intrinsic that makes runtime choice whether to revert to java

Krystal Mok rednaxelafx at gmail.com
Thu Jul 5 16:38:48 PDT 2012


I might have made wrong comments because I wasn't getting the whole picture.
I thought the code you commented out was part of the predicate path. Sorry
for adding the noise

- Kris

On Fri, Jul 6, 2012 at 7:21 AM, Deneau, Tom <tom.deneau at amd.com> wrote:

> Krystal --
>
> Vladimir added the ability for an intrinsic to execute some predicated
> code and then
> if the predication is false to take the regular java code path instead of
> the instrinsic
> code path.
>
> In my predicated check path, I am doing the same instanceof check which I
> commented out below.
> So if I've made it to the intrinsic setup code, I don't understand why I
> have to do it again.
> Or does the second check actually get optimized away by the compiler?
>
> -- Tom
>
>
>
>
> From: Krystal Mok [mailto:rednaxelafx at gmail.com]
> Sent: Thursday, July 05, 2012 6:04 PM
> To: Deneau, Tom
> Cc: Vladimir Kozlov; hotspot-compiler-dev at openjdk.java.net
> Subject: Re: intrinsic that makes runtime choice whether to revert to java
>
> Hi Tom,
>
> I think you'd still need an explicit subtype check. See the example
> in Parse::catch_inline_exceptions():
>
>     // Check the type of the exception against the catch type
>     const TypeKlassPtr *tk = TypeKlassPtr::make(klass);
>     Node* con = _gvn.makecon(tk);
>     Node* not_subtype_ctrl = gen_subtype_check(ex_klass_node, con);
>     if (!stopped()) {
>       PreserveJVMState pjvms(this);
>       const TypeInstPtr* tinst =
> TypeOopPtr::make_from_klass_unique(klass)->cast_to_ptr_type(TypePtr::NotNull)->is_instptr();
>       assert(klass->has_subklass() || tinst->klass_is_exact(), "lost
> exactness");
>       Node* ex_oop = _gvn.transform(new (C, 2) CheckCastPPNode(control(),
> ex_node, tinst));
>       push_ex_oop(ex_oop);      // Push exception oop for handler
>
> The CheckCastPP node is only meant to tell later parts of the graph that
> "we're sure we're getting the expected type on this path", instead of the
> actually checking logic.
>
> - Kris
>
> On Fri, Jul 6, 2012 at 6:50 AM, Deneau, Tom <tom.deneau at amd.com> wrote:
> Vladimir --
>
> Limiting here to your reponse to my second question...
> The code you show for casting, I assume I can safely eliminate the
> instanceOf check
> (the lines commented out below)
> because we already checked for this in the predicated code path. so we
> would not have gotten to this intrinsic setup code if the runtime object
> were the wrong type.
>
> -- Tom
>
>
>    const TypeKlassPtr* aklass = TypeKlassPtr::make(klass_AESCrypt);
> //   _sp += nargs;          // gen_instanceof might do an uncommon trap
> //   Node* instof = gen_instanceof(embeddedCipherObj, makecon(aklass));
> //   _sp -= nargs;
> //   Node* cmp_instof  = _gvn.transform(new (C, 3) CmpINode(instof,
> intcon(1)));
> //   Node* bool_instof  = _gvn.transform(new (C, 2) BoolNode(cmp_instof,
> BoolTest::ne));
>
> //   Node* instof_false = generate_guard(bool_instof, NULL, PROB_MIN);
>    // fall through if the instance exactly matches the desired type
>    const TypeOopPtr* xtype = aklass->as_instance_type();
>    Node* cast = new(C, 2) CheckCastPPNode(control(), embeddedCipherObj,
> xtype);
>    cast = _gvn.transform(cast);
>    _gvn.replace_in_map(embeddedCipherObj, cast);
>    Node* k_len = get_key_len_from_aescrypt_object(cast);
>
> -----Original Message-----
> From: Vladimir Kozlov [mailto:vladimir.kozlov at oracle.com]
> Sent: Thursday, July 05, 2012 4:55 PM
> To: Deneau, Tom
> Cc: hotspot-compiler-dev at openjdk.java.net
> Subject: Re: intrinsic that makes runtime choice whether to revert to java
>
> Deneau, Tom wrote:
> > Vladimir --
> >
> > The code you provided helps a lot, thank you.
> > I am still testing it, but it seems to work for the basic cases.
> >
> > A couple of questions based on my not having done much with GraphKit:
> >
> >    1) I want to do a test at compile time (or maybe even earlier at
> >       stub generation time) as to whether a certain library class is a
> >       version that has a certain field.  This would fail if are
> >       mistakenly using the old library with a new JVM, which would
> >       indicate we cannot use the intrinsics.  I suspect this is done
> >       using the class from the systemDictionary but I'm not sure.
>
> Look on usage of find_local_field() method in thread.cpp and other places.
>
> >
> >    2) At compile time, when generating the code for the fast path, I
> >       want to generate a Node* to load a certain field from the
> >       embeddedCipher object (since we have made it past the predicate,
> >       we know that the embeddedCipher object is an instance of the
> >       class we expect).  I need to do this so that I can pass the
> >       field to the stub.  But at compile time, the particular instance
> >       that triggered compilation might not have an embeddedCipher
> >       object of the proper type.  Still I want to generate a Node*
> >       that will load a field from the embeddedCipher object as if it
> >       were the proper type.  And I am not sure how to do that.  (My
> >       current code failes to generate the intrinsic unless the
> >       particular instance that triggered compilation is the correct
> >       type).  I hope this question makes sense.
>
> I assume by the "fast path" you mean the intrinsic for whole encrypt()
> method.
> Right? You need to cast field object's type to AESCrypt if I understand
> your
> question correctly:
>
>    const TypeKlassPtr* aklass = TypeKlassPtr::make(klass_AESCrypt);
>    _sp += nargs;          // gen_instanceof might do an uncommon trap
>    Node* instof = gen_instanceof(embeddedCipherObj, makecon(aklass));
>    _sp -= nargs;
>    Node* cmp_instof  = _gvn.transform(new (C, 3) CmpINode(instof,
> intcon(1)));
>    Node* bool_instof  = _gvn.transform(new (C, 2) BoolNode(cmp_instof,
> BoolTest::ne));
>
>    Node* instof_false = generate_guard(bool_instof, NULL, PROB_MIN);
>    // fall through if the instance exactly matches the desired type
>    const TypeOopPtr* xtype = aklass->as_instance_type();
>    Node* cast = new(C, 2) CheckCastPPNode(control(), embeddedCipherObj,
> xtype);
>    cast = _gvn.transform(cast);
>    _gvn.replace_in_map(embeddedCipherObj, cast);
>    Node* k_len = get_key_len_from_aescrypt_object(cast);
>
> >
> >    3) If I want my predicate to be based on two Boolean tests,
> >       similar to the following java code
> >
> >       if ((obj instanceof XXXClass) && ((XXXClass)(obj).field ==
> SomeConstant))
> >
> >       and I want to of course skip the second test if the first test
> fails.
> >       Is it something like the following?
>
> You need Region node to merge 2 false paths:
>
>    RegionNode* region = new(C, 3) RegionNode(3);
> ...
>    region->init_req(1, instof_false);
> ...
>    region->init_req(2, klen_false);
>    record_for_igvn(region);
>    return _gvn.transform(region);
>
> >
> >   _sp += nargs;          // gen_instanceof might do an uncommon trap
> >   Node* instof = gen_instanceof(embeddedCipherObj,
> makecon(TypeKlassPtr::make(klass_AESCrypt)));
> >   _sp -= nargs;
> >   Node* cmp_instof  = _gvn.transform(new (C, 3) CmpINode(instof,
> intcon(1)));
> >   Node* bool_instof  = _gvn.transform(new (C, 2) BoolNode(cmp_instof,
> BoolTest::ne));
> >
> >   Node* instof_false = generate_guard(bool_instof, NULL, PROB_MIN);
> >   //instanceOf == true, fallthrough
> >
> >   Node* k_len = get_key_len_from_aescrypt_object(embeddedCipherObj);
> >   Node* cmp_klen  = _gvn.transform(new (C, 3) CmpINode(k_len,
> intcon(44)));   // corresponds to keys we can handle
> >   Node* bool_klen  = _gvn.transform(new (C, 2) BoolNode(cmp_klen,
> BoolTest::ne));
>
> Why exact 44 and not <= ?
>
> Vladimir
>
> >   Node* klen_false = generate_guard(bool_klen, NULL, PROB_MIN);
> >   return klen_false;
> >
> > -- Tom
> >
> > -----Original Message-----
> > From: Vladimir Kozlov [mailto:vladimir.kozlov at oracle.com]
> > Sent: Monday, July 02, 2012 9:57 PM
> > To: Deneau, Tom
> > Cc: hotspot-compiler-dev at openjdk.java.net
> > Subject: Re: intrinsic that makes runtime choice whether to revert to
> java
> >
> > I finally had time today to look on this. Here is code:
> >
> > http://cr.openjdk.java.net/~kvn/pred_intr/webrev
> >
> > But I did not test or optimize it (part of new code in callGenerator.cpp
> should
> > be shared with PredictedCallGenerator from which it was cloned).
> >
> > Vladimir
> >
> > Deneau, Tom wrote:
> >> Hi all --
> >>
> >> I am writing a hotspot intrinsic but I want it to make a runtime
> >> choice whether to execute the intrinsic code or to execute the regular
> >> java code.
> >>
> >> I got the suggestion below from Vladimir but I am not experienced
> >> enough with the graphkit functionality to see how to do this.  Would
> >> someone be able to provide the code skeleton for this?  I can generate
> >> the region to actually do my intrinsic and I believe I can generate the
> >> BoolNode which determines which path to take.
> >>
> >> The other choice would be to modify the actual JDK library routine to
> >> do the runtime tests and call a new routine which the intrinsic would
> >> hook into.  I have done this for testing but I am assuming this is more
> >> intrusive since on some architectures the intrinsic will not even be
> generated.
> >>
> >> -- Tom Deneau
> >>
> >>> We don't have such mechanism currently. But it is not difficult to
> implement.
> >>> Look on the code in doCall.cpp and callGenerator files. Instead of
> calling
> >>> find_intrinsic() you need to do something special for your case. Like
> code for
> >>> CallGenerator::for_method_handle_call() where you will generate class
> check and
> >>> on one path you will get intrinsic (by calling find_intrinsic()) and
> on other
> >>> path is regular CallGenerator::for_inline().
> >>
> >
> >
>
>
>
>
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