[Bug lto/92674] [8/9/10 Regression] ICE in gimple_phi_arg, at gimple.h:4406 since r240291

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92674

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Created attachment 47360
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47360&action=edit
patch

I am testing the attached.  The testcase seems to be too much reduced to be
useful for the testsuite.