Range invariant global values are also always current.

when a range evolves to the point where it becomes a constant, it is
marked as invariant.  Rather than marking it as always_current in the
timestamp, give it the correct timestamp and just never flag it as stale.
This will allow other names which use this value to become stale and be
recomputed using the newly invariant value.

	gcc/
	PR tree-optimization/100774
	* gimple-range-cache.cc (ranger_cache::get_non_stale_global_range):
	Constant values are also not stale.
	(ranger_cache::set_global_range): Range invariant values should also
	have the correct timestamp.

	gcc/testsuite
	PR tree-optimization/100774
	* g++.dg/pr100774.C: New.

2 files changed, 32 insertions, 8 deletions

diff --git a/gcc/gimple-range-cache.cc b/gcc/gimple-range-cache.cc
index 889cac1..ef3bc04 100644
--- a/gcc/gimple-range-cache.cc
+++ b/gcc/gimple-range-cache.cc
@@ -639,7 +639,9 @@ ranger_cache::get_non_stale_global_range (irange &r, tree name)
 {
   if (m_globals.get_global_range (r, name))
     {
-      if (m_temporal->current_p (name, depend1 (name), depend2 (name)))
+      // Use this value if the range is constant or current.
+      if (r.singleton_p ()
+	  || m_temporal->current_p (name, depend1 (name), depend2 (name)))
 	return true;
     }
   else
@@ -674,15 +676,13 @@ ranger_cache::set_global_range (tree name, const irange &r)
   // undefined. Propagation works better with constants. PR 100512.
   // Pointers which resolve to non-zero also do not need
   // tracking in the cache as they will never change.  See PR 98866.
-  // Otherwise mark the value as up-to-date.
+  // Timestamp must always be updated, or dependent calculations may
+  // not include this latest value. PR 100774.
+
   if (r.singleton_p ()
       || (POINTER_TYPE_P (TREE_TYPE (name)) && r.nonzero_p ()))
-    {
-      set_range_invariant (name);
-      m_temporal->set_always_current (name);
-    }
-  else
-    m_temporal->set_timestamp (name);
+    set_range_invariant (name);
+  m_temporal->set_timestamp (name);
 }
 
 // Push a request for a new lookup in block BB of name.  Return true if
diff --git a/gcc/testsuite/g++.dg/pr100774.C b/gcc/testsuite/g++.dg/pr100774.C
new file mode 100644
index 0000000..345fcfa
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr100774.C
@@ -0,0 +1,24 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-tree-forwprop --param=evrp-mode=ranger -fcompare-debug  " } */
+
+extern void __attribute__((noreturn)) error();
+
+int x;
+
+static inline int bar(void) {
+  char n = 1;
+  int i = x & 1U << n - 1;
+  return i;
+}
+
+void foo()
+{
+  int a = bar();
+  for (;;) {
+    bool b;
+    int d = a;
+    b = a < 2;
+    if (!b)
+      error();
+  }
+}