[Bug bootstrap/78705] ICE in ix86_test_dumping_memory_blockage

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78705

--- Comment #5 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
i386.md's define_expand "memory_blockage" has:
  operands[0] = gen_rtx_MEM (BLKmode, gen_rtx_SCRATCH (Pmode));
so it's due to the difference in Pmode between i386 and x86_64.