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paraj · 02 August 2022, 07:49

If you extend the table to cover 90 degrees more (repeat the 64 first entries at the end) you can do the double lookup in 32 cycles (and 7 memory accesses):

Code:

    ext.w     d0
    move.b    64(a0,d0.w),d1
    move.b    (a0,d0.w),d0

Doesn't extend as nicely to larger tables (or word sized values), but the idea of having an extra pi/2 values at the end (or start) of a sin/cos table can often be used for a slight speed-up at the cost of extra memory usage.

02 August 2022, 07:49	#227
paraj Registered User Join Date: Feb 2017 Location: Denmark Posts: 1,105	If you extend the table to cover 90 degrees more (repeat the 64 first entries at the end) you can do the double lookup in 32 cycles (and 7 memory accesses): Code: ext.w d0 move.b 64(a0,d0.w),d1 move.b (a0,d0.w),d0 Doesn't extend as nicely to larger tables (or word sized values), but the idea of having an extra pi/2 values at the end (or start) of a sin/cos table can often be used for a slight speed-up at the cost of extra memory usage.