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Old June 24th 03, 01:36 PM
Jungrae Kim
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Default How to turn off spontaneous deferral on Itanium?

Hi,
I'm a graduate student developing JAVA JIT compiler on Itanium.
Working with Itanium, I got a problem with speculative loads and needs
your kind help to get out of it.

Here's my situation,
I'm trying to use the "speculative load" feature of IA64 for
performance. But I found speculative loads sometimes mark target
register with NaT bits even if all the conditions are successful.

I suspect the reason for the unexpected deferrals is "spontaneous
deferral". According to "Intel Itanium architecture software
developer's manual (revision 2.1)",
"In addition to the deferral of exceptional conditions, speculative
loads may be deferred automatically by hardware based on
implementation-dependent criteria, such as the detection of a cache
miss. Such deferral is referred to as 'spontaneous deferral', and is
done in order to increase performance"(volume 2, section 5.5.5
"deferral of speculative load faults")

I wonder spontaneous deferral is turned on by default on Itanium.
If so, I wanna know how to turn it off or bypass it.
(I found several options on the manual to turn the spontaneous
deferral off, but they all required system privilege.

Your kind help will be GREATLY appreciated.

Thanks in advance.