https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117874
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> --- For reference, mult_su3_na is almost the same: typedef struct { double real; double imag; } complex; typedef struct { complex e[3][3]; } su3_matrix; void mult_su3_na( su3_matrix *a, su3_matrix *b, su3_matrix *c ) { int i,j; double t,ar,ai,br,bi,cr,ci; for(i=0;i<3;i++)for(j=0;j<3;j++) { ar=a->e[i][0].real; ai=a->e[i][0].imag; br=b->e[j][0].real; bi=b->e[j][0].imag; cr=ar*br; t=ai*bi; cr += t; ci=ai*br; t=ar*bi; ci -= t; ar=a->e[i][1].real; ai=a->e[i][1].imag; br=b->e[j][1].real; bi=b->e[j][1].imag; t=ar*br; cr += t; t=ai*bi; cr += t; t=ar*bi; ci -= t; t=ai*br; ci += t; ar=a->e[i][2].real; ai=a->e[i][2].imag; br=b->e[j][2].real; bi=b->e[j][2].imag; t=ar*br; cr += t; t=ai*bi; cr += t; t=ar*bi; ci -= t; t=ai*br; ci += t; c->e[i][j].real=cr; c->e[i][j].imag=ci; } }