[Bug tree-optimization/117922] New: [15 Regression] 1000% compilation time slow down on the testcase from pr26854

[pheeck at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117922

            Bug ID: 117922
           Summary: [15 Regression] 1000% compilation time slow down on
                    the testcase from pr26854
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Keywords: compile-time-hog, needs-bisection
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pheeck at gcc dot gnu.org
  Target Milestone: ---
              Host: x86_64-linux
            Target: x86_64-linux

Compiling the all.i testcase from pr26854 slowed down 10x (you can get the
testcase here:
http://www.math.purdue.edu/~lucier/gcc/test-files/bugzilla/1/all.i.gz, gunzip
it twice).

Running

time gcc -O2 all.i

with GCC 14.2 gets me

real    2m57.090s
user    2m36.641s
sys     0m20.309s

but running the same thing with trunk GCC gets me

real    25m36.666s
user    25m14.545s
sys     0m21.044s

Richi's additional findings:

> It also takes 24GB of ram.  -fno-ext-dce does not seem to fix it, neither
> -fno-crc-optimize.
> 
> -O1 seems "fine".