Multiply32.cc

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#include "Multiply32.hh"
#include "PixelOperations.hh"
#include <cstring>
 
namespace openmsx {
 
// class Multiply32<uint32_t>
 
Multiply32<uint32_t>::Multiply32(const PixelOperations<uint32_t>& /*pixelOps*/)
{
        // nothing
}
 
 
// class Multiply32<uint16_t>
 
// gcc can optimize these rotate functions to just one instruction.
// We don't really need a rotate, but we do need a shift over a positive or
// negative (not known at compile time) distance, rotate handles this just fine.
// Note that 0 <= n < 32; on x86 this doesn't matter but on PPC it does.
static inline uint32_t rotLeft(uint32_t a, unsigned n)
{
        return (a << n) | (a >> (32 - n));
}
 
Multiply32<uint16_t>::Multiply32(const PixelOperations<uint16_t>& pixelOps)
{
        Rmask1 = pixelOps.getRmask();
        Gmask1 = pixelOps.getGmask();
        Bmask1 = pixelOps.getBmask();
 
        Rshift1 = ((2 + pixelOps.getRloss()) - pixelOps.getRshift()) & 31;
        Gshift1 = ((2 + pixelOps.getGloss()) - pixelOps.getGshift()) & 31;
        Bshift1 = ((2 + pixelOps.getBloss()) - pixelOps.getBshift()) & 31;
 
        Rmask2 = ((1 << (2 + pixelOps.getRloss())) - 1) <<
                        (10 + pixelOps.getRshift() - 2 * (2 + pixelOps.getRloss()));
        Gmask2 = ((1 << (2 + pixelOps.getGloss())) - 1) <<
                        (10 + pixelOps.getGshift() - 2 * (2 + pixelOps.getGloss()));
        Bmask2 = ((1 << (2 + pixelOps.getBloss())) - 1) <<
                        (10 + pixelOps.getBshift() - 2 * (2 + pixelOps.getBloss()));
 
        Rshift2 = (2 * (2 + pixelOps.getRloss()) - pixelOps.getRshift() - 10) & 31;
        Gshift2 = (2 * (2 + pixelOps.getGloss()) - pixelOps.getGshift() - 10) & 31;
        Bshift2 = (2 * (2 + pixelOps.getBloss()) - pixelOps.getBshift() - 10) & 31;
 
        Rshift3 = (Rshift1 +  0) & 31;
        Gshift3 = (Gshift1 + 10) & 31;
        Bshift3 = (Bshift1 + 20) & 31;
 
        factor = 0;
        memset(tab, 0, sizeof(tab));
}
 
void Multiply32<uint16_t>::setFactor32(unsigned f)
{
        if (factor == f) {
                return;
        }
        factor = f;
 
        for (unsigned p = 0; p < 0x10000; ++p) {
                uint32_t r = rotLeft((p & Rmask1), Rshift1) |
                             rotLeft((p & Rmask2), Rshift2);
                uint32_t g = rotLeft((p & Gmask1), Gshift1) |
                             rotLeft((p & Gmask2), Gshift2);
                uint32_t b = rotLeft((p & Bmask1), Bshift1) |
                             rotLeft((p & Bmask2), Bshift2);
                tab[p] = (((r * factor) >> 8) <<  0) |
                         (((g * factor) >> 8) << 10) |
                         (((b * factor) >> 8) << 20);
        }
}
 
} // namespace openmsx