re PR tree-optimization/80281 (Wrong constant folding)

2017-04-04  Richard Biener  <rguenther@suse.de>

	PR middle-end/80281
	* match.pd (A + (-B) -> A - B): Make sure to preserve unsigned
	arithmetic done for the negate or the plus.  Simplify.
	(A - (-B) -> A + B): Likewise.
	* fold-const.c (split_tree): Make sure to not negate pointers.

	* gcc.dg/torture/pr80281.c: New testcase.

From-SVN: r246674

gcc/ChangeLog

+2017-04-04  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/80281
+	* match.pd (A + (-B) -> A - B): Make sure to preserve unsigned
+	arithmetic done for the negate or the plus.  Simplify.
+	(A - (-B) -> A + B): Likewise.
+	* fold-const.c (split_tree): Make sure to not negate pointers.
+
 2017-04-04  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	PR rtl-optimization/60818

gcc/fold-const.c

@@ -831,8 +831,12 @@ split_tree (location_t loc, tree in, tree type, enum tree_code code,
       /* Now do any needed negations.  */
       if (neg_litp_p)
 	*minus_litp = *litp, *litp = 0;
-      if (neg_conp_p)
-	*conp = negate_expr (*conp);
+      if (neg_conp_p && *conp)
+	{
+	  /* Convert to TYPE before negating.  */
+	  *conp = fold_convert_loc (loc, type, *conp);
+	  *conp = negate_expr (*conp);
+	}
       if (neg_var_p && var)
 	{
 	  /* Convert to TYPE before negating.  */
@@ -859,7 +863,12 @@ split_tree (location_t loc, tree in, tree type, enum tree_code code,
 	*minus_litp = *litp, *litp = 0;
       else if (*minus_litp)
 	*litp = *minus_litp, *minus_litp = 0;
-      *conp = negate_expr (*conp);
+      if (*conp)
+	{
+	  /* Convert to TYPE before negating.  */
+	  *conp = fold_convert_loc (loc, type, *conp);
+	  *conp = negate_expr (*conp);
+	}
       if (var)
 	{
 	  /* Convert to TYPE before negating.  */

gcc/match.pd

@@ -1148,19 +1148,31 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
  /* Contract negates.  */
  /* A + (-B) -> A - B */
  (simplify
-  (plus:c (convert1? @0) (convert2? (negate @1)))
-  /* Apply STRIP_NOPS on @0 and the negate.  */
-  (if (tree_nop_conversion_p (type, TREE_TYPE (@0))
-       && tree_nop_conversion_p (type, TREE_TYPE (@1))
+  (plus:c @0 (convert? (negate @1)))
+  /* Apply STRIP_NOPS on the negate.  */
+  (if (tree_nop_conversion_p (type, TREE_TYPE (@1))
        && !TYPE_OVERFLOW_SANITIZED (type))
-   (minus (convert @0) (convert @1))))
+   (with
+    {
+     tree t1 = type;
+     if (INTEGRAL_TYPE_P (type)
+	 && TYPE_OVERFLOW_WRAPS (type) != TYPE_OVERFLOW_WRAPS (TREE_TYPE (@1)))
+       t1 = TYPE_OVERFLOW_WRAPS (type) ? type : TREE_TYPE (@1);
+    }
+    (convert (minus (convert:t1 @0) (convert:t1 @1))))))
  /* A - (-B) -> A + B */
  (simplify
-  (minus (convert1? @0) (convert2? (negate @1)))
-  (if (tree_nop_conversion_p (type, TREE_TYPE (@0))
-       && tree_nop_conversion_p (type, TREE_TYPE (@1))
+  (minus @0 (convert? (negate @1)))
+  (if (tree_nop_conversion_p (type, TREE_TYPE (@1))
        && !TYPE_OVERFLOW_SANITIZED (type))
-   (plus (convert @0) (convert @1))))
+   (with
+    {
+     tree t1 = type;
+     if (INTEGRAL_TYPE_P (type)
+	 && TYPE_OVERFLOW_WRAPS (type) != TYPE_OVERFLOW_WRAPS (TREE_TYPE (@1)))
+       t1 = TYPE_OVERFLOW_WRAPS (type) ? type : TREE_TYPE (@1);
+    }
+    (convert (plus (convert:t1 @0) (convert:t1 @1))))))
  /* -(-A) -> A */
  (simplify
   (negate (convert? (negate @1)))

gcc/testsuite/ChangeLog

 2017-04-04  Richard Biener  <rguenther@suse.de>
 
+	PR middle-end/80281
+	* gcc.dg/torture/pr80281.c: New testcase.
+
+2017-04-04  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/80275
 	* g++.dg/opt/pr80275.C: Make g static.
 

gcc/testsuite/gcc.dg/torture/pr80281.c

+/* { dg-run } */
+/* { dg-require-effective-target int32plus } */
+
+int
+main ()
+{
+  volatile int a = 0;
+  long long b = 2147483648LL;
+  int c = a % 2;
+  int x = ((int) -b + c) % -2147483647;
+  if (x != -1)
+    __builtin_abort ();
+  return 0;
+}