On Thu, Aug 20, 2015 at 8:46 PM, Jeff Law <l...@redhat.com> wrote: > On 08/17/2015 10:25 AM, Ilya Enkovich wrote: >> >> Hi, >> >> This patch intoriduces a new vectorizer hook use_scalar_mask_p which >> affects code generated by if-conversion pass (and affects patterns in later >> patches). >> >> Thanks, >> Ilya >> -- >> 2015-08-17 Ilya Enkovich <enkovich....@gmail.com> >> >> * doc/tm.texi (TARGET_VECTORIZE_USE_SCALAR_MASK_P): New. >> * doc/tm.texi.in: Regenerated. >> * target.def (use_scalar_mask_p): New. >> * tree-if-conv.c: Include target.h. >> (predicate_mem_writes): Don't convert boolean predicates into >> integer when scalar masks are used. > > Presumably this is how you prevent the generation of scalar masks rather > than boolean masks on targets which don't have the former? > > I hate to ask, but how painful would it be to go from a boolean to integer > masks later such as during expansion? Or vice-versa. > > WIthout a deep knowledge of the entire patchkit, it feels like we're > introducing target stuff in a place where we don't want it and that we'd be > better served with a canonical representation through gimple, then dropping > into something more target specific during gimple->rtl expansion.
Indeed. I don't remember my exact comments during the talk at the Cauldron but the scheme used there was sth like mask = GEN_MASK <vec1 < vec2>; b = a + 1; x = VEC_COND <mask, a, b> to model conditional execution already at the if-conversion stage (for all scalar stmts made executed unconditionally rather than just the PHI results). I was asking for the condition to be removed from GEN_MASK (patch 1 has this fixed now AFAICS). And I also asked why it was necessary to do this "lowering" here and not simply do mask = vec1 < vec2; // regular vector mask! b = a + 1; x = VEC_COND <mask, a, b> and have the lowering to an integer mask done later. You'd still change if-conversion to predicate _all_ statements, not just those with side-effects. So I think there still needs to be a new target hook to trigger this, similar to how the target capabilities trigger the masked load/store path in if-conversion. But I don't like changing our IL so much as to allow 'integer' masks everywhere. Richard. > > Jeff
