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-12-07 13:34:36 UTC ---
rguenth at gcc dot gnu.org wrote:
>  spill in class 'R0_REG'

Spilling is a bug in the register allocator, or am I missing something.

Besides that, I am getting this mail because I am CCed to PR54814
but your comment

  spill in class 'R0_REG'

is missing in PR54814 so nobody can really follow what is going on for what
reason.

Johann

> 
> Date: Fri, 07 Dec 2012 11:46:42 +0000
> 
> X-Bugzilla-Reason: Reporter
> 
> X-Bugzilla-Type: changed
> 
> X-Bugzilla-Watch-Reason: None
> 
> X-Bugzilla-Product: gcc
> 
> X-Bugzilla-Component: other
> 
> X-Bugzilla-Keywords: ice-on-valid-code, ra
> 
> X-Bugzilla-Severity: normal
> 
> X-Bugzilla-Who: rguenth at gcc dot gnu.org
> 
> X-Bugzilla-Status: NEW
> 
> X-Bugzilla-Priority: P4
> 
> X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
> 
> X-Bugzilla-Target-Milestone: 4.8.0
> 
> X-Bugzilla-Changed-Fields: Priority
> 
> Message-ID: <bug-54814-20453-4HTXOBm3vX@http.gcc.gnu.org/bugzilla/>
> 
> In-Reply-To: <bug-54814-20453@http.gcc.gnu.org/bugzilla/>
> 
> References: <bug-54814-20453@http.gcc.gnu.org/bugzilla/>
> 
> X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
> 
> Auto-Submitted: auto-generated
> 
> Content-Type: text/plain; charset="UTF-8"
> 
> MIME-Version: 1.0
> 
> 
> 
> 
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814
> 
> 
> 
> Richard Biener <rguenth at gcc dot gnu.org> changed:
> 
> 
> 
>            What    |Removed                     |Added
> 
> ----------------------------------------------------------------------------
> 
>            Priority|P3                          |P4
> 
> 
>

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

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

--- Comment #3 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-12-07 17:59:02 UTC ---
Richard, would you explain why this is a target issue?

R0 is a fixed register, it should not be used for spilling or be allocated by
IRA.

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

--- Comment #4 from Steven Bosscher <steven at gcc dot gnu.org> 2012-12-07 22:02:43 UTC ---
(In reply to comment #3)
> R0 is a fixed register, it should not be used for spilling or be allocated by
> IRA.

But apparently RA believes it has to, to satisfy some constraints.
Difficult to say exactly, without a little more context.  Cross-compiler
from what to what? What else does spill_failure print? spills.txt only
shows the ICEs, but spill_failure prints a lot of information about what
failed -- that's actually useful information for folks willing to help
here but not willing to build a cross-compiler for it ;-)

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

Steven Bosscher <steven at gcc dot gnu.org> changed:

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

--- Comment #5 from Steven Bosscher <steven at gcc dot gnu.org> 2012-12-07 22:41:02 UTC ---
For 20010426-1.c at -O1:
(gdb) p debug_rtx(insn)
(insn 168 167 169 10 (set (reg:QI 3 r3 [orig:118 a_I_m_lsm.5+1 ] [118])
        (subreg:QI (reg/f:HI 105 [ a_I_m_lsm.5 ]) 1)) 20010426-1.c:12 70
{movqi_insn}
     (nil))
$1 = void
(gdb) p debug_reload_to_stream(stderr)
Reload 0: reload_in (HI) = (symbol_ref/f:HI ("*.LC0") [flags 0x2] <var_decl
0x7ffff63f0720 *.LC0>)
        R0_REG, RELOAD_FOR_INPUT (opnum = 1)
        reload_in_reg: (symbol_ref/f:HI ("*.LC0") [flags 0x2] <var_decl
0x7ffff63f0720 *.LC0>)
Reload 1: reload_in (QI) = (subreg:QI (symbol_ref/f:HI ("*.LC0") [flags 0x2]
<var_decl 0x7ffff63f0720 *.LC0>) 1)
        GENERAL_REGS, RELOAD_FOR_INPUT (opnum = 1), can't combine
        reload_in_reg: (subreg:QI (reg/f:HI 105 [ a_I_m_lsm.5 ]) 1)
        reload_reg_rtx: (reg:QI 3 r3 [orig:118 a_I_m_lsm.5+1 ] [118])
$2 = void


For 930120-1.c at -O2:
Breakpoint 1, spill_failure (insn=0x7ffff6444990, rclass=R0_REG) at
../../trunk/gcc/reload1.c:2108
2108      if (asm_noperands (PATTERN (insn)) >= 0)
(gdb) p debug_rtx(insn)
(insn 173 170 176 28 (set (mem:QI (post_dec:HI (reg/f:HI 32 __SP_L__)) [0 S1
A8])
        (subreg:QI (reg/f:HI 487) 1)) 930120-1.c:67 1 {pushqi1}
     (expr_list:REG_ARGS_SIZE (const_int 3 [0x3])
        (nil)))
$1 = void
(gdb) p debug_reload_to_stream(stderr)
Reload 0: reload_in (HI) = (symbol_ref/f:HI ("*.LC2") [flags 0x2] <var_decl
0x7ffff6420850 *.LC2>)
        R0_REG, RELOAD_FOR_INPUT (opnum = 0)
        reload_in_reg: (symbol_ref/f:HI ("*.LC2") [flags 0x2] <var_decl
0x7ffff6420850 *.LC2>)
Reload 1: reload_in (QI) = (subreg:QI (symbol_ref/f:HI ("*.LC2") [flags 0x2]
<var_decl 0x7ffff6420850 *.LC2>) 1)
        GENERAL_REGS, RELOAD_FOR_INPUT (opnum = 0), can't combine
        reload_in_reg: (subreg:QI (reg/f:HI 487) 1)
$2 = void
(gdb) 

In both cases reload is trying to reload a symbol_ref to an R0_REG class.

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

--- Comment #6 from Steven Bosscher <steven at gcc dot gnu.org> 2012-12-07 22:50:28 UTC ---
Difficult to bisect, there are no test results posted on gcc-testresults...

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

--- Comment #7 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-12-08 10:28:07 UTC ---
Many thanks for your help!

Mike Stein stopped posting test results quite some time ago.  Dunno why, 
he does not respond to email.

avr.h defines R0_REG as register class with 1 fixed register, r0.

This regclass is subset of NO_LD_REGS and GENERAL_REGS, which is odd.

R0_REG does not make much sense to me, thus remove it from NO_LD_REGS 
and GENERAL_REGS or delete that regclass and constraint "t" completely.

I'll try next week and report back.

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

Steven Bosscher <steven at gcc dot gnu.org> changed:

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

--- Comment #8 from Steven Bosscher <steven at gcc dot gnu.org> 2012-12-08 13:16:23 UTC ---
Trying to bisect down to the revision where this problem appeared:

Fail: 193053 (1 Nov 2012)
Fail: 191882 (1 Oct 2012)
Pass: 188094 (1 Jun 2012)
Pass: 190028 (1 Aug 2012)
Fail: 190845 (1 Sep 2012)
Fail: 190426 (16 Aug 2012) -- does not build, double_int issues
Fail: 190521 (20 Aug 2012)
Pass: 190219 (8 Aug 2012)
Fail: 190324 (12 Aug 2012)
Fail: 190277 (10 Aug 2012)
Pass: 190246 (9 Aug 2012)
Fail: 190257 (9 Aug 2012)
Fail: 190252 (9 Aug 2012)
Pass: 190251 (9 Aug 2012)

Thus, caused by: http://gcc.gnu.org/ml/gcc-cvs/2012-08/msg00229.html

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[bernds at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

--- Comment #9 from Bernd Schmidt <bernds at gcc dot gnu.org> 2012-12-08 14:08:52 UTC ---
Created attachment 28900
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28900
Candidate patch

Try this.

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

--- Comment #10 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-12-10 14:33:29 UTC ---
(In reply to comment #9)
> Created attachment 28900 [details]
> Candidate patch
> 
> Try this.

It works. There are no more "spill in class 'R0_REG'" ICEs wozj your patch
(atop trunk 194354)

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

--- Comment #11 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-12-14 18:56:34 UTC ---
(In reply to comment #9)
> Created attachment 28900 [details]
> Candidate patch
> 
> Try this.

Bernd, do you intend to apply this, or should I post it for review?

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[bernds at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

Bernd Schmidt <bernds at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #28900|0                           |1
        is obsolete|                            |

--- Comment #12 from Bernd Schmidt <bernds at gcc dot gnu.org> 2012-12-18 04:50:04 UTC ---
Created attachment 28990
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28990
Better patch

Sorry for doing this, but here's a slightly improved version of the patch. Does
this also fix the issue?

This one was bootstrapped and tested on x86_64-linux, so it could go in if it
works; not sure I want to do that before I stop reading email for the next two
weeks though.

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

--- Comment #13 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-12-18 22:33:41 UTC ---
(In reply to comment #12)
> Created attachment 28990 [details]
> Better patch
> 
> Sorry for doing this, but here's a slightly improved version of the patch. Does
> this also fix the issue?

Yes, at least I don't see "spill in class 'R0_REG'" in the testsuite with
attachment 28990.

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch
      Known to work|                            |4.7.0, 4.7.2

--- Comment #14 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2013-01-25 20:55:53 UTC ---
Attachment 28990 is pending review at

http://gcc.gnu.org/ml/gcc-patches/2013-01/msg01255.html

with the following ChangeLog:

    PR other/54814
    * reload.c (find_valid_class_1): Use in_hard_reg_set_p instead of
    TEST_HARD_REG_BIT.

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

--- Comment #15 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2013-01-28 20:03:34 UTC ---
Author: gjl
Date: Mon Jan 28 20:03:26 2013
New Revision: 195515

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=195515
Log:
    PR other/54814
    * reload.c (find_valid_class_1): Use in_hard_reg_set_p instead of
    TEST_HARD_REG_BIT.


Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/reload.c

[Bug other/54814] [4.8 Regression] ICE: unable to find a register to spill in class 'R0_REG'

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54814

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

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

--- Comment #16 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2013-01-28 20:05:29 UTC ---
Fixed for the milestone.