Re: [COMMITTED] Make irange dependency explicit for range_of_ssa_name_with_loop_info.

[Aldy Hernandez <aldyh@redhat.com>]

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On Tue, Aug 2, 2022 at 9:19 AM Richard Biener
<richard.guenther@gmail.com> wrote:
>
> On Mon, Aug 1, 2022 at 8:17 AM Aldy Hernandez via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > Even though ranger is type agnostic, SCEV seems to only work with
> > integers.  This patch removes some FIXME notes making it explicit that
> > bounds_of_var_in_loop only works with iranges.
>
> SCEV also handles floats, where do you see this failing?  Yes, support is
> somewhat limited, but still.

Oh, it does?  We could convert  range_of_ssa_name_with_loop_info to
the type agnostic vrange if so... (see attached untested patch).

I'm looking at the testcase for 24021 with the attached patch, and
bounds_of_var_in_loop() is returning false because SCEV couldn't
figure out the direction of the loop:

  dir = scev_direction (chrec);
  if (/* Do not adjust ranges if we do not know whether the iv increases
     or decreases,  ... */
      dir == EV_DIR_UNKNOWN
      /* ... or if it may wrap.  */
      || scev_probably_wraps_p (NULL_TREE, init, step, stmt,
                get_chrec_loop (chrec), true))
    return false;

The chrec in question is rather simple... a loop increasing by 0.01:

(gdb) p debug(chrec)
{1.00000000000000002081668171172168513294309377670288085938e-2, +,
1.00000001490116119384765625e-1}_1

I also see that bounds_of_var_in_loop() calls niter's
max_loop_iterations(), which if I understand things correctly, bails
at several points if the step is not integral.

I'd be happy to adapt our code, if SCEV can give me useful information.

Aldy

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From 86752bb57b0534b496b51559ec8e28e56fb3ea4e Mon Sep 17 00:00:00 2001
From: Aldy Hernandez <aldyh@redhat.com>
Date: Tue, 2 Aug 2022 13:27:16 +0200
Subject: [PATCH] Make range_of_ssa_name_with_loop_info type agnostic.

gcc/ChangeLog:

	* gimple-range-fold.cc (fold_using_range::range_of_phi): Remove
	irange check.
	(tree_lower_bound): New.
	(tree_upper_bound): New.
	(fold_using_range::range_of_ssa_name_with_loop_info): Convert to
	vrange.
	* gimple-range-fold.h (range_of_ssa_name_with_loop_info): Change
	argument to vrange.
---
 gcc/gimple-range-fold.cc | 46 ++++++++++++++++++++++++++++++----------
 gcc/gimple-range-fold.h  |  2 +-
 2 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/gcc/gimple-range-fold.cc b/gcc/gimple-range-fold.cc
index 7665c954f2b..923094abd62 100644
--- a/gcc/gimple-range-fold.cc
+++ b/gcc/gimple-range-fold.cc
@@ -854,13 +854,12 @@ fold_using_range::range_of_phi (vrange &r, gphi *phi, fur_source &src)
 
   // If SCEV is available, query if this PHI has any knonwn values.
   if (scev_initialized_p ()
-      && !POINTER_TYPE_P (TREE_TYPE (phi_def))
-      && irange::supports_p (TREE_TYPE (phi_def)))
+      && !POINTER_TYPE_P (TREE_TYPE (phi_def)))
     {
       class loop *l = loop_containing_stmt (phi);
       if (l && loop_outer (l))
 	{
-	  int_range_max loop_range;
+	  Value_Range loop_range (type);
 	  range_of_ssa_name_with_loop_info (loop_range, phi_def, l, phi, src);
 	  if (!loop_range.varying_p ())
 	    {
@@ -1330,10 +1329,32 @@ fold_using_range::range_of_cond_expr  (vrange &r, gassign *s, fur_source &src)
   return true;
 }
 
+// Return the lower bound of R as a tree.
+
+static inline tree
+tree_lower_bound (const vrange &r, tree type)
+{
+  if (is_a <irange> (r))
+    return wide_int_to_tree (type, as_a <irange> (r).lower_bound ());
+  // ?? Handle floats when they contain endpoints.
+  return NULL;
+}
+
+// Return the upper bound of R as a tree.
+
+static inline tree
+tree_upper_bound (const vrange &r, tree type)
+{
+  if (is_a <irange> (r))
+    return wide_int_to_tree (type, as_a <irange> (r).upper_bound ());
+  // ?? Handle floats when they contain endpoints.
+  return NULL;
+}
+
 // If SCEV has any information about phi node NAME, return it as a range in R.
 
 void
-fold_using_range::range_of_ssa_name_with_loop_info (irange &r, tree name,
+fold_using_range::range_of_ssa_name_with_loop_info (vrange &r, tree name,
 						    class loop *l, gphi *phi,
 						    fur_source &src)
 {
@@ -1341,24 +1362,27 @@ fold_using_range::range_of_ssa_name_with_loop_info (irange &r, tree name,
   tree min, max, type = TREE_TYPE (name);
   if (bounds_of_var_in_loop (&min, &max, src.query (), l, phi, name))
     {
-      if (TREE_CODE (min) != INTEGER_CST)
+      if (!is_gimple_constant (min))
 	{
 	  if (src.query ()->range_of_expr (r, min, phi) && !r.undefined_p ())
-	    min = wide_int_to_tree (type, r.lower_bound ());
+	    min = tree_lower_bound (r, type);
 	  else
 	    min = vrp_val_min (type);
 	}
-      if (TREE_CODE (max) != INTEGER_CST)
+      if (!is_gimple_constant (max))
 	{
 	  if (src.query ()->range_of_expr (r, max, phi) && !r.undefined_p ())
-	    max = wide_int_to_tree (type, r.upper_bound ());
+	    max = tree_upper_bound (r, type);
 	  else
 	    max = vrp_val_max (type);
 	}
-      r.set (min, max);
+      if (min && max)
+	{
+	  r.set (min, max);
+	  return;
+	}
     }
-  else
-    r.set_varying (type);
+  r.set_varying (type);
 }
 
 // -----------------------------------------------------------------------
diff --git a/gcc/gimple-range-fold.h b/gcc/gimple-range-fold.h
index fbf66275f74..c2f381dffec 100644
--- a/gcc/gimple-range-fold.h
+++ b/gcc/gimple-range-fold.h
@@ -173,7 +173,7 @@ protected:
   void range_of_builtin_ubsan_call (irange &r, gcall *call, tree_code code,
 				    fur_source &src);
   bool range_of_phi (vrange &r, gphi *phi, fur_source &src);
-  void range_of_ssa_name_with_loop_info (irange &, tree, class loop *, gphi *,
+  void range_of_ssa_name_with_loop_info (vrange &, tree, class loop *, gphi *,
 					 fur_source &src);
   void relation_fold_and_or (irange& lhs_range, gimple *s, fur_source &src);
 };
-- 
2.37.1