Do not calculate new values when evaluating a debug statement.

Add a flag to enable/disable immediately improving poor values found during
cache propagation. Then disable it when processing debug statements.

	gcc/
	PR tree-optimization/100781
	* gimple-range-cache.cc (ranger_cache::ranger_cache): Enable new
	value calculation by default.
	(ranger_cache::enable_new_values): New.
	(ranger_cache::disable_new_values): New.
	(ranger_cache::push_poor_value): Check if new values are allowed.
	* gimple-range-cache.h (class ranger_cache): New member/methods.
	* gimple-range.cc (gimple_ranger::range_of_expr): Check for debug
	statement, and disable/renable new value calculation.

	gcc/testsuite/
	PR tree-optimization/100781
	* gcc.dg/pr100781.c: New.

gcc/gimple-range-cache.cc

@@ -586,6 +586,7 @@ ranger_cache::ranger_cache (gimple_ranger &q) : query (q)
       if (bb)
 	m_gori.exports (bb);
     }
+  enable_new_values ();
 }
 
 ranger_cache::~ranger_cache ()
@@ -606,6 +607,23 @@ ranger_cache::dump (FILE *f)
   fprintf (f, "\n");
 }
 
+// Allow the cache to flag and query new values when propagation is forced
+// to use an unknown value.
+
+void
+ranger_cache::enable_new_values ()
+{
+  m_new_value_p = true;
+}
+
+// Disable new value querying.
+
+void
+ranger_cache::disable_new_values ()
+{
+  m_new_value_p = false;
+}
+
 // Dump the caches for basic block BB to file F.
 
 void
@@ -689,6 +707,8 @@ ranger_cache::set_global_range (tree name, const irange &r)
 bool
 ranger_cache::push_poor_value (basic_block bb, tree name)
 {
+  if (!m_new_value_p)
+    return false;
   if (m_poor_value_list.length ())
     {
       // Don't push anything else to the same block.  If there are multiple 

gcc/gimple-range-cache.h

@@ -100,6 +100,8 @@ public:
   bool get_non_stale_global_range (irange &r, tree name);
   void set_global_range (tree name, const irange &r);
 
+  void enable_new_values ();
+  void disable_new_values ();
   non_null_ref m_non_null;
   gori_compute m_gori;
 
@@ -131,6 +133,7 @@ private:
   bool push_poor_value (basic_block bb, tree name);
   vec<update_record> m_poor_value_list;
   class gimple_ranger &query;
+  bool m_new_value_p;
 };
 
 #endif // GCC_SSA_RANGE_CACHE_H

gcc/gimple-range.cc

@@ -971,6 +971,15 @@ gimple_ranger::range_of_expr (irange &r, tree expr, gimple *stmt)
       return true;
     }
 
+  // For a debug stmt, pick the best value currently available, do not
+  // trigger new value calculations.  PR 100781.
+  if (is_gimple_debug (stmt))
+    {
+      m_cache.disable_new_values ();
+      m_cache.range_of_expr (r, expr, stmt);
+      m_cache.enable_new_values ();
+      return true;
+    }
   basic_block bb = gimple_bb (stmt);
   gimple *def_stmt = SSA_NAME_DEF_STMT (expr);
 

gcc/testsuite/gcc.dg/pr100781.c

@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 --param=evrp-mode=ranger -fcompare-debug  " } */
+
+struct a {
+  int b;
+};
+long c(short d, long e, struct a f) {
+g:;
+  int h = f.b <= e, i = d, n = h >= d;
+  if (!n)
+    goto j;
+  goto k;
+j:;
+  long l = 5;
+  if (l)
+    goto m;
+  d = 0;
+m:
+  if (d)
+    return f.b;
+k:
+  goto g;
+}
+int main() { }
+