java aliasing rules

Sat Mar 30 06:37:00 GMT 2002

On 2002年3月30日, Bryce McKinlay wrote:
> With this code, if "ps2" is null then the second load (lhz) will throw 
> before the ps1.f1 is seen as incremented.

That's a shame.
> The optimal, correct code for 
> Java is really something like:
>> lhz r9, [ps1.f1]
> addi r9,r9,1
> sth r9, [ps1.f1]

Wouldn't accessing r9 immediately after the load cause a pipeline stall?
Assuming an in-order processor? That would be a significant performance
hit.
Come to think of it, what happens on an out-of-order processor (e.g.
Alpha EV6) when an instruction traps? Are preceding instructions 
guaranteed to have completed? I'm curious.
Jeff