[Bug tree-optimization/97199] ICE in process_bb at gcc/tree-ssa-sccvn.c:7250

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97199

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
(gdb) p debug_gimple_stmt (phi)
.MEM_104 = PHI <(4), .MEM_97(41)>

so clearly bogus IL here.  The issue is the virtual operand update in
if-conversion combine_blocks which does

      /* We release virtual PHIs late because we have to propagate them
         out using the current VUSE.  The def might be the one used
         after the loop.  */
      vphi = get_virtual_phi (bb);
      if (vphi)
        {
          /* When there's just loads inside the loop a stray virtual
             PHI merging the uses can appear, update last_vdef from
             it.  */
          if (!last_vdef)
            last_vdef = gimple_phi_arg_def (vphi, 0);

but this doesn't work since we already removed all edges which clears
the PHI arg defs.