如何重寫這段代碼上證所內在

Question

林新在上證所內部函數，並會在使用該9AS此欣賞一些線索協助尚未大霧給我）

我有這樣的代碼

for(int k=0; k<=n-4; k+=4) 
{ 

    int xc0 = 512 + ((idx + k*iddx)>>6); 
    int yc0 = 512 + ((idy + k*iddy)>>6); 

    int xc1 = 512 + ((idx + (k+1)*iddx)>>6); 
    int yc1 = 512 + ((idy + (k+1)*iddy)>>6); 

    int xc2 = 512 + ((idx + (k+2)*iddx)>>6); 
    int yc2 = 512 + ((idy + (k+2)*iddy)>>6); 

    int xc3 = 512 + ((idx + (k+3)*iddx)>>6); 
    int yc3 = 512 + ((idy + (k+3)*iddy)>>6); 

    unsigned color0 = working_buffer[yc0*working_buffer_size_x + xc0]; 
    unsigned color1 = working_buffer[yc1*working_buffer_size_x + xc1]; 
    unsigned color2 = working_buffer[yc2*working_buffer_size_x + xc2]; 
    unsigned color3 = working_buffer[yc3*working_buffer_size_x + xc3]; 

    int adr = base_adr + k; 

    frame_bitmap[adr] = color0; 
    frame_bitmap[adr+1]= color1; 
    frame_bitmap[adr+2]= color2; 
    frame_bitmap[adr+3]= color3; 
} 

都在這裏是int/unsigned，這是循環的關鍵部分，不確定整數sse是否會在速度上有所幫助，但不知道它是否會起作用？有人可以幫忙嗎？

（即時通訊使用的mingw32）

Answer 1

我SSE是有點生疏，但你應該做的是：

xmm0: [k, k+1, k+2, k+3] //xc0, xc1,.... 
xmm1: [k, k+1, k+2, k+3] //yc0, yc1,.... 
//initialize before the loop 
xmm2: [512, 512, 512, 512] 
xmm3: [idx, idx, idx, idx] 
xmm4: [iddx, iddx, iddx, iddx] 
xmm5: [idy, idy, idy, idy] 
xmm6: [iddy, iddy, iddy, iddy] 
xmm7: [working_buffer_size_x, working_buffer_size_x, working_buffer_size_x, working_buffer_size_x] 

計算：

xmm0 * xmm4 
xmm0 + xmm3 
xmm0 >> 6 
xmm0 + xmm2 

xmm0: [xc0, xc1, xc2, xc3] 
/////////////////////////////// 

xmm1 * xmm6 
xmm1 + xmm5 
xmm1 >> 6 
xmm1 + xmm2 

xmm1: [yc0, yc1, yc2, yc3] 

xmm1 * xmm7 
xmm1 + xmm0 

現在xmm1是：

xmm1: [yc0*working_buffer_size_x + xc0, yc1*working_buffer_size_x + xc1, yc2*working_buffer_size_x + xc2, yc3*working_buffer_size_x + xc3] 

您正在讀寫每個循環（working_buffer，frame_bitmap數組）中的內存，這些操作比計算本身的速度要慢得多，所以速度的提升不會像預期的那麼大。

編輯

你需要working_buffer和frame_bitmap陣列被對準並且被SSE4.1：

#include <emmintrin.h> 
#include <smmintrin.h> //SSE4.1 

int a[4] __attribute__((aligned(16))); 
__m128i xmm0, xmm1, xmm2, xmm3, xmm4, xmm5, xmm6, xmm7; 

xmm2 = _mm_set1_epi32(512); 
xmm3 = _mm_set1_epi32(idx); 
xmm4 = _mm_set1_epi32(iddx); 
xmm5 = _mm_set1_epi32(idy); 
xmm6 = _mm_set1_epi32(iddy); 
xmm7 = _mm_set1_epi32(working_buffer_size_x); 

for(k = 0; k <= n - 4; k +=4){ 
    xmm0 = _mm_set_epi32(k + 3, k + 2, k + 1, k); 
    xmm1 = _mm_set_epi32(k + 3, k + 2, k + 1, k); 

    //xmm0 * xmm4 
    xmm0 = _mm_mullo_epi32(xmm0, xmm4); 

    //xmm0 + xmm3 
    xmm0 = _mm_add_epi32(xmm0, xmm3); 

    //xmm0 >> 6 
    xmm0 = _mm_srai_epi32(xmm0, 6); 

    //xmm0 + xmm2 
    xmm0 = _mm_add_epi32(xmm0, xmm2); 



    //xmm1 * xmm6 
    xmm1 = _mm_mullo_epi32(xmm1, xmm6); 

    //xmm1 + xmm5 
    xmm1 = _mm_add_epi32(xmm1, xmm5); 

    //xmm1 >> 6 
    xmm1 = _mm_srai_epi32(xmm1, 6); 

    //xmm1 + xmm2 
    xmm1 = _mm_add_epi32(xmm1, xmm2); 


    //xmm1 * xmm7 
    xmm1 = _mm_mullo_epi32(xmm1, xmm7); 
    //xmm1 + xmm0 
    xmm1 = _mm_add_epi32(xmm1, xmm0); 


    //a[0] = yc0*working_buffer_size_x + xc0 
    //a[1] = yc1*working_buffer_size_x + xc1 
    //a[2] = yc2*working_buffer_size_x + xc2 
    //a[3] = yc3*working_buffer_size_x + xc3 
    _mm_store_si128((__m128i *)&a[0], xmm1); 

    unsigned color0 = working_buffer[ a[0] ]; 
    unsigned color1 = working_buffer[ a[1] ]; 
    unsigned color2 = working_buffer[ a[2] ]; 
    unsigned color3 = working_buffer[ a[3] ]; 

    int adr = base_adr + k; 

    frame_bitmap[adr] = color0; 
    frame_bitmap[adr+1]= color1; 
    frame_bitmap[adr+2]= color2; 
    frame_bitmap[adr+3]= color3; 
} 

您可以優化它更通過避免_mm_store_si128((__m128i *)&a[0], xmm1);或int adr = base_adr + k;使用直接處理內存的程序集。