[Bug rtl-optimization/53595] New: Code size increase of +10% between two 4.7.1 snapshot

[Bug rtl-optimization/53595] New: Code size increase of +10% between two 4.7.1 snapshot

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53595

             Bug #: 53595
           Summary: Code size increase of +10% between two 4.7.1 snapshot
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: gjl@gcc.gnu.org


Created attachment 27568
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27568
C source

This problem report is about a +10% of code size increase between the following
two 4.7.1 versions of gcc:

V1: SVN 185693 gcc-4_7-branch from 2012-03-22, 4.7.1 (prerelease)
V2: SVN 188257 gcc-4_7-branch from 2012-06-06, 4.7.1 (prerelease)

The attached test case is a reduced test case out of many other sources that
suffer from the same problem, so that the overall performance degradation is
unpleasant.

The RTL dumps show that the first pass that differs is IRA.

== Command line ==

$ avr-gcc -mmcu=atmega168 -c -std=gnu99 -Os -mstrict-X -ffixed-2 -ffixed-3 -dp
-fdump-rtl-ira-details -fdump-rtl-reload-details -fdump-rtl-postreload-details
bresenham-i.c -o bresenham-i-1.o -save-temps=obj

resp. with  -o bresenham-i-2.o for the second 4.7.1 snapshot.

== GCC configure ==

Target: avr
Configured with: ../../gcc.gnu.org/gcc-4_7-branch/configure --target=avr
--prefix=/local/gnu/install/gcc-4.7-mingw32 --host=i386-mingw32
--build=i686-linux-gnu --enable-languages=c,c++ --disable-nls --disable-shared
--with-dwarf2
Thread model: single
gcc version 4.7.1 20120606 (prerelease) (GCC) 

GNU C (GCC) version 4.7.1 20120606 (prerelease) (avr)
    compiled by GNU C version 3.4.5 (mingw-vista special r2), GMP version
4.3.2, MPFR version 2.4.2, MPC version 0.8.2

It's a canadian cross, but that surely does not matter here...

[Bug rtl-optimization/53595] Code size increase of +10% between two 4.7.1 snapshot

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53595

--- Comment #1 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-06-06 19:54:34 UTC ---
Created attachment 27570
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27570
ira dump of older version (good)

[Bug rtl-optimization/53595] Code size increase of +10% between two 4.7.1 snapshot

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53595

--- Comment #2 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-06-06 19:55:49 UTC ---
Created attachment 27571
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27571
ira dump of newer version (+10%)

[Bug rtl-optimization/53595] Code size increase of +10% between two 4.7.1 snapshot

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53595

--- Comment #3 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-06-06 19:56:57 UTC ---
Created attachment 27572
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27572
reload dump of older version (good)

[Bug rtl-optimization/53595] Code size increase of +10% between two 4.7.1 snapshot

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53595

--- Comment #4 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-06-06 19:58:10 UTC ---
Created attachment 27573
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27573
reload dump of newer version (+10%)

[Bug rtl-optimization/53595] Code size increase of +10% between two 4.7.1 snapshot

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53595

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

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

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-06-06 20:01:06 UTC ---
That's not very narrow interval.  Please bisect what affected it (or what
affected it most).

[Bug rtl-optimization/53595] Code size increase of +10% between two 4.7.1 snapshot

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53595

--- Comment #6 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-06-06 20:05:02 UTC ---
And here is the first part of the diff of the reload dumps that shows that
something weird is going on:

--- bresenham-i-1.198r.reload    Wed Jun  6 19:59:24 2012
+++ bresenham-i-2.198r.reload    Wed Jun  6 19:59:26 2012
@@ -273,123 +273,378 @@
 changing reg in insn 251
 changing reg in insn 249
 changing reg in insn 252
+Spilling for insn 40.
+Using reg 30 for reload 0
+Spilling for insn 44.
+Using reg 26 for reload 0
+Spilling for insn 45.
+Using reg 28 for reload 0
 Spilling for insn 65.
+Using reg 28 for reload 0
 Spilling for insn 68.
+Using reg 28 for reload 0
 Spilling for insn 71.
+Using reg 28 for reload 0
 Spilling for insn 75.
+Using reg 28 for reload 0
 Spilling for insn 76.
+Using reg 28 for reload 0
 Spilling for insn 78.
+Using reg 26 for reload 0
+Spilling for insn 248.
+Using reg 30 for reload 0
+Spilling for insn 249.
+Using reg 30 for reload 0
 Spilling for insn 202.
+Using reg 30 for reload 0
 Spilling for insn 203.
+Using reg 30 for reload 0
+Spilling for insn 96.
+Using reg 30 for reload 0
+Spilling for insn 204.
+Using reg 30 for reload 0
+Spilling for insn 205.
+Using reg 30 for reload 0
+Spilling for insn 108.
+Using reg 28 for reload 0
+Spilling for insn 112.
+Using reg 28 for reload 0
+Spilling for insn 114.
+Using reg 28 for reload 0
 Spilling for insn 142.
+Using reg 28 for reload 0
 Spilling for insn 143.
+Using reg 30 for reload 0
 Spilling for insn 144.
+Using reg 30 for reload 0
 Spilling for insn 145.
+Using reg 30 for reload 0
 Spilling for insn 146.
+Using reg 30 for reload 0
+Spilling for insn 154.
+Using reg 30 for reload 0
+Spilling for insn 159.
+Using reg 30 for reload 0
+Spilling for insn 165.
+Using reg 30 for reload 0
+Spilling for insn 170.
+Using reg 30 for reload 0
 Spilling for insn 176.
+Using reg 30 for reload 0
 Spilling for insn 179.
+Using reg 30 for reload 0
+Spilling for insn 40.
+Using reg 30 for reload 0
+Spilling for insn 44.
+Using reg 26 for reload 0
+Spilling for insn 45.
+Using reg 28 for reload 0
+Spilling for insn 65.
+Using reg 28 for reload 0
+Spilling for insn 68.
+Using reg 28 for reload 0
+Spilling for insn 71.
+Using reg 28 for reload 0
+Spilling for insn 75.
+Using reg 28 for reload 0
+Spilling for insn 76.
+Using reg 28 for reload 0
+Spilling for insn 78.
+Using reg 26 for reload 0
+Spilling for insn 248.
+Using reg 30 for reload 0
+Spilling for insn 249.
+Using reg 30 for reload 0
+Spilling for insn 202.
+Using reg 30 for reload 0
+Spilling for insn 203.
+Using reg 30 for reload 0
+Spilling for insn 96.
+Using reg 30 for reload 0
+Spilling for insn 204.
+Using reg 30 for reload 0
+Spilling for insn 205.
+Using reg 30 for reload 0
+Spilling for insn 108.
+Using reg 28 for reload 0
+Spilling for insn 112.
+Using reg 28 for reload 0
+Spilling for insn 114.
+Using reg 28 for reload 0
+Spilling for insn 142.
+Using reg 28 for reload 0
+Spilling for insn 143.
+Using reg 30 for reload 0
+Spilling for insn 144.
+Using reg 30 for reload 0
+Spilling for insn 145.
+Using reg 30 for reload 0
+Spilling for insn 146.
+Using reg 30 for reload 0
+Spilling for insn 154.
+Using reg 30 for reload 0
+Spilling for insn 159.
+Using reg 30 for reload 0
+Spilling for insn 165.
+Using reg 30 for reload 0
+Spilling for insn 170.
+Using reg 30 for reload 0
+Spilling for insn 176.
+Using reg 30 for reload 0
+Spilling for insn 179.
+Using reg 30 for reload 0

[Bug rtl-optimization/53595] Code size increase of +10% between two 4.7.1 snapshot

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53595

--- Comment #7 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-06-06 20:12:19 UTC ---
(In reply to comment #5)
> That's not very narrow interval.  Please bisect what affected it (or what
> affected it most).

The only changes to 4_7-branch in the IRA/reload area was for PR52804.
Will take until friday to before I can look deeper into it.

[Bug rtl-optimization/53595] Code size increase of +10% between two 4.7.1 snapshot

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53595

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |avr
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-06-07
                 CC|                            |vmakarov at redhat dot com
     Ever Confirmed|0                           |1

--- Comment #8 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-06-07 13:24:51 UTC ---
(In reply to comment #5)
> That's not very narrow interval.  Please bisect what affected it (or what
> affected it most).

CCing Vladimir

It is caused by fix for PR53065 in

http://gcc.gnu.org/viewcvs?view=revision&revision=186770

--- branches/gcc-4_7-branch/gcc/config/avr/avr.h    2012/04/24 15:23:22   
186769
+++ branches/gcc-4_7-branch/gcc/config/avr/avr.h    2012/04/24 15:23:46   
186770
@@ -394,6 +394,11 @@

 #define REGNO_OK_FOR_INDEX_P(NUM) 0

+#define HARD_REGNO_CALL_PART_CLOBBERED(REGNO, MODE)                    \
+  (((REGNO) < 18 && (REGNO) + GET_MODE_SIZE (MODE) > 18)               \
+   || ((REGNO) < REG_Y && (REGNO) + GET_MODE_SIZE (MODE) > REG_Y)      \
+   || ((REGNO) < REG_Z && (REGNO) + GET_MODE_SIZE (MODE) > REG_Z))
+

What's really confusing to me is that this macro is called with invalid
registers, i.e with registers that HARD_REGNO_MODE_OK will reject.

If the macro returns false for the invalid registers, the performance
regression goes away.

Vladimir, is it save to return 0 for invalid hard registers?

What's the point with generating different code when invalid registers are
treated differently?  As far as I can see the hard register is not about
SUBREGs, it contains a pointer.

[Bug rtl-optimization/53595] Code size increase of +10% between two 4.7.1 snapshot

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53595

--- Comment #9 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-06-07 13:27:33 UTC ---
Created attachment 27576
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27576
pr53595.diff

And here is a tentative patch:

Let HARD_REGNO_CALL_PART_CLOBBERED return false if HARD_REGNO_MODE_OK is false.

[Bug rtl-optimization/53595] Code size increase of +10% between two 4.7.1 snapshot

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53595

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #27576|0                           |1
        is obsolete|                            |

--- Comment #10 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-06-07 13:31:32 UTC ---
Created attachment 27577
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27577
pr53595.diff: tentative patch

Better return 0 as false...

[Bug rtl-optimization/53595] Code size increase of +10% between two 4.7.1 snapshot

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53595

--- Comment #11 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-06-08 17:04:41 UTC ---
FYI, the patch attachment 27568 also resolves the strange error described in
PR53615, at least for the test case given there.

[Bug rtl-optimization/53595] Code size increase of +10% between two 4.7.1 snapshot

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53595

--- Comment #12 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-06-28 13:53:59 UTC ---
Author: gjl
Date: Thu Jun 28 13:53:51 2012
New Revision: 189049

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=189049
Log:
    PR 53595
    * config/avr/avr.c (avr_hard_regno_call_part_clobbered): New.
    * config/avr/avr-protos.h (avr_hard_regno_call_part_clobbered): New.
    * config/avr/avr.h (HARD_REGNO_CALL_PART_CLOBBERED): Forward to
    avr_hard_regno_call_part_clobbered.


Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/avr/avr-protos.h
    trunk/gcc/config/avr/avr.c
    trunk/gcc/config/avr/avr.h

[Bug rtl-optimization/53595] Code size increase of +10% between two 4.7.1 snapshot

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53595

--- Comment #13 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-06-28 13:58:37 UTC ---
Author: gjl
Date: Thu Jun 28 13:58:32 2012
New Revision: 189050

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=189050
Log:
    Backport from 2012-06-28 mainline r189049
    PR 53595
    * config/avr/avr.c (avr_hard_regno_call_part_clobbered): New.
    * config/avr/avr-protos.h (avr_hard_regno_call_part_clobbered): New.
    * config/avr/avr.h (HARD_REGNO_CALL_PART_CLOBBERED): Forward to
    avr_hard_regno_call_part_clobbered.


Modified:
    branches/gcc-4_7-branch/gcc/ChangeLog
    branches/gcc-4_7-branch/gcc/config/avr/avr-protos.h
    branches/gcc-4_7-branch/gcc/config/avr/avr.c
    branches/gcc-4_7-branch/gcc/config/avr/avr.h

[Bug other/53595] Code size increase of +10% between two 4.7.1 snapshot

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53595

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ra
             Status|NEW                         |RESOLVED
          Component|rtl-optimization            |other
         Resolution|                            |FIXED
   Target Milestone|---                         |4.7.2

--- Comment #14 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-06-28 14:02:39 UTC ---
Rather worked around than a proper fix of the call site, e.g.
ira-costs.c:ira_tune_allocno_costs