On Tue, Sep 15, 2020 at 08:51:09AM +0200, Richard Biener wrote: > On Tue, Sep 15, 2020 at 5:56 AM luoxhu <luo...@linux.ibm.com> wrote: > > > u[n % 4] = i; > > > > > > I guess. Is the % 4 mandated by the vec_insert semantics btw?
(As an aside -- please use "& 3" instead: that works fine if n is signed as well, but modulo doesn't. Maybe that is in the patch already, I didn't check, sorry.) > note this is why I asked about the actual CPU instruction - as I read > Seghers mail > the instruction modifies a vector register, not memory. But note that the builtin is not the same as the machine instruction -- here there shouldn't be a difference if compiling for a new enough ISA, but the builtin is available on anything with at least AltiVec. Segher
