tm.texi (FUNCTION_MODE): Update and extend documentation.

2007-04-02  Dave Korn  <dave.korn@artimi.com>

	* doc/tm.texi (FUNCTION_MODE):  Update and extend documentation.

From-SVN: r123419

gcc/ChangeLog

 2007-04-02  Dave Korn  <dave.korn@artimi.com>
 
+	* doc/tm.texi (FUNCTION_MODE):  Update and extend documentation.
+	
+2007-04-02  Dave Korn  <dave.korn@artimi.com>
+
 	* libgcc2.h (exception_descriptor):  Don't forward-declare.
 	(__get_eh_table_language, __get_eh_table_version):  Delete
 	prototypes of long-dead functions.

gcc/doc/tm.texi

@@ -9577,8 +9577,11 @@ to @code{Pmode}.
 
 @defmac FUNCTION_MODE
 An alias for the machine mode used for memory references to functions
-being called, in @code{call} RTL expressions.  On most machines this
-should be @code{QImode}.
+being called, in @code{call} RTL expressions.  On most CISC machines,
+where an instruction can begin at any byte address, this should be 
+@code{QImode}.  On most RISC machines, where all instructions have fixed
+size and alignment, this should be a mode with the same size and alignment
+as the machine instruction words - typically @code{SImode} or @code{HImode}.
 @end defmac
 
 @defmac STDC_0_IN_SYSTEM_HEADERS