Combine new calculated ranges with existing range.

When a range is recalculated, retain what was previously known as IL changes
can produce different results from un-executed code.   This also paves
the way for external injection of ranges.

	gcc/
	PR tree-optimization/97737
	PR tree-optimization/97741
	* gimple-range.cc: (gimple_ranger::range_of_stmt): Intersect newly
	calculated ranges with the existing known global range.
	gcc/testsuite/
	* gcc.dg/pr97737.c: New.
	* gcc.dg/pr97741.c: New.

1 files changed, 8 insertions, 2 deletions

diff --git a/gcc/gimple-range.cc b/gcc/gimple-range.cc
index 0c8ec40..92a6335 100644
--- a/gcc/gimple-range.cc
+++ b/gcc/gimple-range.cc
@@ -1026,8 +1026,14 @@ gimple_ranger::range_of_stmt (irange &r, gimple *s, tree name)
   if (m_cache.get_non_stale_global_range (r, name))
     return true;
 
-  // Otherwise calculate a new value and save it.
-  calc_stmt (r, s, name);
+  // Otherwise calculate a new value.
+  int_range_max tmp;
+  calc_stmt (tmp, s, name);
+
+  // Combine the new value with the old value.  This is required because
+  // the way value propagation works, when the IL changes on the fly we
+  // can sometimes get different results.  See PR 97741.
+  r.intersect (tmp);
   m_cache.set_global_range (name, r);
   return true;
 }