Messages in this thread | | | From | Andi Kleen <> | Subject | Re: [PATCH] mark read_crX() asm code as volatile | Date | Wed, 3 Oct 2007 10:45:05 +0200 |
| |
> > How does the compiler know it doesn't depend on memory?
When it has no m (or equivalent like g) constrained argument and no memory clobber.
> How do you say it depends on memory?
You add any of the above.
> You really need something as heavy as volatile?
You could do a memory clobber, but it would be heavier than the volatile because the memory clobber clobbers all cached variables. volatile essentially just says "don't remove; has side effects". Normally gcc does that automatically for something without outputs, but this one has.
Besides a CRx access does not actually clobber memory.
-Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |