make tune fails on a Loongson processor
tg at gmplib.org
Mon Oct 18 19:36:29 CEST 2010
Some more information about mips timing under the kernel Linux:
The function clock_gettime claims accuracy, but is rejected by GMP's
sanity checks. And getrusage seems to be accurate, but is actually only
updated about 250 times per second!
I see two ways of fixing this.
(1) Make GMP be smarter about rejecting broken getrusage. See the remark
"getrusage_microseconds_p is fundamentally flawed" in tune/time.c.
(2) Make GMP use the instruction rdhwr where available. To make the
assembler accept it, one needs to pass -mips32r2 or -mips64r2 to the
it (depending which ABI we're using).
I do not intend to work more on this. Some person interested in MIPS
need to take it from here. Figuring out which MIPS processors support
rdhwr might be a place to start. Then you need to improve the mips cpu
recognition in configure.in, so that GMP can use rdhwr on just adequate
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