[Bug target/60040] AVR: error: unable to find a register to spill in class 'POINTER_REGS'

[Bug target/60040] AVR: error: unable to find a register to spill in class 'POINTER_REGS'

[sebastian.huber@embedded-brains.de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60040

--- Comment #1 from Sebastian Huber <sebastian.huber@embedded-brains.de> ---
Created attachment 32024
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32024&action=edit
Test case.

[Bug target/60040] New: AVR: error: unable to find a register to spill in class 'POINTER_REGS'

[sebastian.huber@embedded-brains.de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60040

            Bug ID: 60040
           Summary: AVR: error: unable to find a register to spill in
                    class 'POINTER_REGS'
           Product: gcc
           Version: 4.8.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sebastian.huber@embedded-brains.de

avr-rtems4.11-gcc -fpreprocessed -w -mmcu=atmega128 -O2 -s test.i -o /dev/null
test.i: In function 'rtems_fdisk_recycle_segment':
test.i:107:1: error: unable to find a register to spill in class 'POINTER_REGS'
 }
 ^
test.i:107:1: error: this is the insn:
(insn 30 29 31 2 (set (reg:HI 26 r26)
        (reg/v/f:HI 51 [ dpd ])) test.i:95 82 {*movhi}
     (nil))
test.i:107: confused by earlier errors, bailing out

[Bug other/60040] AVR: error: unable to find a register to spill in class 'POINTER_REGS'

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60040

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #2 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
Seems like PR58545

*** This bug has been marked as a duplicate of bug 58545 ***

[Bug other/60040] AVR: error: unable to find a register to spill in class 'POINTER_REGS'

[sebastian.huber@embedded-brains.de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60040

--- Comment #3 from Sebastian Huber <sebastian.huber@embedded-brains.de> ---
With avr-rtems4.11-gcc (GCC) 4.9.0 20140218 (experimental) I still get the
error:

avr-rtems4.11-gcc -fpreprocessed -w -mmcu=atmega128 -O2 -s test.i -o /dev/null
test.i: In function 'rtems_fdisk_recycle_segment':
test.i:107:1: error: unable to find a register to spill in class 'POINTER_REGS'
 }
 ^
test.i:107:1: error: this is the insn:
(insn 30 29 31 2 (set (reg:HI 26 r26)
        (reg/v/f:HI 51 [ dpd ])) test.i:95 82 {*movhi}
     (nil))
test.i:107:1: internal compiler error: in spill_failure, at reload1.c:2106
0x825135 _fatal_insn(char const*, rtx_def const*, char const*, int, char
const*)
        /home/sh/archive/gcc-git/gcc/rtl-error.c:109
0x81a888 spill_failure
        /home/sh/archive/gcc-git/gcc/reload1.c:2106
0x81a888 find_reload_regs
        /home/sh/archive/gcc-git/gcc/reload1.c:2032
0x8230a7 select_reload_regs
        /home/sh/archive/gcc-git/gcc/reload1.c:2052
0x8230a7 reload(rtx_def*, int)
        /home/sh/archive/gcc-git/gcc/reload1.c:973
0x72c04d do_reload
        /home/sh/archive/gcc-git/gcc/ira.c:5469
0x72c04d rest_of_handle_reload
        /home/sh/archive/gcc-git/gcc/ira.c:5598
0x72c04d execute
        /home/sh/archive/gcc-git/gcc/ira.c:5627
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.

The output is different though.

[Bug other/60040] AVR: error: unable to find a register to spill in class 'POINTER_REGS'

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60040

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |NEW
   Last reconfirmed|                            |2014-02-18
         Resolution|DUPLICATE                   |---
     Ever confirmed|0                           |1

[Bug other/60040] AVR: error: unable to find a register to spill in class 'POINTER_REGS'

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60040

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |4.8.3, 4.9.0

--- Comment #4 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
Confirmed on current 4.9 trunk from 2014-02-18 (SVN 207837).

[Bug other/60040] AVR: error: unable to find a register to spill in class 'POINTER_REGS'

[amylaar at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60040

Jorn Wolfgang Rennecke <amylaar at gcc dot gnu.org> changed:

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

--- Comment #5 from Jorn Wolfgang Rennecke <amylaar at gcc dot gnu.org> ---
Created attachment 32372
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32372&action=edit
tentative patch for tentative reloads

In this case, reload already knows that it has to re-do the reloads, but it
goes ahead anyway and computes reloads registers for this iteration.
Unfortunately, when find_reload_regs fails, it then calls spill_failure,
giving a hard error for a reload that we don't need in the first place.

The patch in this attachment passes down something_changed from reload
as tentative to select_reload_regs and then on to find_reload_regs to
not worry about the failure.
Also, in reload, I made it not 'goto failure' in that case.

[Bug other/60040] AVR: error: unable to find a register to spill in class 'POINTER_REGS'

[sebastian.huber@embedded-brains.de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60040

--- Comment #6 from Sebastian Huber <sebastian.huber@embedded-brains.de> ---
GCC 4.9.0 20140407 with the proposed patch fixes the problem for me.

[Bug other/60040] AVR: error: unable to find a register to spill in class 'POINTER_REGS'

[joel at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60040

Joel Sherrill <joel at gcc dot gnu.org> changed:

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

--- Comment #7 from Joel Sherrill <joel at gcc dot gnu.org> ---
Was the proposed patch ever committed so this can be closed?

[Bug other/60040] AVR: error: unable to find a register to spill in class 'POINTER_REGS'

[matthijs at stdin dot nl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60040

Matthijs Kooijman <matthijs at stdin dot nl> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |matthijs at stdin dot nl

--- Comment #8 from Matthijs Kooijman <matthijs at stdin dot nl> ---
Seems not - just tried with avr-gcc 5.1 and it is still broken:

$ avr-gcc -fpreprocessed -w -mmcu=atmega128 -O2 -s test.i -o /dev/null
        test.i: In function 'rtems_fdisk_recycle_segment':
        test.i:107:1: error: unable to find a register to spill in class
'POINTER_REGS'
         }
         ^
        test.i:107:1: error: this is the insn:
        (insn 30 29 31 2 (set (reg:HI 26 r26)
                (reg/v/f:HI 51 [ dpd ])) /home/matthijs/test.i:95 83 {*movhi}
             (nil))
        test.i:107: confused by earlier errors, bailing out

$ avr-gcc --version
        avr-gcc (GCC) 5.1.0
        Copyright (C) 2015 Free Software Foundation, Inc.
        This is free software; see the source for copying conditions.  There is
NO
        warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE.

On the Arduino bugtracker [1], another testcase with the same symptoms was
reported. I'm attaching that here. This testcase works with -O2, but
breaks when -Os is used.

$ avr-gcc -c -Os  -mmcu=atmega328p  test2.c -o /dev/null

        test2.c: In function 'getSlope':
        test2.c:22:1: error: unable to find a register to spill in class
'POINTER_REGS'
         }
         ^
        test2.c:22:1: error: this is the insn:
        (insn 40 38 42 3 (set (reg:SF 63 [ D.1613 ])
                (mem:SF (post_inc:HI (reg:HI 16 r16 [orig:73 ivtmp.13 ] [73]))
[1 MEM[base: _27, offset: 0B]+0 S4 A8])) /home/matthijs/test.c:15 100 {*movsf}
             (expr_list:REG_INC (reg:HI 16 r16 [orig:73 ivtmp.13 ] [73])
                (nil)))
        test2.c:22: confused by earlier errors, bailing out

[1]: https://github.com/arduino/Arduino/issues/3972

[Bug other/60040] AVR: error: unable to find a register to spill in class 'POINTER_REGS'

[matthijs at stdin dot nl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60040

--- Comment #9 from Matthijs Kooijman <matthijs at stdin dot nl> ---
Created attachment 36499
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36499&action=edit
Second testcase, needs -Os to break