re PR c/61240 (Incorrect warning "integer overflow in expression" on pointer-pointer subtraction)

	PR c/61240
	* match.pd ((P + A) - P, P - (P + A), (P + A) - (P + B)): For
	pointer_diff optimizations use view_convert instead of convert.

	* gcc.dg/pr61240.c: New test.

From-SVN: r256838

gcc/ChangeLog

+2018-01-18  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/61240
+	* match.pd ((P + A) - P, P - (P + A), (P + A) - (P + B)): For
+	pointer_diff optimizations use view_convert instead of convert.
+
 2018-01-17  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>
 
 	* config/rs6000/rs6000.md (*call_indirect_nonlocal_sysv<mode>):

gcc/match.pd

@@ -1832,7 +1832,10 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
     /* The second argument of pointer_plus must be interpreted as signed, and
        thus sign-extended if necessary.  */
     (with { tree stype = signed_type_for (TREE_TYPE (@1)); }
-     (convert (convert:stype @1))))
+     /* Use view_convert instead of convert here, as POINTER_PLUS_EXPR
+	second arg is unsigned even when we need to consider it as signed,
+	we don't want to diagnose overflow here.  */
+     (convert (view_convert:stype @1))))
 
   /* (T)P - (T)(P + A) -> -(T) A */
   (simplify
@@ -1876,7 +1879,10 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
     /* The second argument of pointer_plus must be interpreted as signed, and
        thus sign-extended if necessary.  */
     (with { tree stype = signed_type_for (TREE_TYPE (@1)); }
-     (negate (convert (convert:stype @1)))))
+     /* Use view_convert instead of convert here, as POINTER_PLUS_EXPR
+	second arg is unsigned even when we need to consider it as signed,
+	we don't want to diagnose overflow here.  */
+     (negate (convert (view_convert:stype @1)))))
 
   /* (T)(P + A) - (T)(P + B) -> (T)A - (T)B */
   (simplify
@@ -1927,7 +1933,11 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
     /* The second argument of pointer_plus must be interpreted as signed, and
        thus sign-extended if necessary.  */
     (with { tree stype = signed_type_for (TREE_TYPE (@1)); }
-     (minus (convert (convert:stype @1)) (convert (convert:stype @2)))))))
+     /* Use view_convert instead of convert here, as POINTER_PLUS_EXPR
+	second arg is unsigned even when we need to consider it as signed,
+	we don't want to diagnose overflow here.  */
+     (minus (convert (view_convert:stype @1))
+	    (convert (view_convert:stype @2)))))))
 
 
 /* Simplifications of MIN_EXPR, MAX_EXPR, fmin() and fmax().  */

gcc/testsuite/ChangeLog

+2018-01-18  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/61240
+	* gcc.dg/pr61240.c: New test.
+
 2018-01-17  Harald Anlauf  <anlauf@gmx.de>
 
 	PR fortran/83864

gcc/testsuite/gcc.dg/pr61240.c

+/* PR c/61240 */
+/* { dg-do compile } */
+
+typedef __PTRDIFF_TYPE__ ptrdiff_t;
+
+ptrdiff_t
+foo (ptrdiff_t a[4])
+{
+  int i[4];
+  int *p = i + 2;
+  static ptrdiff_t b = p - (p - 1);	/* { dg-bogus "integer overflow in expression" } */
+  static ptrdiff_t c = (p - 1) - p;	/* { dg-bogus "integer overflow in expression" } */
+  static ptrdiff_t d = (p - 2) - (p - 1);/* { dg-bogus "integer overflow in expression" } */
+  static ptrdiff_t e = (p - 1) - (p - 2);/* { dg-bogus "integer overflow in expression" } */
+  a[0] = p - (p - 1);			/* { dg-bogus "integer overflow in expression" } */
+  a[1] = (p - 1) - p;			/* { dg-bogus "integer overflow in expression" } */
+  a[2] = (p - 2) - (p - 1);		/* { dg-bogus "integer overflow in expression" } */
+  a[3] = (p - 1) - (p - 2);		/* { dg-bogus "integer overflow in expression" } */
+  return b + c + d + e;
+}