Re: [PATCH GCC8][31/33]Set range information for niter bound of vectorized loop

[Richard Biener <richard.guenther@gmail.com>]

On Tue, Apr 18, 2017 at 12:54 PM, Bin Cheng <Bin.Cheng@arm.com> wrote
> Hi,
> Based on vect_peeling algorithm, we know for sure that vectorized loop must iterates at least once.
> This patch sets range information for niter bounds of vectorized loop.  This helps niter analysis,
> so iv elimination too.
> Is it OK?

       niters_vector = force_gimple_operand (niters_vector, &stmts, true, var);
       gsi_insert_seq_on_edge_immediate (pe, stmts);
+      /* Peeling algorithm guarantees that vector loop bound is at least ONE,
+        we set range information to make niters analyzer's life easier.  */
+      if (TREE_CODE (niters_vector) == SSA_NAME)
+       set_range_info (niters_vector, VR_RANGE, build_int_cst (type, 1),
+                       fold_build2 (RSHIFT_EXPR, type,
+                                    TYPE_MAX_VALUE (type), log_vf));

if all of niters_vector folds to an original SSA name then
niters_vector after gimplification
is not a new SSA name and thus you can't set range-info on it.

Likewise for the other case where LOOP_VINFO_NITERS is just an SSA name.

Richard.

> Thanks,
> bin
> 2017-04-11  Bin Cheng  <bin.cheng@arm.com>
>
>         * tree-vect-loop-manip.c (vect_gen_vector_loop_niters): Refactor.
>         Set range information for vector loop bound variable.
>         (vect_do_peeling): Ditto.