Re: [PATCH 2/4] Allow match-and-simplified phiopt to run in early phiopt

[Andrew Pinski <pinskia@gmail.com>]

On Tue, Jun 29, 2021 at 12:14 PM Martin Sebor via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> On 6/27/21 5:24 PM, apinski--- via Gcc-patches wrote:
> > From: Andrew Pinski <apinski@marvell.com>
> >
> > To move a few things more to match-and-simplify from phiopt,
> > we need to allow match_simplify_replacement to run in early
> > phiopt. To do this we add a replacement for gimple_simplify
> > that is explictly for phiopt.
> >
> > OK? Bootstrapped and tested on x86_64-linux-gnu with no
> > regressions.
> >
> > gcc/ChangeLog:
> >
> >       * tree-ssa-phiopt.c (match_simplify_replacement):
> >       Add early_p argument. Call gimple_simplify_phiopt
> >       instead of gimple_simplify.
> >       (tree_ssa_phiopt_worker): Update call to
> >       match_simplify_replacement and allow unconditionally.
> >       (phiopt_early_allow): New function.
> >       (gimple_simplify_phiopt): New function.
> > ---
> >   gcc/tree-ssa-phiopt.c | 89 ++++++++++++++++++++++++++++++++++---------
> >   1 file changed, 70 insertions(+), 19 deletions(-)
> >
> > diff --git a/gcc/tree-ssa-phiopt.c b/gcc/tree-ssa-phiopt.c
> > index ab12e85569d..17bc597851b 100644
> > --- a/gcc/tree-ssa-phiopt.c
> > +++ b/gcc/tree-ssa-phiopt.c
> > @@ -50,12 +50,13 @@ along with GCC; see the file COPYING3.  If not see
> >   #include "gimple-fold.h"
> >   #include "internal-fn.h"
> >   #include "gimple-range.h"
> > +#include "gimple-match.h"
> >
> >   static unsigned int tree_ssa_phiopt_worker (bool, bool, bool);
> >   static bool two_value_replacement (basic_block, basic_block, edge, gphi *,
> >                                  tree, tree);
> >   static bool match_simplify_replacement (basic_block, basic_block,
> > -                                     edge, edge, gphi *, tree, tree);
> > +                                     edge, edge, gphi *, tree, tree, bool);
> >   static gphi *factor_out_conditional_conversion (edge, edge, gphi *, tree, tree,
> >                                               gimple *);
> >   static int value_replacement (basic_block, basic_block,
> > @@ -345,9 +346,9 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool do_hoist_loads, bool early_p)
> >         /* Do the replacement of conditional if it can be done.  */
> >         if (!early_p && two_value_replacement (bb, bb1, e2, phi, arg0, arg1))
> >           cfgchanged = true;
> > -       else if (!early_p
> > -                && match_simplify_replacement (bb, bb1, e1, e2, phi,
> > -                                               arg0, arg1))
> > +       else if (match_simplify_replacement (bb, bb1, e1, e2, phi,
> > +                                            arg0, arg1,
> > +                                            early_p))
> >           cfgchanged = true;
> >         else if (abs_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
> >           cfgchanged = true;
> > @@ -811,6 +812,67 @@ two_value_replacement (basic_block cond_bb, basic_block middle_bb,
> >     return true;
> >   }
> >
> > +/* Return TRUE if CODE should be allowed during early phiopt.
> > +   Currently this is to allow MIN/MAX and ABS/NEGATE.  */
> > +static bool
> > +phiopt_early_allow (enum tree_code code)
> > +{
> > +  switch (code)
> > +    {
> > +      case MIN_EXPR:
> > +      case MAX_EXPR:
> > +      case ABS_EXPR:
> > +      case ABSU_EXPR:
> > +      case NEGATE_EXPR:
> > +      case SSA_NAME:
> > +     return true;
> > +      default:
> > +     return false;
> > +    }
> > +}
> > +
> > +/* gimple_simplify_phiopt is like gimple_simplify but designed for PHIOPT.
> > +   Return NULL if nothing can be simplified or the resulting simplified value
> > +   with parts pushed if EARLY_P was true. Also rejects non allowed tree code
> > +   if EARLY_P is set.
> > +   Takes the comparison from COMP_STMT and two args, ARG0 and ARG1 and tries
> > +   to simplify CMP ? ARG0 : ARG1.  */
> > +static tree
> > +gimple_simplify_phiopt (bool early_p, tree type, gimple *comp_stmt,
> > +                     tree arg0, tree arg1,
> > +                     gimple_seq *seq)
> > +{
> > +  tree result;
> > +  enum tree_code comp_code = gimple_cond_code (comp_stmt);
> > +  location_t loc = gimple_location (comp_stmt);
> > +  tree cmp0 = gimple_cond_lhs (comp_stmt);
> > +  tree cmp1 = gimple_cond_rhs (comp_stmt);
> > +  /* To handle special cases like floating point comparison, it is easier and
> > +     less error-prone to build a tree and gimplify it on the fly though it is
> > +     less efficient.
> > +     Don't use fold_build2 here as that might create (bool)a instead of just
> > +     "a != 0".  */
> > +  tree cond = build2_loc (loc, comp_code, boolean_type_node,
> > +                       cmp0, cmp1);
> > +  gimple_match_op op (gimple_match_cond::UNCOND,
> > +                   COND_EXPR, type, cond, arg0, arg1);
> > +
> > +  if (op.resimplify (early_p ? NULL : seq, follow_all_ssa_edges))
> > +    {
> > +      /* Early we want only to allow some generated tree codes. */
> > +      if (!early_p
> > +       || op.code.is_tree_code ()
> > +       || phiopt_early_allow ((tree_code)op.code))
> > +     {
> > +       result = maybe_push_res_to_seq (&op, seq);
> > +       if (result)
> > +         return result;
>
> It looks to me like the last if statement is redundant and could
> be replaced by
>
>    return maybe_push_res_to_seq (&op, seq);
>
> thus also making the result variable redundant, further simplifying
> the code.

The next patch after this one will change it anyways.

Thanks,
Andrew


>
> Martin
>
> > +     }
> > +    }
> > +
> > +  return NULL;
> > +}
> > +
> >   /*  The function match_simplify_replacement does the main work of doing the
> >       replacement using match and simplify.  Return true if the replacement is done.
> >       Otherwise return false.
> > @@ -820,10 +882,9 @@ two_value_replacement (basic_block cond_bb, basic_block middle_bb,
> >   static bool
> >   match_simplify_replacement (basic_block cond_bb, basic_block middle_bb,
> >                           edge e0, edge e1, gphi *phi,
> > -                         tree arg0, tree arg1)
> > +                         tree arg0, tree arg1, bool early_p)
> >   {
> >     gimple *stmt;
> > -  tree cond;
> >     gimple_stmt_iterator gsi;
> >     edge true_edge, false_edge;
> >     gimple_seq seq = NULL;
> > @@ -884,15 +945,6 @@ match_simplify_replacement (basic_block cond_bb, basic_block middle_bb,
> >
> >     stmt = last_stmt (cond_bb);
> >
> > -  /* To handle special cases like floating point comparison, it is easier and
> > -     less error-prone to build a tree and gimplify it on the fly though it is
> > -     less efficient.
> > -     Don't use fold_build2 here as that might create (bool)a instead of just
> > -     "a != 0".  */
> > -  cond = build2_loc (gimple_location (stmt),
> > -                  gimple_cond_code (stmt), boolean_type_node,
> > -                  gimple_cond_lhs (stmt), gimple_cond_rhs (stmt));
> > -
> >     /* We need to know which is the true edge and which is the false
> >        edge so that we know when to invert the condition below.  */
> >     extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);
> > @@ -900,10 +952,9 @@ match_simplify_replacement (basic_block cond_bb, basic_block middle_bb,
> >       std::swap (arg0, arg1);
> >
> >     tree type = TREE_TYPE (gimple_phi_result (phi));
> > -  result = gimple_simplify (COND_EXPR, type,
> > -                         cond,
> > -                         arg0, arg1,
> > -                         &seq, NULL);
> > +  result = gimple_simplify_phiopt (early_p, type, stmt,
> > +                                arg0, arg1,
> > +                                &seq);
> >     if (!result)
> >       return false;
> >
> >
>