[16/67] Add scalar_int_mode_pod

[Richard Sandiford <richard dot sandiford at arm dot com>]

This patch adds a POD class for scalar integers, as an instance
of a new pod_mode template.  Later patches will use pod_mode in
situations that really do need to be POD; in this patch we're
simply using PODs to remove load-time initialisation.

gcc/
2016-11-24  Richard Sandiford  <richard.sandiford@arm.com>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

	* coretypes.h (pod_mode): New type.
	(scalar_int_mode_pod): New typedef.
	* machmode.h (pod_mode): New class.
	(int_n_data_t::m): Change type to scalar_int_mode_pod.
	* genmodes.c (emit_mode_int_n): Update accordingly.

diff --git a/gcc/coretypes.h b/gcc/coretypes.h
index 6dc3e88..5073f35 100644
--- a/gcc/coretypes.h
+++ b/gcc/coretypes.h
@@ -61,6 +61,8 @@ class scalar_float_mode;
 template<typename> class opt_mode;
 typedef opt_mode<scalar_int_mode> opt_scalar_int_mode;
 typedef opt_mode<scalar_float_mode> opt_scalar_float_mode;
+template<typename> class pod_mode;
+typedef pod_mode<scalar_int_mode> scalar_int_mode_pod;
 
 /* Subclasses of rtx_def, using indentation to show the class
    hierarchy, along with the relevant invariant.
diff --git a/gcc/genmodes.c b/gcc/genmodes.c
index eddbff7..8ee0fae6 100644
--- a/gcc/genmodes.c
+++ b/gcc/genmodes.c
@@ -1799,7 +1799,7 @@ emit_mode_int_n (void)
       m = mode_sort[i];
       printf(" {\n");
       tagged_printf ("%u", m->int_n, m->name);
-      printf ("E_%smode,", m->name);
+      printf ("{ E_%smode },", m->name);
       printf(" },\n");
     }
 
diff --git a/gcc/machmode.h b/gcc/machmode.h
index 8c8dd54..bf568c9 100644
--- a/gcc/machmode.h
+++ b/gcc/machmode.h
@@ -247,6 +247,17 @@ opt_mode<T>::exists (U *mode) const
   return false;
 }
 
+/* A POD version of mode class T.  */
+
+template<typename T>
+struct pod_mode
+{
+  machine_mode_enum m_mode;
+  ALWAYS_INLINE operator machine_mode_enum () const { return m_mode; }
+  ALWAYS_INLINE operator T () const { return T::from_int (m_mode); }
+  ALWAYS_INLINE pod_mode &operator = (const T &m) { m_mode = m; return *this; }
+};
+
 /* Return true if mode M has type T.  */
 
 template<typename T>
@@ -649,7 +660,7 @@ extern void init_adjust_machine_modes (void);
 struct int_n_data_t {
   /* These parts are initailized by genmodes output */
   unsigned int bitsize;
-  machine_mode_enum m;
+  scalar_int_mode_pod m;
   /* RID_* is RID_INTN_BASE + index into this array */
 };