[Bug rtl-optimization/49890] New: IRA spill with plenty of available registers

[Bug rtl-optimization/49890] New: IRA spill with plenty of available registers

[pthaugen at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49890

           Summary: IRA spill with plenty of available registers
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: pthaugen@gcc.gnu.org
                CC: vmakarov@gcc.gnu.org, bergner@gcc.gnu.org
              Host: powerpc64-linux
            Target: powerpc64-linux
             Build: powerpc64-linux


Vlad,
  Opening bz as you requested.  Background/detail can be found here:
http://gcc.gnu.org/ml/gcc/2011-05/msg00186.html.

Basically, following testcase compiled with gcc -S -m64 -O3 -mcpu=power7 causes
IRA to spill pseudo used for copy.

void foo(float *f1, float*f2) {
  *f1 = *f2;
}


**** Allocnos coloring:

  Loop 0 (parent -1, header bb0, depth 0)
    bbs: 2
    all: 0r120
    modified regnos: 120
    border:
    Pressure: NON_FLOAT_REGS=2
    Hard reg set forest:
      0:( 0 3-12 14-63 65 66 68-72 74 75 77-108)@0
      Spill a0(r120,l0)
Disposition:
    0:r120 l0   mem

[Bug rtl-optimization/49890] IRA spill with plenty of available registers

[vmakarov at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49890

Vladimir Makarov <vmakarov at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |vmakarov at redhat dot com

--- Comment #1 from Vladimir Makarov <vmakarov at redhat dot com> 2011-08-18 16:12:45 UTC ---
IRA removes some classes for consideration on the 2nd pass to speed up cost
calculation which is very time consuming.  IRA did it in too optimistic way. 
That is the reason of the problem.

I'll send a patch which removes classes in more conservative way and fixes the
problem.

[Bug rtl-optimization/49890] IRA spill with plenty of available registers

[vmakarov at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49890

--- Comment #2 from Vladimir Makarov <vmakarov at gcc dot gnu.org> 2011-08-18 17:06:26 UTC ---
Author: vmakarov
Date: Thu Aug 18 17:06:18 2011
New Revision: 177874

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=177874
Log:
2011-08-18  Vladimir Makarov  <vmakarov@redhat.com>

    PR rtl-optimization/49890
    * ira-costs.c (setup_regno_cost_classes_by_aclass): Don't exclude
    subclasses of class which is superset of a pressure class.


Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/ira-costs.c

[Bug rtl-optimization/49890] IRA spill with plenty of available registers

[pthaugen at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49890

Pat Haugen <pthaugen at gcc dot gnu.org> changed:

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

--- Comment #3 from Pat Haugen <pthaugen at gcc dot gnu.org> 2011-08-23 18:46:21 UTC ---
Fixed