From 36684dde843a4c9556b97bf030cabef8b9430aa4 Mon Sep 17 00:00:00 2001
From: Aldy Hernandez <aldyh@redhat.com>
Date: Tue, 1 Jun 2021 17:48:30 +0200
Subject: [PATCH 2/2] Use known global ranges in export_global_ranges

This patch modifies export_global_ranges to take into account current
global ranges.  It also handles enhances said function to export pointer
global ranges as well.

gcc/ChangeLog:

	* gimple-range.cc (gimple_ranger::export_global_ranges): Call
	  update_global_range.
	* value-query.cc (update_global_range): New.
	* value-query.h (update_global_range): New.

gcc/testsuite/ChangeLog:

	* gcc.dg/pr80776-1.c: XFAIL and document the reason why.
---
 gcc/gimple-range.cc              | 26 ++++++++-------------
 gcc/testsuite/gcc.dg/pr80776-1.c | 12 +++++++++-
 gcc/value-query.cc               | 39 ++++++++++++++++++++++++++++++++
 gcc/value-query.h                |  1 +
 4 files changed, 61 insertions(+), 17 deletions(-)

diff --git a/gcc/gimple-range.cc b/gcc/gimple-range.cc
index ed0a0c9702b..af426207092 100644
--- a/gcc/gimple-range.cc
+++ b/gcc/gimple-range.cc
@@ -1115,7 +1115,7 @@ gimple_ranger::range_of_stmt (irange &r, gimple *s, tree name)
 }
 
 // This routine will export whatever global ranges are known to GCC
-// SSA_RANGE_NAME_INFO fields.
+// SSA_RANGE_NAME_INFO and SSA_NAME_PTR_INFO fields.
 
 void
 gimple_ranger::export_global_ranges ()
@@ -1136,24 +1136,18 @@ gimple_ranger::export_global_ranges ()
 	  && m_cache.get_global_range (r, name)
 	  && !r.varying_p())
 	{
-	  // Make sure the new range is a subset of the old range.
-	  int_range_max old_range;
-	  old_range = gimple_range_global (name);
-	  old_range.intersect (r);
-	  /* Disable this while we fix tree-ssa/pr61743-2.c.  */
-	  //gcc_checking_assert (old_range == r);
-
-	  // WTF? Can't write non-null pointer ranges?? stupid set_range_info!
-	  if (!POINTER_TYPE_P (TREE_TYPE (name)) && !r.undefined_p ())
+	  bool updated = update_global_range (r, name);
+
+	  if (updated && dump_file)
 	    {
 	      value_range vr = r;
-	      set_range_info (name, vr);
-	      if (dump_file)
+	      print_generic_expr (dump_file, name , TDF_SLIM);
+	      fprintf (dump_file, " --> ");
+	      vr.dump (dump_file);
+	      fprintf (dump_file, "\n");
+	      int_range_max same = vr;
+	      if (same != r)
 		{
-		  print_generic_expr (dump_file, name , TDF_SLIM);
-		  fprintf (dump_file, " --> ");
-		  vr.dump (dump_file);
-		  fprintf (dump_file, "\n");
 		  fprintf (dump_file, "         irange : ");
 		  r.dump (dump_file);
 		  fprintf (dump_file, "\n");
diff --git a/gcc/testsuite/gcc.dg/pr80776-1.c b/gcc/testsuite/gcc.dg/pr80776-1.c
index f3a120b6744..eca5e805ae2 100644
--- a/gcc/testsuite/gcc.dg/pr80776-1.c
+++ b/gcc/testsuite/gcc.dg/pr80776-1.c
@@ -17,5 +17,15 @@ Foo (void)
     __builtin_unreachable ();
   if (! (0 <= i && i <= 999999))
     __builtin_unreachable ();
-  sprintf (number, "%d", i); /* { dg-bogus "writing" "" } */
+
+  /* Legacy evrp sets the range of i to [0, MAX] *before* the first conditional,
+     and to [0,999999] *before* the second conditional.  This is because both
+     evrp and VRP use trickery to set global ranges when this particular use of
+     a __builtin_unreachable is in play (see uses of
+     assert_unreachable_fallthru_edge_p).
+
+     Setting these ranges at the definition site, causes VRP to remove the
+     unreachable code altogether, leaving the following sprintf unguarded.  This
+     causes the bogus warning below.  */
+  sprintf (number, "%d", i); /* { dg-bogus "writing" "" { xfail *-*-* } } */
 }
diff --git a/gcc/value-query.cc b/gcc/value-query.cc
index f8b457d362c..070d706166e 100644
--- a/gcc/value-query.cc
+++ b/gcc/value-query.cc
@@ -224,6 +224,45 @@ get_ssa_name_ptr_info_nonnull (const_tree name)
   return !pi->pt.null;
 }
 
+// Update the global range for NAME into the SSA_RANGE_NAME_INFO and
+// SSA_NAME_PTR_INFO fields.  Return TRUE if the range for NAME was
+// updated.
+
+bool
+update_global_range (irange &r, tree name)
+{
+  tree type = TREE_TYPE (name);
+
+  if (r.undefined_p () || r.varying_p ())
+    return false;
+
+  if (INTEGRAL_TYPE_P (type))
+    {
+      // If a global range already exists, incorporate it.
+      if (SSA_NAME_RANGE_INFO (name))
+	{
+	  value_range glob;
+	  get_ssa_name_range_info (glob, name);
+	  r.intersect (glob);
+	}
+      if (r.undefined_p ())
+	return false;
+
+      value_range vr = r;
+      set_range_info (name, vr);
+      return true;
+    }
+  else if (POINTER_TYPE_P (type))
+    {
+      if (r.nonzero_p ())
+	{
+	  set_ptr_nonnull (name);
+	  return true;
+	}
+    }
+  return false;
+}
+
 // Return the legacy global range for NAME if it has one, otherwise
 // return VARYING.
 
diff --git a/gcc/value-query.h b/gcc/value-query.h
index 97da6637747..d0512e40c5a 100644
--- a/gcc/value-query.h
+++ b/gcc/value-query.h
@@ -115,5 +115,6 @@ public:
 
 extern global_range_query global_ranges;
 extern value_range gimple_range_global (tree name);
+extern bool update_global_range (irange &r, tree name);
 
 #endif // GCC_QUERY_H
-- 
2.31.1

