e752058b86
[Why&How] 1. Stack usage is pretty high as fixed31_32 struct is 8 bytes and we have functions with >30 vars on the stack. 2. Optimize gamma calculation by reducing number of calls to dc_fixpt_pow Our X points are divided into 32 regions wth 16 pts each. Each region is 2x the previous, meaning x[i] = 2*x[i-16] for i>=16. Using (2x)^gamma = 2^gamma * x^gamma, we can recursively compute powers of gamma, we just need first 16 pts to start it up. dc_fixpt_pow() is expensive, it computes x^y by doing exp(y*logx) Exp is done by Taylor series approximation, and log by Newton-like approximation that also uses exp internally. In short, it's significantly heavier than run-of-the-mill addition/subtraction/multiply. Signed-off-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com> Reviewed-by: Anthony Koo <Anthony.Koo@amd.com> Acked-by: Aric Cyr <Aric.Cyr@amd.com> Acked-by: Leo Li <sunpeng.li@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> |
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