https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123482
--- Comment #4 from Pascal Cuoq <pascal_cuoq at hotmail dot com> --- @Vincent Lefèvre Since the rounding mode is set by calling a function, technically, the same rounding mode can only be in effect everywhere in a program that doesn't call fesetround or only calls it with FE_TONEAREST. I understand -frounding-math is partially implemented, but the description of how it is implemented is not useful if it amounts to “GCC will put ‘false’ in the hypotheses of the optimizer if the program calls fesetround with an argument other than FE_TONEAREST”.
