[Bug middle-end/123105] New: avx512 slows compile time by 2.5x vs avx2 in testcase with eigen

[peter0x44 at disroot dot org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123105

            Bug ID: 123105
           Summary: avx512 slows compile time by 2.5x vs avx2 in testcase
                    with eigen
           Product: gcc
           Version: 15.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: peter0x44 at disroot dot org
  Target Milestone: ---

Compiling these two testcases shows a large discrepancy in compile time:

$ time g++ eigen_test_avx2.ii -O3 -march=skylake -std=c++23 -c

real    0m7.418s
user    0m6.966s
sys     0m0.452s

$ time g++ eigen_test_avx512.ii -O3 -march=znver5 -std=c++23 -c

real    0m21.449s
user    0m20.326s
sys     0m1.107s

I don't know if it's expected or not, so I'm reporting it.