[Bug c/33949] gcc-4.2.2 generates bad code on ARM

[zero at colonel-panic dot org]

------- Comment #4 from zero at colonel-panic dot org  2007-10-30 16:45 -------
Subject: Re:  gcc-4.2.2 generates bad code on ARM

rguenth at gcc dot gnu dot org wrote:
> ------- Comment #3 from rguenth at gcc dot gnu dot org  2007-10-30 15:54 -------
> It doesn't matter that you store the address of param to a volatile variable
> (this store is not removed), but that
> 
>               DMA_ADDR_REG = (unsigned long) data;
> 
> does not make the stack local live longer than the frame of outer_func and
> *data is not used after the assignment.  Probably your code kicking off
> the DMA engine lacks a memory barrier and a use of DMA_ADDR_REG.
> 
> 

Thanks for the explanation. Seems like an optimisation too far. I can't 
see that using the address of a variable and not it's contents is a 
particularly common practice, and having to use a GCC specific barrier 
to get simple embedded code to work sucks.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33949