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      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      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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Turns out my garbage collection woes are over.

I was strongly suspicious of the inliner in my last post, and it turns out that this hunch was (albeit indirectly) completely correct.

The obvious thing to do when facing a bug like this is to compare the code generated; dump out a listing of the version that works, and a listing of the version that doesn't, and run a diff tool to see what's mismatched between the two.

Thankfully, LLVM comes with a handy dump() function that lets us easily see what the IR bitcode looks like for a given program, so it's trivial to arrange this.

Combing through the diff, I noticed that there was indeed some inlining going on - but not of the functions that I suspected were causing problems. Moreover, suppressing inlining on the functions I did think were problematic made no difference!

As I looked closer, I noticed another interesting distinction between the working and broken versions of code: the @llvm.lifetime.start and @llvm.lifetime.end intrinsics.

It took some digging on the googles to figure out what exactly these mean. Semantically, they just define when two variables (supposedly) do not overlap in lifetime, and can theoretically be given the same stack slot. Except if we marked one of those stack slots as containing a GC root... well, I'm sure you can figure out the rest.

The intrinsics are inserted by the optimizers at the IR level but not paid attention to until native code emission phases, so all I needed to do was strip them out of the IR. Thankfully I already have a late-running pass over the optimized code for GC setup purposes, which is actually part of what generates the stack maps in the first place. I modified this pass to obliterate calls to those intrinsics, re-enabled function inlining everywhere I had tried to club it to death previously, and...

Everything works!

Incidentally, there are already bugs filed against the so-called "Stack Coloring" pass which uses these intrinsics. One that actually helped me track this issue down is filed at http://llvm.org/bugs/show_bug.cgi?id=16095

I'm pondering filing a second bug just to note that stack coloring/slot lifetime in the presence of GC roots is a bad idea.

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