https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64020
--- Comment #3 from joseph at codesourcery dot com <joseph at codesourcery dot com> --- On Mon, 24 Nov 2014, dmalcolm at gcc dot gnu.org wrote: > [would it be even better to optimize this to just a sin (2 * theta) ?] Only with -funsafe-math-optimizations (it's unsafe for large arguments where 2 * theta overflows, and that transformation can also lose underflow exceptions for small arguments where sin (theta) is in the tiny range but sin (2 * theta) isn't).