Intermediate writes to array slot not eliminated by optimizer

[Vladimir Kozlov]

I would need to look on ideal graph to find what is going on.
My guess is that the problem is Store node has control edge pointing to 
loop head so we can't move it from loop. Or stupid staff like we only do 
it for index increment and not for decrement (which I doubt).

Most possible scenario is we convert this loop to canonical Counted and 
split it (creating 3 loops: pre, main, post) before we had a chance to 
collapse it.

Regards,
Vladimir

On 5/12/15 10:05 AM, Vitaly Davidovich wrote:
> Anyone? :)
>
> Thanks
>
> On Mon, May 11, 2015 at 8:25 PM, Vitaly Davidovich <vitalyd at gmail.com
> <mailto:vitalyd at gmail.com>> wrote:
>
>     Hi guys,
>
>     Suppose we have the following code:
>
>     private static final long[] ARR = new long[10];
>     private static final int ITERATIONS = 500 * 1000 * 1000;
>
>
>     static void loop() {
>          int i = ITERATIONS;
>          while(--i >= 0) {
>               ARR[4] = i;
>           }
>     }
>
>     My expectation would be that loop() effectively compiles to:
>     ARR[4] = 0;
>     ret;
>
>     However, an actual loop is compiled.  This example is a reduction of
>     a slightly more involved case that I had in mind, but I'm curious if
>     I'm missing something here.
>
>     I tested this with 8u40 and tiered compilation disabled, for what
>     it's worth.
>
>     Thanks
>
>