[wwwdocs,committed] 4.5/changes.html: Add link to manual for -flto

[wwwdocs,committed] 4.5/changes.html: Add link to manual for -flto

[Tobias Burnus]

I have added a hyperlink to http://gcc.gnu.org/gcc-4.5/changes.html 's
-flto entry, linking to -flto in the manual.

My hope is that this increases the chance that people read the relevant
entry in the manual and that they thus realize
a) that -flto has to be used at both compile and link time -- and
b) that -fwhole-program is not implied by -flto

Especially (b) was (is?) assumed by several people; thus one could
actually think of mentioning -fwhole-program in the release notes.

Tobias


Index: changes.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.5/changes.html,v
retrieving revision 1.39
diff -u -r1.39 changes.html
--- changes.html        10 Oct 2009 21:19:22 -0000      1.39
+++ changes.html        15 Oct 2009 13:25:49 -0000
@@ -48,7 +48,9 @@
     supported before; for those a fall back is used if MPC is not
     available.</li>

-    <li>A new link-time optimizer has been added (<code>-flto</code>).
+    <li>A new link-time optimizer has been added (<code><a
+    href="http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-flto-795"
+    >-flto</a></code>).
     When this flag is used, GCC generates a bytecode representation of
     each input file and writes it to special ELF sections in each
     object file.  When the object files are linked together, all the


cvs commit: Examining .
Checking in changes.html;
/cvs/gcc/wwwdocs/htdocs/gcc-4.5/changes.html,v  <--  changes.html
new revision: 1.40; previous revision: 1.39
done

Re: [wwwdocs,committed] 4.5/changes.html: Add link to manual for -flto

[Gerald Pfeifer]

On Thu, 15 Oct 2009, Tobias Burnus wrote:
> My hope is that this increases the chance that people read the relevant
> entry in the manual and that they thus realize
> a) that -flto has to be used at both compile and link time -- and
> b) that -fwhole-program is not implied by -flto

Yes, those are two pitfalls we'll encounter regularily.  I wonder 
whether in addition to adding the link (which is surely fine), you
may want to put these two points into the changes.html file as well?

Gerald

Re: [wwwdocs,committed] 4.5/changes.html: Add link to manual for -flto

[Tobias Burnus]

On 10/16/2009 11:31 PM, Gerald Pfeifer wrote:
> On Thu, 15 Oct 2009, Tobias Burnus wrote:
>   
>> My hope is that this increases the chance that people read the relevant
>> entry in the manual and that they thus realize
>> a) that -flto has to be used at both compile and link time -- and
>> b) that -fwhole-program is not implied by -flto
>>     
> Yes, those are two pitfalls we'll encounter regularily.  I wonder 
> whether in addition to adding the link (which is surely fine), you
> may want to put these two points into the changes.html file as well?
>   

How about the following? (I copied the strings from the -flto entry. It
indirectly points to -fwhopr, which is presumably okay: That way the
option is made know, but not too prominently - especially as -fwhopr
does not work properly, yet.)

Tobias


Index: changes.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.5/changes.html,v
retrieving revision 1.42
diff -U10 -r1.42 changes.html
--- changes.html        17 Oct 2009 11:20:34 -0000      1.42
+++ changes.html        19 Oct 2009 15:09:29 -0000
@@ -51,21 +51,29 @@
     <li>A new link-time optimizer has been added (<code><a
    
href="http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-flto-795"
     >-flto</a></code>).
     When this flag is used, GCC generates a bytecode representation of
     each input file and writes it to special ELF sections in each
     object file.  When the object files are linked together, all the
     function bodies are read from these ELF sections and instantiated
     as if they had been part of the same translation unit.  This
     enables interprocedural optimizations to work across different
     files (and even different languages), potentially improving the
-    performance of the generated code.</li>
+    performance of the generated code. To use the link-timer optimizer,
+    <code>-flto</code> needs to be specified at compile time and during
+    the final link. If the program does not require any symbols to be
+    exported, it is possible to combine -flto and <code><a
+   
href="http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-fwhopr-796"
+    >-fwhopr</a></code> with <code><a
+   
href="http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-fwhole_002dprogram-794"
+    >-fwhole-program</a></code> to allow the interprocedural optimizers
+    to use more aggressive assumptions.</li>

   </ul>

 <h2>New Languages and Language specific improvements</h2>

 <h3>All languages</h3>
   <ul>
     <li>The <code>-fshow-column</code> option is now on by default.  This
     means error messages now have a column associated with them.</li>
   </ul>

Re: [wwwdocs,committed] 4.5/changes.html: Add link to manual for -flto

[Gerald Pfeifer]

On Mon, 19 Oct 2009, Tobias Burnus wrote:

> How about the following? (I copied the strings from the -flto entry. It
> indirectly points to -fwhopr, which is presumably okay: That way the
> option is made know, but not too prominently - especially as -fwhopr
> does not work properly, yet.)

Looks good to me, but let's see what Diego thinks, so wait a day or two
before committing.

(There is one instance of -flto where you may want to add 
<code>...</code>.)

Thanks,
Gerald

Re: [wwwdocs,committed] 4.5/changes.html: Add link to manual for -flto

[Diego Novillo]

On Mon, Oct 19, 2009 at 11:10, Tobias Burnus <burnus@net-b.de> wrote:

> +    performance of the generated code. To use the link-timer optimizer,
> +    <code>-flto</code> needs to be specified at compile time and during
> +    the final link. If the program does not require any symbols to be
> +    exported, it is possible to combine -flto and <code><a

<code>-flto</code>

Looks fine otherwise.


Diego.