review(S): 7058510: multinewarray with 6 dimensions uncommon traps in server compiler (original) (raw)

Vladimir Kozlov vladimir.kozlov at oracle.com
Fri Jul 1 14:48:37 PDT 2011

Looks good.

Thanks, Vladimir

Igor Veresov wrote:

John, Vladimir, Peter,

Thank you for your comments. I've made the changes and tested with my microbenchmark and DeoptimizeALot. Webrev: http://cr.openjdk.java.net/~iveresov/7058510/webrev.03/ Thanks! igor On 7/1/11 2:00 PM, Vladimir Kozlov wrote: John Rose wrote:

On Jul 1, 2011, at 1:26 PM, Vladimir Kozlov wrote:

Wrap new java dimension allocation into PreserveReexecuteState scope and restore stack. Is this in case the initial allocation deoptimizes (due to some external event)? I suppose that should be tested with DeoptimizeALot. The allocation of dimension array may go slow path (no space left in TLAB) into runtime and on return the method could be deoptimized so we need restore stack so that interpreter can reexecute multinewarray allocation. There are several places where we do this already (for example, around the call to expandmultianewarray()). And yes, it should be tested with DeoptimizeALot. Vladimir

Igor, the extraction from the dope array bothers me: + jint jdims = (jint)dims->base(TINT); + jint *cdims = NEWRESOURCEARRAY(jint, len); + memcpy(cdims, jdims, sizeof(jint)*len); It is correct, but I'd rather see more use of Hotspot machinery, with stronger typing: + jint *jdims = typeArrayOop(dims)->intataddr(0); + jint *cdims = NEWRESOURCEARRAY(jint, len); + Copy::conjointjintsatomic(cdims, jdims, sizeof(jint)*len); Note that Copy::* strongly outnumbers memcpy in the opto directory. The distinction is mostly stylistic, but Copy:: is more strongly typed in this case. (In other uses, Copy:: is more explicit and careful about some of the things we need to care about, such as overlaps and word-tearing.) Also, use istypeArray instead of isarray in the previous assert. That will make the cast to typeArrayOop safe. -- John

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