match: Extend `-(a ptrdiff b)` pattern by allowing a nop conversion between the neg...

When I tried to fix this before I didn't realize there was already a pattern for
`-(a ptrdiff b) -> (b ptrdiff a)`, I had added a complex pattern to match `ptr0 - (ptr0 - ptr1)`.
But with there being a pattern for `-(a ptrdiff b)`, we just need to extend the pattern
to support a nop conversion inbetween the negative and the ptrdiff.
Also the check for TYPE_OVERFLOW_UNDEFINED was wrong, in the case of `-(a - b) -> (b - a)`, the check
is !TYPE_OVERFLOW_SANITIZED so this pattern should use the same check.

Bootstrapped and tested on x86_64-linux-gnu.

Changes since v1:
* v2: Use the old type of the pointer_diff rather than ssizetype.

	PR tree-optimization/121921

gcc/ChangeLog:

	* match.pd (`-(a ptrdiff b)`): Extend for a nop_convert
	between the neg and ptrdiff.

gcc/testsuite/ChangeLog:

	* gcc.dg/pr121921-1.c: New test.

Signed-off-by: Andrew Pinski <andrew.pinski@oss.qualcomm.com>

diff --git a/gcc/match.pd b/gcc/match.pd
index 10a2c5e72d69788793b829a6205ba573b2b2633a..4d0a803eaef0cca5f1dc1f158c6ea71bb98e6436 100644 (file)
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -2133,9 +2133,10 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
          && !HONOR_SIGNED_ZEROS (type)))
   (minus @1 @0)))
 (simplify
- (negate (pointer_diff @0 @1))
- (if (TYPE_OVERFLOW_UNDEFINED (type))
-  (pointer_diff @1 @0)))
+ (negate (nop_convert? (pointer_diff@2 @0 @1)))
+ (if (ANY_INTEGRAL_TYPE_P (type) && !TYPE_OVERFLOW_SANITIZED (type))
+  (with { tree ptrdifftype = TREE_TYPE (@2); }
+   (convert (pointer_diff:ptrdifftype @1 @0)))))
 
 /* A - B -> A + (-B) if B is easily negatable.  */
 (simplify

diff --git a/gcc/testsuite/gcc.dg/pr121921-1.c b/gcc/testsuite/gcc.dg/pr121921-1.c
new file mode 100644 (file)
index 0000000..828472a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr121921-1.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-cddce1" } */
+
+/* PR tree-optimization/121921 */
+
+int *
+fx (int *b, int *e)
+{
+  __SIZE_TYPE__ p = b - e;
+  /* The first forwprop pass should optimize this to return e;  */
+  return b - p;
+}
+
+/* { dg-final { scan-tree-dump "return e" "cddce1" } } */
+