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Refactor the waveshaper function to save some bytes.

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This commit is contained in:
Veikko Sariola
2020-05-03 17:02:08 +03:00
parent 3c3fe6caf8
commit 6be7959cd1
2 changed files with 12 additions and 18 deletions
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30
src/4klang.asm
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@ -131,7 +131,7 @@ EXPORT MANGLE_FUNC(FloatRandomNumber,0)
;-------------------------------------------------------------------------------
; Input: st0 : a - the shaping coefficient
; st1 : x - input value
; Output: st0 : (1+k)*x/(1+k*abs(x)), where k=2*m/(1-m) and m=2*a-1
; Output: st0 : x*a/(1-a+(2*a-1)*abs(x))
; and x is clamped first if GO4K_USE_WAVESHAPER_CLIP
;-------------------------------------------------------------------------------
%ifdef INCLUDE_WAVESHAPER
@ -151,23 +151,17 @@ go4kWaveshaper_clip:
fstp st1 ; x' a, where x' = clamp(x)
fxch ; a x' (from now on just called x)
%endif
fsub dword [c_0_5] ; a-.5 x
fadd st0 ; 2*a-1 x
fst dword [esp-4] ; m=2*a-1 x
fadd st0 ; 2*m x
fld1 ; 1 2*m x
fsub dword [esp-4] ; 1-m 2*m x
fdivp st1, st0 ; k=2*m/(1-m) x
fld st1 ; x k x
fabs ; abs(x) k x
fmul st1 ; k*abs(x) k x
fld1 ; 1 k*abs(x) k x
faddp st1, st0 ; 1+k*abs(x) k x
fxch st1 ; k 1+k*abs(x) x
fld1 ; 1 k 1+k*abs(x) x
faddp st1, st0 ; 1+k 1+k*abs(x) x
fmulp st2 ; 1+k*abs(x) (1+k)*x
fdivp st1, st0 ; (1+k)*x/(1+k*abs(x))
fld st0 ; a a x
fsub dword [c_0_5] ; a-.5 a x
fadd st0 ; 2*a-1 a x
fld st2 ; x 2*a-1 a x
fabs ; abs(x) 2*a-1 a x
fmulp st1 ; (2*a-1)*abs(x) a x
fld1 ; 1 (2*a-1)*abs(x) a x
faddp st1 ; 1+(2*a-1)*abs(x) a x
fsub st1 ; 1-a+(2*a-1)*abs(x) a x
fdivp st1, st0 ; a/(1-a+(2*a-1)*abs(x)) x
fmulp st1 ; x*a/(1-a+(2*a-1)*abs(x))
ret
%endif ; INCLUDE_WAVESHAPER

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tests/expected_output/test_dst_modulation.raw
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