openmp - Use omp simd without a for -

i have following instructions:

unsigned long int xdiff = seq1.x ^ seq2.x; unsigned long int ydiff = seq1.y ^ seq2.y; unsigned long int zdiff = seq1.z ^ seq2.z; 

it's possible vectorize using omp simd?

actually if define positions array, don't need anything, compiler vectorize you.

struct position {   unsigned long pos[3]; };  struct position foo( struct position seq1, struct position seq2) {   struct position diff;    for( int = 0; < 2; ++i )     diff.pos[i] = seq1.pos[i] ^ seq2.pos[i];    return diff; } 

gcc since 4.6 vectorize using -o3 flag. if provide architecture specific flags (for example intel vector extensions: -msse42, -mavx, etc.), can control vector instruction set compiler has use. if want build own machine, can compile -march=native.

foo(position, position):     movdqu  xmm1, xmmword ptr [rsp+32]     mov     rax, rdi     movdqu  xmm0, xmmword ptr [rsp+8]     pxor    xmm0, xmm1     movdqu  xmmword ptr [rdi], xmm0     ret 

if "unroll loop manually" (like in example)

diff.pos[0] = seq1.pos[0] ^ seq2.pos[0]; diff.pos[1] = seq1.pos[1] ^ seq2.pos[1]; diff.pos[2] = seq1.pos[2] ^ seq2.pos[2]; 

this no longer case:

foo(position, position):     mov     rdx, qword ptr [rsp+32]     xor     rdx, qword ptr [rsp+8]     mov     rax, rdi     mov     qword ptr [rdi], rdx     mov     rdx, qword ptr [rsp+40]     xor     rdx, qword ptr [rsp+16]     mov     qword ptr [rdi+8], rdx     mov     rdx, qword ptr [rsp+48]     xor     rdx, qword ptr [rsp+24]     mov     qword ptr [rdi+16], rdx     ret 

also, #pragma omp simd directive can applied loops:

simd [2.8.1] applied loop indicate loop can transformed simd loop.

#pragma omp simd [clause[,] clause] ...]   for-loops