[Bug ipa/87615] Possible excessive compile time with -O2

[jamborm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87615

--- Comment #12 from Martin Jambor <jamborm at gcc dot gnu.org> ---
I have just posted the patch for review in:

https://gcc.gnu.org/ml/gcc-patches/2018-12/msg00456.html

With it the compile time of the testcase goes down from approximately
340 seconds to about 160 seconds (With -fno-ipa-cp -fno-inline the
compile time is only 30 seconds, however) the relevant bits
of-ftime-report -ftime-report-details are below:

Time variable                                   usr           sys          wall
              GGC
 phase setup                        :   0.00 (  0%)   0.00 (  0%)   0.01 (  0%)
   1215 kB (  0%)
 phase parsing                      :   1.07 (  1%)   1.12 ( 38%)   2.20 (  1%)
  37151 kB (  7%)
 phase opt and generate             : 161.38 ( 99%)   1.85 ( 62%) 163.28 ( 99%)
 469241 kB ( 92%)
...
 ipa function summary               :   0.11 (  0%)   0.00 (  0%)   0.10 (  0%)
    554 kB (  0%)
 `- tree STMT verifier              :   0.04 (  0%)   0.00 (  0%)   0.04 (  0%)
      0 kB (  0%)
 `- loop init                       :   0.04 (  0%)   0.00 (  0%)   0.04 (  0%)
     11 kB (  0%)
 `- tree SSA verifier               :   0.02 (  0%)   0.00 (  0%)   0.02 (  0%)
      0 kB (  0%)
 `- dominance computation           :   0.02 (  0%)   0.00 (  0%)   0.03 (  0%)
      0 kB (  0%)
...
 ipa cp                             :   0.12 (  0%)   0.02 (  1%)   0.10 (  0%)
   9656 kB (  2%)
 `- tree STMT verifier              :   0.05 (  0%)   0.00 (  0%)   0.05 (  0%)
      0 kB (  0%)
 `- alias stmt walking              :   0.00 (  0%)   0.00 (  0%)   0.02 (  0%)
      0 kB (  0%)
 `- tree SSA verifier               :   0.02 (  0%)   0.00 (  0%)   0.02 (  0%)
      0 kB (  0%)
 `- dominance computation           :   0.02 (  0%)   0.00 (  0%)   0.03 (  0%)
      0 kB (  0%)
...
 ipa icf                            :   2.98 (  2%)   0.00 (  0%)   2.99 (  2%)
      0 kB (  0%)
 `- tree STMT verifier              :   0.04 (  0%)   0.00 (  0%)   0.04 (  0%)
      0 kB (  0%)
 `- tree SSA verifier               :   0.02 (  0%)   0.00 (  0%)   0.02 (  0%)
      0 kB (  0%)
 `- dominance computation           :   0.01 (  0%)   0.00 (  0%)   0.01 (  0%)
      0 kB (  0%)
...
 CFG verifier                       :   2.27 (  1%)   0.00 (  0%)   2.37 (  1%)
      0 kB (  0%)
...
 df reaching defs                   :   1.59 (  1%)   0.01 (  0%)   1.59 (  1%)
      0 kB (  0%)
 df live regs                       :   1.74 (  1%)   0.00 (  0%)   1.73 (  1%)
      0 kB (  0%)
 df live&initialized regs           :   5.32 (  3%)   0.00 (  0%)   5.37 (  3%)
      0 kB (  0%)
...
 alias stmt walking                 :   3.19 (  2%)   0.30 ( 10%)   3.35 (  2%)
      5 kB (  0%)
...
 tree VRP                           :  36.88 ( 23%)   0.15 (  5%)  37.00 ( 22%)
  58212 kB ( 11%)
 `- tree SSA incremental            :   0.10 (  0%)   0.07 (  2%)   0.19 (  0%)
  16219 kB (  3%)
 `- CFG verifier                    :   0.02 (  0%)   0.00 (  0%)   0.02 (  0%)
      0 kB (  0%)
 `- repair loop structures          :   0.01 (  0%)   0.00 (  0%)   0.02 (  0%)
      0 kB (  0%)
 `- dominance computation           :   0.02 (  0%)   0.00 (  0%)   0.02 (  0%)
      0 kB (  0%)
 `- tree operand scan               :   0.09 (  0%)   0.04 (  1%)   0.14 (  0%)
   9616 kB (  2%)
 `- tree SSA verifier               :   0.10 (  0%)   0.00 (  0%)   0.10 (  0%)
      0 kB (  0%)
 `- loop init                       :   0.03 (  0%)   0.00 (  0%)   0.03 (  0%)
     23 kB (  0%)
 `- tree STMT verifier              :   0.13 (  0%)   0.00 (  0%)   0.15 (  0%)
      0 kB (  0%)
 tree Early VRP                     :   6.53 (  4%)   0.00 (  0%)   6.52 (  4%)
   1621 kB (  0%)
 `- CFG verifier                    :   0.01 (  0%)   0.00 (  0%)   0.01 (  0%)
      0 kB (  0%)
 `- repair loop structures          :   0.01 (  0%)   0.00 (  0%)   0.01 (  0%)
      0 kB (  0%)
 `- dominance computation           :   0.01 (  0%)   0.00 (  0%)   0.01 (  0%)
      0 kB (  0%)
 `- tree operand scan               :   0.00 (  0%)   0.00 (  0%)   0.01 (  0%)
      0 kB (  0%)
 `- tree SSA verifier               :   0.04 (  0%)   0.00 (  0%)   0.04 (  0%)
      0 kB (  0%)
 `- loop init                       :   0.05 (  0%)   0.00 (  0%)   0.05 (  0%)
     39 kB (  0%)
 `- tree STMT verifier              :   0.05 (  0%)   0.00 (  0%)   0.05 (  0%)
      0 kB (  0%)
 tree FRE                           :  59.08 ( 36%)   0.69 ( 23%)  59.93 ( 36%)
   1822 kB (  0%)
 `- CFG verifier                    :   0.02 (  0%)   0.00 (  0%)   0.03 (  0%)
      0 kB (  0%)
 `- repair loop structures          :   0.01 (  0%)   0.00 (  0%)   0.01 (  0%)
      0 kB (  0%)
 `- dominance computation           :   0.01 (  0%)   0.00 (  0%)   0.01 (  0%)
      0 kB (  0%)
 `- tree SSA verifier               :   0.08 (  0%)   0.00 (  0%)   0.08 (  0%)
      0 kB (  0%)
 `- loop init                       :   0.06 (  0%)   0.00 (  0%)   0.05 (  0%)
      0 kB (  0%)
 `- alias stmt walking              :   0.78 (  0%)   0.01 (  0%)   0.69 (  0%)
      5 kB (  0%)
 `- tree STMT verifier              :   0.09 (  0%)   0.00 (  0%)   0.09 (  0%)
      0 kB (  0%)
 tree SSA verifier                  :   5.00 (  3%)   0.00 (  0%)   4.86 (  3%)
      0 kB (  0%)
 `- dominance computation           :   0.32 (  0%)   0.00 (  0%)   0.40 (  0%)
      0 kB (  0%)
 tree STMT verifier                 :   6.82 (  4%)   0.03 (  1%)   6.82 (  4%)
      0 kB (  0%)
...
 verify RTL sharing                 :   3.95 (  2%)   0.00 (  0%)   3.91 (  2%)
      0 kB (  0%)