[Bug debug/59992] [4.9 Regression] Compilation of insn-recog.c too slow due to var-tracking

[aoliva at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59992

--- Comment #9 from Alexandre Oliva <aoliva at gcc dot gnu.org> ---
Created attachment 32213
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32213&action=edit
avoid quadratic behavior for the removal of useless values

This is the first of the two patches; it extends the condition that protects
from quadratic behavior in dropping useless values to the second path that
calls this function.  This is enough to cut down the vt_initialize time from
over 1700 to about 500 seconds for the insn-recog testcase.