[PATCH] [ranger] Force buffer alignment in Value_Range [PR114912]

[Aldy Hernandez]

Sparc requires strict alignment and is choking on the byte vector in
Value_Range.  Is this the right approach, or is there a more canonical
way of forcing alignment?

If this is correct, OK for trunk?

gcc/ChangeLog:

        * value-range.h (class Value_Range): Use a union.
---
 gcc/value-range.h | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/gcc/value-range.h b/gcc/value-range.h
index 934eec9e386..31af7888018 100644
--- a/gcc/value-range.h
+++ b/gcc/value-range.h
@@ -740,9 +740,14 @@ private:
   void init (const vrange &);
 
   vrange *m_vrange;
-  // The buffer must be at least the size of the largest range.
-  static_assert (sizeof (int_range_max) > sizeof (frange), "");
-  char m_buffer[sizeof (int_range_max)];
+  union {
+    // The buffer must be at least the size of the largest range, and
+    // be aligned on a word boundary for strict alignment targets
+    // such as sparc.
+    static_assert (sizeof (int_range_max) > sizeof (frange), "");
+    char m_buffer[sizeof (int_range_max)];
+    void *align;
+  } u;
 };
 
 // The default constructor is uninitialized and must be initialized
@@ -816,11 +821,11 @@ Value_Range::init (tree type)
   gcc_checking_assert (TYPE_P (type));
 
   if (irange::supports_p (type))
-    m_vrange = new (&m_buffer) int_range_max ();
+    m_vrange = new (&u.m_buffer) int_range_max ();
   else if (frange::supports_p (type))
-    m_vrange = new (&m_buffer) frange ();
+    m_vrange = new (&u.m_buffer) frange ();
   else
-    m_vrange = new (&m_buffer) unsupported_range ();
+    m_vrange = new (&u.m_buffer) unsupported_range ();
 }
 
 // Initialize object with a copy of R.
@@ -829,11 +834,12 @@ inline void
 Value_Range::init (const vrange &r)
 {
   if (is_a <irange> (r))
-    m_vrange = new (&m_buffer) int_range_max (as_a <irange> (r));
+    m_vrange = new (&u.m_buffer) int_range_max (as_a <irange> (r));
   else if (is_a <frange> (r))
-    m_vrange = new (&m_buffer) frange (as_a <frange> (r));
+    m_vrange = new (&u.m_buffer) frange (as_a <frange> (r));
   else
-    m_vrange = new (&m_buffer) unsupported_range (as_a <unsupported_range> 
(r));
+    m_vrange
+      = new (&u.m_buffer) unsupported_range (as_a <unsupported_range> (r));
 }
 
 // Assignment operator.  Copying incompatible types is allowed.  That
-- 
2.44.0