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[Bug rtl-optimization/59811] [4.8/4.9 Regression] Huge increase in memory usage and compile time with gfortran 4.8


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59811

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
      Known to work|                            |4.7.3
           Keywords|                            |compile-time-hog
   Last reconfirmed|                            |2014-01-15
          Component|fortran                     |rtl-optimization
     Ever confirmed|0                           |1
            Summary|Huge increase in memory     |[4.8/4.9 Regression] Huge
                   |usage and compile time with |increase in memory usage
                   |gfortran 4.8                |and compile time with
                   |                            |gfortran 4.8
   Target Milestone|---                         |4.8.3
      Known to fail|                            |4.8.2, 4.9.0

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.  At -O2 I see for 4.8

 alias stmt walking      :   4.90 ( 8%) usr   0.02 ( 3%) sys   5.05 ( 8%) wall 
     0 kB ( 0%) ggc
 tree copy propagation   :   0.02 ( 0%) usr   0.00 ( 0%) sys   0.02 ( 0%) wall 
   513 kB ( 0%) ggc
 combiner                :  45.94 (71%) usr   0.57 (83%) sys  46.57 (71%) wall
1612812 kB (96%) ggc
 integrated RA           :   0.59 ( 1%) usr   0.01 ( 1%) sys   0.58 ( 1%) wall 
 12481 kB ( 1%) ggc
 LRA hard reg assignment :   7.53 (12%) usr   0.03 ( 4%) sys   7.56 (11%) wall 
     0 kB ( 0%) ggc
 TOTAL                 :  65.03             0.69            65.92           
1681500 kB

and for 4.7

 alias stmt walking      :   2.77 (28%) usr   0.02 (17%) sys   2.80 (28%) wall 
     0 kB ( 0%) ggc
 tree copy propagation   :   1.64 (17%) usr   0.01 ( 8%) sys   1.67 (17%) wall 
   513 kB ( 1%) ggc
 integrated RA           :   0.66 ( 7%) usr   0.02 (17%) sys   0.68 ( 7%) wall 
  6295 kB (10%) ggc
 reload                  :   0.45 ( 5%) usr   0.01 ( 8%) sys   0.46 ( 5%) wall 
  1593 kB ( 3%) ggc
 reload CSE regs         :   0.74 ( 7%) usr   0.00 ( 0%) sys   0.75 ( 7%) wall 
  1103 kB ( 2%) ggc
 TOTAL                 :   9.87             0.12            10.01             
61922 kB

the combiner slowdown and the LRA thing are worth investigating.  I suppose
the generated code differs quite a bit ;)  It's a very large function
with some very large basic-block(s).  Current trunk behaves comparable
to GCC 4.8.


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