Re: [PATCH] Move ~X | X -> -1 folding

[Richard Biener <rguenther at suse dot de>]

On Tue, 30 Jun 2015, Marek Polacek wrote:

> This moves a simple optimization.  Here it's plain to see how :c
> removes the need to duplicate code to handle commutativity.
> 
> I put some more converts into the pattern, but then it's turned
> out that I also need the tree_nop_conversion_p (otherwise we'd
> regress binop-notor2.c that uses booleans).
> 
> I did a regtest with the patterns in fold-const.c removed to see
> whether we have some testing for this folding -- and there were
> no regressions, so I had to write a test.
> 
> Bootstrapped/regtested on x86_64-linux, ok for trunk?

Ok.

Thanks,
Richard.

> 2015-06-29  Marek Polacek  <polacek@redhat.com>
> 
> 	* fold-const.c (fold_binary_loc): Move ~X | X folding ...
> 	* match.pd: ... here.
> 
> 	* gcc.dg/fold-ior-2.c: New test.
> 
> diff --git gcc/fold-const.c gcc/fold-const.c
> index a447452..caba0cf 100644
> --- gcc/fold-const.c
> +++ gcc/fold-const.c
> @@ -10928,24 +10928,6 @@ fold_binary_loc (location_t loc,
>  
>      case BIT_IOR_EXPR:
>      bit_ior:
> -      /* ~X | X is -1.  */
> -      if (TREE_CODE (arg0) == BIT_NOT_EXPR
> -	  && operand_equal_p (TREE_OPERAND (arg0, 0), arg1, 0))
> -	{
> -	  t1 = build_zero_cst (type);
> -	  t1 = fold_unary_loc (loc, BIT_NOT_EXPR, type, t1);
> -	  return omit_one_operand_loc (loc, type, t1, arg1);
> -	}
> -
> -      /* X | ~X is -1.  */
> -      if (TREE_CODE (arg1) == BIT_NOT_EXPR
> -	  && operand_equal_p (arg0, TREE_OPERAND (arg1, 0), 0))
> -	{
> -	  t1 = build_zero_cst (type);
> -	  t1 = fold_unary_loc (loc, BIT_NOT_EXPR, type, t1);
> -	  return omit_one_operand_loc (loc, type, t1, arg0);
> -	}
> -
>        /* Canonicalize (X & C1) | C2.  */
>        if (TREE_CODE (arg0) == BIT_AND_EXPR
>  	  && TREE_CODE (arg1) == INTEGER_CST
> diff --git gcc/match.pd gcc/match.pd
> index 0cf3d21..5dcbc1a 100644
> --- gcc/match.pd
> +++ gcc/match.pd
> @@ -283,6 +283,12 @@ along with GCC; see the file COPYING3.  If not see
>    (bit_and @0 integer_zerop@1)
>    @1)
>  
> +/* ~x | x -> -1 */
> +(simplify
> + (bit_ior:c (convert? @0) (convert? (bit_not @0)))
> + (if (tree_nop_conversion_p (type, TREE_TYPE (@0)))
> +  { build_all_ones_cst (type); }))
> +
>  /* x ^ x -> 0 */
>  (simplify
>    (bit_xor @0 @0)
> diff --git gcc/testsuite/gcc.dg/fold-ior-2.c gcc/testsuite/gcc.dg/fold-ior-2.c
> index e69de29..6abac9e 100644
> --- gcc/testsuite/gcc.dg/fold-ior-2.c
> +++ gcc/testsuite/gcc.dg/fold-ior-2.c
> @@ -0,0 +1,47 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-cddce1" } */
> +
> +int
> +fn1 (int x)
> +{
> +  return ~x | x;
> +}
> +
> +int
> +fn2 (int x)
> +{
> +  return x | ~x;
> +}
> +
> +unsigned int
> +fn3 (unsigned int x)
> +{
> +  return ~x | x;
> +}
> +
> +unsigned int
> +fn4 (unsigned int x)
> +{
> +  return ~x | x;
> +}
> +
> +int
> +fn5 (int x)
> +{
> +  return ~x | (unsigned) x;
> +}
> +
> +int
> +fn6 (int x)
> +{
> +  return (unsigned) ~x | x;
> +}
> +
> +int
> +fn7 (int x)
> +{
> +  return ~(unsigned) x | x;
> +}
> +
> +/* { dg-final { scan-tree-dump-not "~" "cddce1" } } */
> +/* { dg-final { scan-tree-dump-not " \\| " "cddce1" } } */
> 
> 	Marek
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Dilip Upmanyu, Graham Norton, HRB 21284 (AG Nuernberg)