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258 discussions

Backend Register Assignment Issues
by Maxime Chevalier-Boisvert 06 Nov '10

06 Nov '10

I'm in the process of coding the register assignment for the DivInstr in the backend and running into a slight issue. The way it's setup now, we block some registers for the instruction, and give register hints for the input and output arguments. However, there seems to be no way to make those register hints mandatory (force the allocator to respect them). On x86, idiv requires the dividend to be in EAX:EDX, and puts the quotient in EAX. This means I need to block both registers. I also need to block a third register to write the divisor into when the divisor is an immediate integer. However, when I tested this with a non-constant divisor, it ended up being assigned into EDX (a part of the dividend value). This forces me to always reserve an extra scratch register to put the divisor in, and check which register it ends up assigned to, in case it ends up into the dividend registers. I also have to check that the dividend is indeed in EAX, and move it there if it isn't. Also, I must say I don't like the idea of having to reserve a *specific* scratch register (seems inefficient if I don't care which one it is). I would propose the following changes/additions to the current back-end design: 1. A way to *force* specific operands into some specific registers (strong register assignment constraint). This should work even if the operands are immediate values. 2. A way to reserve some number of extra scratch registers, without having to specify which ones. - Maxime

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Presentation
by Marc Feeley 04 Nov '10

04 Nov '10

Maxime, the best of luck for your presentation! Don't forget that I would like a copy of your slides so that I can send a copy to Allen Wirfs-Brock at Microsoft. Marc

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Meeting
by Marc Feeley 26 Oct '10

26 Oct '10

Can someone tell me when we are meeting on Thursday? Will we do a group meeting and practice presentation at that time? Note that I am not available for the usual Wednesday meeting time. Marc

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Naming
by Marc Feeley 23 Oct '10

23 Oct '10

Here's an interesting blog article from Stephen Wolfram on naming functions. http://blog.stephenwolfram.com/2010/10/the-poetry-of-function-naming/ Marc

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Fwd: [gambit-list] Gambit Scheme Inside Out talk at ILC2010
by Marc Feeley 21 Oct '10

21 Oct '10

In case you haven't seen this... Marc Begin forwarded message: > From: Marc Feeley <feeley(a)iro.umontreal.ca> > Date: October 21, 2010 3:38:45 PM PDT > To: Gambit List <Gambit-list(a)iro.umontreal.ca> > Subject: [gambit-list] Gambit Scheme Inside Out talk at ILC2010 > > Hello. I gave a talk on Gambit at ILC2010 yesterday. It presents highlights of both the Gambit Scheme language and its implementation. > > You can find it at: > > http://www.iro.umontreal.ca/~gambit/Gambit-inside-out.pdf > > The .pdf is 24MB so it might be a longish download... > > Many thanks to Guillaume Cartier, James Long and Robert Lizee for providing some nice demos. For the record, some participants said that now that they know Gambit they see less of a reason to use Common Lisp (whatever that means!). > > Marc > > _______________________________________________ > Gambit-list mailing list > Gambit-list(a)iro.umontreal.ca > https://webmail.iro.umontreal.ca/mailman/listinfo/gambit-list

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Re: [Tachyon-list] Abstract for Compiler-Driven Performance Workshop
by Maxime Chevalier-Boisvert 20 Oct '10

20 Oct '10

It won't pose a problem. - Maxime On 10-10-20 02:40 PM, Clark Verbrugge wrote: > Hi Maxime, > > FYI, I need to move you around in the schedule I sent earlier this > week. Your talk will be in the morning instead (9:30-10:00). Let me > know asap if that would pose a problem. > > ttfn, > clark verbrugge > associate professor > school of computer science > mcgill university > clump(a)cs.mcgill.ca > > > > Clark Verbrugge wrote: >> Hi, >> >> On behalf of the organizing committee of the 9th Workshop on >> Compiler-Driven Performance, I am happy to inform you that your >> presentation has been selected for the workshop. >> >> A detailed schedule will also be sent out soon. >> >> Please be sure to register for both CASCON and the CDP workshop. >> >> I look forward to your presentation and seeing you at CDP2010. >> >> 9th Compiler-Driven Performance Workshop >> November 4, 2010 (Thursday) >> >> Hilton Suites Toronto/Markham Conference Centre >> Associated with CASCON 2010 >> (http://www.cas.ibm.com/cascon) >> (Nov 1-4 2010) >> >> Steering Committee: >> Jose Nelson Amaral - University of Alberta >> Kit Barton - IBM Toronto >> David Grove - IBM Watson >> Ondrej Lhotak - University of Waterloo >> J. Gregory Steffan - University of Toronto >> Mark Stoodley - IBM Toronto Lab >> Clark Verbrugge - McGill University >> >> ttfn, >> clark verbrugge >> associate professor >> school of computer science >> mcgill university >> clump(a)cs.mcgill.ca >> >> >> >> Maxime Chevalier-Boisvert wrote: >>> We would like to submit a talk proposal for the Compiler-Driven >>> Performance Workshop. >>> >>> Talk title: Tachyon: a Meta-circular Optimizing JavaScript Virtual >>> Machine >>> >>> Author list: >>> Maxime Chevalier-Boisvert >>> Erick Lavoie >>> Marc Feeley >>> Bruno Dufour >>> >>> Speaker: Maxime Chevalier-Boisvert >>> >>> Abstract: >>> >>> JavaScript is now the most widely supported dynamic programming >>> language in existence; it is the language that powers the >>> client-side of the web, and large companies such as Google and >>> Microsoft have clearly stated their intent to build web applications >>> intended to replace current desktop software based on this >>> technology. Finding ways to get better performance out of JavaScript >>> code and to provide more portable implementations of the language >>> have become foremost concerns. >>> >>> The Tachyon project is a research initiative involving the creation >>> of a meta-circular JavaScript virtual machine. This virtual machine >>> is meta-circular because it is itself written in JavaScript and >>> intended to compile and optimize itself just-in-time, along with >>> client code, to platform-specific machine code. This project was >>> officially started this year, and while still in early stages, has >>> the potential to offer researchers a simpler and powerful >>> alternative to explore novel dynamic language optimization >>> techniques and study the behavior or dynamic languages. >>> >>> We intend to use this project to demonstrate the potential >>> performance and design benefits of meta-circularity, to explore >>> novel optimization techniques based on dynamic analysis, dynamic >>> recompilation and on-stack replacement and to experiment with the >>> idea of a virtual machine capable of serializing its own state. We >>> plan to integrate Tachyon in a real web browser so as to test and >>> demonstrate its capabilities in real-world situations, on >>> non-synthetic JavaScript code. We further intend to make our system >>> open source and available to other researchers. >>> >>> - Maxime Chevalier-Boisvert >>

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Allen Wirfs-Brock
by Marc Feeley 19 Oct '10

19 Oct '10

I attended Allen Wirfs-Brock's keynote presentation on JavaScript at DLS yesterday. It was really interesting and I found we share a similar design philosophy, in particular a "holistic" approach to language implementation where all aspects of the system have to be of concern at the very start of the development. I'm hoping to get his slides to pass on to the rest of the group. He also mentioned that there might be some informal meeting of JavaScript implementors in the next 6 months. I've asked him to keep me informed of any such meeting so that we can attend. Marc

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Fwd: Schedule for 9th Compiler-Driven Performance Workshop - CASCON 2010
by Maxime Chevalier-Boisvert 18 Oct '10

18 Oct '10

---------- Forwarded message ---------- From: clark verbrugge <clump(a)cs.mcgill.ca> Date: Mon, Oct 18, 2010 at 9:19 AM Subject: Schedule for 9th Compiler-Driven Performance Workshop - CASCON 2010 To: Hi, A preliminary schedule for the 9th Compiler-Driven Performance Workshop is available: http://www.sable.mcgill.ca/~clump/cdp2010/<http://www.sable.mcgill.ca/%7Eclump/cdp2010/> * Please check that the speaker (in bold), co-authors, affiliations, and title are correct for your talk. * Talks are scheduled to be 30 minutes each (20-25 minutes of presentation, 5-10 minutes for questions/discussion). Please plan your presentation to fit in the alloted time. * If the work has been filed for a patent by IBM, please indicate so in your talk. * If for any reason you are unable attend or give the presentation (at the workshop on Thursday Nov 4) please let me know ASAP. I look forward to your presentation and seeing you at CDP! Just a reminder to also register for the CASCON and the CDP workshop. -- ttfn, clark verbrugge associate professor school of computer science mcgill university clump(a)cs.mcgill.ca

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Division by a constant
by Marc Feeley 18 Oct '10

18 Oct '10

Here is the algorithm for division by a constant, which does a multiplication and a shift. The first command-line argument is the divisor, and the second argument is the width of the word (in the example, 32 bit words). The machine multiplication instruction typically produces a result that is twice the word width, in 2 registers (the hi 32 bits and the lo 32 bits of the result). So if a 34 bit right shift is needed (for example when dividing by 5), it is really a right shift of the hi 32 bit register by 2 bits. Marc % ./div.scm 5 32 given x is a 32 bit wide integer: x/5 = (x * 3435973837) / 2^34 % ./div.scm 17 32 given x is a 32 bit wide integer: x/17 = (x * 4042322161) / 2^36 % ./div.scm 128 32 given x is a 32 bit wide integer: x/128 = (x * 1) / 2^7 % cat div.scm #!/usr/bin/env gsi-script (define (log2 x) ;; retourne le plus petit k tel que 2^k >= x (if (= x 1) 0 (+ 1 (log2 (quotient x 2))))) (define (div2 x) ;; retourne le plus grand k tel que x mod 2^k = 0 (if (odd? x) 0 (+ 1 (div2 (quotient x 2))))) (define (div divisor width) (let* ((a (+ (log2 (- divisor 1)) 1)) (m (ceiling (/ (expt 2 (+ width a)) divisor))) (b (div2 m)) (shift (+ width (- a b))) (m/2^b (quotient m (expt 2 b)))) (list m/2^b shift))) (define (main divisor-str width-str) (let* ((divisor (string->number divisor-str)) (width (string->number width-str)) (params (div divisor width)) (m/2^b (car params)) (shift (cadr params))) (print "given x is a " width " bit wide integer:\n") (print "x/" divisor " = (x * " m/2^b ") / 2^" shift "\n")))

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Statistical profiler
by Bruno Dufour 17 Oct '10

17 Oct '10

Hi, I have a first simple implementation for the statistical profiler. Do you have any recommendations/guidelines regarding where it should be placed in the git repository? Thanks, Bruno

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