On Wed, Aug 29, 2018 at 11:10 AM Jakub Jelinek <ja...@redhat.com> wrote: > > On Wed, Aug 29, 2018 at 09:59:07AM +0100, Richard Sandiford wrote: > > Jakub Jelinek <ja...@redhat.com> writes: > > > On Tue, Aug 28, 2018 at 12:24:06PM +0100, Richard Sandiford wrote: > > >> The point of this patch is to put pattern statements in the same > > >> vec_basic_block as the statements they replace, with the pattern > > >> statements for S coming between S and S's original predecessor. > > >> This removes the need to handle them specially in various places. > > > > > > My preferred way to handle pattern stmts would be to do what we do in > > > tree-if-conversion, i.e. whenever creating first pattern stmt for certain > > > loop, duplicate that loop directly in the IL guarded with an ifn > > > and modify directly one copy of the loop (the one meant to be vectorized). > > > If we aren't cycling over multiple vectorization factors, that could be > > > even > > > done directly on the tree-if-conversion created vector loop copy, > > > otherwise > > > we'd need more. > > > > I'd originally tried adding the pattern stmts to the gimple bb as well > > as the vec_basic_block, but the problem is that we create pattern stmts > > before duplicating the scalar loop for peeling. So I think we'd need to > > copy the loop even for the single-size case, or arrange some other way of > > temporarily restoring the original code. > > Sure, if tree-if-conversion doesn't copy the loop and for single-size case, > we'd need to do that copy (once per loop), if it already copied the loop, > there is already the scalar and for vectorization only loop. > With those copies you don't need to roll back anything, just ensure the > guarding internal fns fold to constants when the vectorization is over based > on if the loop was vectorized and with what vf, and cfg cleanup will do the > rest. > The vectorizer already has code to find the scalar loop in the > LOOP_VECTORIZED condition guarded else block.
My hope is still that we can eventually get rid of pattern stmts - I see how they make things easier, esp. for the issue of computing a vectorization factor ... Note the duplication comes at a cost - we do not version loops for if-conversion before we know we'll apply if-conversion and it will succeed. It would be bad if we start to duplicate each loop just because we start vectorization analysis (and pattern recog is done very early). Richard. > Jakub
