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Re: stmw/lmw [Was: CVS commit: src/sys/arch/powerpc/powerpc]




On Monday, August 4, 2003, at 07:51 AM, Jason Thorpe wrote:


On Sunday, August 3, 2003, at 06:31  PM, Simon Burge wrote:

Does this have any measurable impact on trap response and context switch
times (simply because of more instruction fetches)?  It's also larger
code, so we have greater I$ pollution...

It might be worth #ifdef'ing the use of those insns, using __OPTIMIZE_SIZE__ to use the load/store-multiple insns on non-PPC64.

I thought of that. But use of stmw/lmw are usually buried inside other macros and makes even more messy. The amount of instructions is relatively minor
and is (IMO) not worth the effort.

It's worth noting, however, that individual load/store insns are probably going to be faster than the load/store-multiple on most modern PPCs (like, probably everything since the 601).

That has been my experience.
--
Matt Thomas                     email: matt%3am-software.com@localhost
3am Software Foundry www: http://3am-software.com/bio/matt/ Cupertino, CA disclaimer: I avow all knowledge of this message.




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