[Bug tree-optimization/102943] [12 Regression] Jump threader compile-time hog with 521.wrf_r

["hubicka at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102943

--- Comment #31 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
With g:r12-5872-gf157c5362b4844f7676cae2aba81a4cf75bd68d5 I limited inliner to
not produce such a large function, so bumping up --param
max-inline-functions-called-once-insns will be necessary to reproduce the
problem.

I will re-do time stats for 1-partition cc1plus LTO build, but I did the same
for linking clang with LTO and passes with over 2% time are:
Time variable                                   usr           sys          wall
          GGC
 garbage collection                 :  26.88 (  3%)   0.27 (  1%)  28.53 (  3%)
    0  (  0%)
 ipa lto gimple in                  :  19.84 (  2%)   1.86 (  4%)  28.42 (  3%)
 3660M ( 13%)
 cfg cleanup                        :  15.36 (  2%)   0.39 (  1%)  16.38 (  2%)
  154M (  1%)
 df live&initialized regs           :  16.20 (  2%)   0.35 (  1%)  18.29 (  2%)
    0  (  0%)
 df reg dead/unused notes           :  17.94 (  2%)   0.43 (  1%)  19.35 (  2%)
  361M (  1%)
 alias analysis                     :  19.87 (  2%)   0.24 (  1%)  21.05 (  2%)
  853M (  3%)
 alias stmt walking                 :  22.90 (  2%)   1.25 (  3%)  25.44 (  2%)
   68M (  0%)
 tree VRP                           :  22.79 (  2%)   1.06 (  2%)  24.22 (  2%)
  488M (  2%)
 tree PTA                           :  30.37 (  3%)   1.84 (  4%)  32.71 (  3%)
  215M (  1%)
 tree operand scan                  :  19.04 (  2%)   0.86 (  2%)  21.70 (  2%)
 1233M (  5%)
 dominator optimization             :  28.85 (  3%)   1.66 (  4%)  32.00 (  3%)
  531M (  2%)
 backwards jump threading           :  23.00 (  2%)   1.37 (  3%)  24.52 (  2%)
  154M (  1%)
 tree PRE                           :  21.81 (  2%)   1.11 (  3%)  24.55 (  2%)
  500M (  2%)
 tree FRE                           :  18.69 (  2%)   1.40 (  3%)  20.12 (  2%)
  221M (  1%)
 expand                             :  21.35 (  2%)   1.14 (  3%)  23.27 (  2%)
 2399M (  9%)
 CSE                                :  20.69 (  2%)   0.78 (  2%)  21.82 (  2%)
  124M (  0%)
 CPROP                              :  16.27 (  2%)   0.62 (  1%)  17.10 (  2%)
  419M (  2%)
 combiner                           :  27.46 (  3%)   0.81 (  2%)  30.46 (  3%)
  854M (  3%)
 integrated RA                      :  70.76 (  7%)   1.82 (  4%)  72.74 (  7%)
 3795M ( 14%)
 LRA non-specific                   :  19.51 (  2%)   0.54 (  1%)  20.89 (  2%)
  159M (  1%)
 reload CSE regs                    :  20.32 (  2%)   0.49 (  1%)  19.98 (  2%)
  290M (  1%)
 scheduling 2                       :  44.95 (  5%)   0.98 (  2%)  48.23 (  4%)
  163M (  1%)
 rest of compilation                :  30.44 (  3%)   1.92 (  4%)  32.03 (  3%)
  366M (  1%)
 TOTAL                              : 985.14         42.92       1082.89       
27226M

So dominators, VRP, and backward searching seems to be still slow on trunk from
20211204