diff mbox

Improve "str" + 2 > "str" folding (PR c++/71448)

Message ID 20160608124332.GC7387@tucnak.redhat.com
State New
Headers show

Commit Message

Jakub Jelinek June 8, 2016, 12:43 p.m. UTC 
Hi!

For the purposes of fold_comparison, various constants (in this case
STRING_CST) work the same as decls, in particular we know the objects
extents and can determine possible pointer wrapping.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk
(and maybe later for 6.x)?

2016-06-08  Jakub Jelinek  <jakub@redhat.com>
	    Richard Biener  <rguenther@suse.de>

	PR c++/71448
	* fold-const.c (fold_comparison): Handle CONSTANT_CLASS_P (base0)
	the same as DECL_P (base0) for indirect_base0.  Use equality_code
	in one further place.

	* g++.dg/torture/pr71448.C: New test.


	Jakub

Comments

Richard Biener June 8, 2016, 12:48 p.m. UTC | #1 
On Wed, 8 Jun 2016, Jakub Jelinek wrote:

> Hi!
> 
> For the purposes of fold_comparison, various constants (in this case
> STRING_CST) work the same as decls, in particular we know the objects
> extents and can determine possible pointer wrapping.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk
> (and maybe later for 6.x)?

Ok.

Thanks,
Richard.

> 
> 2016-06-08  Jakub Jelinek  <jakub@redhat.com>
> 	    Richard Biener  <rguenther@suse.de>
> 
> 	PR c++/71448
> 	* fold-const.c (fold_comparison): Handle CONSTANT_CLASS_P (base0)
> 	the same as DECL_P (base0) for indirect_base0.  Use equality_code
> 	in one further place.
> 
> 	* g++.dg/torture/pr71448.C: New test.
> 
> --- gcc/fold-const.c.jj	2016-06-06 19:39:40.000000000 +0200
> +++ gcc/fold-const.c	2016-06-08 10:23:15.129178865 +0200
> @@ -8527,9 +8527,9 @@ fold_comparison (location_t loc, enum tr
>  	  if ((offset0 == offset1
>  	       || (offset0 && offset1
>  		   && operand_equal_p (offset0, offset1, 0)))
> -	      && (code == EQ_EXPR
> -		  || code == NE_EXPR
> -		  || (indirect_base0 && DECL_P (base0))
> +	      && (equality_code
> +		  || (indirect_base0
> +		      && (DECL_P (base0) || CONSTANT_CLASS_P (base0)))
>  		  || POINTER_TYPE_OVERFLOW_UNDEFINED))
>  
>  	    {
> @@ -8568,7 +8568,8 @@ fold_comparison (location_t loc, enum tr
>  	     6.5.6/8 and /9 with respect to the signed ptrdiff_t.  */
>  	  else if (bitpos0 == bitpos1
>  		   && (equality_code
> -		       || (indirect_base0 && DECL_P (base0))
> +		       || (indirect_base0
> +			   && (DECL_P (base0) || CONSTANT_CLASS_P (base0)))
>  		       || POINTER_TYPE_OVERFLOW_UNDEFINED))
>  	    {
>  	      /* By converting to signed sizetype we cover middle-end pointer
> --- gcc/testsuite/g++.dg/torture/pr71448.C.jj	2016-06-08 10:32:17.409952602 +0200
> +++ gcc/testsuite/g++.dg/torture/pr71448.C	2016-06-08 10:33:38.396872265 +0200
> @@ -0,0 +1,27 @@
> +// PR c++/71448
> +// { dg-do compile }
> +// { dg-additional-options "-std=c++11" }
> +
> +static constexpr const char foo[] = "foo";
> +static constexpr const char *bar = "bar";
> +
> +static_assert ((foo + 3 - foo) == 3, "check");
> +static_assert (foo + 2 != foo, "check");
> +static_assert (foo + 2 >= foo, "check");
> +static_assert (3 + foo >= foo, "check");
> +static_assert (foo <= foo + 2, "check");
> +static_assert (foo <= 3 + foo, "check");
> +static_assert (foo + 2 > foo, "check");
> +static_assert (3 + foo > foo, "check");
> +static_assert (foo < 2 + foo, "check");
> +static_assert (foo < foo + 3, "check");
> +static_assert ((bar + 3 - bar) == 3, "check");
> +static_assert (bar + 2 != bar, "check");
> +static_assert (2 + bar >= bar, "check");
> +static_assert (bar + 3 >= bar, "check");
> +static_assert (bar <= bar + 2, "check");
> +static_assert (bar <= 3 + bar, "check");
> +static_assert (bar + 2 > bar, "check");
> +static_assert (3 + bar > bar, "check");
> +static_assert (bar < 2 + bar, "check");
> +static_assert (bar < bar + 3, "check");
> 
> 	Jakub
> 
>
diff mbox

Patch

--- gcc/fold-const.c.jj	2016-06-06 19:39:40.000000000 +0200
+++ gcc/fold-const.c	2016-06-08 10:23:15.129178865 +0200
@@ -8527,9 +8527,9 @@  fold_comparison (location_t loc, enum tr
 	  if ((offset0 == offset1
 	       || (offset0 && offset1
 		   && operand_equal_p (offset0, offset1, 0)))
-	      && (code == EQ_EXPR
-		  || code == NE_EXPR
-		  || (indirect_base0 && DECL_P (base0))
+	      && (equality_code
+		  || (indirect_base0
+		      && (DECL_P (base0) || CONSTANT_CLASS_P (base0)))
 		  || POINTER_TYPE_OVERFLOW_UNDEFINED))
 
 	    {
@@ -8568,7 +8568,8 @@  fold_comparison (location_t loc, enum tr
 	     6.5.6/8 and /9 with respect to the signed ptrdiff_t.  */
 	  else if (bitpos0 == bitpos1
 		   && (equality_code
-		       || (indirect_base0 && DECL_P (base0))
+		       || (indirect_base0
+			   && (DECL_P (base0) || CONSTANT_CLASS_P (base0)))
 		       || POINTER_TYPE_OVERFLOW_UNDEFINED))
 	    {
 	      /* By converting to signed sizetype we cover middle-end pointer
--- gcc/testsuite/g++.dg/torture/pr71448.C.jj	2016-06-08 10:32:17.409952602 +0200
+++ gcc/testsuite/g++.dg/torture/pr71448.C	2016-06-08 10:33:38.396872265 +0200
@@ -0,0 +1,27 @@ 
+// PR c++/71448
+// { dg-do compile }
+// { dg-additional-options "-std=c++11" }
+
+static constexpr const char foo[] = "foo";
+static constexpr const char *bar = "bar";
+
+static_assert ((foo + 3 - foo) == 3, "check");
+static_assert (foo + 2 != foo, "check");
+static_assert (foo + 2 >= foo, "check");
+static_assert (3 + foo >= foo, "check");
+static_assert (foo <= foo + 2, "check");
+static_assert (foo <= 3 + foo, "check");
+static_assert (foo + 2 > foo, "check");
+static_assert (3 + foo > foo, "check");
+static_assert (foo < 2 + foo, "check");
+static_assert (foo < foo + 3, "check");
+static_assert ((bar + 3 - bar) == 3, "check");
+static_assert (bar + 2 != bar, "check");
+static_assert (2 + bar >= bar, "check");
+static_assert (bar + 3 >= bar, "check");
+static_assert (bar <= bar + 2, "check");
+static_assert (bar <= 3 + bar, "check");
+static_assert (bar + 2 > bar, "check");
+static_assert (3 + bar > bar, "check");
+static_assert (bar < 2 + bar, "check");
+static_assert (bar < bar + 3, "check");