Alan Cox <[email protected]> writes:
>
> You can stop the compiler but not the CPU - and some processors will
> certainly speculatively load across conditionals, reorder writes etc
The difference is that the CPU knows how to cancel most[1] side effects
of these speculative accesses (e.g. by not issuing exceptions[2] etc.).
The compiler doesn't normally (except on some architectures with special support like IA64;
but I'm not sure gcc supports it there)
[1] In some it can't and we've had problems with that in the past. e.g. in
a few cases speculative reads can be a problem. But we generally fix or
workaround those cases in the code.
[2] Modulo hardware bugs -- see the hall of shame in x86_64 fault.c
-Andi
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