SSE Interpolazione bilineare

Question

Sto implementando l'interpolazione bilineare in un circuito chiuso e cerco di ottimizzarlo con SSE, ma ottengo zero accelerazioni da esso.

Ecco il codice, la versione non SIMD utilizza una semplice struttura vettore che potrebbe essere definito come struct Vec3f { float x, y, z; } con operatori di moltiplicazione e addizione attuate:

#ifdef USE_SIMD 
    const Color c11 = pixelCache[y1 * size.x + x1]; 
    const Color c12 = pixelCache[y2 * size.x + x1]; 
    const Color c22 = pixelCache[y2 * size.x + x2]; 
    const Color c21 = pixelCache[y1 * size.x + x2]; 

    __declspec(align(16)) float mc11[4] = { 1.0, c11.GetB(), c11.GetG(), c11.GetR() }; 
    __declspec(align(16)) float mc12[4] = { 1.0, c12.GetB(), c12.GetG(), c12.GetR() }; 
    __declspec(align(16)) float mc22[4] = { 1.0, c22.GetB(), c22.GetG(), c22.GetR() }; 
    __declspec(align(16)) float mc21[4] = { 1.0, c21.GetB(), c21.GetG(), c21.GetR() }; 

    // scalars in vector form for SSE 
    const float s11 = (x2-x)*(y2-y); 
    const float s12 = (x2-x)*(y-y1); 
    const float s22 = (x-x1)*(y-y1); 
    const float s21 = (x-x1)*(y2-y); 

    __declspec(align(16)) float ms11[4] = {1.0, s11, s11, s11}; 
    __declspec(align(16)) float ms12[4] = {1.0, s12, s12, s12}; 
    __declspec(align(16)) float ms22[4] = {1.0, s22, s22, s22}; 
    __declspec(align(16)) float ms21[4] = {1.0, s21, s21, s21}; 

    __asm { 
     movaps xmm0, mc11 
     movaps xmm1, mc12 
     movaps xmm2, mc22 
     movaps xmm3, mc21 

     movaps xmm4, ms11 
     movaps xmm5, ms12 
     movaps xmm6, ms22 
     movaps xmm7, ms21 

     mulps xmm0, xmm4 
     mulps xmm1, xmm5 
     mulps xmm2, xmm6 
     mulps xmm3, xmm7 

     addps xmm0, xmm1 
     addps xmm0, xmm2 
     addps xmm0, xmm3 

     movaps mc11, xmm0 
    } 
#else 
    const Vec3f c11 = toFloat(pixelCache[y1 * size.x + x1]); 
    const Vec3f c12 = toFloat(pixelCache[y2 * size.x + x1]); 
    const Vec3f c22 = toFloat(pixelCache[y2 * size.x + x2]); 
    const Vec3f c21 = toFloat(pixelCache[y1 * size.x + x2]); 

    const Vec3f colour = 
      c11*(x2-x)*(y2-y) + 
      c21*(x-x1)*(y2-y) + 
      c12*(x2-x)*(y-y1) + 
      c22*(x-x1)*(y-y1); 
#endif 

Riordinando il codice asm riutilizzare i registri (finito con soli tre registri xmm) non ha dato alcun effetto. Ho anche provato a usare intrinsec:

// perform bilinear interpolation 
const Vec3f c11 = toFloat(pixelCache[y1 * size.x + x1]); 
const Vec3f c12 = toFloat(pixelCache[y2 * size.x + x1]); 
const Vec3f c22 = toFloat(pixelCache[y2 * size.x + x2]); 
const Vec3f c21 = toFloat(pixelCache[y1 * size.x + x2]); 

// scalars in vector form for SSE 
const float s11 = (x2-x)*(y2-y); 
const float s12 = (x2-x)*(y-y1); 
const float s22 = (x-x1)*(y-y1); 
const float s21 = (x-x1)*(y2-y); 

__m128 mc11 = _mm_set_ps(1.f, c11.b, c11.g, c11.r); 
__m128 mc12 = _mm_set_ps(1.f, c12.b, c12.g, c12.r); 
__m128 mc22 = _mm_set_ps(1.f, c22.b, c22.g, c22.r); 
__m128 mc21 = _mm_set_ps(1.f, c21.b, c21.g, c21.r); 

__m128 ms11 = _mm_set_ps(1.f, s11, s11, s11); 
__m128 ms12 = _mm_set_ps(1.f, s12, s12, s12); 
__m128 ms22 = _mm_set_ps(1.f, s22, s22, s22); 
__m128 ms21 = _mm_set_ps(1.f, s21, s21, s21); 

mc11 = _mm_mul_ps(mc11, ms11); 
mc12 = _mm_mul_ps(mc12, ms12); 
mc22 = _mm_mul_ps(mc22, ms22); 
mc21 = _mm_mul_ps(mc21, ms21); 

mc11 = _mm_add_ps(mc11, mc12); 
mc11 = _mm_add_ps(mc11, mc22); 
mc11 = _mm_add_ps(mc11, mc21); 

Vec3f colour; 
_mm_storeu_ps(colour.array, mc11); 

E inutilmente. Mi sto perdendo qualcosa, o è impossibile ottenere velocità extra qui?

Answer 1

Perché virgola mobile? Dato ARGB del pixel al sacco per a, b, c, d, e XERR, Yerr nel range 0-256, un semplice esempio è:

// ================================================================================================================= 
// xs_Bilerp 
// ================================================================================================================= 
finline uint32 xs_Bilerp (uint32 a, uint32 b, uint32 c, uint32 d, uint32 xerr, uint32 yerr) 
{ 
    #define xs_rbmask 0x00ff00ff 
    #define xs_agmask 0xff00ff00 

    if (a==b && c==d && a==d) return a; 

    const uint32 arb  = a & xs_rbmask; 
    const uint32 crb  = c & xs_rbmask; 
    const uint32 aag  = a & xs_agmask; 
    const uint32 cag  = c & xs_agmask; 

    const uint32 rbdx1  = (b & xs_rbmask) - arb; 
    const uint32 rbdx2  = (d & xs_rbmask) - crb; 
    const uint32 agdx1  = ((b & xs_agmask)>>8) - (aag >> 8); 
    const uint32 agdx2  = ((d & xs_agmask)>>8) - (cag >> 8); 

    const uint32 rb1  = (arb  + ((rbdx1 * xerr) >> 8)) & xs_rbmask; 
    const uint32 ag1  = (aag  + ((agdx1 * xerr) )) & xs_agmask; 
    const uint32 rbdy  = ((crb  + ((rbdx2 * xerr) >> 8)) & xs_rbmask)  - rb1; 
    const uint32 agdy  = (((cag + ((agdx2 * xerr) )) & xs_agmask)>>8) - (ag1 >> 8); 

    const uint32 rb   = (rb1 + ((rbdy * yerr) >> 8)) & xs_rbmask; 
    const uint32 ag   = (ag1 + ((agdy * yerr) )) & xs_agmask; 

    return ag | rb; 
}