Intel® 64 and IA-32 Architectures Optimization Reference Manual

OPTIMIZING FOR SIMD INTEGER APPLICATIONSExample 5-21. Basic C Implementation of RGBA to BGRA Conversionvoid BGRA_RGBA_Convert(BGRA *source, RGBA *dest, int num_pixels){for(int i = 0; i < num_pixels; i++){dest[i].r = source[i].r;dest[i].g = source[i].g;dest[i].b = source[i].b;dest[i].a = source[i].a;}}Example 5-22 and Example 5-23 show SSE2 code and SSSE3 code for pixel formatconversion. In the SSSE3 example, PSHUFB replaces six SSE2 instructions.Example 5-22. Color Pixel Format Conversion Using SSE2; Optimized for SSE2mov esi, srcmov edi, destmov ecx, iterationsmovdqa xmm0, ag_mask //{0,ff,0,ff,0,ff,0,ff,0,ff,0,ff,0,ff,0,ff}movdqa xmm5, rb_mask //{ff,0,ff,0,ff,0,ff,0,ff,0,ff,0,ff,0,ff,0}mov eax, remainderconvert16Pixs: // 16 pixels, 64 byte per iterationmovdqa xmm1, [esi] // xmm1 = [r3g3b3a3,r2g2b2a2,r1g1b1a1,r0g0b0a0]movdqa xmm2, xmm1movdqa xmm7, xmm1 //xmm7 abgrpsrld xmm2, 16 //xmm2 00abpslld xmm1, 16 //xmm1 gr00por xmm1, xmm2 //xmm1 grabpand xmm7, xmm0 //xmm7 a0g0pand xmm1, xmm5 //xmm1 0r0bpor xmm1, xmm7 //xmm1 argbmovdqa [edi], xmm15-22