Re: [PATCH] Fix alter_output_for_subst_insn (PR other/77421)

[Richard Biener <rguenther@suse.de>]

On Fri, 2 Sep 2016, Jakub Jelinek wrote:

> Hi!
> 
> The two ports that use define_subst (ix86 and visium) don't do anything in
> this function, other than returning early - return insn_out, so all I could
> do is look at the intent.
> The *insn_out == '*' || *insn_out != '@' got flagged by some tool, the
> "*insn_out == '*' || " part is unnecessary, since '*' != '@'.  I guess the
> reason for it being there is that template starting with * is C code (which
> this function has nothing to do for), template starting with @ is what the
> function wants to do something about and other template strings it wants to
> ignore too.
> 
> But, when I got to this function, I found various weirdo formatting and
> other issues, the most important is that it leaks memory and in my
> understanding allocates that buffer completely uselessly, as it is pretty
> much a strdup of the insn_out after skipping initial spaces (and all @,
> which is weird, IMNSHO the only @ that it should skip is the very first
> one), except that '\0' isn't there and the length is remembered.  But, we
> don't change it at all, so we can as well use the original insn_out.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

Ok.

Thanks,
Richard.

> 2016-09-02  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR other/77421
> 	* gensupport.c (alter_output_for_subst_insn): Remove redundant
> 	*insn_out == '*' test.  Don't copy unnecessary to yet another
> 	memory buffer, and don't leak it.
> 
> --- gcc/gensupport.c.jj	2016-08-12 17:33:38.000000000 +0200
> +++ gcc/gensupport.c	2016-09-02 14:55:01.217182312 +0200
> @@ -1632,33 +1632,30 @@ duplicate_each_alternative (const char *
>  static const char *
>  alter_output_for_subst_insn (rtx insn, int alt)
>  {
> -  const char *insn_out, *sp ;
> -  char *old_out, *new_out, *cp;
> -  int i, j, new_len;
> +  const char *insn_out, *old_out;
> +  char *new_out, *cp;
> +  size_t old_len, new_len;
> +  int j;
>  
>    insn_out = XTMPL (insn, 3);
>  
> -  if (alt < 2 || *insn_out == '*' || *insn_out != '@')
> +  if (alt < 2 || *insn_out != '@')
>      return insn_out;
>  
> -  old_out = XNEWVEC (char, strlen (insn_out)),
> -  sp = insn_out;
> +  old_out = insn_out + 1;
> +  while (ISSPACE (*old_out))
> +    old_out++;
> +  old_len = strlen (old_out);
>  
> -  while (ISSPACE (*sp) || *sp == '@')
> -    sp++;
> -
> -  for (i = 0; *sp;)
> -    old_out[i++] = *sp++;
> -
> -  new_len = alt * (i + 1) + 1;
> +  new_len = alt * (old_len + 1) + 1;
>  
>    new_out = XNEWVEC (char, new_len);
>    new_out[0] = '@';
>  
> -  for (j = 0, cp = new_out + 1; j < alt; j++, cp += i + 1)
> +  for (j = 0, cp = new_out + 1; j < alt; j++, cp += old_len + 1)
>      {
> -      memcpy (cp, old_out, i);
> -      *(cp+i) = (j == alt - 1) ? '\0' : '\n';
> +      memcpy (cp, old_out, old_len);
> +      cp[old_len] = (j == alt - 1) ? '\0' : '\n';
>      }
>  
>    return new_out;
> 
> 	Jakub
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)