On 8/29/2014 6:41 AM, Paul Gilmartin wrote:
On Thu, 28 Aug 2014 12:15:57 -0700, Ed Jaffe wrote:
ISTR it used to be that prefetched cache lines were thrown away on a key
change. I'm not sure if that's true any more.
That might be a design decision, that it's less costly to discard the
entire cache line infrequently than to verify the key on every access.
The key value for SPKA is provided in a register (more accurately, by a
base+displacement calculation), so the target key cannot be known early
unless the base register is coded as GPR0. Even then, the instruction
might be updated in storage before it executes. If there has been an
optimization in this processing over the years, it's likely to assume,
at prefetch time, that SPKAs coded with GPR0 are exactly what they
appear to be...
--
Edward E Jaffe
Phoenix Software International, Inc
831 Parkview Drive North
El Segundo, CA 90245
http://www.phoenixsoftware.com/
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