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PLI instruction on cortex-A8

sapthagiri baratam over 11 years ago

Note: This was originally posted on 11th October 2012 at http://forums.arm.com

Hi, I tried PLI at couple of places in my h264 video decoder code, But didn't get any gain in Mhz. I am running my decoder on Begel board (i.e. OMAP3530, cortex-A8, ARMV7a architecture).
Does PLI work on cortex-A8 processor?
One example of my code seems like below

"PLI of reconstuction module code (code size of 400 bytes, Only addition and storing output into buffer)
Inverse Quant & InverseTransform operation
Reconstruction module operation (only addition and storing output into buffer)"

Thanks,
Sapthagiri

Martin Weidmann over 11 years ago

Note: This was originally posted on 11th October 2012 at http://forums.arm.com

I've never tried it, but a quick search of the A8 documentation from ARM's website suggests not:

"ARMv7-A specifies the PLI instruction as a preload hint instruction. Because the processor implements a blocking L1 cache and to avoid the penalty associated with a cache miss, the processor handles the PLI instruction as a NOP."

http://infocenter.arm.com/help/topic/com.arm.doc.ddi0344k/Cbbbahfg.html
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Peter Harris over 11 years ago

Note: This was originally posted on 11th October 2012 at http://forums.arm.com

Hmm - assuming most CODEC code has quite dense loops, I doubt instruction fetch is on the critical path. PLD for data fetch tends to be more useful for this kind of thing.
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