Re: Re: [PATCH] Middle-end: Fix bug of induction variable vectorization for RVV

[Richard Biener <rguenther@suse.de>]

On Fri, 10 Nov 2023, juzhe.zhong@rivai.ai wrote:

> Thanks a lot. I think I finally understand what you mean now :).
> 
> Could you confirm this following codes:?
> 
> diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> index 8abc1937d74..5615b16bdcd 100644
> --- a/gcc/tree-vect-loop.cc
> +++ b/gcc/tree-vect-loop.cc
> @@ -10306,10 +10306,39 @@ vectorizable_induction (loop_vec_info loop_vinfo,
> 
> 
>    /* Create the vector that holds the step of the induction.  */
> +  gimple_stmt_iterator *step_iv_si = NULL;
>    if (nested_in_vect_loop)
> -    /* iv_loop is nested in the loop to be vectorized. Generate:
> -       vec_step = [S, S, S, S]  */
> -    new_name = step_expr;
> +    {
> +      /* iv_loop is nested in the loop to be vectorized. Generate:
> +        vec_step = [S, S, S, S]  */
> +      new_name = step_expr;
> +      /* We expect LOOP_VINFO_USING_SELECT_VL_P to be false in nested loop.  */
> +      gcc_assert (!LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo));
> +    }
> +  else if (LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo))
> +    {
> +      /* When we're using loop_len produced by SELEC_VL, the non-final
> +        iterations are not always processing VF elements.  So vectorize
> +        induction variable instead of
> +
> +          _21 = vect_vec_iv_.6_22 + { VF, ... };
> +
> +        We should generate:
> +
> +          _35 = .SELECT_VL (ivtmp_33, VF);
> +          vect_cst__22 = [vec_duplicate_expr] _35;
> +          _21 = vect_vec_iv_.6_22 + vect_cst__22;  */
> +      gimple_seq seq = NULL;
> +      vec_loop_lens *lens = &LOOP_VINFO_LENS (loop_vinfo);
> +      tree len = vect_get_loop_len (loop_vinfo, NULL, lens, 1, vectype, 0, 0);
> +      expr = force_gimple_operand (fold_convert (TREE_TYPE (step_expr),
> +                                                unshare_expr (len)),
> +                                  &seq, true, NULL_TREE);
> +      new_name = gimple_build (&seq, MULT_EXPR, TREE_TYPE (step_expr), expr,
> +                              step_expr);
> +      gsi_insert_seq_before (&si, seq, GSI_SAME_STMT);
> +      step_iv_si = &si;
> +    }
>    else
>      {
>        /* iv_loop is the loop to be vectorized. Generate:
> @@ -10336,7 +10365,7 @@ vectorizable_induction (loop_vec_info loop_vinfo,
>               || TREE_CODE (new_name) == SSA_NAME);
>    new_vec = build_vector_from_val (step_vectype, t);
>    vec_step = vect_init_vector (loop_vinfo, stmt_info,
> -                              new_vec, step_vectype, NULL);
> +                              new_vec, step_vectype, step_iv_si);
> 
> 
>    /* Create the following def-use cycle:
> @@ -10382,6 +10411,8 @@ vectorizable_induction (loop_vec_info loop_vinfo,
>        gimple_seq seq = NULL;
>        /* FORNOW. This restriction should be relaxed.  */
>        gcc_assert (!nested_in_vect_loop);
> +      /* We expect LOOP_VINFO_USING_SELECT_VL_P to be false if ncopies > 1.  */
> +      gcc_assert (!LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo));
> 
> 
> If it is Ok for you. I am gonna testing it on X86 bootstrap + regtest.

Yep.

> Thanks.
> 
> 
> 
> juzhe.zhong@rivai.ai
>  
> From: Richard Biener
> Date: 2023-11-10 18:19
> To: juzhe.zhong@rivai.ai
> CC: Richard Biener; gcc-patches; richard.sandiford; kito.cheng; Kito.cheng
> Subject: Re: Re: [PATCH] Middle-end: Fix bug of induction variable vectorization for RVV
> On Fri, 10 Nov 2023, juzhe.zhong@rivai.ai wrote:
>  
> > Hi, Richard.
> > 
> > I am sorry for bothering you. I am trying to understand what you mean.
> > 
> > Is this following codes that you want ?
> > 
> >   /* Create the vector that holds the step of the induction.  */
> >   if (nested_in_vect_loop)
> >     {
> >       /* iv_loop is nested in the loop to be vectorized. Generate:
> >          vec_step = [S, S, S, S]  */
> >       new_name = step_expr;
> >       /* We expect LOOP_VINFO_USING_SELECT_VL_P to be false in nested loop.  */
> >       gcc_assert (!LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo));
> >       t = unshare_expr (new_name);
> >       gcc_assert (CONSTANT_CLASS_P (new_name)
> >                   || TREE_CODE (new_name) == SSA_NAME);
> >       new_vec = build_vector_from_val (step_vectype, t);
> >       vec_step
> >         = vect_init_vector (loop_vinfo, stmt_info, new_vec, step_vectype, NULL);
> >     }
> >   else if (LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo))
> >     {
> >       /* When we're using loop_len produced by SELEC_VL, the non-final
> >          iterations are not always processing VF elements.  So vectorize
> >          induction variable instead of
> > 
> >            _21 = vect_vec_iv_.6_22 + { VF, ... };
> > 
> >          We should generate:
> > 
> >            _35 = .SELECT_VL (ivtmp_33, VF);
> >            vect_cst__22 = [vec_duplicate_expr] _35;
> >            _21 = vect_vec_iv_.6_22 + vect_cst__22;  */
> >       vec_loop_lens *lens = &LOOP_VINFO_LENS (loop_vinfo);
> >       tree len = vect_get_loop_len (loop_vinfo, NULL, lens, 1, vectype, 0, 0);
> >       expr = force_gimple_operand (fold_convert (TREE_TYPE (step_expr),
> >                                                  unshare_expr (len)),
> >                                    &seq, true, NULL_TREE);
> >       gsi_insert_seq_before (&si, seq, GSI_SAME_STMT);
> >       t = unshare_expr (new_name);
> >       gcc_assert (CONSTANT_CLASS_P (new_name)
> >                   || TREE_CODE (new_name) == SSA_NAME);
> >       new_vec = build_vector_from_val (step_vectype, t);
> >       vec_step
> >         = vect_init_vector (loop_vinfo, stmt_info, new_vec, step_vectype, &si);
> >     }
> >   else
> >     {
> >       /* iv_loop is the loop to be vectorized. Generate:
> >           vec_step = [VF*S, VF*S, VF*S, VF*S]  */
> >       gimple_seq seq = NULL;
> >       if (SCALAR_FLOAT_TYPE_P (TREE_TYPE (step_expr)))
> >         {
> >           expr = build_int_cst (integer_type_node, vf);
> >           expr = gimple_build (&seq, FLOAT_EXPR, TREE_TYPE (step_expr), expr);
> >         }
> >       else
> >         expr = build_int_cst (TREE_TYPE (step_expr), vf);
> >       new_name = gimple_build (&seq, MULT_EXPR, TREE_TYPE (step_expr),
> >                                expr, step_expr);
> >       if (seq)
> >         {
> >           new_bb = gsi_insert_seq_on_edge_immediate (pe, seq);
> >           gcc_assert (!new_bb);
> >         }
> >       t = unshare_expr (new_name);
> >       gcc_assert (CONSTANT_CLASS_P (new_name)
> >                   || TREE_CODE (new_name) == SSA_NAME);
> >       new_vec = build_vector_from_val (step_vectype, t);
> >       vec_step
> >         = vect_init_vector (loop_vinfo, stmt_info, new_vec, step_vectype, NULL);
> >     }
> > 
> > It seems that this following codes:
> > 
> >       t = unshare_expr (new_name);
> >       gcc_assert (CONSTANT_CLASS_P (new_name)
> >                   || TREE_CODE (new_name) == SSA_NAME);
> >       new_vec = build_vector_from_val (step_vectype, t);
> >       vec_step
> >         = vect_init_vector 
> > 
> > appears 3 times.  I am not sure whether it is the way you want?
>  
> I'd avoid that particular bit by having
>  
>    gimple_stmt_iterator *si = NULL;
>  
> before the if () and set that accordingly only in the
> LOOP_VINFO_USING_SELECT_VL_P path.  But otherwise yes.
>  
> Richard.
>  
> > 
> > Thanks.
> > 
> > 
> > 
> > juzhe.zhong@rivai.ai
> >  
> > From: Richard Biener
> > Date: 2023-11-10 17:46
> > To: ???
> > CC: richard.guenther; gcc-patches; richard.sandiford; kito.cheng; kito.cheng
> > Subject: Re: Re: [PATCH] Middle-end: Fix bug of induction variable vectorization for RVV
> > On Thu, 9 Nov 2023, ??? wrote:
> >  
> > > Hi, Richard.
> > > 
> > > >> I think it would be better to split out building a tree from VF from both
> > > >> arms and avoid using 'vf' when LOOP_VINFO_USING_SELECT_VL_P.
> > > 
> > > I am trying to split out building tree from both arms as you suggested..
> > > Could you take a look the following codes ?
> > > 
> > > diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> > > index 8abc1937d74..24a86187d11 100644
> > > --- a/gcc/tree-vect-loop.cc
> > > +++ b/gcc/tree-vect-loop.cc
> > > @@ -10315,19 +10315,47 @@ vectorizable_induction (loop_vec_info loop_vinfo,
> > >        /* iv_loop is the loop to be vectorized. Generate:
> > >     vec_step = [VF*S, VF*S, VF*S, VF*S]  */
> > >        gimple_seq seq = NULL;
> > > -      if (SCALAR_FLOAT_TYPE_P (TREE_TYPE (step_expr)))
> > > +      if (LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo))
> > >   {
> > > -   expr = build_int_cst (integer_type_node, vf);
> > > -   expr = gimple_build (&seq, FLOAT_EXPR, TREE_TYPE (step_expr), expr);
> > > +   /* When we're using loop_len produced by SELEC_VL, the non-final
> > > +      iterations are not always processing VF elements.  So vectorize
> > > +      induction variable instead of
> > > +
> > > +        _21 = vect_vec_iv_.6_22 + { VF, ... };
> > > +
> > > +      We should generate:
> > > +
> > > +       _35 = .SELECT_VL (ivtmp_33, VF);
> > > +       vect_cst__22 = [vec_duplicate_expr] _35;
> > > +       _21 = vect_vec_iv_.6_22 + vect_cst__22;  */
> > > +   vec_loop_lens *lens = &LOOP_VINFO_LENS (loop_vinfo);
> > > +   tree len
> > > +     = vect_get_loop_len (loop_vinfo, NULL, lens, 1, vectype, 0, 0);
> > > +   expr = force_gimple_operand (fold_convert (TREE_TYPE (step_expr),
> > > +      unshare_expr (len)),
> > > +        &seq, true, NULL_TREE);
> > >   }
> > >        else
> > > - expr = build_int_cst (TREE_TYPE (step_expr), vf);
> > > + {
> > > +   bool float_p = SCALAR_FLOAT_TYPE_P (TREE_TYPE (step_expr));
> > > +   expr = build_int_cst (float_p ? integer_type_node
> > > + : TREE_TYPE (step_expr),
> > > + vf);
> > > +   if (float_p)
> > > +     expr = gimple_build (&seq, FLOAT_EXPR, TREE_TYPE (step_expr), expr);
> > > + }
> > > +
> >  
> > I meant you keep the existing flow in the function, specifically
> > I think you should handle SCALAR_FLOAT_TYPE_P like it was previously
> > handled, just build 'vf' in the dynamic way.
> >  
> > >        new_name = gimple_build (&seq, MULT_EXPR, TREE_TYPE (step_expr),
> > >          expr, step_expr);
> > >        if (seq)
> > >   {
> > > -   new_bb = gsi_insert_seq_on_edge_immediate (pe, seq);
> > > -   gcc_assert (!new_bb);
> > > +   if (LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo))
> > > +     gsi_insert_seq_before (&si, seq, GSI_SAME_STMT);
> > > +   else
> > > +     {
> > > +       new_bb = gsi_insert_seq_on_edge_immediate (pe, seq);
> > > +       gcc_assert (!new_bb);
> > > +     }
> > >   }
> > >      }
> > >  
> > > @@ -10335,9 +10363,9 @@ vectorizable_induction (loop_vec_info loop_vinfo,
> > >    gcc_assert (CONSTANT_CLASS_P (new_name)
> > >         || TREE_CODE (new_name) == SSA_NAME);
> > >    new_vec = build_vector_from_val (step_vectype, t);
> > > -  vec_step = vect_init_vector (loop_vinfo, stmt_info,
> > > -        new_vec, step_vectype, NULL);
> > > -
> > > +  vec_step
> > > +    = vect_init_vector (loop_vinfo, stmt_info, new_vec, step_vectype,
> > > + LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo) ? &si : NULL);
> >  
> > again this makes the flow hard to follow.  I suppose refactoring this
> > overall to
> >  
> >     if (nested_in_vect_loop)
> > ...
> >     else if (LOOP_VINFO_USING_SELECT_VL_P (..))
> > ...
> >     else
> > ...
> >  
> > and duplicate this tail into the cases makes it easier to follow.
> >  
> > For nested_in_vect_loop we never have LOOP_VINFO_USING_SELECT_VL_P?
> >  
> > Richard.
> >  
> >  
> > > Thanks.
> > > 
> > > 
> > > juzhe.zhong@rivai.ai
> > >  
> > > From: Richard Biener
> > > Date: 2023-11-09 20:16
> > > To: Juzhe-Zhong
> > > CC: gcc-patches; richard.sandiford; rguenther; kito.cheng; kito.cheng
> > > Subject: Re: [PATCH] Middle-end: Fix bug of induction variable vectorization for RVV
> > > On Wed, Nov 8, 2023 at 11:53?AM Juzhe-Zhong <juzhe.zhong@rivai.ai> wrote:
> > > >
> > > > PR: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112438
> > > >
> > > > SELECT_VL result is not necessary always VF in non-final iteration.
> > > >
> > > > Current GIMPLE IR is wrong:
> > > >
> > > > # vect_vec_iv_.21_25 = PHI <_24(4), { 0, 1, 2, ... }(3)>
> > > > ...
> > > > _24 = vect_vec_iv_.21_25 + { POLY_INT_CST [4, 4], ... };
> > > >
> > > > After this patch which is correct for SELECT_VL:
> > > >
> > > > # vect_vec_iv_.8_22 = PHI <_21(4), { 0, 1, 2, ... }(3)>
> > > > ...
> > > > _35 = .SELECT_VL (ivtmp_33, POLY_INT_CST [4, 4]);
> > > > _21 = vect_vec_iv_.8_22 + { POLY_INT_CST [4, 4], ... };
> > > >
> > > > kito, could you give more explanation ?
> > > >
> > > >         PR middle/112438
> > > >
> > > > gcc/ChangeLog:
> > > >
> > > >         * tree-vect-loop.cc (vectorizable_induction): Fix bug.
> > > >
> > > > gcc/testsuite/ChangeLog:
> > > >
> > > >         * gcc.target/riscv/rvv/autovec/pr112438.c: New test.
> > > >
> > > > ---
> > > >  .../gcc.target/riscv/rvv/autovec/pr112438.c   | 35 +++++++++++++++++
> > > >  gcc/tree-vect-loop.cc                         | 39 +++++++++++++++----
> > > >  2 files changed, 67 insertions(+), 7 deletions(-)
> > > >  create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/autovec/pr112438.c
> > > >
> > > > diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr112438.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr112438.c
> > > > new file mode 100644
> > > > index 00000000000..b326d56a52c
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr112438.c
> > > > @@ -0,0 +1,35 @@
> > > > +/* { dg-do compile } */
> > > > +/* { dg-options "-march=rv64gcv -mabi=lp64d -O3 -fno-vect-cost-model -ffast-math -fdump-tree-optimized-details" } */
> > > > +
> > > > +void
> > > > +foo (int n, int *__restrict in, int *__restrict out)
> > > > +{
> > > > +  for (int i = 0; i < n; i += 1)
> > > > +    {
> > > > +      out[i] = in[i] + i;
> > > > +    }
> > > > +}
> > > > +
> > > > +void
> > > > +foo2 (int n, float * __restrict in,
> > > > +float * __restrict out)
> > > > +{
> > > > +  for (int i = 0; i < n; i += 1)
> > > > +    {
> > > > +      out[i] = in[i] + i;
> > > > +    }
> > > > +}
> > > > +
> > > > +void
> > > > +foo3 (int n, float * __restrict in,
> > > > +float * __restrict out, float x)
> > > > +{
> > > > +  for (int i = 0; i < n; i += 1)
> > > > +    {
> > > > +      out[i] = in[i] + i* i;
> > > > +    }
> > > > +}
> > > > +
> > > > +/* We don't want to see vect_vec_iv_.21_25 + { POLY_INT_CST [4, 4], ... }.  */
> > > > +/* { dg-final { scan-tree-dump-not "\\+ \{ POLY_INT_CST" "optimized" } } */
> > > > +
> > > > diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> > > > index a544bc9b059..3e103946168 100644
> > > > --- a/gcc/tree-vect-loop.cc
> > > > +++ b/gcc/tree-vect-loop.cc
> > > > @@ -10309,10 +10309,30 @@ vectorizable_induction (loop_vec_info loop_vinfo,
> > > >      new_name = step_expr;
> > > >    else
> > > >      {
> > > > +      gimple_seq seq = NULL;
> > > > +      if (LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo))
> > > > +       {
> > > > +         /* When we're using loop_len produced by SELEC_VL, the non-final
> > > > +            iterations are not always processing VF elements.  So vectorize
> > > > +            induction variable instead of
> > > > +
> > > > +              _21 = vect_vec_iv_.6_22 + { VF, ... };
> > > > +
> > > > +            We should generate:
> > > > +
> > > > +              _35 = .SELECT_VL (ivtmp_33, VF);
> > > > +              vect_cst__22 = [vec_duplicate_expr] _35;
> > > > +              _21 = vect_vec_iv_.6_22 + vect_cst__22;  */
> > > > +         vec_loop_lens *lens = &LOOP_VINFO_LENS (loop_vinfo);
> > > > +         tree len
> > > > +           = vect_get_loop_len (loop_vinfo, NULL, lens, 1, vectype, 0, 0);
> > > > +         expr = force_gimple_operand (fold_convert (TREE_TYPE (step_expr),
> > > > +                                                    unshare_expr (len)),
> > > > +                                      &seq, true, NULL_TREE);
> > > > +       }
> > >  
> > > I think it would be better to split out building a tree from VF from both
> > > arms and avoid using 'vf' when LOOP_VINFO_USING_SELECT_VL_P.
> > >  
> > > Btw, you are not patching the SLP path here which I believe has the same
> > > problem but is currently exempt from non-constant VF at least.
> > >  
> > > Richard.
> > >  
> > > >        /* iv_loop is the loop to be vectorized. Generate:
> > > >           vec_step = [VF*S, VF*S, VF*S, VF*S]  */
> > > > -      gimple_seq seq = NULL;
> > > > -      if (SCALAR_FLOAT_TYPE_P (TREE_TYPE (step_expr)))
> > > > +      else if (SCALAR_FLOAT_TYPE_P (TREE_TYPE (step_expr)))
> > > >         {
> > > >           expr = build_int_cst (integer_type_node, vf);
> > > >           expr = gimple_build (&seq, FLOAT_EXPR, TREE_TYPE (step_expr), expr);
> > > > @@ -10323,8 +10343,13 @@ vectorizable_induction (loop_vec_info loop_vinfo,
> > > >                                expr, step_expr);
> > > >        if (seq)
> > > >         {
> > > > -         new_bb = gsi_insert_seq_on_edge_immediate (pe, seq);
> > > > -         gcc_assert (!new_bb);
> > > > +         if (LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo))
> > > > +           gsi_insert_seq_before (&si, seq, GSI_SAME_STMT);
> > > > +         else
> > > > +           {
> > > > +             new_bb = gsi_insert_seq_on_edge_immediate (pe, seq);
> > > > +             gcc_assert (!new_bb);
> > > > +           }
> > > >         }
> > > >      }
> > > >
> > > > @@ -10332,9 +10357,9 @@ vectorizable_induction (loop_vec_info loop_vinfo,
> > > >    gcc_assert (CONSTANT_CLASS_P (new_name)
> > > >               || TREE_CODE (new_name) == SSA_NAME);
> > > >    new_vec = build_vector_from_val (step_vectype, t);
> > > > -  vec_step = vect_init_vector (loop_vinfo, stmt_info,
> > > > -                              new_vec, step_vectype, NULL);
> > > > -
> > > > +  vec_step
> > > > +    = vect_init_vector (loop_vinfo, stmt_info, new_vec, step_vectype,
> > > > +                       LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo) ? &si : NULL);
> > > >
> > > >    /* Create the following def-use cycle:
> > > >       loop prolog:
> > > > --
> > > > 2.36.3
> > > >
> > >  
> > > 
> >  
> > 
>  
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)