[Bug target/17503] New: Huge performance regression in invalid_mode_change_p

[Bug target/17503] New: Huge performance regression in invalid_mode_change_p

[drow at gcc dot gnu dot org]

Compiling insn-attrtab.i with compilers from a few weeks ago, this function is
way down the profile.  Now it's at the very top.

                               :bool
                               :invalid_mode_change_p (unsigned int regno, enum
reg_class class,
                               :                       enum machine_mode from_mode)
   625  0.1102    55  0.5528   :{ /* invalid_mode_change_p total: 117807 20.7631
 4747 47.7085 */
                               :  enum machine_mode to_mode;
                               :  int n;
   113  0.0199    17  0.1709   :  int start = regno * MAX_MACHINE_MODE;
                               :
116873 20.5985  4675 46.9849   :  EXECUTE_IF_SET_IN_BITMAP (&subregs_of_mode,
start, n,
                               :    if (n >= MAX_MACHINE_MODE + start)
                               :      return 0;
                               :    to_mode = n - start;
                               :    if (CANNOT_CHANGE_MODE_CLASS (from_mode,
to_mode, class))
                               :      return 1;
                               :  );
                               :  return 0;
   196  0.0345     0 0.0e+00   :}

I am not positive whether the function is being called more, or just spending
more time in the bitmap, but it looks like the latter - we're creating many more
entries in subregs_of_mode.  I selected a random call to invalid_mode_change_p,
and compared the size of the bitmap in both compilers.  In the older compiler,
the high entry in the bitmap was around 10,000 bits; in the newer, around 450,000.

The newer compiler was updated this morning.

-- 
           Summary: Huge performance regression in invalid_mode_change_p
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: drow at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17503

[Bug middle-end/17503] [4.0 Regression] Huge performance regression in invalid_mode_change_p

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-09-15 17:49 -------
Most likely caused by:
2004-09-14  Roger Sayle  <roger@eyesopen.com>

        PR rtl-optimization/9771
        * regclass.c (CALL_REALLY_USED_REGNO_P): New macro to eliminate
        conditional compilation in init_reg_sets_1.
        (init_reg_sets_1): Let global_regs[i] take priority over the frame
        (but not stack) pointer exceptions to regs_invalidated_by_call.
        (globalize_reg): Globalizing a fixed register may need to update
        regs_invalidated_by_call.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |roger at eyesopen dot com
           Severity|normal                      |critical
          Component|target                      |middle-end
           Keywords|                            |compile-time-hog
            Summary|Huge performance regression |[4.0 Regression] Huge
                   |in invalid_mode_change_p    |performance regression in
                   |                            |invalid_mode_change_p
   Target Milestone|---                         |4.0.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17503

[Bug middle-end/17503] [4.0 Regression] Huge performance regression in invalid_mode_change_p

[roger at eyesopen dot com]

------- Additional Comments From roger at eyesopen dot com  2004-09-15 19:09 -------
I find it extremely unlikely that the patch mentioned in comment #2 could have
any performance impact, even on code that declares register variables which
should be the only observable functionality change.

Daniel, I wonder whether you could re-run your profiles after reverting my
patch and confirm there's no performance change, i.e. that it's innocent?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17503

[Bug middle-end/17503] [4.0 Regression] Huge performance regression in invalid_mode_change_p

[drow at gcc dot gnu dot org]

------- Additional Comments From drow at gcc dot gnu dot org  2004-09-20 19:23 -------
Yes, Roger's patch is innocent.

Richard, I haven't narrowed it down to one patch yet, but it's down to the
six-hour window in which you committed the patch for PR 9997.  That's my
suspect.  There is no substantive difference in the RTL diffs except that
numbers for pseudoregisters get larger:
-(insn 9 8 10 1 (set (reg:SI 59 [ T.665 ])
+(insn 9 8 10 1 (set (reg:SI 11374 [ T.665 ])
         (mem/s/j:SI (plus:SI (reg/f:SI 11377)

and stack offsets fluctuate a bit.

I'll verify that I've pegged the right patch.  Do we need to do this at -O0?

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17503

[Bug middle-end/17503] [4.0 Regression] Huge performance regression in invalid_mode_change_p

[drow at gcc dot gnu dot org]

------- Additional Comments From drow at gcc dot gnu dot org  2004-09-20 19:54 -------
Yes, definitely caused by that patch.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|roger at eyesopen dot com   |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17503

[Bug middle-end/17503] quadratic behaviour in invalid_mode_change_p

[rth at gcc dot gnu dot org]

------- Additional Comments From rth at gcc dot gnu dot org  2004-09-20 21:41 -------
"Huge"?  Ok, so the thing's now at the top of the profile, but it still only uses
four (4) seconds of cpu time, so fixing it isn't going to help *that* much.  I've
reduced the severity of the pr.

I suspect that you can only see this effect at -O0 with Truely Large synthetic
functions, as seen in insn-attrtab.c.  So I am caring only a little at the moment.

Note that the "regression" comes not from the stack slot sharing per-se, but 
actually honoring use_register_for_decl, which is true for scalar temporaries.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|critical                    |normal
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2004-09-20 21:41:01
               date|                            |
            Summary|[4.0 Regression] Huge       |quadratic behaviour in
                   |performance regression in   |invalid_mode_change_p
                   |invalid_mode_change_p       |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17503

[Bug rtl-optimization/17503] quadratic behaviour in invalid_mode_change_p

[rth at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|rth at gcc dot gnu dot org  |
         AssignedTo|unassigned at gcc dot gnu   |rth at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED
          Component|middle-end                  |rtl-optimization


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17503

[Bug rtl-optimization/17503] quadratic behaviour in invalid_mode_change_p

[rth at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |WAITING
           Keywords|                            |patch


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17503

[Bug middle-end/17503] quadratic behaviour in invalid_mode_change_p

[drow at gcc dot gnu dot org]

------- Additional Comments From drow at gcc dot gnu dot org  2004-09-21 15:21 -------
Thanks.  Patch bootstrapped on ia64-hpux, i386-linux, and powerpc-linux with no
regressions.  Clears up the performance spike for cc1-i-files at -O0 and
decreases page faults on some other testing by a (very) small amount.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW
          Component|rtl-optimization            |middle-end
   Last reconfirmed|2004-09-20 21:41:01         |2004-09-21 15:21:21
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17503

[Bug middle-end/17503] quadratic behaviour in invalid_mode_change_p

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-09-24 19:47 -------
Subject: Bug 17503

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	rth@gcc.gnu.org	2004-09-24 19:47:06

Modified files:
	gcc            : ChangeLog combine.c flow.c regclass.c regs.h 
	                 rtl.h 

Log message:
	PR rtl-opt/17503
	* regclass.c (subregs_of_mode): Turn into an htab.  Make static.
	(som_hash, som_eq): New.
	(init_subregs_of_mode, record_subregs_of_mode): New.
	(cannot_change_mode_set_regs): Rewrite for htab implementation.
	(invalid_mode_change_p): Likewise.
	* combine.c (gen_lowpart_for_combine): Use record_subregs_of_mode.
	* flow.c (mark_used_regs): Likewise.
	(life_analysis): Use init_subregs_of_mode.
	* regs.h (subregs_of_mode): Remove.
	* rtl.h (init_subregs_of_mode, record_subregs_of_mode): Declare.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.5606&r2=2.5607
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/combine.c.diff?cvsroot=gcc&r1=1.454&r2=1.455
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/flow.c.diff?cvsroot=gcc&r1=1.597&r2=1.598
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/regclass.c.diff?cvsroot=gcc&r1=1.197&r2=1.198
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/regs.h.diff?cvsroot=gcc&r1=1.35&r2=1.36
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/rtl.h.diff?cvsroot=gcc&r1=1.509&r2=1.510



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17503

[Bug middle-end/17503] quadratic behaviour in invalid_mode_change_p

[rth at gcc dot gnu dot org]

------- Additional Comments From rth at gcc dot gnu dot org  2004-09-24 20:00 -------
Fixed.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17503

[Bug middle-end/17503] quadratic behaviour in invalid_mode_change_p

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-10-12 23:35 -------
Subject: Bug 17503

CVSROOT:	/cvs/gcc
Module name:	gcc
Branch: 	gcc-3_4-branch
Changes by:	rth@gcc.gnu.org	2004-10-12 23:35:39

Modified files:
	gcc            : ChangeLog combine.c flow.c regclass.c regs.h 
	                 rtl.h 

Log message:
	PR rtl-opt/17503
	* regclass.c (subregs_of_mode): Turn into an htab.  Make static.
	(som_hash, som_eq): New.
	(init_subregs_of_mode, record_subregs_of_mode): New.
	(cannot_change_mode_set_regs): Rewrite for htab implementation.
	(invalid_mode_change_p): Likewise.
	* combine.c (gen_lowpart_for_combine): Use record_subregs_of_mode.
	* flow.c (mark_used_regs): Likewise.
	(life_analysis): Use init_subregs_of_mode.
	* regs.h (subregs_of_mode): Remove.
	* rtl.h (init_subregs_of_mode, record_subregs_of_mode): Declare.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=2.2326.2.653&r2=2.2326.2.654
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/combine.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.400.4.10&r2=1.400.4.11
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/flow.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.572.4.2&r2=1.572.4.3
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/regclass.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.183.4.1&r2=1.183.4.2
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/regs.h.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.31&r2=1.31.4.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/rtl.h.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.448.4.6&r2=1.448.4.7



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17503

[Bug middle-end/17503] quadratic behaviour in invalid_mode_change_p

[rth at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.0.0                       |3.4.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17503

[Bug middle-end/17503] quadratic behaviour in invalid_mode_change_p

[rth at gcc dot gnu dot org]

------- Additional Comments From rth at gcc dot gnu dot org  2004-10-13 16:59 -------
*** Bug 16834 has been marked as a duplicate of this bug. ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jozef dot kruger at philips
                   |                            |dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17503

[Bug middle-end/17503] quadratic behaviour in invalid_mode_change_p

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-12-04 00:37 -------
Subject: Bug 17503

CVSROOT:	/cvs/gcc
Module name:	gcc
Branch: 	gcc-3_3-branch
Changes by:	rth@gcc.gnu.org	2004-12-04 00:36:41

Modified files:
	gcc            : ChangeLog combine.c flow.c regclass.c regs.h 
	                 rtl.h 

Log message:
	PR rtl-opt/17503
	* regclass.c (subregs_of_mode): Turn into an htab.  Make static.
	(som_hash, som_eq): New.
	(init_subregs_of_mode, record_subregs_of_mode): New.
	(cannot_change_mode_set_regs): Rewrite for htab implementation.
	(invalid_mode_change_p): Likewise.
	* combine.c (gen_lowpart_for_combine): Use record_subregs_of_mode.
	* flow.c (mark_used_regs): Likewise.
	(life_analysis): Use init_subregs_of_mode.
	* regs.h (subregs_of_mode): Remove.
	* rtl.h (init_subregs_of_mode, record_subregs_of_mode): Declare.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.16114.2.1031&r2=1.16114.2.1032
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/combine.c.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.325.2.17&r2=1.325.2.18
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/flow.c.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.541.2.6&r2=1.541.2.7
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/regclass.c.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.160.4.7&r2=1.160.4.8
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/regs.h.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.26.4.2&r2=1.26.4.3
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/rtl.h.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.375.2.8&r2=1.375.2.9



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17503

[Bug middle-end/17503] quadratic behaviour in invalid_mode_change_p

[rth at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4.3                       |3.3.6


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17503