Re: optimization/8165: builtin string functions SEGV on alpha-pc-linux-gnu at -O2

[Glen Nakamura <glen@imodulo.com>]

The following reply was made to PR optimization/8165; it has been noted by GNATS.

From: Glen Nakamura <glen@imodulo.com>
To: Richard Henderson <rth@redhat.com>, gcc-gnats@gcc.gnu.org,
	gcc-bugs@gcc.gnu.org, gcc-patches@gcc.gnu.org
Cc:  
Subject: Re: optimization/8165: builtin string functions SEGV on alpha-pc-linux-gnu at -O2
Date: Sat, 12 Oct 2002 08:39:25 -1000

 On Fri, Oct 11, 2002 at 05:51:43PM -0700, Richard Henderson wrote:
 > I guess your original patch is probably correct.  I was 
 > focused so much on the LO_SUM/HIGH simplification that
 > I missed the fact that we were failing to process the
 > internal regs of the LO_SUM at all.
 
 Looking at try_replace_reg() again, I noticed that the REG_EQUAL note
 isn't always replaced.  Is the "else" really okay?
 
 
 static int
 try_replace_reg (from, to, insn)
      rtx from, to, insn;
 {
   rtx note = find_reg_equal_equiv_note (insn);
   ...
 
   if (!success && set && reg_mentioned_p (from, SET_SRC (set)))
     {
       ...
 
       /* If we've failed to do replacement, have a single SET, and don't already
 	 have a note, add a REG_EQUAL note to not lose information.  */
       if (!success && note == 0 && set != 0)
 	note = set_unique_reg_note (insn, REG_EQUAL, copy_rtx (src));
     }
 
   /* If there is already a NOTE, update the expression in it with our
      replacement.  */
   else if (note != 0)
   ^^^^
     XEXP (note, 0) = simplify_replace_rtx (XEXP (note, 0), from, to);