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102 lines
1.9 KiB
C++
102 lines
1.9 KiB
C++
//========= Copyright <20> 1996-2005, Valve Corporation, All rights reserved. ============//
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//
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// Purpose:
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//
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//=====================================================================================//
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#include "core/stdafx.h"
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#include "mathlib/ssemath.h"
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// NOTE: This has to be the last file included!
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//#include "tier0/memdbgon.h"
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fltx4 Pow_FixedPoint_Exponent_SIMD(const fltx4& x, int exponent)
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{
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fltx4 rslt = Four_Ones; // x^0=1.0
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int xp = abs(exponent);
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if (xp & 3) // fraction present?
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{
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fltx4 sq_rt = SqrtEstSIMD(x);
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if (xp & 1) // .25?
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rslt = SqrtEstSIMD(sq_rt); // x^.25
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if (xp & 2)
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rslt = MulSIMD(rslt, sq_rt);
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}
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xp >>= 2; // strip fraction
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fltx4 curpower = x; // curpower iterates through x,x^2,x^4,x^8,x^16...
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while (1)
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{
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if (xp & 1)
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rslt = MulSIMD(rslt, curpower);
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xp >>= 1;
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if (xp)
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curpower = MulSIMD(curpower, curpower);
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else
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break;
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}
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if (exponent < 0)
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return ReciprocalEstSaturateSIMD(rslt); // pow(x,-b)=1/pow(x,b)
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else
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return rslt;
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}
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#ifndef _PS3 // these aren't fast (or correct) on the PS3
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/*
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* (c) Ian Stephenson
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*
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* ian@dctsystems.co.uk
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*
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* Fast pow() reference implementation
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*/
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static float shift23 = (1 << 23);
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static float OOshift23 = 1.0 / (1 << 23);
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float FastLog2(float i)
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{
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float LogBodge = 0.346607f;
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float x;
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float y;
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x = float(*(int*)&i);
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x *= OOshift23; //1/pow(2,23);
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x = x - 127;
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y = x - floorf(x);
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y = (y - y * y) * LogBodge;
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return x + y;
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}
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float FastPow2(float i)
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{
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float PowBodge = 0.33971f;
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float x;
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float y = i - floorf(i);
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y = (y - y * y) * PowBodge;
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x = i + 127 - y;
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x *= shift23; //pow(2,23);
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*(int*)&x = (int)x;
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return x;
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}
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float FastPow(float a, float b)
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{
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if (a <= OOshift23)
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{
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return 0.0f;
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}
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return FastPow2(b * FastLog2(a));
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}
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float FastPow10(float i)
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{
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return FastPow2(i * 3.321928f);
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}
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#else
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#pragma message("TODO: revisit fast logs on all PPC hardware")
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#endif
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