Messages in this thread | | | From | David Howells <> | Subject | Re: [PATCH] Document Linux's memory barriers [try #4] | Date | Tue, 14 Mar 2006 20:31:57 +0000 |
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Sergei Organov <osv@javad.com> 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?
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