> || vsetvl_insn_p (expr.get_insn ()->rtl ())) > continue; > new_info = expr.global_merge (expr, eg->src->index); > @@ -3317,6 +3335,25 @@ pass_vsetvl::earliest_fusion (void) > prob = profile_probability::uninitialized (); > } > else if (!src_block_info.reaching_out.compatible_p (expr) > + /* We don't do fusion across BBs for user explicit > + vsetvl instruction for these following reasons: > + > + - The user vsetvl instruction is configured as > + no side effects that the previous passes > + (GSCE, Loop-invariant, ..., etc) > + should be able to do a good job on optimization > + of user explicit vsetvls so we don't need to > + PRE optimization (The user vsetvls should be > + on the optimal local already before this pass) > + again for user vsetvls in VSETVL PASS here > + (Phase 3 && Phase 4). > + > + - Allowing user vsetvls be optimized in PRE > + optimization here (Phase 3 && Phase 4) will > + complicate the codes so much so we prefer user > + vsetvls be optimized in post-optimization > + (Phase 5 && Phase 6). */ > + && !vsetvl_insn_p (expr.get_insn ()->rtl ()) > && dest_block_info.probability > > src_block_info.probability)
This is OK but do we need the same comment twice? The first one doesn't seem to refer to a change but also to vsetvl_insn_p (expr.get_insn()...). And where is the !empty block property enforced? I would prefer to have the longer comment at a top level and shortly describe here why !vsetvl_insn_p ensures we don't have an EMPTY block. Don't we usually have a state for this (i.e. empty_p)? No need for a V2 though, it can also stay as is and be cleaned up later. Regards Robin
