[LAD] Optimisations

Fons Adriaensen fons at linuxaudio.org
Mon Aug 18 18:36:35 UTC 2014

On Mon, Aug 18, 2014 at 06:11:33PM +0100, Will Godfrey wrote:
> A long time ago ... in a land far away :)
> I did some assembler programming on the Acorn Archimedes (ARM 2/3) and worked
> out a series of additions and subtractions that would perform very fast
> multiplication of awkward numbers by known amounts.
> Is there any point in doing this for C programs, or are modern compilers
> sophisticated enough to do such things themselves?
> If anyone is interested *7 is:
> RSB R1, R0, R0, LSL #3

:-) Memories... I love ARM assembly... 

Modern compilers will do such things. If they exploit other
features of the ARM (such as all instructions being conditional)
I don't know, but it's very well possible.



A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

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