Sergei Organov <[email protected]> wrote:
> "You can prevent an `asm' instruction from being deleted by writing the
> keyword `volatile' after the `asm'. [...]
> The `volatile' keyword indicates that the instruction has important
> side-effects. GCC will not delete a volatile `asm' if it is reachable.
> (The instruction can still be deleted if GCC can prove that
> control-flow will never reach the location of the instruction.) *Note
> that even a volatile `asm' instruction can be moved relative to other
> code, including across jump instructions.*"
Ummm... If "asm volatile" statements don't form compiler barriers, then how do
you specify a compiler barrier? Or is that what the "memory" bit in:
#define barrier() __asm__ __volatile__("": : :"memory")
does?
David
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