On Mon, May 29, 2017 at 2:21 PM, Segher Boessenkool <seg...@kernel.crashing.org> wrote: > On Mon, May 29, 2017 at 01:35:22PM +0200, Richard Biener wrote: >> >> What's the documented behavior for vec_abs with respect to an >> >argument >> >> of value INT_MIN? >> > >> >The documentation says: >> > >> > "For integer vectors, the arithmetic is modular." >> >> This means that folding as ABS_EXPR is not safe for !TYPE_OVERFLOW_WRAPS >> Integral vector types. > > Is it still fine if TYPE_OVERFLOW_UNDEFINED? So essentially always > except with -ftrapv?
The docs say it needs to wrap so the correct check is TYPE_OVERFLOW_WRAPS. It's not fine with TYPE_OVERFLOW_UNDEFINED as we will conclude the result can never be INT_MIN while the spec says it can. Richard. > > > Segher
