On 23.07.2016 01:25, John Rose wrote:
On May 31, 2016, at 12:41 PM, Mark Roos <mr...@roos.com> wrote:
It looks like, from some fine timing, that each time the Smalltalk class
changes there is a large amount
of time added to the call. Which I would expect if there was a deopt whenever
a different GWT triggered.
There are 6 GWTs in this chain ( idleValue can be one of six Smalltalk classes).
Has anybody on this list played with using a short @Stable array to represent a
PIC?
Editing the PIC would involve changing the array instead of recompiling a call
site.
How about making a list of all those annotations that influence
invokedynamic and inlining? And how likely is it that some of them get
promoted to official API? And will they be available in JDK9 to non-JDK
modules?
The effect would be to preserve existing inlinings of the PIC site (unless they
self-invalidate) but allow the PIC to update itself over time as new cases
arise.
Previously compiled uses of the PIC would stay optimized as-is.
>
The @Stable array would always have a series of zero or more non-null entries,
followed by at least one null entry. The search in the @Stable array would
inline
and short-circuit over irrelevant PIC entries, if the pattern-matching logic
were
inlinable. Entries could be as simple as @Stable 2-arrays of guard MH and
target MH.
(If they are objects, some care with TrustFinalFields would also be needed.)
which means you cannot reorder, nor can you evict the oldest handle
Using this technique would probably lead to fewer deopts. The @Stable array
could
also be shared by several PIC sites, if that helps with footprint.
class PIC {
@Stable final MethodHandle[][] cache = new MethodHandle[PIC_SIZE+1][];
// cache[0] = new MethodHandle[] { guard, target }, etc.
// cache[cache.length-1] is either null or some permanent catch-all logic
}
I would have expected a MethodHandle[] only. The documentation of stable
is also not so clear to me here. is assumed to be stable, allows only
setting the element of an array with a stable element... ok... but a 2D
array is an array of arrays. So the stable values are the arrays itself
and they are not stable? I wouldn´t have expected this to work.
bye Jochen
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