earmv4 binaries on RPI3 won't work?

[Izumi Tsutsui <tsutsui%ceres.dti.ne.jp@localhost>]

Hi,

Now I'm playing NetBSD/hpcarm 8.0 on SHARP W-ZERO3 and at least
it seems to boot to multiuser:
 https://dmesgd.nycbug.org/index.cgi?do=view&id=4862

Next, I'd like to build earmv4 pkgsrc binaries for NetBSD/hpcarm
so I build NetBSD/evbarm binaries with MACHINE_ARCH=earmv4 to
compile earmv4 binaries on Raspberry Pi 3B.

A RPI2 kernel built with MACHINE_ARCH=earmv4 boot, but
several userland binaries causes "Illegal instruction" errors:

---
 :

Starting root file system check:
fsck: /dev/rld0a: Illegal instruction
Automatic file system check failed; help!
ERROR: ABORTING BOOT (sending SIGTERM to parent)!
[1]   Terminated              (stty status "^T...
Enter pathname of shell or RETURN for /bin/sh:

---

gdb(1) also gets SIGILL so I have not investigated
which instruction actually causes the SIGILL.

Is this backward incompatibility (earmv4 EABI5 binaries
on earmv6/v7 processors) expected?

If so, is there any gcc options to keep compatibilities?
(like "-m68020-60" option on m68k)

Thanks,

---
Izumi Tsutsui