RE: [ping][vect-patterns] Refactor widen_plus/widen_minus as internal_fns

[Joel Hutton <Joel.Hutton@arm.com>]

Thanks Richard,

> I thought the potential problem with the above is that gimple_build is a
> folding interface, so in principle it's allowed to return an existing SSA_NAME
> set by an existing statement (or even a constant).
> I think in this context we do need to force a new statement to be created.

Before I make any changes, I'd like to check we're all on the same page.

richi, are you ok with the gimple_build function, perhaps with a different name if you are concerned with overloading? we could use gimple_ch_build or gimple_code_helper_build?

Similarly are you ok with the use of gimple_extract_op? I would lean towards using it as it is cleaner, but I don't have strong feelings.

Joel

> -----Original Message-----
> From: Richard Sandiford <richard.sandiford@arm.com>
> Sent: 07 June 2022 09:18
> To: Joel Hutton <Joel.Hutton@arm.com>
> Cc: Richard Biener <rguenther@suse.de>; gcc-patches@gcc.gnu.org
> Subject: Re: [ping][vect-patterns] Refactor widen_plus/widen_minus as
> internal_fns
> 
> Joel Hutton <Joel.Hutton@arm.com> writes:
> >> > Patches attached. They already incorporated the .cc rename, now
> >> > rebased to be after the change to tree.h
> >>
> >> @@ -1412,8 +1412,7 @@ vect_recog_widen_op_pattern (vec_info *vinfo,
> >>                        2, oprnd, half_type, unprom, vectype);
> >>
> >>    tree var = vect_recog_temp_ssa_var (itype, NULL);
> >> -  gimple *pattern_stmt = gimple_build_assign (var, wide_code,
> >> -                                             oprnd[0], oprnd[1]);
> >> +  gimple *pattern_stmt = gimple_build (var, wide_code, oprnd[0],
> >> oprnd[1]);
> >>
> >>
> >> you should be able to do without the new gimple_build overload by
> >> using
> >>
> >>    gimple_seq stmts = NULL;
> >>    gimple_build (&stmts, wide_code, itype, oprnd[0], oprnd[1]);
> >>    gimple *pattern_stmt = gimple_seq_last_stmt (stmts);
> >>
> >> because 'gimple_build' is an existing API.
> >
> > Done.
> >
> > The gimple_build overload was at the request of Richard Sandiford, I
> assume removing it is ok with you Richard S?
> > From Richard Sandiford:
> >> For example, I think we should hide this inside a new:
> >>
> >>   gimple_build (var, wide_code, oprnd[0], oprnd[1]);
> >>
> >> that works directly on code_helper, similarly to the new code_helper
> >> gimple_build interfaces.
> 
> I thought the potential problem with the above is that gimple_build is a
> folding interface, so in principle it's allowed to return an existing SSA_NAME
> set by an existing statement (or even a constant).
> I think in this context we do need to force a new statement to be created.
> 
> Of course, the hope is that there wouldn't still be such folding opportunities
> at this stage, but I don't think it's guaranteed (especially with options
> fuzzing).
> 
> Sind I was mentioned :-) ...
> 
> Could you run the patch through contrib/check_GNU_style.py?
> There seem to be a few long lines.
> 
> > +  if (res_op.code.is_tree_code ())
> 
> Do you need this is_tree_code ()?  These comparisons…
> 
> > +  {
> > +      widen_arith = (code == WIDEN_PLUS_EXPR
> > +		     || code == WIDEN_MINUS_EXPR
> > +		     || code == WIDEN_MULT_EXPR
> > +		     || code == WIDEN_LSHIFT_EXPR);
> 
> …ought to be safe unconditionally.
> 
> > + }
> > +  else
> > +      widen_arith = false;
> > +
> > +  if (!widen_arith
> > +      && !CONVERT_EXPR_CODE_P (code)
> > +      && code != FIX_TRUNC_EXPR
> > +      && code != FLOAT_EXPR)
> > +    return false;
> >
> >    /* Check types of lhs and rhs.  */
> > -  scalar_dest = gimple_assign_lhs (stmt);
> > +  scalar_dest = gimple_get_lhs (stmt);
> >    lhs_type = TREE_TYPE (scalar_dest);
> >    vectype_out = STMT_VINFO_VECTYPE (stmt_info);
> >
> > @@ -4938,10 +4951,14 @@ vectorizable_conversion (vec_info *vinfo,
> >
> >    if (op_type == binary_op)
> >      {
> > -      gcc_assert (code == WIDEN_MULT_EXPR || code ==
> WIDEN_LSHIFT_EXPR
> > -		  || code == WIDEN_PLUS_EXPR || code ==
> WIDEN_MINUS_EXPR);
> > +      gcc_assert (code == WIDEN_MULT_EXPR
> > +		  || code == WIDEN_LSHIFT_EXPR
> > +		  || code == WIDEN_PLUS_EXPR
> > +		  || code == WIDEN_MINUS_EXPR);
> >
> > -      op1 = gimple_assign_rhs2 (stmt);
> > +
> > +      op1 = is_gimple_assign (stmt) ? gimple_assign_rhs2 (stmt) :
> > +				     gimple_call_arg (stmt, 0);
> >        tree vectype1_in;
> >        if (!vect_is_simple_use (vinfo, stmt_info, slp_node, 1,
> >  			       &op1, &slp_op1, &dt[1], &vectype1_in)) […] @@
> -12181,7
> > +12235,6 @@ supportable_widening_operation (vec_info *vinfo,
> >    return false;
> >  }
> >
> > -
> >  /* Function supportable_narrowing_operation
> >
> >     Check whether an operation represented by the code CODE is a
> 
> Seems like a spurious change.
> 
> > @@ -12205,7 +12258,7 @@ supportable_widening_operation (vec_info
> > *vinfo,  bool  supportable_narrowing_operation (enum tree_code code,
> >  				 tree vectype_out, tree vectype_in,
> > -				 enum tree_code *code1, int *multi_step_cvt,
> > +				 tree_code* _code1, int *multi_step_cvt,
> 
> The original formatting (space before the “*”) was correct.
> Names beginning with _ are reserved, so I think we need a different
> name here.  Also, the name in the comment should stay in sync with
> the name in the code.
> 
> That said though, I'm not sure…
> 
> >                                   vec<tree> *interm_types)
> >  {
> >    machine_mode vec_mode;
> > @@ -12217,8 +12270,8 @@ supportable_narrowing_operation (enum
> tree_code code,
> >    tree intermediate_type, prev_type;
> >    machine_mode intermediate_mode, prev_mode;
> >    int i;
> > -  unsigned HOST_WIDE_INT n_elts;
> >    bool uns;
> > +  tree_code * code1 = (tree_code*) _code1;
> 
> …the combination of these two changes makes sense on their own.
> 
> >
> >    *multi_step_cvt = 0;
> >    switch (code)
> > @@ -12227,9 +12280,8 @@ supportable_narrowing_operation (enum
> tree_code code,
> >        c1 = VEC_PACK_TRUNC_EXPR;
> >        if (VECTOR_BOOLEAN_TYPE_P (narrow_vectype)
> >  	  && VECTOR_BOOLEAN_TYPE_P (vectype)
> > -	  && SCALAR_INT_MODE_P (TYPE_MODE (vectype))
> > -	  && TYPE_VECTOR_SUBPARTS (vectype).is_constant (&n_elts)
> > -	  && n_elts < BITS_PER_UNIT)
> > +	  && TYPE_MODE (narrow_vectype) == TYPE_MODE (vectype)
> > +	  && SCALAR_INT_MODE_P (TYPE_MODE (vectype)))
> >  	optab1 = vec_pack_sbool_trunc_optab;
> >        else
> >  	optab1 = optab_for_tree_code (c1, vectype, optab_default);
> > @@ -12320,9 +12372,8 @@ supportable_narrowing_operation (enum
> tree_code code,
> >  	  = lang_hooks.types.type_for_mode (intermediate_mode, uns);
> >        if (VECTOR_BOOLEAN_TYPE_P (intermediate_type)
> >  	  && VECTOR_BOOLEAN_TYPE_P (prev_type)
> > -	  && SCALAR_INT_MODE_P (prev_mode)
> > -	  && TYPE_VECTOR_SUBPARTS (intermediate_type).is_constant
> (&n_elts)
> > -	  && n_elts < BITS_PER_UNIT)
> > +	  && intermediate_mode == prev_mode
> > +	  && SCALAR_INT_MODE_P (prev_mode))
> >  	interm_optab = vec_pack_sbool_trunc_optab;
> >        else
> >  	interm_optab
> 
> This part looks like a behavioural change, so I think it should be part
> of a separate patch.
> 
> > diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h
> > index
> 642eb0aeb21264cd736a479b1ec25357abef29cd..50ff8eeac1e6b9859302bd78
> 4f10ee3d8ff4b4dc 100644
> > --- a/gcc/tree-vectorizer.h
> > +++ b/gcc/tree-vectorizer.h
> > @@ -2120,13 +2120,12 @@ extern bool vect_is_simple_use (vec_info *,
> stmt_vec_info, slp_tree,
> >  				enum vect_def_type *,
> >  				tree *, stmt_vec_info * = NULL);
> >  extern bool vect_maybe_update_slp_op_vectype (slp_tree, tree);
> > -extern bool supportable_widening_operation (vec_info *,
> > -					    enum tree_code, stmt_vec_info,
> > -					    tree, tree, enum tree_code *,
> > -					    enum tree_code *, int *,
> > -					    vec<tree> *);
> > +extern bool supportable_widening_operation (vec_info*, code_helper,
> > +					    stmt_vec_info, tree, tree,
> > +					    code_helper*, code_helper*,
> > +					    int*, vec<tree> *);
> >  extern bool supportable_narrowing_operation (enum tree_code, tree,
> tree,
> > -					     enum tree_code *, int *,
> > +					     tree_code *, int *,
> >  					     vec<tree> *);
> >
> >  extern unsigned record_stmt_cost (stmt_vector_for_cost *, int,
> > diff --git a/gcc/tree.h b/gcc/tree.h
> > index
> f84958933d51144bb6ce7cc41eca5f7f06814550..00b0e4d1c696633fe38baad5
> 295b1f90398d53fc 100644
> > --- a/gcc/tree.h
> > +++ b/gcc/tree.h
> > @@ -92,6 +92,10 @@ public:
> >    bool is_fn_code () const { return rep < 0; }
> >    bool is_internal_fn () const;
> >    bool is_builtin_fn () const;
> > +  enum tree_code safe_as_tree_code () const { return is_tree_code () ?
> > +    (tree_code)* this : MAX_TREE_CODES; }
> > +  combined_fn safe_as_fn_code () const { return is_fn_code () ?
> (combined_fn) *this
> > +    : CFN_LAST;}
> 
> Since these don't fit on a line, the coding convention says that they
> should be defined outside of the class.
> 
> Thanks,
> Richard
> 
> >    int get_rep () const { return rep; }
> >    bool operator== (const code_helper &other) { return rep == other.rep; }
> >    bool operator!= (const code_helper &other) { return rep != other.rep; }