[src/trunk]: src/doc Update aes_ccm_tag() hack for m68k.

[rin <rin%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/a8a0ee0da8cd
branches:  trunk
changeset: 940177:a8a0ee0da8cd
user:      rin <rin%NetBSD.org@localhost>
date:      Mon Oct 05 13:20:30 2020 +0000

description:
Update aes_ccm_tag() hack for m68k.

Even with ``memcmp fix'', GCC 9.4 miscompiles this function for -O[12].
But the situation was slightly changed from that with GCC 8.3:

* -O0 and -O1 work but -O2 fails for 68060 and 68040 (real hardware)
* -O0 and -O2 work but -O1 fails for 68020 and 68010 (TME)

diffstat:

 doc/HACKS |  17 ++++++++---------
 1 files changed, 8 insertions(+), 9 deletions(-)

diffs (32 lines):

diff -r 6aeeb3a184e3 -r a8a0ee0da8cd doc/HACKS
--- a/doc/HACKS Mon Oct 05 12:28:45 2020 +0000
+++ b/doc/HACKS Mon Oct 05 13:20:30 2020 +0000
@@ -1,4 +1,4 @@
-# $NetBSD: HACKS,v 1.210 2020/10/05 10:44:09 rin Exp $
+# $NetBSD: HACKS,v 1.211 2020/10/05 13:20:30 rin Exp $
 #
 # This file is intended to document workarounds for currently unsolved
 # (mostly) compiler bugs.
@@ -985,15 +985,14 @@
 kcah
 
 port   m68k
-hack   compile aes_ccm_tag() with -O0 for GCC8
+hack   compile aes_ccm_tag() with -O0 for GCC8 and GCC9
 cdate  Mon Aug 10 06:27:29 UTC 2020
+mdate  Mon Oct  5 22:00:00 JST 2020
 who    rin
 file   src/sys/crypto/aes/aes_ccm.c: 1.5
-descr  GCC 8.4 miscompiles aes_ccm_tag() for m68k with optimization level
-       -O[12], which results in failure in aes_ccm_selftest().
-       This is observed for amiga (A1200, 68060), mac68k (Quadra 840AV,
-       68040), and luna68k (nono, 68030 emulator). However, it is not for
-       sun3 (TME, 68020 emulator) and sun2 (TME, 68010 emulator).
-       At the moment, it is unclear whether this is due to differences b/w
-       68010-20 vs 68030-60, or something wrong with TME.
+descr  GCC 9.4 and 8.3 miscompile aes_ccm_tag() for m68k with optimization
+       level -O[12], which results in failure in aes_ccm_selftest().
+       For 9.4, -O0 and -O1 work but -O2 fails for amiga (A1200, 68060) and
+       mac68k (Quadra 840AV, 68040). Whereas -O0 and -O2 work but -O1 fails
+       for sun3 (TME, 68020 emulator) and sun2 (TME, 68010 emulator).
 kcah