On 09/01/2012 12:43, JMGross wrote:
>
> A 'trick' that has helped in the past to put code into a 'cage' is
> doing just that: put it into a cage.
>
> do {...}while(0);
>
> The compiler shouldn't optimize across the code block barrier. I'm
> not sure what the C standard says about this, but in the past, this
> perfectly worked. I use this as default for critical section in my
> atomic macro:
>
> #define ATOMIC(x) do{ intcount++; __disable_interrupts();
> do{x}while(0); if (!(--intcount))__enable_interrupts();}while(0)
> (reconstructed from memory)
>
> The only disadvantage I encuntered so far is that the round macro
> parameter brackets are not identified as code block delimites by the
> editor.
>The compiler /should/ optimise across the code blocks - it is not a barrier of any sort. You may accidentally have achieved your purpose because some optimisations are limited to a single code block - but there is absolutely no reason to expect it to work. You have to remember that the compiler generates code /as if/ it translated your code directly - which means it follows volatile accesses, but can re-arrange the rest of the code as it sees fit. mvh., David > JMGross > > ----- Ursprüngliche Nachricht ----- Von: David Brown An: Peter Bigot > Gesendet am: 08 Jan 2012 02:08:50 Betreff: Re: [Mspgcc-users] > Simulation and algorithm timing > > Not only /may/ actions (calculations, non-volatile read/write > accesses, etc.) be moved across volatile accesses, but it has been > seen to happen in practice, causing some confusion to posters on > lists like this and the equivalent avr-gcc mailing lists. > > In particular, people seem to get quite upset when the compiler > moves code back and forth across interrupt disable/restore pairs! > > > ------------------------------------------------------------------------------ > > Ridiculously easy VDI. With Citrix VDI-in-a-Box, you don't need a complex > infrastructure or vast IT resources to deliver seamless, secure > access to virtual desktops. With this all-in-one solution, easily > deploy virtual desktops for less than the cost of PCs and save 60% on > VDI infrastructure costs. Try it free! > http://p.sf.net/sfu/Citrix-VDIinabox ------------------------------------------------------------------------------ Ridiculously easy VDI. With Citrix VDI-in-a-Box, you don't need a complex infrastructure or vast IT resources to deliver seamless, secure access to virtual desktops. With this all-in-one solution, easily deploy virtual desktops for less than the cost of PCs and save 60% on VDI infrastructure costs. Try it free! http://p.sf.net/sfu/Citrix-VDIinabox _______________________________________________ Mspgcc-users mailing list Mspgcc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mspgcc-users
