recursive rtl bug

[Bernd Schmidt]

On Tue, 23 Nov 1999, Tom Truscott wrote:

> I reported this SEGV a while back, but alas it is still happening:
> GNU C version 2.96 19991122 (experimental) (i686-pc-linux-gnu)
> 
>  /* "gcc -O foo.c" gets a SEGV */
>  void foo(double bar[], double *zp, int n)
>  {
>     int i, j;
> 
>     i = 0;
>     for(j = 0; j < n; j++)
>     {
>        i += j+1;
>        bar[i] *= (1.0 + *zp);
>     }
>  }
> 
> Here is some rudimentary debugging that might help.
> A self-referent rtl is created, which can be trapped with:

Here's a patch to fix it.  The problem is that we're generating shared rtl
in combine.  Later, we substitute in one expression and the other one
gets magically changed as well.

Bernd

	* combine.c (combine_simplify_rtx): Don't create shared rtl.

Index: combine.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/combine.c,v
retrieving revision 1.102
diff -c -p -r1.102 combine.c
*** combine.c	1999/12/12 01:34:39	1.102
--- combine.c	1999/12/13 14:57:29
*************** combine_simplify_rtx (x, op0_mode, last,
*** 4190,4196 ****
  			 gen_binary (MULT, mode,
  				     XEXP (XEXP (x, 0), 0), XEXP (x, 1)),
  			 gen_binary (MULT, mode,
! 				     XEXP (XEXP (x, 0), 1), XEXP (x, 1))));
  
  	  if (GET_CODE (x) != MULT)
  	    return x;
--- 4190,4197 ----
  			 gen_binary (MULT, mode,
  				     XEXP (XEXP (x, 0), 0), XEXP (x, 1)),
  			 gen_binary (MULT, mode,
! 				     XEXP (XEXP (x, 0), 1),
! 				     copy_rtx (XEXP (x, 1)))));
  
  	  if (GET_CODE (x) != MULT)
  	    return x;