I don't know what happened here, unfortunately. The version of dsp_mixer.s added to libogc on Nov 14, 2008 in c76d8b851f uses andcf and jlz here, and the version we have matches the one from Feb 5, 2009 in ae5c3a5fb5 exactly (prior to the fixes in my previous commit). I can't see any reason why wait_for_dsp_mail would be changed like this.
ANDCF and ANDF were previously swapped and JNE/JEQ/JZR/JNZ became JNZ/JZ/JLNZ/JLZ on Apr 3, 2009 in 7c4e654253, corresponding to a change Hermes made on Nov 10, 2008 in 2cea6d99ad. But these predate the test being added.
The only other information I can find is that ASNDLIB 1.0 released on November 11, 2008, at https://web.archive.org/web/20120326145022/http://www.entuwii.net/foro/viewtopic.php?f=6&t=87 (but there aren't any surviving links from there).
This change makes assembling DSPTestText match DSPTestBinary, though HermesText doesn't yet match HermesBinary.
The test data was originally added on April 18, 2009 in e7e4ef4481. Then, set16 and set40 were swapped on April 22, 2009 89178f411c, which updated the DSPSpy version of dsp_code, but not the version in DSPTool used for testing. So, when the test was made, the assembled data matched the text, but a few days after it no longer did.
Similarly, on Jul 7, 2009 in 1654c582ab the conditional instructions were adjusted, and 0x1706 was changed from JRL to JRNC and 0x0297 was changed from JGE to JC.
For what it's worth, devkitPro made the same changes on May 31, 2010 in 8a65c85c9b and updated their version of the asnd ucode (which is this ucode) on June 11, 2011 in b1b8ecab3a (though this update also includes other feature changes). Note that at the time, they didn't reassemble the ucode unless they made changes to it; the assembled was stored in the repo until bfb705fe16~...d20f9bdcfb43260c6c759f4fb98d724931443f93.
This fixes the following failures with Hermes:
!! 0015 : 8e00 vs 8f00 - set16 vs set40
!! 016f : 8e00 vs 8f00 - set16 vs set40
and with Hermes:
!! 0014 : 8e00 vs 8f00 - set16 vs set40
!! 0063 : 8e00 vs 8f00 - set16 vs set40
!! 019b : 1706 vs 1701 - jrnc $AR0 vs jrl $AR0
!! 01bf : 0297 vs 0290 - jc 0x01dc vs jge 0x01dc
!! 01d2 : 0297 vs 0290 - jc 0x01dc vs jge 0x01dc
Hermes has the remaining failures:
!! 027b : 03c0 vs 03a0 - andcf $AC1.M, #0x8000 vs andf $AC1.M, #0x8000
!! 027d : 029d vs 0294 - jlz 0x027a vs jnz 0x027a
Page faults should only occur on architectures that support exception
handlers, so skip the test on other architectures to avoid spurious test
failures.
SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
Merry