Here is what I discovered about this problem.
The MIPSpro 7.4.1 C compiler apparently has a structure assignment code
generation bug that is triggered at backend/access/transam/xlog.c:2683
LogwrtResult.Write = LogwrtResult.Flush = EndOfLog;
EndOfLog and LogwrtResult.Write are correct, but LogwrtResult.Flush ends
up corrupted.
I've opened a problem report with SGI (case ID 2505985 "MIPSpro 7.4.1 C
structure assignment bug") for those of you who need to track it. From
what I can see, PostgreSQL 7.3.x is vulnerable, PostgreSQL 7.4.1 seems
to pass its regression test, but I'd probably think twice about using
it when compiled with MIPSpro 7.4.1.
Everything seems ok when compiled with the SGI provided version of GCC 3.2.2.