https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79207
--- Comment #2 from joseph at codesourcery dot com <joseph at codesourcery dot com> --- It's hardly specific to those arguments. Any case of two or more calls of (sin or cos) (+/- x + constant) for same x, possibly different constant, could be converted (given -funsafe-math-optimizations) to sincos plus multiplications by constants (i.e. by +/- sin and cos of the constant part of the argument in the original call) and additions. (You also need -funsafe-math-optimizations to convert the example cos((alpha+2*M_PI)*ONETHIRD) into cos(alpha*ONETHIRD+2*M_PI*ONETHIRD) to get all three expressions using the same x.) (This is not an assertion of whether or not such a transformation is a good idea, simply that the transformation is generic for arbitrary constants. It may be that recognizing particular constants helps you get a form like > ret[1] = -0.5 * (t_ss3 + t_cos); > ret[2] = 0.5 * (t_ss3 - t_cos); rather than something more complicated where there are four slightly different constants multiplied by the outputs of sincos.)
