[Bug middle-end/84040] New: [8 regression] compilation time of gcc.c-torture/compile/limits-blockid.c is 50x slower

[nsz at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84040

            Bug ID: 84040
           Summary: [8 regression] compilation time of
                    gcc.c-torture/compile/limits-blockid.c is 50x slower
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nsz at gcc dot gnu.org
  Target Milestone: ---

noticed on aarch64 recently that

gcc -c -O3 -g gcc/gcc/testsuite/gcc.c-torture/compile/limits-blockid.c

is much slower with gcc-8 (about 2min here) than with gcc-7 (about 2s).

times with -ftime-report -ftime-report-details : usr/sys/wall/mem

gcc-8 -g
 phase opt and generate:   0.59 (28%) usr   0.04 ( 6%) sys   0.62 (22%) wall  
78453 kB (61%) ggc
 TOTAL                 :   2.11             0.71             2.83            
129464 kB

gcc-8 -O3
 phase opt and generate:   0.14 (12%) usr   0.01 ( 1%) sys   0.15 ( 8%) wall   
2121 kB ( 4%) ggc
 TOTAL                 :   1.18             0.67             1.86             
50773 kB

gcc-8 -O3 -g
 phase opt and generate  : 105.10 (99%) usr   0.22 (23%) sys 105.33 (98%) wall 
110874 kB (67%) ggc
...
 scheduling              :  34.45 (32%) usr   0.03 ( 3%) sys  34.49 (32%) wall 
  3906 kB ( 2%) ggc
 scheduling fusion       :  34.72 (33%) usr   0.02 ( 2%) sys  34.75 (32%) wall 
  3908 kB ( 2%) ggc
 scheduling 2            :  34.39 (32%) usr   0.01 ( 1%) sys  34.39 (32%) wall 
  3906 kB ( 2%) ggc
...
 TOTAL                 : 106.59             0.97           107.57            
166572 kB

gcc-7 -O3 -g
 phase opt and generate:   0.61 (31%) usr   0.02 ( 3%) sys   0.63 (23%) wall  
42520 kB (46%) ggc
 TOTAL                 :   2.00             0.76             2.78             
93398 kB