[PATCH] middle-end: fix de-optimizations with bitclear patterns on signed values

Tamar Christina Tamar.Christina@arm.com
Fri Nov 19 08:52:11 GMT 2021


Ping

> -----Original Message-----
> From: Tamar Christina
> Sent: Friday, November 12, 2021 7:31 AM
> To: Jakub Jelinek <jakub@redhat.com>
> Cc: Jonathan Wakely <jwakely@redhat.com>; Richard Biener
> <rguenther@suse.de>; gcc-patches@gcc.gnu.org; nd <nd@arm.com>
> Subject: RE: [PATCH] middle-end: fix de-optimizations with bitclear patterns
> on signed values
> 
> 
> 
> > -----Original Message-----
> > From: Jakub Jelinek <jakub@redhat.com>
> > Sent: Thursday, November 4, 2021 4:11 PM
> > To: Tamar Christina <Tamar.Christina@arm.com>
> > Cc: Jonathan Wakely <jwakely@redhat.com>; Richard Biener
> > <rguenther@suse.de>; gcc-patches@gcc.gnu.org; nd <nd@arm.com>
> > Subject: Re: [PATCH] middle-end: fix de-optimizations with bitclear
> > patterns on signed values
> >
> > On Thu, Nov 04, 2021 at 12:19:34PM +0000, Tamar Christina wrote:
> > > I'm not sure the precision matters since if the conversion resulted
> > > in not enough precision such that It influences the compare it would
> > > have
> > been optimized out.
> >
> > You can't really rely on other optimizations being performed.  They
> > will usually happen, but might not because such code only materialized
> > short time ago without folding happening in between, or some debug
> > counters or -
> > fno-* disabling some passes, ...
> 
> Fair point, I have separated out the logic as you requested and added the
> debug fix.
> 
> Bootstrapped Regtested on aarch64-none-linux-gnu, x86_64-pc-linux-gnu
> and no regressions.
> 
> Ok for master?
> 
> Thanks,
> Tamar
> 
> gcc/ChangeLog:
> 
> 	* tree-ssa-phiopt.c (spaceship_replacement): Handle new canonical
> 	codegen.
> 
> --- inline copy of patch ---
> 
> diff --git a/gcc/tree-ssa-phiopt.c b/gcc/tree-ssa-phiopt.c index
> 0e339c46afa29fa97f90d9bc4394370cd9b4b396..3ad5b23885a37eec0beff229e2
> a96e86658b2d1a 100644
> --- a/gcc/tree-ssa-phiopt.c
> +++ b/gcc/tree-ssa-phiopt.c
> @@ -2038,11 +2038,36 @@ spaceship_replacement (basic_block cond_bb,
> basic_block middle_bb,
>    gimple *orig_use_stmt = use_stmt;
>    tree orig_use_lhs = NULL_TREE;
>    int prec = TYPE_PRECISION (TREE_TYPE (phires));
> -  if (is_gimple_assign (use_stmt)
> -      && gimple_assign_rhs_code (use_stmt) == BIT_AND_EXPR
> -      && TREE_CODE (gimple_assign_rhs2 (use_stmt)) == INTEGER_CST
> -      && (wi::to_wide (gimple_assign_rhs2 (use_stmt))
> -	  == wi::shifted_mask (1, prec - 1, false, prec)))
> +  bool is_cast = false;
> +
> +  /* Deal with the case when match.pd has rewritten the (res & ~1) == 0
> +     into res <= 1 and has left a type-cast for signed types.  */
> +  if (gimple_assign_cast_p (use_stmt))
> +    {
> +      orig_use_lhs = gimple_assign_lhs (use_stmt);
> +      /* match.pd would have only done this for a signed type,
> +	 so the conversion must be to an unsigned one.  */
> +      tree ty1 = TREE_TYPE (gimple_assign_rhs1 (use_stmt));
> +      tree ty2 = TREE_TYPE (orig_use_lhs);
> +
> +      if (!TYPE_UNSIGNED (ty2) || !INTEGRAL_TYPE_P (ty2))
> +	return false;
> +      if (TYPE_PRECISION (ty1) != TYPE_PRECISION (ty2))
> +	return false;
> +      if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig_use_lhs))
> +	return false;
> +      if (EDGE_COUNT (phi_bb->preds) != 4)
> +	return false;
> +      if (!single_imm_use (orig_use_lhs, &use_p, &use_stmt))
> +	return false;
> +
> +      is_cast = true;
> +    }
> +  else if (is_gimple_assign (use_stmt)
> +	   && gimple_assign_rhs_code (use_stmt) == BIT_AND_EXPR
> +	   && TREE_CODE (gimple_assign_rhs2 (use_stmt)) == INTEGER_CST
> +	   && (wi::to_wide (gimple_assign_rhs2 (use_stmt))
> +	       == wi::shifted_mask (1, prec - 1, false, prec)))
>      {
>        /* For partial_ordering result operator>= with unspec as second
>  	 argument is (res & 1) == res, folded by match.pd into @@ -2099,7
> +2124,7 @@ spaceship_replacement (basic_block cond_bb, basic_block
> middle_bb,
>        || !tree_fits_shwi_p (rhs)
>        || !IN_RANGE (tree_to_shwi (rhs), -1, 1))
>      return false;
> -  if (orig_use_lhs)
> +  if (orig_use_lhs && !is_cast)
>      {
>        if ((cmp != EQ_EXPR && cmp != NE_EXPR) || !integer_zerop (rhs))
>  	return false;
> @@ -2310,62 +2335,101 @@ spaceship_replacement (basic_block cond_bb,
> basic_block middle_bb,
>      one_cmp = GT_EXPR;
> 
>    enum tree_code res_cmp;
> -  switch (cmp)
> +
> +  if (is_cast)
>      {
> -    case EQ_EXPR:
> -      if (integer_zerop (rhs))
> -	res_cmp = EQ_EXPR;
> -      else if (integer_minus_onep (rhs))
> -	res_cmp = one_cmp == LT_EXPR ? GT_EXPR : LT_EXPR;
> -      else if (integer_onep (rhs))
> -	res_cmp = one_cmp;
> -      else
> +      if (TREE_CODE (rhs) != INTEGER_CST)
>  	return false;
> -      break;
> -    case NE_EXPR:
> -      if (integer_zerop (rhs))
> -	res_cmp = NE_EXPR;
> -      else if (integer_minus_onep (rhs))
> -	res_cmp = one_cmp == LT_EXPR ? LE_EXPR : GE_EXPR;
> -      else if (integer_onep (rhs))
> -	res_cmp = one_cmp == LT_EXPR ? GE_EXPR : LE_EXPR;
> -      else
> -	return false;
> -      break;
> -    case LT_EXPR:
> -      if (integer_onep (rhs))
> -	res_cmp = one_cmp == LT_EXPR ? GE_EXPR : LE_EXPR;
> -      else if (integer_zerop (rhs))
> -	res_cmp = one_cmp == LT_EXPR ? GT_EXPR : LT_EXPR;
> -      else
> -	return false;
> -      break;
> -    case LE_EXPR:
> -      if (integer_zerop (rhs))
> -	res_cmp = one_cmp == LT_EXPR ? GE_EXPR : LE_EXPR;
> -      else if (integer_minus_onep (rhs))
> -	res_cmp = one_cmp == LT_EXPR ? GT_EXPR : LT_EXPR;
> -      else
> -	return false;
> -      break;
> -    case GT_EXPR:
> -      if (integer_minus_onep (rhs))
> -	res_cmp = one_cmp == LT_EXPR ? LE_EXPR : GE_EXPR;
> -      else if (integer_zerop (rhs))
> -	res_cmp = one_cmp;
> -      else
> -	return false;
> -      break;
> -    case GE_EXPR:
> -      if (integer_zerop (rhs))
> -	res_cmp = one_cmp == LT_EXPR ? LE_EXPR : GE_EXPR;
> -      else if (integer_onep (rhs))
> -	res_cmp = one_cmp;
> -      else
> -	return false;
> -      break;
> -    default:
> -      gcc_unreachable ();
> +      /* As for -ffast-math we assume the 2 return to be
> +	 impossible, canonicalize (unsigned) res <= 1U or
> +	 (unsigned) res < 2U into res >= 0 and (unsigned) res > 1U
> +	 or (unsigned) res >= 2U as res < 0.  */
> +      switch (cmp)
> +	{
> +	case LE_EXPR:
> +	  if (!integer_onep (rhs))
> +	    return false;
> +	  res_cmp = GE_EXPR;
> +	  break;
> +	case LT_EXPR:
> +	  if (wi::ne_p (wi::to_widest (rhs), 2))
> +	    return false;
> +	  res_cmp = GE_EXPR;
> +	  break;
> +	case GT_EXPR:
> +	  if (!integer_onep (rhs))
> +	    return false;
> +	  res_cmp = LT_EXPR;
> +	  break;
> +	case GE_EXPR:
> +	  if (wi::ne_p (wi::to_widest (rhs), 2))
> +	    return false;
> +	  res_cmp = LT_EXPR;
> +	  break;
> +	default:
> +	  return false;
> +	}
> +      rhs = build_zero_cst (TREE_TYPE (phires));
> +    }
> +  else
> +    {
> +      switch (cmp)
> +      {
> +      case EQ_EXPR:
> +	if (integer_zerop (rhs))
> +	  res_cmp = EQ_EXPR;
> +	else if (integer_minus_onep (rhs))
> +	  res_cmp = one_cmp == LT_EXPR ? GT_EXPR : LT_EXPR;
> +	else if (integer_onep (rhs))
> +	  res_cmp = one_cmp;
> +	else
> +	  return false;
> +	break;
> +      case NE_EXPR:
> +	if (integer_zerop (rhs))
> +	  res_cmp = NE_EXPR;
> +	else if (integer_minus_onep (rhs))
> +	  res_cmp = one_cmp == LT_EXPR ? LE_EXPR : GE_EXPR;
> +	else if (integer_onep (rhs))
> +	  res_cmp = one_cmp == LT_EXPR ? GE_EXPR : LE_EXPR;
> +	else
> +	  return false;
> +	break;
> +      case LT_EXPR:
> +	if (integer_onep (rhs))
> +	  res_cmp = one_cmp == LT_EXPR ? GE_EXPR : LE_EXPR;
> +	else if (integer_zerop (rhs))
> +	  res_cmp = one_cmp == LT_EXPR ? GT_EXPR : LT_EXPR;
> +	else
> +	  return false;
> +	break;
> +      case LE_EXPR:
> +	if (integer_zerop (rhs))
> +	  res_cmp = one_cmp == LT_EXPR ? GE_EXPR : LE_EXPR;
> +	else if (integer_minus_onep (rhs))
> +	  res_cmp = one_cmp == LT_EXPR ? GT_EXPR : LT_EXPR;
> +	else
> +	  return false;
> +	break;
> +      case GT_EXPR:
> +	if (integer_minus_onep (rhs))
> +	  res_cmp = one_cmp == LT_EXPR ? LE_EXPR : GE_EXPR;
> +	else if (integer_zerop (rhs))
> +	  res_cmp = one_cmp;
> +	else
> +	  return false;
> +	break;
> +      case GE_EXPR:
> +	if (integer_zerop (rhs))
> +	  res_cmp = one_cmp == LT_EXPR ? LE_EXPR : GE_EXPR;
> +	else if (integer_onep (rhs))
> +	  res_cmp = one_cmp;
> +	else
> +	  return false;
> +	break;
> +      default:
> +	  gcc_unreachable ();
> +      }
>      }
> 
>    if (gimple_code (use_stmt) == GIMPLE_COND) @@ -2394,6 +2458,7 @@
> spaceship_replacement (basic_block cond_bb, basic_block middle_bb,
>        use_operand_p use_p;
>        imm_use_iterator iter;
>        bool has_debug_uses = false;
> +      bool has_cast_debug_uses = false;
>        FOR_EACH_IMM_USE_FAST (use_p, iter, phires)
>  	{
>  	  gimple *use_stmt = USE_STMT (use_p); @@ -2405,12 +2470,14 @@
> spaceship_replacement (basic_block cond_bb, basic_block middle_bb,
>  	}
>        if (orig_use_lhs)
>  	{
> -	  if (!has_debug_uses)
> +	  if (!has_debug_uses || is_cast)
>  	    FOR_EACH_IMM_USE_FAST (use_p, iter, orig_use_lhs)
>  	      {
>  		gimple *use_stmt = USE_STMT (use_p);
>  		gcc_assert (is_gimple_debug (use_stmt));
>  		has_debug_uses = true;
> +		if (is_cast)
> +		  has_cast_debug_uses = true;
>  	      }
>  	  gimple_stmt_iterator gsi = gsi_for_stmt (orig_use_stmt);
>  	  tree zero = build_zero_cst (TREE_TYPE (orig_use_lhs)); @@ -2448,7
> +2515,23 @@ spaceship_replacement (basic_block cond_bb, basic_block
> middle_bb,
>  	  gsi_insert_before (&gsi, g, GSI_SAME_STMT);
>  	  replace_uses_by (phires, temp2);
>  	  if (orig_use_lhs)
> -	    replace_uses_by (orig_use_lhs, temp2);
> +	    {
> +	      if (has_cast_debug_uses)
> +		{
> +		  tree temp3 = make_node (DEBUG_EXPR_DECL);
> +		  DECL_ARTIFICIAL (temp3) = 1;
> +		  TREE_TYPE (temp3) = TREE_TYPE (orig_use_lhs);
> +		  SET_DECL_MODE (temp3, TYPE_MODE (type));
> +		  t = build2 (EQ_EXPR, boolean_type_node, lhs1, rhs2);
> +		  t = build3 (COND_EXPR, type, t, build_zero_cst (type),
> +			      temp1);
> +		  g = gimple_build_debug_bind (temp3, t, phi);
> +		  gsi_insert_before (&gsi, g, GSI_SAME_STMT);
> +		  replace_uses_by (orig_use_lhs, temp3);
> +		}
> +	      else
> +		replace_uses_by (orig_use_lhs, temp2);
> +	    }
>  	}
>      }



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