intrinsic that makes runtime choice whether to revert to java
tom.deneau at amd.com
Thu Jul 5 10:13:52 PDT 2012
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.
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.
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?
_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));
Node* klen_false = generate_guard(bool_klen, NULL, PROB_MIN);
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:
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).
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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