extend.texi: Clarify some issues related to local variables assigned to explicit registers.

        * extend.texi: Clarify some issues related to local variables
        assigned to explicit registers.

From-SVN: r21159

gcc/ChangeLog

@@ -6,6 +6,9 @@ Tue Jul 14 14:15:30 1998  Nick Clifton  <nickc@cygnus.com>
 
 Tue Jul 14 14:46:08 1998  Jeffrey A Law  (law@cygnus.com)
 
+	* extend.texi: Clarify some issues related to local variables
+	assigned to explicit registers.
+
 	* mn10300.md (mulsi): Turn into expander + pattern.
 
 	* mn10300.md (movsi, movsf, movdi, movdf): Remove "x" from I -> a

gcc/extend.texi

@@ -2593,7 +2593,9 @@ very often.
 Local register variables in specific registers do not reserve the
 registers.  The compiler's data flow analysis is capable of determining
 where the specified registers contain live values, and where they are
-available for other uses.
+available for other uses.  Stores into local register variables may deleted
+when they appear to be dead according to dataflow analysis.  References
+to local register variables may be deleted or moved or simplified.
 
 These local variables are sometimes convenient for use with the extended
 @code{asm} feature (@pxref{Extended Asm}), if you want to write one
@@ -2744,6 +2746,10 @@ this variable in the register you specify at all times.  You may not
 code an explicit reference to this register in an @code{asm} statement
 and assume it will always refer to this variable.
 
+Stores into local register variables may deleted when they appear to be dead
+according to dataflow analysis.  References to local register variables may
+be deleted or moved or simplified.
+
 @node Alternate Keywords
 @section Alternate Keywords
 @cindex alternate keywords