[Bug c++/45462] Bad optimization in -O3 sometimes

["pinskia at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #9 from pinskia at gmail dot com  2010-09-01 06:17 -------
Subject: Re:  Bad optimization in -O3 sometimes

I am not talking about a library solution at all. I am talking about a  
solution inside the compiler. Gcc will optimize memcpy; how much for  
MIPS is a good question. Try it out and see. Oh if you are using  
scei's gcc you really should be reporting issues to them.

On Aug 31, 2010, at 10:03 PM, "yotambarnoy at gmail dot com"
<gcc-bugzilla@gcc.gnu.org 
 > wrote:

>
>
> ------- Comment #8 from yotambarnoy at gmail dot com  2010-09-01  
> 05:03 -------
> Unfortunately, a lib based solutions are difficult for me to  
> implement. The
> reason is that the current PSP SDK uses newlib. I can probably  
> change my
> personal toolchain with some work, but then it's a custom  
> modification that
> needs to be replicated to every other ScummVM dev as well as our  
> buildbot. Not
> impossible, but not work I'd like to get in to right now.
>
> In any case, it sounds like what you're saying is that memcpy has asm
> instructions in the right place to use lwl and lwr. I can also do  
> that in my
> implementation.
>
> My request was more general, as in gcc needs some kind of custom  
> keyword to
> tell it to allow unaligned pointers and to generate appropriate  
> unaligned code,
> so we don't have to trick the compiler into doing it in a way that  
> ruins
> optimization. Something like __unaligned__ uint32 *ptr32 = bytePtr;
>
>
> -- 
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45462
>


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45462