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Cortex-A9 : NEON assembly code is not giving expected performance compared with ARM assembly code

Note: This was originally posted on 27th November 2012 at http://forums.arm.com

I am facing one problem, like I have handmade ARM9 assembly code and NEON assembly code. I expected NEON assembly should get 4X % improvement for the speed compared with ARM assembly code. But I could not see that improvement in NEON assembly code.

Can you please explain me what could be the reason?

I am using Cortex-A9 processor and configuration in my Makefile : "CFLAGS=--cpu=Cortex-A9 -O2 -Otime --apcs=/fpic --no_hide_all"

Please let me know is there anything I need to change the make file settings to get NEON performance improvement?

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Martin Weidmann over 12 years ago

Note: This was originally posted on 27th November 2012 at http://forums.arm.com

First off, your flags looks fine.

I think you problem is more fundamental. NEON is not some magic wand that will immediately make you code run faster. How much you will see depends almost entirely on what kind of processing you do, and how well you write the code.
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Martin Weidmann over 12 years ago

Note: This was originally posted on 27th November 2012 at http://forums.arm.com

First off, your flags looks fine.

I think you problem is more fundamental. NEON is not some magic wand that will immediately make you code run faster. How much you will see depends almost entirely on what kind of processing you do, and how well you write the code.
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