Fwd: RE: Fwd: Question wrt ppc.ad (for 64b PPC)
Ruchika Kharwar
ruchika.k at servergy.com
Thu May 15 15:24:38 UTC 2014
Goetz,
Thank you so much for your reply:
On 5/13/2014 11:39 AM, Lindenmaier, Goetz wrote:
>
> Hi Ruchika,
>
> > As per "64-bit PowerPC ELF Application Binary Interface Supplement
> 1.7" register r2 holds the "TOC base" so why not use r2 instead of
> using using another register r29.
> Because |r2 -- r29| >> 2^32 is possible, and we introduced our toc in
> r29 to reach the constants with a small offset < 2^32.
>
> > You say we don't need a coop on 32b machines because the oop pointer is <= 32 bits anyways since the
> memory span is 32GB, yes ?
> Yes.
>
> > Now deviating some from the original question a little:
> > Now for the 32b port of the code base referring to the e500 ABI doc,
> r2 holds the TOC and r13 the small data area and I need to use those 2
> together instead of the r2 toc on the 64b. If that information is
> handy, do you know which files would need change in the openjdk ?
>
> The file ppc.ad specifies the nodes of the low IR of the C2 compiler,
> as well as rules for register allocation, matching etc.. The compiled
> code will not read the abi content of the registers. r13 is just left
> alone, r2 is saved and used for allocation, so it basically does not
> matter what they contain. On 32-bit I would just load constants
> directly, as only two instructions are needed, so you don't need a toc
> there at all. But freeing r29 and r30 and using them for register
> allocation in the C2 compiler is one of the last things you should
> address because it's only an optimization.
>
[RK] Thank you , this is very helpful. I may need to understand more
but thanks for the pointer.
>
> I can't enumber all files you need to edit, but a lot of code issued
> by the compiler is implemented in macroAssembler_ppc.*. The biggest
> effort will probably be to identify all loads of pointers and replace
> 64-bit loads with 32-bit loads there.
>
[RK] Thank you , I ported over the macroAssembler_ppc.* file (not
tested yet in any way)
>
> > Secondly, the 64 b 1.7 eabi has register r13 dedicated to the system thread id, there isn't one dedicated in
> the e500 abi doc, any recommendation on how that would need to get
> handled ?
>
> I don't remember that we use the system thread, we just don't touch
> the register.
>
> How do you plan to do the port? Will you do the template interpreter
> right away? Or will you start with the cpp interpreter? I would first
> port a 'core' build that only contains one of interpreters without any
> compiler, because that will get you to a running VM much faster.
> There is a build target 'debugcore' in hotspot. The abi relevant
> stuff needed for the interpreter is specified in the frame_ppc.* files.
>
[RK] I am working with the Cpp interpreter for now.
Thanks again for the input..
>
> Best regards, Goetz.
>
>
>
> Thank you
> Regards,
> Ruchika
>
> On 5/13/2014 7:05 AM, Monica Beckwith wrote:
>
> Thanks Goetz. As requested, I am forwarding to the alias so this
> gets documented. :)
>
>
> Regards,
> -Monica
>
> -------- Original Message --------
>
> *Subject: *
>
>
>
> RE: Fwd: Question wrt ppc.ad (for 64b PPC)
>
> *Date: *
>
>
>
> Tue, 13 May 2014 07:34:50 +0000
>
> *From: *
>
>
>
> Lindenmaier, Goetz <goetz.lindenmaier at sap.com>
> <mailto:goetz.lindenmaier at sap.com>
>
> *To: *
>
>
>
> Monica Beckwith <monica.b at servergy.com>
> <mailto:monica.b at servergy.com>, "Simonis, Volker"
> <volker.simonis at sap.com> <mailto:volker.simonis at sap.com>
>
> *CC: *
>
>
>
> Ruchika <ruchika.k at servergy.com> <mailto:ruchika.k at servergy.com>
>
>
>
>
> Hi Ruchika,
>
> these are values needed for the runtime functionality of the VM,
> so they are not
>
> found in an official ppc document.
>
> R16 points to a thread of class Thread from runtime/thread.hpp.
>
> R29 is the global TOC we use to compute the tocs for methods with
>
> few instructions. Loading a 64-bit address requires 5 instructions,
>
> so it's cheaper to have some address nearby in a register and compute
>
> the address by an offset to that.
>
> (toc: pointer to the constant section of a method)
>
> R30 is used for compressed oops. This is a feature only needed on
> 64-bit
>
> machines. If the Java heap is < 32GB, oop pointers are compressed
> to 32-bit
>
> by cOop = (oop -- heap_base) >> 3. heap_base is held in R30
> (cOop: compressed oop)
>
> Best regards,
>
> Goetz.
>
> *Question:*
>
> While reading the ppc.ad file for ppc
> (./hotspot/src/cpu/ppc/vm/ppc.ad) I came across these lines
> wrt the register definitions (line 434 in file)
> /*R13*/ // system thread id <-- THis is as per
> "64-bit PowerPC ELF Application Binary
> Interface Supplement 1.7" so it is ok
> R14,
> R15,
> /*R16*/ // R16_thread <--- Where does this
> convention arise from ? Which document/supplement?
> R17,
> R18,
> R19,
> R20,
> R21,
> R22,
> R23,
> R24,
> R25,
> R26,
> R27,
> R28,
> /*R29*/ // global TOC <--- Where does this
> convention arise from ? Which document/supplement?
> /*R30*/ // Narrow Oop Base<--- Where does this
> convention arise from ? Which document/supplement?
>
> Thank you
> Regards
> Ruchika
>
>
>
> --
>
> Ruchika Kharwar
>
> Senior Validation Engineer
>
> Servergy, Inc.
>
> Mobile:(469) 919-5635
>
> Fax:(972) 542-5633
>
> Email:ruchika.k at servergy.com <mailto:Email:ruchika.k at servergy.com>
>
> Website:Servergy.com
>
> Twitter:Twitter.com/Servergy
>
>
>
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>
>
> CONFIDENTIALITY NOTICE: Copyright © 2014 by Servergy, Inc. All Rights Reserved. This communication contains privileged and/or confidential information to be maintained with the strictest confidence. It is intended solely for the use of the person or entity in which it is addressed. If you are not the intended recipient, you are STRICTLY PROHIBITED from disclosing, copying, distributing or using any of this information. If you received this communication in error, please contact the sender immediately and destroy the material in its entirety, whether electronic or hard copy.
>
>
>
> --
> Ruchika Kharwar
> Senior Validation Engineer
> Servergy, Inc.
> Mobile:(469) 919-5635
> Fax:(972) 542-5633
> Email:ruchika.k at servergy.com <mailto:Email:ruchika.k at servergy.com>
> Website:Servergy.com
> Twitter:Twitter.com/Servergy
>
> Servergy Makes # 4 on the EE Times 2013 Global Top 10 List of Most Disruptive Tech Start-up Plays!
> O Energy-efficiency is #1 reason data centers look to expand. -- Digital Realty Trust
> O Green Data Centers spending to increase 300% worldwide by 2016. -- Pike Research
> O Data Centers have become as vital to the functioning of society as power stations. -- The Economist
> O By 2015, 30% of investments in $150B+ data center market will be in energy-efficiency plays [like Servergy]. -- Pike Research
> O By 2015 there will be 2B+ more people online and 10X more servers in the world. -- IDC Research
>
> CONFIDENTIALITY NOTICE: Copyright © 2014 by Servergy, Inc. All Rights Reserved. This communication contains privileged and/or confidential information to be maintained with the strictest confidence. It is intended solely for the use of the person or entity in which it is addressed. If you are not the intended recipient, you are STRICTLY PROHIBITED from disclosing, copying, distributing or using any of this information. If you received this communication in error, please contact the sender immediately and destroy the material in its entirety, whether electronic or hard copy.
>
>
>
> --
> Ruchika Kharwar
> Senior Validation Engineer
> Servergy, Inc.
> Mobile:(469) 919-5635
> Fax:(972) 542-5633
> Email:ruchika.k at servergy.com <mailto:Email:ruchika.k at servergy.com>
> Website:Servergy.com
> Twitter:Twitter.com/Servergy
>
> Servergy Makes # 4 on the EE Times 2013 Global Top 10 List of Most Disruptive Tech Start-up Plays!
> O Energy-efficiency is #1 reason data centers look to expand. -- Digital Realty Trust
> O Green Data Centers spending to increase 300% worldwide by 2016. -- Pike Research
> O Data Centers have become as vital to the functioning of society as power stations. -- The Economist
> O By 2015, 30% of investments in $150B+ data center market will be in energy-efficiency plays [like Servergy]. -- Pike Research
> O By 2015 there will be 2B+ more people online and 10X more servers in the world. -- IDC Research
>
> CONFIDENTIALITY NOTICE: Copyright © 2014 by Servergy, Inc. All Rights Reserved. This communication contains privileged and/or confidential information to be maintained with the strictest confidence. It is intended solely for the use of the person or entity in which it is addressed. If you are not the intended recipient, you are STRICTLY PROHIBITED from disclosing, copying, distributing or using any of this information. If you received this communication in error, please contact the sender immediately and destroy the material in its entirety, whether electronic or hard copy.
>
--
Ruchika Kharwar
Senior Validation Engineer
Servergy, Inc.
Mobile:(469) 919-5635
Fax:(972) 542-5633
Email:ruchika.k at servergy.com
Website:Servergy.com
Twitter:Twitter.com/Servergy
Servergy Makes # 4 on the EE Times 2013 Global Top 10 List of Most Disruptive Tech Start-up Plays!
O Energy-efficiency is #1 reason data centers look to expand. -- Digital Realty Trust
O Green Data Centers spending to increase 300% worldwide by 2016. -- Pike Research
O Data Centers have become as vital to the functioning of society as power stations. -- The Economist
O By 2015, 30% of investments in $150B+ data center market will be in energy-efficiency plays [like Servergy]. -- Pike Research
O By 2015 there will be 2B+ more people online and 10X more servers in the world. -- IDC Research
CONFIDENTIALITY NOTICE: Copyright © 2014 by Servergy, Inc. All Rights Reserved. This communication contains privileged and/or confidential information to be maintained with the strictest confidence. It is intended solely for the use of the person or entity in which it is addressed. If you are not the intended recipient, you are STRICTLY PROHIBITED from disclosing, copying, distributing or using any of this information. If you received this communication in error, please contact the sender immediately and destroy the material in its entirety, whether electronic or hard copy.
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