[Bug debug/31412] var-tracking.c is slow

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31412

--- Comment #20 from Richard Biener <rguenth at gcc dot gnu.org> ---
Seems to be gone on trunk (4.9)

variable tracking       :   0.01 ( 0%) usr   0.00 ( 0%) sys   0.01 ( 0%) wall  
   48 kB ( 0%) ggc
 var-tracking dataflow   :   0.00 ( 0%) usr   0.00 ( 0%) sys   0.01 ( 0%) wall 
     4 kB ( 0%) ggc
 var-tracking emit       :   0.02 ( 1%) usr   0.00 ( 0%) sys   0.00 ( 0%) wall 
     0 kB ( 0%) ggc

4.8 still has

 variable tracking       :   1.29 (35%) usr   0.01 ( 6%) sys   1.30 (33%) wall 
  2556 kB ( 4%) ggc

not sure what fixed it.