<html> <head> <meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type"> </head> <body text="#000000" bgcolor="#FFFFFF"> <div class="moz-cite-prefix">Hi Vadim, nice work, I think you've made quite a progress here, but on the other hand it should be clear that the LLVM backend is the future and we should concentrate on that. To sum it up I'm not sure what we should do with this branch :) As Dragomir already wrote even if the code won't be used much the know-how you gained while coding it will stay, believe me that this is or far more value than the code itself. Christian. Am 14.02.2013 11:10, schrieb Dragomir Ivanov: </div> <blockquote cite="mid:CANi1Oh1W2-RQZi-bqNWyZQWTU6euVmc_9zfof1fn2xBUxWjG8w@mail.gmail.com" type="cite"> <div dir="ltr">Greetings, <div>I hope that, even if you work will be short-lived, e.g. until LLVM bytecode compiler takes off, the know-how is still very useful. <div class="gmail_extra"> <div class="gmail_quote"> On Thu, Feb 14, 2013 at 4:04 AM, Vadim Girlin <<a moz-do-not-send="true" href="mailto:vadimgirlin@gmail.com" target="_blank">vadimgirlin@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi, Last month I finally found the time to work on the rewrite of my previous shader optimization branch, now it's mostly done in terms of the correctness of produced code and feature support (at least on evergreen), though it's still a work in progress in terms of the efficiency of generated shader code and the efficiency of the backend itself. I spent some time last year studying the LLVM infrastructure and R600 LLVM backend and trying to improve it, but after all I came to the conclusion that for me it might be easier to implement all that I wanted in the custom backend. This allows for more simple and efficient implementation - e.g. I don't have to deal with CFGs because in fact we have structured code, so it's possible to use more simple and efficient algorithms. Currently the branch has no regressions with piglit's quick-driver.tests on evergreen (it doesn't rely on the fallback to unoptimized code for the shaders with relative addressing and other cases unlike the previous branch), and so far I don't see any rendering issues with the apps that I used for testing - Lightsmark 2008, Unigine Heaven 3.0 and some others.. There are also some performance improvements with the gpu-bound apps. I tried to keep in mind the differences between chip classes, so I hope it should only require minor fixes to make it work on non-evergreen chips, but I doubt that it will work out of the box - support for some non-evergreen hw-specific features is still missing, e.g. I'm sure that indirect addressing currently won't work on R6xx, though basic tests might work in theory. Fixing this shouldn't require a lot of work though. The branch can be found in my freedesktop repo: <a moz-do-not-send="true" href="http://cgit.freedesktop.org/%7Evadimg/mesa/log/?h=r600-sb" target="_blank">http://cgit.freedesktop.org/~vadimg/mesa/log/?h=r600-sb</a> Regarding the differences from the previous branch - there are some additional optimizations, e.g. global value numbering with some basic support for constant folding (not all instructions are currently handled, but it's easy to extend), global code motion that can hoist invariant code out of the loops etc. Some optimizations that were implemented in the previous branch are not implemented in the new branch (yet), e.g. propagation of modifiers (I'm not even sure if it has any noticeable effect on performance). Unlike the previous branch, there is support for indirect addressing on registers - currently it uses my previously posted patch (that was not very welcome) for obtaining the information about addressable register ranges, but it's not required and can be dropped, I just used that patch for testing. Without that information opportunities for optimization are limited though, and perhaps it makes sense to not try to optimize the shaders with indirect gpr addressing at all and rely on the old backend until we'll have the proper solution to pass that information to the drivers. There is also initial support for ALU predication, but it's not complete and currently unused, I'm not sure if predication support will have significant effect on performance that will justify more complex and expensive algorithms for register allocator and scheduler, probably I'll look into it later, I consider this as a low priority. In the case of predicated source code (from LLVM backend) the predication is eliminated using speculative execution and conditional moves, same as with the simple if-conversion pass that is also implemented. The branch currently uses as source the bytecode built by the old backend (that may also come from LLVM backend) and some additional information (about inputs etc), final bytecode is built by the new builder in the branch. Building two versions of the bytecode doesn't look very efficient, but currently it simplifies debugging. I'm planning to implement translation from TGSI directly to my representation, it should simplify the translator and allow to get rid of unnecessary intermediate passes. Some old and new environment variables can be used to control the behavior of this backend: R600_SB - 0 - disable new backend completely, 1 - enable (default) R600_SB_USE_NEW_BYTECODE - 0 - disable use of the produced bytecode (useful if you only want to look at the dump of the optimized shader without passing it to hw), 1 - enable (default) R600_DUMP_SHADERS - will also dump the dissasemble of the optimized shader after original bytecode (if backend is not disabled with R600_SB=0). Produced shader code is not ideal - e.g. you may notice not very necessary MOVs inserted before DOT4 instructions, it's a known issue and I'm going to look into it - this may require rework of the regalloc/scheduler. I had to sacrifice some features to make it work correctly with Heaven first, so that now I can try to improve it while being able to test for regressions. Also probably there are some issues with the cleanness of the code - I had to rework some parts a few times while fixing all problems, so there is possibly unused code and other remnants of the previous versions. Anyway, I still consider it as a work in progress and some things are going to be reworked. I'm not sure what will be the destiny of this branch, taking into account that we also have actively developed LLVM backend that is required for OpenCL anyway. Your opinions are welcome. Vadim _______________________________________________ mesa-dev mailing list <a moz-do-not-send="true" href="mailto:mesa-dev@lists.freedesktop.org" target="_blank">mesa-dev@lists.freedesktop.org</a> <a moz-do-not-send="true" href="http://lists.freedesktop.org/mailman/listinfo/mesa-dev" target="_blank">http://lists.freedesktop.org/mailman/listinfo/mesa-dev</a> </blockquote> </div> </div> </div> </div> <fieldset class="mimeAttachmentHeader"></fieldset> <pre wrap="">_______________________________________________ mesa-dev mailing list <a class="moz-txt-link-abbreviated" href="mailto:mesa-dev@lists.freedesktop.org">mesa-dev@lists.freedesktop.org</a> <a class="moz-txt-link-freetext" href="http://lists.freedesktop.org/mailman/listinfo/mesa-dev">http://lists.freedesktop.org/mailman/listinfo/mesa-dev</a> </pre> </blockquote> </body> </html>