Messages in this thread | | | Date | Thu, 7 Sep 2000 19:28:14 +0200 (CEST) | From | Andrea Arcangeli <> | Subject | Re: spin_lock forgets to clobber memory and other smp fixes [was |
| |
On Thu, 7 Sep 2000, Jamie Lokier wrote:
>Common Subexpression Elimination. > >If the compiler sees an expression equivalent to one it evaluated >earlier, there is no need to evaluate it a second time. > >So "a = x+x; b = x+x" will evaluate "x+x" just once and store it twice.
I didn't know the name of that particular optimization, thanks.
>In more complicated cases, where the result of the first read is >actually used before the "asm", the "memory" clobber causes the second >read to occur as well as the first.
Indeed.
Andrea
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
| |