Re: VRP: make range_includes_zero_p handle value_ranges

[Aldy Hernandez <aldyh@redhat.com>]

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On 08/23/2018 05:59 AM, Richard Biener wrote:
> On Wed, Aug 22, 2018 at 11:31 AM Aldy Hernandez <aldyh@redhat.com> wrote:
>>
>>
>>
>> On 08/21/2018 05:46 AM, Richard Biener wrote:
>>> On Wed, Aug 15, 2018 at 3:33 AM Aldy Hernandez <aldyh@redhat.com> wrote:
>>
>>>> Finally, my apologies for including a tiny change to the
>>>> POINTER_PLUS_EXPR handling code as well.  It came about the same set of
>>>> auditing tests.
>>>
>>> Bah, please split up things here ;)  I've done a related change there
>>> yesterday...
>>>
>>>>
>>>> It turns out we can handle POINTER_PLUS_EXPR(~[0,0], [X,Y]) without
>>>> bailing as VR_VARYING in extract_range_from_binary_expr_1.  In doing so,
>>>> I also noticed that ~[0,0] is not the only non-null.  We could also have
>>>> ~[0,2] and still know that the pointer is not zero.  I have adjusted
>>>> range_is_nonnull accordingly.
>>>
>>> But there are other consumers and it would have been better to
>>> change range_includes_zero_p to do the natural thing (get a VR) and
>>> then remove range_is_nonnull as redundant if possible.
>>
>> Indeed.  Cleaning up range_includes_zero_p makes VRP and friends a lot
>> cleaner.  Thanks for the suggestion.
>>
>> I lazily avoided cleaning up the division code affected in this patch
>> too much, since it's going to be superseded by my division changes in
>> the other patch.
>>
>> OK pending tests?
> 
> -/* Return 1 if [MIN, MAX] includes the value zero, 0 if it does not
> -   include the value zero, -2 if we cannot tell.  */
> +/* Return 1 if *VR includes the value zero, 0 if it does not include
> +   the value zero, or -2 if we cannot tell.  */
> 
>   int
> -range_includes_zero_p (tree min, tree max)
> +range_includes_zero_p (const value_range *vr)
>   {
> -  tree zero = build_int_cst (TREE_TYPE (min), 0);
> -  return value_inside_range (zero, min, max);
> +  if (vr->type == VR_UNDEFINED || vr->type == VR_VARYING)
> +    return -2;
> +
> +  tree zero = build_int_cst (TREE_TYPE (vr->min), 0);
> +  if (vr->type == VR_RANGE)
> +    return value_inside_range (zero, vr->min, vr->max);
> +  else
> +    return !value_inside_range (zero, vr->min, vr->max);
>   }
> 
> please make it return a bool.  VR_VARYING means the range does
> include zero.  For VR_UNDEFINED we could say it doesn't or we choose
> to not possibly optimize and thus return true (just do that for now).
> That's because VR_VARYING is [-INF, INF] and VR_UNDEFINED is
> an empty range.

Done.

> 
> I suppose the -2 for we cannot tell was for the case of symbolic
> ranges where again we can conservatively return true
> (and your return !value_inside_range for VR_ANTI_RANGE botched
> the tri-state return value anyways...).

Bah!  I sure botched up the anti range return.  That was the last 
bootstrap failure I was investigating.  You'd be amazed how many things 
mysteriously fail when things like ~[SYMBOL, SYMBOL] are assumed to be 
non-zero.

Thanks for spotting this.  Bootstrap is happy now :-P.

> 
> So, can you please rework that?

Sure can!

Attached.


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gcc/

	* gimple-ssa-evrp-analyze.c (set_ssa_range_info): Pass value_range
	to range_includes_zero_p.  Do not special case VR_ANTI_RANGE.
	* tree-vrp.c (range_is_nonnull): Remove.
	(range_includes_zero_p): Accept value_range instead of min/max.
	(extract_range_from_binary_expr_1): Do not early bail on
	POINTER_PLUS_EXPR.
	Use range_includes_zero_p instead of range_is_nonnull.
	(extract_range_from_unary_expr): Use range_includes_zero_p instead
	of range_is_nonnull.
	(vrp_meet_1): Pass value_range to range_includes_zero_p.  Do not
	special case VR_ANTI_RANGE.
	(vrp_finalize): Same.
	* tree-vrp.h (range_includes_zero_p): Pass value_range as argument
	instead of min/max.
	(range_is_nonnull): Remove.
	* vr-values.c (vrp_stmt_computes_nonzero): Use
	range_includes_zero_p instead of range_is_nonnull.
	(extract_range_basic): Pass value_range to range_includes_zero_p
	instead of range_is_nonnull.

diff --git a/gcc/gimple-ssa-evrp-analyze.c b/gcc/gimple-ssa-evrp-analyze.c
index b9dcf906ff7..e9afa80e191 100644
--- a/gcc/gimple-ssa-evrp-analyze.c
+++ b/gcc/gimple-ssa-evrp-analyze.c
@@ -119,12 +119,7 @@ evrp_range_analyzer::set_ssa_range_info (tree lhs, value_range *vr)
 			wi::to_wide (vr->max));
     }
   else if (POINTER_TYPE_P (TREE_TYPE (lhs))
-	   && ((vr->type == VR_RANGE
-		&& range_includes_zero_p (vr->min,
-					  vr->max) == 0)
-	       || (vr->type == VR_ANTI_RANGE
-		   && range_includes_zero_p (vr->min,
-					     vr->max) == 1)))
+	   && range_includes_zero_p (vr) == 0)
     set_ptr_nonnull (lhs);
 }
 
diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index 735b3646e81..84da2635624 100644
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -502,17 +502,6 @@ vrp_bitmap_equal_p (const_bitmap b1, const_bitmap b2)
 	      && bitmap_equal_p (b1, b2)));
 }
 
-/* Return true if VR is ~[0, 0].  */
-
-bool
-range_is_nonnull (value_range *vr)
-{
-  return vr->type == VR_ANTI_RANGE
-	 && integer_zerop (vr->min)
-	 && integer_zerop (vr->max);
-}
-
-
 /* Return true if VR is [0, 0].  */
 
 static inline bool
@@ -880,14 +869,25 @@ value_ranges_intersect_p (value_range *vr0, value_range *vr1)
 }
 
 
-/* Return 1 if [MIN, MAX] includes the value zero, 0 if it does not
-   include the value zero, -2 if we cannot tell.  */
+/* Return TRUE if *VR includes the value zero.  */
 
-int
-range_includes_zero_p (tree min, tree max)
+bool
+range_includes_zero_p (const value_range *vr)
 {
-  tree zero = build_int_cst (TREE_TYPE (min), 0);
-  return value_inside_range (zero, min, max);
+  if (vr->type == VR_VARYING)
+    return true;
+
+  /* Ughh, we don't know.  We choose not to optimize.  */
+  if (vr->type == VR_UNDEFINED)
+    return true;
+
+  tree zero = build_int_cst (TREE_TYPE (vr->min), 0);
+  if (vr->type == VR_ANTI_RANGE)
+    {
+      int res = value_inside_range (zero, vr->min, vr->max);
+      return res == 0 || res == -2;
+    }
+  return value_inside_range (zero, vr->min, vr->max) != 0;
 }
 
 /* Return true if *VR is know to only contain nonnegative values.  */
@@ -1407,7 +1407,10 @@ extract_range_from_binary_expr_1 (value_range *vr,
       && code != POINTER_PLUS_EXPR
       && (vr0.type == VR_VARYING
 	  || vr1.type == VR_VARYING
-	  || vr0.type != vr1.type
+	  || (vr0.type != vr1.type
+	      /* We can handle POINTER_PLUS_EXPR(~[0,0], [x,y]) below,
+		 even though we have differing range kinds.  */
+	      && code != POINTER_PLUS_EXPR)
 	  || symbolic_range_p (&vr0)
 	  || symbolic_range_p (&vr1)))
     {
@@ -1424,7 +1427,7 @@ extract_range_from_binary_expr_1 (value_range *vr,
 	     nullness, if both are non null, then the result is nonnull.
 	     If both are null, then the result is null. Otherwise they
 	     are varying.  */
-	  if (range_is_nonnull (&vr0) && range_is_nonnull (&vr1))
+	  if (!range_includes_zero_p (&vr0) && !range_includes_zero_p (&vr1))
 	    set_value_range_to_nonnull (vr, expr_type);
 	  else if (range_is_null (&vr0) && range_is_null (&vr1))
 	    set_value_range_to_null (vr, expr_type);
@@ -1435,11 +1438,8 @@ extract_range_from_binary_expr_1 (value_range *vr,
 	{
 	  /* For pointer types, we are really only interested in asserting
 	     whether the expression evaluates to non-NULL.  */
-	  if (range_is_nonnull (&vr0)
-	      || range_is_nonnull (&vr1)
-	      || (vr1.type == VR_RANGE
-		  && !symbolic_range_p (&vr1)
-		  && !range_includes_zero_p (vr1.min, vr1.max)))
+	  if (!range_includes_zero_p (&vr0)
+	      || !range_includes_zero_p (&vr1))
 	    set_value_range_to_nonnull (vr, expr_type);
 	  else if (range_is_null (&vr0) && range_is_null (&vr1))
 	    set_value_range_to_null (vr, expr_type);
@@ -1450,7 +1450,7 @@ extract_range_from_binary_expr_1 (value_range *vr,
 	{
 	  /* For pointer types, we are really only interested in asserting
 	     whether the expression evaluates to non-NULL.  */
-	  if (range_is_nonnull (&vr0) && range_is_nonnull (&vr1))
+	  if (!range_includes_zero_p (&vr0) && !range_includes_zero_p (&vr1))
 	    set_value_range_to_nonnull (vr, expr_type);
 	  else if (range_is_null (&vr0) || range_is_null (&vr1))
 	    set_value_range_to_null (vr, expr_type);
@@ -1888,7 +1888,7 @@ extract_range_from_unary_expr (value_range *vr,
 	 determining if it evaluates to NULL [0, 0] or non-NULL (~[0, 0]).  */
       if (POINTER_TYPE_P (type))
 	{
-	  if (range_is_nonnull (&vr0))
+	  if (!range_includes_zero_p (&vr0))
 	    set_value_range_to_nonnull (vr, type);
 	  else if (range_is_null (&vr0))
 	    set_value_range_to_null (vr, type);
@@ -6020,17 +6020,9 @@ vrp_meet_1 (value_range *vr0, const value_range *vr1)
     {
       /* Failed to find an efficient meet.  Before giving up and setting
 	 the result to VARYING, see if we can at least derive a useful
-	 anti-range.  FIXME, all this nonsense about distinguishing
-	 anti-ranges from ranges is necessary because of the odd
-	 semantics of range_includes_zero_p and friends.  */
-      if (((saved.type == VR_RANGE
-	    && range_includes_zero_p (saved.min, saved.max) == 0)
-	   || (saved.type == VR_ANTI_RANGE
-	       && range_includes_zero_p (saved.min, saved.max) == 1))
-	  && ((vr1->type == VR_RANGE
-	       && range_includes_zero_p (vr1->min, vr1->max) == 0)
-	      || (vr1->type == VR_ANTI_RANGE
-		  && range_includes_zero_p (vr1->min, vr1->max) == 1)))
+	 anti-range.  */
+      if (range_includes_zero_p (&saved) == 0
+	  && range_includes_zero_p (vr1) == 0)
 	{
 	  set_value_range_to_nonnull (vr0, TREE_TYPE (saved.min));
 
@@ -6540,10 +6532,7 @@ vrp_prop::vrp_finalize (bool warn_array_bounds_p)
 	continue;
 
       if (POINTER_TYPE_P (TREE_TYPE (name))
-	  && ((vr->type == VR_RANGE
-	       && range_includes_zero_p (vr->min, vr->max) == 0)
-	      || (vr->type == VR_ANTI_RANGE
-		  && range_includes_zero_p (vr->min, vr->max) == 1)))
+	  && range_includes_zero_p (vr) == 0)
 	set_ptr_nonnull (name);
       else if (!POINTER_TYPE_P (TREE_TYPE (name)))
 	set_range_info (name, vr->type,
diff --git a/gcc/tree-vrp.h b/gcc/tree-vrp.h
index 0c1fb3637cf..f8c1c0c8f72 100644
--- a/gcc/tree-vrp.h
+++ b/gcc/tree-vrp.h
@@ -86,7 +86,7 @@ extern void register_edge_assert_for (tree, edge, enum tree_code,
 				      tree, tree, vec<assert_info> &);
 extern bool stmt_interesting_for_vrp (gimple *);
 extern void set_value_range_to_varying (value_range *);
-extern int range_includes_zero_p (tree, tree);
+extern bool range_includes_zero_p (const value_range *);
 extern bool infer_value_range (gimple *, tree, tree_code *, tree *);
 
 extern void set_value_range_to_nonnull (value_range *, tree);
@@ -96,7 +96,6 @@ extern void set_and_canonicalize_value_range (value_range *,
 					      enum value_range_type,
 					      tree, tree, bitmap);
 extern bool vrp_bitmap_equal_p (const_bitmap, const_bitmap);
-extern bool range_is_nonnull (value_range *);
 extern tree value_range_constant_singleton (value_range *);
 extern bool symbolic_range_p (value_range *);
 extern int compare_values (tree, tree);
diff --git a/gcc/vr-values.c b/gcc/vr-values.c
index 33335f3da31..072d9a7b454 100644
--- a/gcc/vr-values.c
+++ b/gcc/vr-values.c
@@ -343,7 +343,7 @@ vr_values::vrp_stmt_computes_nonzero (gimple *stmt)
 	  && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME)
 	{
 	  value_range *vr = get_value_range (TREE_OPERAND (base, 0));
-	  if (range_is_nonnull (vr))
+	  if (!range_includes_zero_p (vr))
 	    return true;
 	}
     }
@@ -1107,12 +1107,8 @@ vr_values::extract_range_basic (value_range *vr, gimple *stmt)
 	  if (TREE_CODE (arg) == SSA_NAME)
 	    {
 	      value_range *vr0 = get_value_range (arg);
-	      /* If arg is non-zero, then ffs or popcount
-		 are non-zero.  */
-	      if ((vr0->type == VR_RANGE
-		   && range_includes_zero_p (vr0->min, vr0->max) == 0)
-		  || (vr0->type == VR_ANTI_RANGE
-		      && range_includes_zero_p (vr0->min, vr0->max) == 1))
+	      /* If arg is non-zero, then ffs or popcount are non-zero.  */
+	      if (range_includes_zero_p (vr0) == 0)
 		mini = 1;
 	      /* If some high bits are known to be zero,
 		 we can decrease the maximum.  */