RFR(S): 8138890: C1: Ambiguous operator delete

[Volker Simonis]

Hi Martin,

as the new/delete operators in StackObj are private (I missed that before)
they shouldn't be visible in LIRGenerator. So this is probably yet another
xlC bug :(
On the other hand the new/delete operators in CompilationResourceObject are
public and are inherited by LIRGenerator. So if we only want to generate
LIRGenerator instances on the stack, your change is good, because it
ensures this. And in that case we surely don't need an implementation.

So thumbs up from me!

Volker


On Wednesday, October 7, 2015, Doerr, Martin <martin.doerr at sap.com> wrote:

> Hi Volker,
>
>
>
> the C1 classes we are talking about should never get instantiated by
> operator new.
>
> A typical way to establish this is to make the new operators private.
>
>
>
> I don’t really care if the delete operators are public or private because
> if the new operator is never used, how can the delete operator get used?
>
> It may be more beautiful to declare them as private as well. Only in the
> case Götz has showed, some Compilers reject the private delete operators.
>
>
>
> Best regards,
>
> Martin
>
>
>
>
>
> *From:* Volker Simonis [mailto:volker.simonis at gmail.com
> <javascript:_e(%7B%7D,'cvml','volker.simonis at gmail.com');>]
> *Sent:* Mittwoch, 7. Oktober 2015 17:57
> *To:* Mikael Gerdin
> *Cc:* Doerr, Martin; Christian Thalinger; hotspot compiler
> *Subject:* Re: RFR(S): 8138890: C1: Ambiguous operator delete
>
>
>
> Hi Martin,
>
> we have:
> class LIRGenerator: public InstructionVisitor, public BlockClosure
>
> and:
>
> class BlockClosure: public CompilationResourceObj
>
> class CompilationResourceObj ALLOCATION_SUPER_CLASS_SPEC {
>  public:
>   void* operator new(size_t size) throw() { return
> Compilation::current()->arena()->Amalloc(size); }
>   void* operator new(size_t size, Arena* arena) throw() {
>     return arena->Amalloc(size);
>   }
>   void  operator delete(void* p) {} // nothing to do
> };
>
> class InstructionVisitor: public StackObj
>
> class StackObj ALLOCATION_SUPER_CLASS_SPEC {
>  private:
>   void* operator new(size_t size) throw();
>   void* operator new [](size_t size) throw();
> #ifdef __IBMCPP__
>  public:
> #endif
>   void  operator delete(void* p);
>   void  operator delete [](void* p);
>
> Now you declare new "new()" and "delete()" operators in the LIRGenerator
> which will actually hide the corresponding operators from the base classes.
> You also provide no implementation for the new operators in LIRGenerator.
> So which new/delete operators will be actually used for allocating new
> LIRGenerator instances?
>
> OK, wait. As far as I can see, LIRGenerator is never dynamically
> allocated, right? In that case it should be a StackObj and you could
> probably solve the problem with "using" directives (e.g. using
> StackObj::operator new, ...). Have you tried that?
>
> Regards,
>
> Volker
>
>
>
>
>
> On Wed, Oct 7, 2015 at 4:55 PM, Mikael Gerdin <mikael.gerdin at oracle.com
> <javascript:_e(%7B%7D,'cvml','mikael.gerdin at oracle.com');>> wrote:
>
> On 2015-10-07 16:17, Doerr, Martin wrote:
>
> Hi,
>
> that’s a good question J
>
> I can only remember that there were problems with some old compilers.
>
> Anyway, xlC 12.1 can deal with the private delete operators.
>
>
> If that's the case, can we also get rid of the workaround in
> allocation.hpp?
>
> Thanks
> /Mikael
>
>
> Here’s the new webrev:
>
> http://cr.openjdk.java.net/~mdoerr/8138890_c1_ambiguous_delete/webrev.01
>
> Best regards,
>
>    Martin
>
> *From:*Christian Thalinger [mailto:christian.thalinger at oracle.com
> <javascript:_e(%7B%7D,'cvml','christian.thalinger at oracle.com');>]
> *Sent:* Mittwoch, 7. Oktober 2015 03:32
> *To:* Doerr, Martin
> *Cc:* hotspot compiler
> *Subject:* Re: RFR(S): 8138890: C1: Ambiguous operator delete
>
>     On Oct 6, 2015, at 3:56 AM, Doerr, Martin <martin.doerr at sap.com
> <javascript:_e(%7B%7D,'cvml','martin.doerr at sap.com');>
>     <mailto:martin.doerr at sap.com
> <javascript:_e(%7B%7D,'cvml','martin.doerr at sap.com');>>> wrote:
>
>     Hi,
>
>     xlC on AIX rejects to compile LIRGenerator and
>     RangeCheckEliminator::Verification due to ambiguous operator delete
>     which gets inherited from multiple base classes.
>
>     This change is a prerequisite for our C1 on PPC64 contribution.
>
>     Webrev is here:
>
>
> http://cr.openjdk.java.net/~mdoerr/8138890_c1_ambiguous_delete/webrev.00
>
> Let me ask my question here:  why do you need the delete methods to be
> public on AIX?
>
>
>
> Please review this change.  I need a sponsor, please.
>
> Best regards,
>
>    Martin
>
>
>
>
>
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