tm.texi (registers): Add entry for REGMODE_NATURAL_SIZE.

	* doc/tm.texi (registers) <Values in Registers>: Add
	entry for REGMODE_NATURAL_SIZE.

From-SVN: r79377

gcc/ChangeLog

+2004-03-12  Eric Botcazou  <ebotcazou@libertysurf.fr>
+
+	* doc/tm.texi (registers) <Values in Registers>: Add
+	entry for REGMODE_NATURAL_SIZE.
+
 2004-03-12  Richard Henderson  <rth@redhat.com>
 
 	PR target/14547

gcc/doc/tm.texi

@@ -2011,6 +2011,15 @@ definition of this macro is
 @end smallexample
 @end defmac
 
+@defmac REGMODE_NATURAL_SIZE (@var{mode})
+Define this macro if the natural size of registers that hold values
+of mode @var{mode} is not the word size.  It is a C expression that
+should give the natural size in bytes for the specified mode.  It is
+used by the register allocator to try to optimize its results.  This
+happens for example on SPARC 64-bit where the natural size of
+floating-point registers is still 32-bit.
+@end defmac
+
 @defmac HARD_REGNO_MODE_OK (@var{regno}, @var{mode})
 A C expression that is nonzero if it is permissible to store a value
 of mode @var{mode} in hard register number @var{regno} (or in several