[COMMITTED] frange::maybe_isnan() should return FALSE for undefined ranges.

[Aldy Hernandez via Gcc-patches]

Undefined ranges have undefined NAN bits.  We can't depend on them,
as they may contain garbage.  This patch returns false from
maybe_isnan() for undefined ranges (the empty set).

gcc/ChangeLog:

        * value-range.h (frange::maybe_isnan): Return false for
        undefined ranges.
---
 gcc/value-range.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/gcc/value-range.h b/gcc/value-range.h
index 7d5584a9294..325ed08f290 100644
--- a/gcc/value-range.h
+++ b/gcc/value-range.h
@@ -1210,6 +1210,8 @@ frange::known_isinf () const
 inline bool
 frange::maybe_isnan () const
 {
+  if (undefined_p ())
+    return false;
   return m_pos_nan || m_neg_nan;
 }
 
-- 
2.37.1