On Thu, Sep 29, 2011 at 3:02 PM, Jakub Jelinek <[email protected]> wrote:
> Hi!
>
> On Mon, Sep 26, 2011 at 04:33:05PM +0200, Richard Guenther wrote:
>> Btw, can you add a changes.html entry for this?
>
> Like this?
Yes.
Thanks,
Richard.
> --- htdocs/gcc-4.7/changes.html 27 Sep 2011 18:42:56 -0000 1.38
> +++ htdocs/gcc-4.7/changes.html 29 Sep 2011 12:56:42 -0000
> @@ -124,6 +124,48 @@ void bar (void)
> possibly only by inlining all calls. Cloning causes a lot less code
> size
> growth.</li>
> </ul></li>
> +
> + <li>String length optimization pass has been added. This pass attempts
> + to track string lengths and optimize various standard C string
> functions
> + like <code>strlen</code>, <code>strchr</code>, <code>strcpy</code>,
> + <code>strcat</code>, <code>stpcpy</code> and their
> + <code>_FORTIFY_SOURCE</code> counterparts into faster alternatives.
> + This pass is enabled by default at <code>-O2</code> or above, unless
> + optimizing for size, and can be disabled by
> + <code>-fno-optimize-strlen</code> option. The pass can e.g. optimize
> + <pre>
> +char *bar (const char *a)
> +{
> + size_t l = strlen (a) + 2;
> + char *p = malloc (l); if (p == NULL) return p;
> + strcpy (p, a); strcat (p, "/"); return p;
> +}
> + </pre>
> + can be optimized into:
> + <pre>
> +char *bar (const char *a)
> +{
> + size_t tmp = strlen (a);
> + char *p = malloc (tmp + 2); if (p == NULL) return p;
> + memcpy (p, a, tmp); memcpy (p + tmp, "/", 2); return p;
> +}
> + </pre>
> + or for hosted compilations where <code>stpcpy</code> is available in
> the
> + runtime and headers provide its prototype, e.g.
> + <pre>
> +void foo (char *a, const char *b, const char *c, const char *d)
> +{
> + strcpy (a, b); strcat (a, c); strcat (a, d);
> +}
> + </pre>
> + into:
> + <pre>
> +void foo (char *a, const char *b, const char *c, const char *d)
> +{
> + strcpy (stpcpy (stpcpy (a, b), c), d);
> +}
> + </pre>
> + </li>
> </ul>
>
> <h2>New Languages and Language specific improvements</h2>
>
>
> Jakub
>
