IA64 xchg -- why only acquire?

[Intel_C_Intel]

Please illuminate.

regards,
alexander.

[ClayB]

Alexander -

Are you wondering about why only acquire semantics? Or are you wondering why not release, instead?

For me, I think this operation requires both, but I have no idea why acquire was chosen. I've looked through the three Itanium programming books I have. Only one addresses this issue and only then to define it as an acquire operation.

I'll see if I can pass you inquiry on to someone else more versed in Itanium processors.

-- clay

[terekhov]

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ClayB wrote:
Alexander -Are you wondering about why only acquire semantics?

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Yes. I need release and all sort of other msync semantics. And also "naked" (no msync) atomic stuff, to begin with. In my book, op.acquire is "equivalent" to op.(hoist_load+hoist_store) and release is nothing but op.(sinkt_load+sink_store). I need less constrained atomic "op"-stuff as well. See http://tinyurl.com/xky8 and http://tinyurl.com/xky9.