Ranger cache - always use range_from_dom when updating.

When updating an existing range, if we dont query the dom tree, we can
get the global range instead of a proper range on some incoming edges
which cause the range to not be refined properly.

	PR tree-optimization/108356
	gcc/
	* gimple-range-cache.cc (ranger_cache::range_on_edge): Always
	do a search of the DOM tree for a range.

	gcc/testsuite/
	* gcc.dg/pr108356.c: New.

2 files changed, 24 insertions, 1 deletions

diff --git a/gcc/gimple-range-cache.cc b/gcc/gimple-range-cache.cc
index a8202f0..20c444b 100644
--- a/gcc/gimple-range-cache.cc
+++ b/gcc/gimple-range-cache.cc
@@ -998,7 +998,7 @@ bool
 ranger_cache::range_on_edge (vrange &r, edge e, tree expr)
 {
   if (gimple_range_ssa_p (expr))
-    return edge_range (r, e, expr, RFD_NONE);
+    return edge_range (r, e, expr, RFD_READ_ONLY);
   return get_tree_range (r, expr, NULL);
 }
 
diff --git a/gcc/testsuite/gcc.dg/pr108356.c b/gcc/testsuite/gcc.dg/pr108356.c
new file mode 100644
index 0000000..1df6b27
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr108356.c
@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+char a;
+static char c = 3;
+char d;
+void foo();
+short(b)(short e, short f) { return e + f; }
+int main() {
+  unsigned g = 0;
+  if (c)
+    ;
+  else
+    foo();
+  for (; g < 2; g = b(g, 2)) {
+    d = g ? 0 : a;
+    if (g)
+      c = 0;
+  }
+}
+
+
+/* { dg-final { scan-tree-dump-not "foo" "optimized" } } */