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

[Martin Sebor]

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.

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;
>   
>