Re: [PATCH] Move A - (A & B) -> ~B & A

[Richard Biener <rguenther at suse dot de>]

On July 17, 2015 5:23:21 PM GMT+02:00, Marek Polacek <polacek@redhat.com> wrote:
>On Fri, Jul 17, 2015 at 02:23:50PM +0200, Richard Biener wrote:
>> >+/* Fold A - (A & B) into ~B & A.  */
>> >+(simplify
>> >+ (minus (convert? @0) (convert? (bit_and:c @0 @1)))
>> 
>> I think you want :s on the bit_and and its convert?
>
>Ok, I keep forgetting about this :(.
> 
>> Are you sure you don't need to check for a nop conversion here?
>
>I thought I didn't need it here, and couldn't find a testcase which
>would break without tree_nop_conversion_p checks, but that doesn't mean
>much.  So for extra safety I put the checks there.
>
>Bootstrapped/regtested on x86_64-linux, ok for trunk?

OK 

Thanks
Richard

>2015-07-17  Marek Polacek  <polacek@redhat.com>
>
>	* fold-const.c (fold_binary_loc): Move A - (A & B) into ~B & A ...
>	* match.pd: ... here.
>
>	* gcc.dg/fold-minus-7.c: New test.
>
>diff --git gcc/fold-const.c gcc/fold-const.c
>index 93dd29d..fa321f4 100644
>--- gcc/fold-const.c
>+++ gcc/fold-const.c
>@@ -9777,30 +9777,6 @@ fold_binary_loc (location_t loc,
> 
>       if (! FLOAT_TYPE_P (type))
> 	{
>-	  /* Fold A - (A & B) into ~B & A.  */
>-	  if (!TREE_SIDE_EFFECTS (arg0)
>-	      && TREE_CODE (arg1) == BIT_AND_EXPR)
>-	    {
>-	      if (operand_equal_p (arg0, TREE_OPERAND (arg1, 1), 0))
>-		{
>-		  tree arg10 = fold_convert_loc (loc, type,
>-						 TREE_OPERAND (arg1, 0));
>-		  return fold_build2_loc (loc, BIT_AND_EXPR, type,
>-				      fold_build1_loc (loc, BIT_NOT_EXPR,
>-						   type, arg10),
>-				      fold_convert_loc (loc, type, arg0));
>-		}
>-	      if (operand_equal_p (arg0, TREE_OPERAND (arg1, 0), 0))
>-		{
>-		  tree arg11 = fold_convert_loc (loc,
>-						 type, TREE_OPERAND (arg1, 1));
>-		  return fold_build2_loc (loc, BIT_AND_EXPR, type,
>-				      fold_build1_loc (loc, BIT_NOT_EXPR,
>-						   type, arg11),
>-				      fold_convert_loc (loc, type, arg0));
>-		}
>-	    }
>-
> 	  /* Fold (A & ~B) - (A & B) into (A ^ B) - B, where B is
> 	     any power of 2 minus 1.  */
> 	  if (TREE_CODE (arg0) == BIT_AND_EXPR
>diff --git gcc/match.pd gcc/match.pd
>index c335ada..700a692 100644
>--- gcc/match.pd
>+++ gcc/match.pd
>@@ -662,6 +662,12 @@ along with GCC; see the file COPYING3.  If not see
>  (bit_ior:c (bit_and:cs @0 (bit_not @2)) (bit_and:cs @1 @2))
>  (bit_xor (bit_and (bit_xor @0 @1) @2) @0))
> 
>+/* Fold A - (A & B) into ~B & A.  */
>+(simplify
>+ (minus (convert? @0) (convert?:s (bit_and:cs @0 @1)))
>+ (if (tree_nop_conversion_p (type, TREE_TYPE (@0))
>+      && tree_nop_conversion_p (type, TREE_TYPE (@1)))
>+  (convert (bit_and (bit_not @1) @0))))
> 
> /* Associate (p +p off1) +p off2 as (p +p (off1 + off2)).  */
> (simplify
>diff --git gcc/testsuite/gcc.dg/fold-minus-7.c
>gcc/testsuite/gcc.dg/fold-minus-7.c
>index e69de29..7a49faa 100644
>--- gcc/testsuite/gcc.dg/fold-minus-7.c
>+++ gcc/testsuite/gcc.dg/fold-minus-7.c
>@@ -0,0 +1,36 @@
>+/* { dg-do compile } */
>+/* { dg-options "-O -fdump-tree-cddce1" } */
>+
>+int
>+f1 (int a, int b)
>+{
>+  int tem = a & b;
>+  return a - tem;
>+}
>+
>+int
>+f2 (int a, int b)
>+{
>+  int tem = b & a;
>+  return a - tem;
>+}
>+
>+int
>+f3 (unsigned int a, int b)
>+{
>+  return a - (a & b);
>+}
>+
>+int
>+f4 (int a, unsigned int b)
>+{
>+  return a - (a & b);
>+}
>+
>+int
>+f5 (int a, int b)
>+{
>+  return a - (unsigned) (b & a);
>+}
>+
>+/* { dg-final { scan-tree-dump-not " - " "cddce1" } } */
>
>	Marek