http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57223
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> --- (In reply to Usishchev Yury from comment #3) > I'm testing it on current trunk, and second loop is not vectorized both with > floating point and integer types. > For floating point types it is not vectorized due to control flow in loop: > > <bb 15>: > // ... > if (t_56 > _61) > goto <bb 16>; > else > goto <bb 17>; > <bb 16>: > <bb 17>: > # iftmp.2_7 = PHI <_61(16), t_56(15)> > > This can be optimized to MIN_EXPR in phiopt pass, but is not because of NaNs: > > tree-ssa-phiopt.c:876: > /* The optimization may be unsafe due to NaNs. */ > if (HONOR_NANS (TYPE_MODE (type))) > return false; > > If compiled with -ffinite-math-only second loop still is not vectorised: > > not_always_good.c:16:7: note: not vectorized: latch block not empty. > > (same occurs with integer types). Latch block it that case is: > > <bb 14>: > pretmp_176 = *prephitmp_173; > goto <bb 13>; > > the statement here is generated in pre pass. > > For vectorization to work we can either not generate it in pre or move it > into head of the loop in vectorizer. > > Right now i'm trying to find how to prevent pre from generating statements > in empty latch blocks. It already has code to avoid this in some situations.
