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[patch] tm.texi: Document HARD_REGNO_RENAME_OK.


Hi,

Attached is a patch to document HARD_REGNO_RENAME_OK.

I wasn't sure if I should mention various checks that are done in
regrename.c before calling this macro, so I didn't.

Bootstrapped on i686-pc-linux-gnu.  OK to apply?

Kazu Hirata

2004-03-05  Kazu Hirata  <kazu@cs.umass.edu>

	* doc/tm.texi (HARD_REGNO_RENAME_OK): Document.

Index: tm.texi
===================================================================
RCS file: /cvs/gcc/gcc/gcc/doc/tm.texi,v
retrieving revision 1.309
diff -u -r1.309 tm.texi
--- tm.texi	4 Mar 2004 00:18:54 -0000	1.309
+++ tm.texi	5 Mar 2004 20:18:45 -0000
@@ -2072,6 +2072,17 @@
 be used unless some pattern's constraint asks for one.
 @end defmac
 
+@defmac HARD_REGNO_RENAME_OK (@var{from}, @var{to})
+A C expression that is nonzero if it is OK to rename a hard register
+@var{from} to another hard register @var{to}.
+
+One common use of this macro is to prevent renaming of a register to
+another register that is not saved by a prologue in an interrupt
+handler.
+
+The default is always nonzero.
+@end defmac
+
 @defmac MODES_TIEABLE_P (@var{mode1}, @var{mode2})
 A C expression that is nonzero if a value of mode
 @var{mode1} is accessible in mode @var{mode2} without copying.


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