optimization/7702: [PATCH] Make reload-cse honor CANNOT_CHANGE_MODE_CLASS

[Falk Hueffner <falk.hueffner@student.uni-tuebingen.de>]

The following reply was made to PR optimization/7702; it has been noted by GNATS.

From: Falk Hueffner <falk.hueffner@student.uni-tuebingen.de>
To: gcc-patches@gcc.gnu.org
Cc: gcc-gnats@gcc.gnu.org, bfkelly@nsa.gov
Subject: optimization/7702: [PATCH] Make reload-cse honor CANNOT_CHANGE_MODE_CLASS
Date: 14 Feb 2003 10:25:54 +0100

 --=-=-=
 
 Hi,
 
 This fixes PR 7702 and a miscompilation of openssh on Alpha ev6 (sshd
 wouldn't accept ssh2 connections). The CSE in reload wants to merge
 registers with equal content and widen them to word_mode while at it,
 but doesn't honor CANNOT_CHANGE_MODE_CLASS. When the register
 allocator is foolish enough to put two identical integer constants
 into floating point registers, this fails.
 
 Because of this dependency on the register allocator, the problem is
 very hard to isolate, both test cases work with mainline. However,
 doing an equivalent patch for 3.2 fixes the problem. Because of the
 ssh miscompilation, it would be nice if it could also be included on
 older branches.
 
 2003-02-14  Falk Hueffner  <falk.hueffner@student.uni-tuebingen.de>
 
         PR optimization/7702
 	* reload1.c (reload_cse_simplify_set): Honor
 	CANNOT_CHANGE_MODE_CLASS.
 
 -- 
 	Falk
 
 
 --=-=-=
 Content-Type: text/x-patch
 Content-Disposition: attachment; filename=reload1.patch
 
 Index: reload1.c
 ===================================================================
 RCS file: /cvs/gcc/gcc/gcc/reload1.c,v
 retrieving revision 1.378
 diff -u -r1.378 reload1.c
 --- reload1.c	11 Feb 2003 03:52:28 -0000	1.378
 +++ reload1.c	13 Feb 2003 21:39:16 -0000
 @@ -8282,7 +8282,13 @@
  	{
  #ifdef LOAD_EXTEND_OP
  	  if (GET_MODE_BITSIZE (GET_MODE (SET_DEST (set))) < BITS_PER_WORD
 -	      && extend_op != NIL)
 +	      && extend_op != NIL
 +#ifdef CANNOT_CHANGE_MODE_CLASS
 +	      && !CANNOT_CHANGE_MODE_CLASS (GET_MODE (SET_DEST (set)),
 +					    word_mode,
 +					    REGNO_REG_CLASS (REGNO (SET_DEST (set))))
 +#endif
 +	      )
  	    {
  	      rtx wide_dest = gen_rtx_REG (word_mode, REGNO (SET_DEST (set)));
  	      ORIGINAL_REGNO (wide_dest) = ORIGINAL_REGNO (SET_DEST (set));
 
 --=-=-=--