[Bug tree-optimization/44563] GCC uses a lot of RAM when compiling a large numbers of functions

[hubicka at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44563

--- Comment #11 from Jan Hubicka <hubicka at gcc dot gnu.org> 2010-12-13 13:22:28 UTC ---
Patched compiler at -O2 now shows:
 integration           : 166.20 (16%) usr   0.19 ( 1%) sys 166.86 (15%) wall  
92691 kB ( 4%) ggc
 tree CCP              : 792.75 (74%) usr   0.15 ( 1%) sys 794.63 (73%) wall  
66560 kB ( 3%) ggc

integration is probably the overhead of splitting BBs, I wonder what makes tree
CCP so slow, it is probably worth investigating.

The profile shows:
2009425  73.3643  cc1                      cc1                     
gsi_for_stmt
398058   14.5331  cc1                      cc1                     
gimple_set_bb                                                                   
22230     0.8116  libc-2.11.1.so           libc-2.11.1.so           _int_malloc
14339     0.5235  cc1                      cc1                     
gimple_split_block                                                              
11727     0.4282  libc-2.11.1.so           libc-2.11.1.so           memset
10411     0.3801  libc-2.11.1.so           libc-2.11.1.so           _IO_vfscanf 
9095      0.3321  cc1                      cc1                      htab_delete
6061      0.2213  cc1                      cc1                     
bitmap_set_bit                                                                  
5990      0.2187  no-vmlinux               no-vmlinux               /no-vmlinux
5912      0.2158  libc-2.11.1.so           libc-2.11.1.so           _int_free   
5077      0.1854  libc-2.11.1.so           libc-2.11.1.so          
malloc_consolidate
4516      0.1649  cc1                      cc1                     
htab_find_slot_with_hash                                                        
4515      0.1648  opreport                 opreport                
/usr/bin/opreport
4284      0.1564  libc-2.11.1.so           libc-2.11.1.so           free        
4234      0.1546  libc-2.11.1.so           libc-2.11.1.so           malloc
4106      0.1499  cc1                      cc1                     
htab_traverse_noresize                                                          
3737      0.1364  libc-2.11.1.so           libc-2.11.1.so           calloc
3197      0.1167  cc1                      cc1                      eq_node     
2996      0.1094  cc1                      cc1                     
df_note_compute
2632      0.0961  cc1                      cc1                     
ggc_internal_alloc_stat                                                         
2476      0.0904  cc1                      cc1                     
bitmap_bit_p
Other passes are sub 10s each.

Maybe tree-ccp just gets the overhead of merging the large BBs into single?

Honza