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      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
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Mike.Popoloski

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My proposal to work on the Mono runtime was accepted for the Google Summer of Code program, so I'll be spending some time on that this summer. The project involves modifying the x86 JIT to use SSE for floating point operations, as opposed to the x87 FP stack that it's using now. The use of SSE registers is much cleaner and faster than using the FP stack, and the amd64 runtime already uses them entirely, since the x64 calling convention dictates that they be used. My work will bring the x86 runtime closer to the 64 bit runtime, and hopefully give a modest performance boost as well.

The coding period for GSoC started last Monday, so I spent the last week getting to know the runtime source code. The whole system is pretty complex, large, and entirely in C, so it hasn't been easy following it all. Luckily my mentor has been great about answering questions whenever I have them. A quick overview of how the runtime works:

  • The JIT is started, internal calls are hooked up, and CPU features are detected
  • The assembly to execute is loaded and its IL instructions loaded.
  • The instructions are all read and converted into IR instructions, which are an expanded internal representation that is still architecture independent but is easier to manipulate and generate code for.
  • A control flow graph is built and the program is broken down into "basic blocks".
  • The IR instructions are running through a "decompose" pass that breaks large instructions down into several smaller ones, or equivalent faster operations.
  • At this point, we have a graph of blocks that are in decoded IR form. From here on out we move into separate paths depending on the architecture we're running, which could be x86, amd64, PowerPC, ARM, etc.
  • The IR opcodes are run through a lowering pass, which converts complex opcodes into simpler ones that more closely map to machine instructions.
  • The opcodes are then run through an initial peephole optimization pass, which performs any optimizations that can be made before register allocation.
  • The register allocator is run on the block to schedule registers for each instruction.
  • Another optimization pass is run on the instruction stream.
  • Finally, the JIT runs through each instruction in the block and outputs the corresponding machine instruction for the given architecture.
    My job will be to modify the x86-specific architecture code to output SSE opcodes for various floating point operations. This sounds rather simple, but the implications of not using the FP stack are wide-reaching. Besides modifying machine code output, I'll also have to modify the register allocator to make use of the XMM registers for floating point values being passed to and from functions, since the current runtime puts them all on the x87 stack.

    Although the register allocator is probably the most complex part of the process, there are plenty of little things to take into account as well. I'll have to modify the P/Invoke and native interop code to save and restore the XMM registers whenever the boundary is crossed. Also, any code that uses Mono.SIMD could possibly conflict with registers that we're now using for FP ops, so checks will have to be put in place to handle that condition. Finally, there are optimizations that open up when SSE registers are used, and hopefully I'll have time to do some work on them as well.

    It's a lot of work ahead of me, but it's interesting getting to know how a large and commercial-grade JIT operates, and the end result should be useful for a wide group of people. I'm looking forward to diving more deeply into this as the summer progresses.

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Sounds pretty cool - I look forward to hearing about your progress as you go along!
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