RFR(M): 8016697: PPC64 (part 5): Use stubs to implement safefetch

[Christian Thalinger]

On Jun 18, 2013, at 1:18 PM, "Lindenmaier, Goetz" <goetz.lindenmaier at sap.com> wrote:

> Ok, I will implement it on x86.  
> 
> To get a single change, you can give me the sparc patch,
> or you extend the webrev once I updated it with the
> x86 code. 

Sounds good.  Let me know when it's there.

-- Chris

> If you prefer, you can also push it to some other repository, it 
> will end up in the ppc repo in time I guess. 
> 
> Best regards,
>  Goetz.
> 
> 
> -----Original Message-----
> From: Christian Thalinger [mailto:christian.thalinger at oracle.com] 
> Sent: Tuesday, June 18, 2013 6:59 PM
> To: Lindenmaier, Goetz
> Cc: Volker Simonis; Vladimir Kozlov; ppc-aix-port-dev at openjdk.java.net; hotspot-dev at openjdk.java.net
> Subject: Re: RFR(M): 8016697: PPC64 (part 5): Use stubs to implement safefetch
> 
> 
> On Jun 18, 2013, at 1:50 AM, "Lindenmaier, Goetz" <goetz.lindenmaier at sap.com> wrote:
> 
>> Hi,
>> 
>> We have it on these platforms:
>> ia64    (nt, linux, hp_ux)
>> parisc (hp_ux)
>> zArch (linux)
>> ppc     (aix, linux)
>> 
>> I would implement it on x86 & friends, you do it on sparc and wherever
>> else you like it?
> 
> That sounds reasonable.  Are we pushing this to the ppc repository then?
> 
> -- Chris
> 
>> 
>> Best regards,
>> Goetz.
>> 
>> 
>> 
>> -----Original Message-----
>> From: Christian Thalinger [mailto:christian.thalinger at oracle.com] 
>> Sent: Dienstag, 18. Juni 2013 07:13
>> To: Volker Simonis
>> Cc: Lindenmaier, Goetz; Vladimir Kozlov; ppc-aix-port-dev at openjdk.java.net; hotspot-dev at openjdk.java.net
>> Subject: Re: RFR(M): 8016697: PPC64 (part 5): Use stubs to implement safefetch
>> 
>> 
>> On Jun 17, 2013, at 10:08 AM, Volker Simonis <volker.simonis at gmail.com> wrote:
>> 
>>> Hi Goetz,
>>> 
>>> I think the change is good and if the other reviewers don't decide to
>>> implement it for the current platforms we can push it.
>> 
>> I talked with Vladimir about this today and I my opinion we should use this stub on all platforms.  On which other platforms are you guys having this?
>> 
>> -- Chris
>> 
>>> 
>>> By the way, the makefile changes in ppc64.make will follow in patch 8 for
>>> linux [1] and patch 14 for aix [2].
>>> The implementation of the stubs will be in patch 9 for linux [3] and patch
>>> 15 for aix [4] (only the signal handling part).
>>> 
>>> Regards,
>>> Volker
>>> 
>>> [1]
>>> http://hg.openjdk.java.net/ppc-aix-port/jdk8/hotspot/file/tip/ppc_patches/0008_linux_ppc_make_changes.patch
>>> [2]
>>> http://hg.openjdk.java.net/ppc-aix-port/jdk8/hotspot/file/tip/ppc_patches/0014_aix_make_changes.patch
>>> [3]
>>> http://hg.openjdk.java.net/ppc-aix-port/jdk8/hotspot/file/tip/ppc_patches/0009_linux_ppc_files.patch
>>> [4]
>>> http://hg.openjdk.java.net/ppc-aix-port/jdk8/hotspot/file/tip/ppc_patches/0015_aix_ppc_files.patch
>>> 
>>> 
>>> 
>>> On Mon, Jun 17, 2013 at 3:55 PM, Lindenmaier, Goetz <
>>> goetz.lindenmaier at sap.com> wrote:
>>> 
>>>> Hi,****
>>>> 
>>>> ** **
>>>> 
>>>> the PPC64 port uses stub routines to implement safefetch. We had and****
>>>> 
>>>> have problems with inline assembly, especially with non-gcc****
>>>> 
>>>> compilers. Stub routines allow to implement safefetch without****
>>>> 
>>>> depending on OS or compiler, as it's the case with the current****
>>>> 
>>>> implementation. This also allows to use a single implementation if an****
>>>> 
>>>> architecture is supported on several os platforms.****
>>>> 
>>>> ** **
>>>> 
>>>> http://cr.openjdk.java.net/~goetz/webrevs/8016697-safefetch/****
>>>> 
>>>> ** **
>>>> 
>>>> Currently, we guard the code with ****
>>>> 
>>>> #ifdef SAFEFETCH_STUBS****
>>>> 
>>>> which is set in ppc64.make.****
>>>> 
>>>> ** **
>>>> 
>>>> I could also imagine an implementation that uses a pd_debug flag****
>>>> 
>>>> or a const flag set in os_<os_cpu>.hpp that allows the C-compiler to ****
>>>> 
>>>> optimize, and writing the code like this:****
>>>> 
>>>> ** **
>>>> 
>>>> extern "C" int pd_SafeFetch32 (int * adr, int errValue) ;****
>>>> 
>>>> extern "C" intptr_t pd_SafeFetchN (intptr_t * adr, intptr_t errValue) ;***
>>>> *
>>>> 
>>>> inline int SafeFetch32(int* adr, int errValue) {****
>>>> 
>>>> if (UseSafefetchStub) {****
>>>> 
>>>>  assert(StubRoutines::SafeFetch32_stub(), "stub not yet generated");***
>>>> *
>>>> 
>>>>  return StubRoutines::SafeFetch32_stub()(adr, errValue);****
>>>> 
>>>> } else {****
>>>> 
>>>>  pd_SafeFetch32(adr, errValue);****
>>>> 
>>>> }****
>>>> 
>>>> }****
>>>> 
>>>> ** **
>>>> 
>>>> Unfortunately this requires ****
>>>> 
>>>> 1) setting the flag on all platforms****
>>>> 
>>>> 2) renaming the safefetch function on all platfoms.****
>>>> 
>>>> ** **
>>>> 
>>>> Actually I would prefer this second solution as it avoids the
>>>> preprocessor, ****
>>>> 
>>>> and am happy to edit the sources accordingly if this finds acceptance.****
>>>> 
>>>> ** **
>>>> 
>>>> For the implementation of a safefetch_stub see****
>>>> 
>>>> 
>>>> http://hg.openjdk.java.net/ppc-aix-port/jdk8/hotspot/file/fce884e5ba0b/src/cpu/ppc/vm/stubGenerator_ppc.cpp
>>>> ****
>>>> 
>>>> ** **
>>>> 
>>>> Could I get a review on this change, please?****
>>>> 
>>>> ** **
>>>> 
>>>> Thanks,****
>>>> 
>>>> Goetz.****
>>>> 
>> 
>