Color.cpp

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/* Copyright (C) 2009 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 * Convert float RGB(A) colors to unsigned byte
 */

#include "precompiled.h"

#include "graphics/Color.h"

#include "maths/MathUtil.h"
#include "graphics/SColor.h"

#if HAVE_SSE
# include <xmmintrin.h>
# include "lib/sysdep/arch/x86_x64/x86_x64.h"
#endif

static SColor4ub fallback_ConvertRGBColorTo4ub(const RGBColor& src)
{
    SColor4ub result;
    result.R=clamp(int(src.X*255),0,255);
    result.G=clamp(int(src.Y*255),0,255);
    result.B=clamp(int(src.Z*255),0,255);
    result.A=0xff;
    return result;
}

// on IA32, this is replaced by an SSE assembly version in ia32.cpp
SColor4ub (*ConvertRGBColorTo4ub)(const RGBColor& src) = fallback_ConvertRGBColorTo4ub;


// Assembler-optimized function for color conversion
#if HAVE_SSE
static SColor4ub sse_ConvertRGBColorTo4ub(const RGBColor& src)
{
    const __m128 zero = _mm_setzero_ps();
    const __m128 _255 = _mm_set_ss(255.0f);
    __m128 r = _mm_load_ss(&src.X);
    __m128 g = _mm_load_ss(&src.Y);
    __m128 b = _mm_load_ss(&src.Z);

    // C = min(255, 255*max(C, 0)) ( == clamp(255*C, 0, 255) )
    r = _mm_max_ss(r, zero);
    g = _mm_max_ss(g, zero);
    b = _mm_max_ss(b, zero);

    r = _mm_mul_ss(r, _255);
    g = _mm_mul_ss(g, _255);
    b = _mm_mul_ss(b, _255);

    r = _mm_min_ss(r, _255);
    g = _mm_min_ss(g, _255);
    b = _mm_min_ss(b, _255);

    // convert to integer and combine channels using bit logic
    int ri = _mm_cvtss_si32(r);
    int gi = _mm_cvtss_si32(g);
    int bi = _mm_cvtss_si32(b);

    return SColor4ub(ri, gi, bi, 0xFF);
}
#endif

void ColorActivateFastImpl()
{
    if(0)
    {
    }
#if HAVE_SSE
    else if (x86_x64::Cap(x86_x64::CAP_SSE))
    {
        ConvertRGBColorTo4ub = sse_ConvertRGBColorTo4ub;
    }
#endif
    else
    {
        debug_printf(L"No SSE available. Slow fallback routines will be used.\n");
    }
}