Re: Testcase for optimizer bug i686-pc-linux-gnulibc1

[Jim Wilson <wilson at cygnus dot com>]

The builtin memset was evaluating its arguments more than once in some
cases.  Here is a patch.

1998-04-28  Jim Wilson  <wilson@cygnus.com>

	* expr.c (expand_builtin, case BUILT_IN_MEMSET): Break if either
	val or len has TREE_SIDE_EFFECTS set.

Index: expr.c
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/expr.c,v
retrieving revision 1.48
diff -p -r1.48 expr.c
*** expr.c	1998/04/16 23:56:03	1.48
--- expr.c	1998/04/29 02:01:45
*************** expand_builtin (exp, target, subtarget, 
*** 8609,8614 ****
--- 8609,8623 ----
  	  if (dest_align == 0)
  	    break;
  
+ 	  /* If the arguments have side-effects, then we can only evaluate
+ 	     them at most once.  The following code evaluates them twice if
+ 	     they are not constants because we break out to expand_call
+ 	     in that case.  They can't be constants if they have side-effects
+ 	     so we can check for that first.  Alternatively, we could call
+ 	     save_expr to make multiple evaluation safe.  */
+ 	  if (TREE_SIDE_EFFECTS (val) || TREE_SIDE_EFFECTS (len))
+ 	    break;
+ 
  	  /* If VAL is not 0, don't do this operation in-line. */
  	  if (expand_expr (val, NULL_RTX, VOIDmode, 0) != const0_rtx)
  	    break;