Re: [PATCH V3] VECT: Change flow of decrement IV

["Kewen.Lin" <linkw@linux.ibm.com>]

Hi,

on 2023/6/1 13:00, juzhe.zhong@rivai.ai wrote:
> This patch is no difference from V2.

I support this patch based on the testing and SPEC2017 evaluation
results on Power (see my comments on patch v2).

> Just add PR tree-optimization/109971 as Kewen's suggested.

Thanks for adding that, I was expecting you will add that when you
are committing it, not really requesting one new version. :)  btw,
the PR marker(s) will trigger scripts to comment some commit info
(commit link, commit log) into the specified PR(s), people can
find some connections between PRs and (fixing or progressing forward)
commits easily.

BR,
Kewen

> 
> Already bootstrapped and Regression on X86 no difference.
> 
> Ok for trunk ?
> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> juzhe.zhong@rivai.ai
> 
>      
>     *From:* juzhe.zhong <mailto:juzhe.zhong@rivai.ai>
>     *Date:* 2023-06-01 12:36
>     *To:* gcc-patches <mailto:gcc-patches@gcc.gnu.org>
>     *CC:* richard.sandiford <mailto:richard.sandiford@arm.com>; rguenther <mailto:rguenther@suse.de>; linkw <mailto:linkw@linux.ibm.com>; Ju-Zhe Zhong <mailto:juzhe.zhong@rivai.ai>
>     *Subject:* [PATCH V3] VECT: Change flow of decrement IV
>     From: Ju-Zhe Zhong <juzhe.zhong@rivai.ai>
>      
>     Follow Richi's suggestion, I change current decrement IV flow from:
>      
>     do {
>        remain -= MIN (vf, remain);
>     } while (remain != 0);
>      
>     into:
>      
>     do {
>        old_remain = remain;
>        len = MIN (vf, remain);
>        remain -= vf;
>     } while (old_remain >= vf);
>      
>     to enhance SCEV.
>      
>     Include fixes from kewen.
>      
>      
>     This patch will need to wait for Kewen's test feedback.
>      
>     Testing on X86 is on-going
>      
>     Co-Authored by: Kewen Lin  <linkw@linux.ibm.com>
>      
>       PR tree-optimization/109971
>      
>     gcc/ChangeLog:
>      
>             * tree-vect-loop-manip.cc (vect_set_loop_controls_directly): Change decrement IV flow.
>             (vect_set_loop_condition_partial_vectors): Ditto.
>      
>     ---
>     gcc/tree-vect-loop-manip.cc | 36 +++++++++++++++++++++++++-----------
>     1 file changed, 25 insertions(+), 11 deletions(-)
>      
>     diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
>     index acf3642ceb2..3f735945e67 100644
>     --- a/gcc/tree-vect-loop-manip.cc
>     +++ b/gcc/tree-vect-loop-manip.cc
>     @@ -483,7 +483,7 @@ vect_set_loop_controls_directly (class loop *loop, loop_vec_info loop_vinfo,
>     gimple_stmt_iterator loop_cond_gsi,
>     rgroup_controls *rgc, tree niters,
>     tree niters_skip, bool might_wrap_p,
>     - tree *iv_step)
>     + tree *iv_step, tree *compare_step)
>     {
>        tree compare_type = LOOP_VINFO_RGROUP_COMPARE_TYPE (loop_vinfo);
>        tree iv_type = LOOP_VINFO_RGROUP_IV_TYPE (loop_vinfo);
>     @@ -538,9 +538,9 @@ vect_set_loop_controls_directly (class loop *loop, loop_vec_info loop_vinfo,
>        ...
>        vect__4.8_28 = .LEN_LOAD (_17, 32B, _36, 0);
>        ...
>     -    ivtmp_35 = ivtmp_9 - _36;
>     +    ivtmp_35 = ivtmp_9 - POLY_INT_CST [4, 4];
>        ...
>     -    if (ivtmp_35 != 0)
>     +    if (ivtmp_9 > POLY_INT_CST [4, 4])
>          goto <bb 4>; [83.33%]
>        else
>          goto <bb 5>; [16.67%]
>     @@ -549,13 +549,15 @@ vect_set_loop_controls_directly (class loop *loop, loop_vec_info loop_vinfo,
>            tree step = rgc->controls.length () == 1 ? rgc->controls[0]
>            : make_ssa_name (iv_type);
>            /* Create decrement IV.  */
>     -      create_iv (nitems_total, MINUS_EXPR, step, NULL_TREE, loop, &incr_gsi,
>     - insert_after, &index_before_incr, &index_after_incr);
>     +      create_iv (nitems_total, MINUS_EXPR, nitems_step, NULL_TREE, loop,
>     + &incr_gsi, insert_after, &index_before_incr,
>     + &index_after_incr);
>            gimple_seq_add_stmt (header_seq, gimple_build_assign (step, MIN_EXPR,
>         index_before_incr,
>         nitems_step));
>            *iv_step = step;
>     -      return index_after_incr;
>     +      *compare_step = nitems_step;
>     +      return index_before_incr;
>          }
>        /* Create increment IV.  */
>     @@ -825,6 +827,7 @@ vect_set_loop_condition_partial_vectors (class loop *loop,
>           arbitrarily pick the last.  */
>        tree test_ctrl = NULL_TREE;
>        tree iv_step = NULL_TREE;
>     +  tree compare_step = NULL_TREE;
>        rgroup_controls *rgc;
>        rgroup_controls *iv_rgc = nullptr;
>        unsigned int i;
>     @@ -861,7 +864,7 @@ vect_set_loop_condition_partial_vectors (class loop *loop,
>     &preheader_seq, &header_seq,
>     loop_cond_gsi, rgc, niters,
>     niters_skip, might_wrap_p,
>     - &iv_step);
>     + &iv_step, &compare_step);
>         iv_rgc = rgc;
>       }
>     @@ -884,10 +887,21 @@ vect_set_loop_condition_partial_vectors (class loop *loop,
>        /* Get a boolean result that tells us whether to iterate.  */
>        edge exit_edge = single_exit (loop);
>     -  tree_code code = (exit_edge->flags & EDGE_TRUE_VALUE) ? EQ_EXPR : NE_EXPR;
>     -  tree zero_ctrl = build_zero_cst (TREE_TYPE (test_ctrl));
>     -  gcond *cond_stmt = gimple_build_cond (code, test_ctrl, zero_ctrl,
>     - NULL_TREE, NULL_TREE);
>     +  gcond *cond_stmt;
>     +  if (LOOP_VINFO_USING_DECREMENTING_IV_P (loop_vinfo))
>     +    {
>     +      gcc_assert (compare_step);
>     +      tree_code code = (exit_edge->flags & EDGE_TRUE_VALUE) ? LE_EXPR : GT_EXPR;
>     +      cond_stmt = gimple_build_cond (code, test_ctrl, compare_step, NULL_TREE,
>     +      NULL_TREE);
>     +    }
>     +  else
>     +    {
>     +      tree_code code = (exit_edge->flags & EDGE_TRUE_VALUE) ? EQ_EXPR : NE_EXPR;
>     +      tree zero_ctrl = build_zero_cst (TREE_TYPE (test_ctrl));
>     +      cond_stmt
>     + = gimple_build_cond (code, test_ctrl, zero_ctrl, NULL_TREE, NULL_TREE);
>     +    }
>        gsi_insert_before (&loop_cond_gsi, cond_stmt, GSI_SAME_STMT);
>        /* The loop iterates (NITERS - 1) / VF + 1 times.
>     -- 
>     2.36.3
>      
>