[Bug tree-optimization/23928] New: Exceptions require an excessive amount of compile-time memory

[rguenth at tat dot physik dot uni-tuebingen dot de]

The tramp3d-v4.cpp testcase with flatten (aka leafify) enabled requires
excessive amount of memory for the compile, if exceptions are not
disabled via -fno-exceptions.

Compiling with -O2 -Dleafify=flatten -fno-exceptions mainline needs
at max. 670MB of ram, while omitting -fno-exceptions it tops out at
2.7GB(!).
 
Testing was done on x86_64 with 8GB ram to avoid hitting swap. ggc
params are --param ggc-min-expand=100 --param ggc-min-heapsize=131072.

The tramp3d-v4.cpp testcase is available from
http://www.tat.physik.uni-tuebingen.de/~rguenth/gcc/tramp3d-v4.cpp.gz

-ftime-report from the -fexceptions run shows

Execution times (seconds)
 garbage collection    :  19.16 ( 4%) usr   1.10 (11%) sys  20.33 ( 4%) wall   
   0 kB ( 0%) ggc
...
 integration           : 188.01 (41%) usr   2.53 (26%) sys 191.29 (40%) wall 
842654 kB (24%) ggc
...
 tree CFG cleanup      :  10.57 ( 2%) usr   0.05 ( 1%) sys  10.69 ( 2%) wall  
33061 kB ( 1%) ggc
 tree VRP              :   5.18 ( 1%) usr   0.14 ( 1%) sys   5.14 ( 1%) wall  
40349 kB ( 1%) ggc
 tree copy propagation :   5.46 ( 1%) usr   0.09 ( 1%) sys   5.56 ( 1%) wall   
5073 kB ( 0%) ggc
 tree store copy prop  :   1.10 ( 0%) usr   0.02 ( 0%) sys   0.97 ( 0%) wall   
1015 kB ( 0%) ggc
 tree find ref. vars   :   3.96 ( 1%) usr   0.05 ( 1%) sys   4.06 ( 1%) wall 
150561 kB ( 4%) ggc
 tree PTA              :  17.47 ( 4%) usr   0.29 ( 3%) sys  17.45 ( 4%) wall  
59716 kB ( 2%) ggc
 tree alias analysis   :  12.44 ( 3%) usr   0.61 ( 6%) sys  12.84 ( 3%) wall  
95403 kB ( 3%) ggc
 tree PHI insertion    :   2.25 ( 0%) usr   0.02 ( 0%) sys   2.49 ( 1%) wall  
35414 kB ( 1%) ggc
 tree SSA rewrite      :  11.87 ( 3%) usr   0.04 ( 0%) sys  11.91 ( 3%) wall 
203499 kB ( 6%) ggc
 tree SSA other        :   2.02 ( 0%) usr   0.22 ( 2%) sys   2.46 ( 1%) wall   
2499 kB ( 0%) ggc
 tree SSA incremental  :  25.40 ( 6%) usr   0.18 ( 2%) sys  26.07 ( 6%) wall  
63750 kB ( 2%) ggc
 tree operand scan     :  10.79 ( 2%) usr   1.18 (12%) sys  12.01 ( 3%) wall 
116147 kB ( 3%) ggc
 dominator optimization:  11.64 ( 3%) usr   0.08 ( 1%) sys  12.08 ( 3%) wall 
168798 kB ( 5%) ggc
...
 expand                :  15.71 ( 3%) usr   0.07 ( 1%) sys  15.54 ( 3%) wall 
194871 kB ( 6%) ggc
...
 TOTAL                 : 461.33             9.78           473.07           
3503243 kB

-- 
           Summary: Exceptions require an excessive amount of compile-time
                    memory
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at tat dot physik dot uni-tuebingen dot de
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23928