Re: [PATCH] Fix PR80281

[Richard Biener <rguenther at suse dot de>]

On Mon, 3 Apr 2017, Marc Glisse wrote:

> On Mon, 3 Apr 2017, Richard Biener wrote:
> 
> > --- gcc/match.pd	(revision 246642)
> > +++ gcc/match.pd	(working copy)
> > @@ -1153,7 +1153,14 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> >   (if (tree_nop_conversion_p (type, TREE_TYPE (@0))
> >        && 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))))))
> 
> Why do we match
> (plus:c (convert1? @0) (convert2? (negate @1)))
> instead of the simpler
> (plus:c @0 (convert? (negate @1)))

Hmm, historic I believe - matching forwprop code 1:1.  The convert on 
@0 is not needed indeed.

> >  /* A - (-B) -> A + B */
> 
> Actually, I believe this transformation has issues as well, it seems possible
> to transform X-INT_MIN into X+INT_MIN if INT_MIN comes as
> (int)(-(unsigned)INT_MIN).

True.  So the same fix applies to this variant.

I'm re-testing the following variant.

Richard.

2017-04-03  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.

Index: gcc/match.pd
===================================================================
--- gcc/match.pd	(revision 246648)
+++ gcc/match.pd	(working copy)
@@ -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)))
Index: gcc/fold-const.c
===================================================================
--- gcc/fold-const.c	(revision 246648)
+++ gcc/fold-const.c	(working copy)
@@ -831,8 +831,12 @@ split_tree (location_t loc, tree in, tre
       /* 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, tre
 	*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.  */
Index: gcc/testsuite/gcc.dg/torture/pr80281.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr80281.c	(nonexistent)
+++ gcc/testsuite/gcc.dg/torture/pr80281.c	(working copy)
@@ -0,0 +1,14 @@
+/* { 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;
+}