RFR: 8025856 - Fix typos in the GC code (original) (raw)

Krystal Mok rednaxelafx at gmail.com
Wed Jan 22 19:43:41 PST 2014

Hi John,

On Wed, Jan 22, 2014 at 6:50 PM, John Coomes <John.Coomes at oracle.com> wrote:

opto/runtime.cpp: fields[TypeFunc::Parms+0] = TypeInt::INT; // trapreason (deopt reason and action) The comment you added is not obviously correct; did someone from the compiler team check this? If the comment is correct, the code is crazily obscure! Yes, I proposed this change. The old comment had been out of date even before JDK6.

duke at 0: line 392 of http://hg.openjdk.java.net/hsx/hotspot-main/hotspot/file/a61af66fc99e/src/share/vm/opto/runtime.cpp

The corresponding runtime call goes through SharedRuntime::uncommon_trap_blob to:

Deoptimization::UnrollBlock* Deoptimization::uncommon_trap(JavaThread* thread, jint trap_request)

The "thread" argument came from uncommon_trap_blob; the "trap_request" argument came from constant embedded in compiled code. And this "trap_request" is the thing described by OptoRuntime::uncommon_trap_Type().

Back in JDK1.4.2-ish or maybe even earlier, the signature of this function was:

Deoptimization::UnrollBlock*, Deoptimization::uncommon_trap(JavaThread* thread, jint unloaded_class_index)

where "unloaded_class_index" was a constant pool index of a class if >= 0, or other deopt cases if < 0.

I'm not sure when it changed to its current form... waiting for someone else to share the history :-) Maybe the comment had been out of date longer then I thought.

Speaking of this, the comment in SharedRuntime::generate_uncommon_trap_blob() is also out of date:

e.g. hotspot/src/cpu/x86/vm/sharedRuntime_x86_64.cpp

// compiler left unloaded_class_index in j_rarg0 move to where the // runtime expects it. __ movl(c_rarg1, j_rarg0);

"unloaded_class_index" should be "trap_reason" now.

-John -- John Coomes Oracle, MS USCA22-3?? john.coomes at oracle.com 4220 Network Circle 408-276-7048 Santa Clara, CA 95054-1778 *** Support GreenPeace and we'll all breathe easier. *** -------------- next part -------------- An HTML attachment was scrubbed... URL: http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/attachments/20140122/a227236e/attachment.html

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