CompareAndSwapNode support

[Christian Thalinger]

On Oct 28, 2013, at 6:11 AM, Deneau, Tom <tom.deneau at amd.com> wrote:

> And Unsafe.getAndAddInt in is the following in 8:
> 
>   public final int getAndAddInt(Object o, long offset, int delta) {
>        int v;
>        do {
>            v = getIntVolatile(o, offset);
>        } while (!compareAndSwapInt(o, offset, v, v + delta));
>        return v;
>    }
> 
> 
> So I guess the volatile read is the difference.
> 
> As further information on this, at the time I was getting this error on 8, I was only enabling Math and Unsafe substitutions in the HSAIL backend.  When I enabled the fuller set of substitutions from GraalMethodSubstitutions, etc, the error on 8 went away.

…that makes it even more mysterious.  Anyway, good for you :-)

> 
> -- Tom
> 
> 
> -----Original Message-----
> From: Christian Thalinger [mailto:christian.thalinger at oracle.com] 
> Sent: Sunday, October 27, 2013 1:18 PM
> To: Deneau, Tom
> Cc: graal-dev at openjdk.java.net
> Subject: Re: CompareAndSwapNode support
> 
> 
> On Oct 25, 2013, at 6:07 AM, Deneau, Tom <tom.deneau at amd.com> wrote:
> 
>> Just to further clarify...
>> 
>> We had a HSAIL  junit test that called AtomicInteger.getAndAddInt from a lambda.  This made it java 8 specific.  This test worked fine (building and running graal with java 8) up until we started doing this merge with the new infrastructure changes.
>> 
>> We now have a version of this test that does the same thing but does not use lambdas.
> 
> By "does the same thing" you mean calling AtomicInteger.getAndAdd?  The code for AtomicInteger.getAndAdd is different on 7 and 8:
> 
> http://hg.openjdk.java.net/jdk7u/jdk7u/jdk/raw-file/tip/src/share/classes/java/util/concurrent/atomic/AtomicInteger.java
> 
>    public final int getAndAdd(int delta) {
>        for (;;) {
>            int current = get();
>            int next = current + delta;
>            if (compareAndSet(current, next))
>                return current;
>        }
>    }
> 
> http://hg.openjdk.java.net/jdk8/jdk8/jdk/raw-file/tip/src/share/classes/java/util/concurrent/atomic/AtomicInteger.java
> 
>    public final int getAndAdd(int delta) {
>        return unsafe.getAndAddInt(this, valueOffset, delta);
>    }
> 
> That's why you get different code in the compiler.
> 
>> So this new version can be invoked from java 7.   This new java7-style junit test still fails when we build our newly merged graal (newly merged with the new infrastructure) with java 8-b109 and try to run the test.  The top of the stack trace is shown below.
>> 
>> But if I build our merged graal with java7 b21 this new junit test succeeds.
>> 
>> -- Toim
>> 
>> ________________________________________
>> From: Christian Thalinger [christian.thalinger at oracle.com]
>> Sent: Thursday, October 24, 2013 8:00 PM
>> To: Deneau, Tom
>> Cc: graal-dev at openjdk.java.net
>> Subject: Re: CompareAndSwapNode support
>> 
>> On Oct 24, 2013, at 3:24 PM, Deneau, Tom <tom.deneau at amd.com> wrote:
>> 
>>> Some additional information on this...
>>> 
>>> The original junit test was written using lambdas and so could not be run under java 7.  Since our junit framework also supports java7 style tests, I rewrote the test to be java 7, and rebuilt graal with java 7.  And with no other changes to graal, the test now passes.
>>> 
>>> Does this make any sense?
>>> 
>>> -- Tom
>>> 
>>> From: Deneau, Tom
>>> Sent: Thursday, October 24, 2013 3:21 PM
>>> To: graal-dev at openjdk.java.net
>>> Subject: CompareAndSwapNode support
>>> 
>>> In the HSAIL backend, we had support for CompareAndSwapNode.  (we had not pushed this out to the trunk yet).
>>> 
>>> As part of the merge with the new runtime infrastructure changes, I see that our CompareAndSwapNode  support is broken.
>>> I'm trying to understand how to get it working again.
>>> 
>>> In the particular test I'm looking at the java code calls atomicInt.getAndAdd(constant)
>> 
>> Do you mean getAndAddInt?  If you are talking about the Unsafe guys these exist since 1.8.  So compiling (and running) with 7 or 8 definitely makes a difference.
>> 
>>> 
>>> First I noticed that we were getting Invoke nodes for things like getIntVolatile and compareAndSwapInt.
>>> So I assumed the UnsafeSubstitutions needed to be enabled for our backend.
>>> 
>>> When I enabled these, I got the following error which doesn't mean anything to me...
>>> 
>>> java.lang.AssertionError: <unknown> has unexpected usage 20|LoadField#value of checkcast 19|GuardingPi at <unknown>
>>>              at com.oracle.graal.replacements.NodeIntrinsificationPhase.checkCheckCastUsage(NodeIntrinsificationPhase.java:387)
>>>              at com.oracle.graal.replacements.NodeIntrinsificationPhase.checkCheckCastUsage(NodeIntrinsificationPhase.java:382)
>>>              at com.oracle.graal.replacements.NodeIntrinsificationPhase.cleanUpReturnCheckCast(NodeIntrinsificationPhase.java:328)
>>>              at com.oracle.graal.replacements.NodeIntrinsificationPhase.run(NodeIntrinsificationPhase.java:67)
>>> 
>>> Any suggestions?
>>> 
>>> -- Tom
>>> 
>> 
>> 
>> 
> 
> 
>