319 lines
9.7 KiB
HTML
319 lines
9.7 KiB
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html lang="en">
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<head>
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<meta http-equiv="content-type" content="text/html; charset=utf-8">
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<title>llvmpipe</title>
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<link rel="stylesheet" type="text/css" href="mesa.css">
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</head>
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<body>
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<div class="header">
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<h1>The Mesa 3D Graphics Library</h1>
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</div>
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<iframe src="contents.html"></iframe>
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<div class="content">
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<h1>Introduction</h1>
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<p>
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The Gallium llvmpipe driver is a software rasterizer that uses LLVM to
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do runtime code generation.
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Shaders, point/line/triangle rasterization and vertex processing are
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implemented with LLVM IR which is translated to x86 or x86-64 machine
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code.
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Also, the driver is multithreaded to take advantage of multiple CPU cores
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(up to 8 at this time).
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It's the fastest software rasterizer for Mesa.
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</p>
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<h1>Requirements</h1>
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<ul>
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<li>
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<p>An x86 or amd64 processor; 64-bit mode recommended.</p>
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<p>
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Support for SSE2 is strongly encouraged. Support for SSSE3 and SSE4.1 will
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yield the most efficient code. The fewer features the CPU has the more
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likely is that you run into underperforming, buggy, or incomplete code.
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</p>
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<p>
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See /proc/cpuinfo to know what your CPU supports.
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</p>
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</li>
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<li>
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<p>LLVM: version 3.4 recommended; 3.3 or later required.</p>
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<p>
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For Linux, on a recent Debian based distribution do:
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</p>
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<pre>
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aptitude install llvm-dev
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</pre>
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<p>
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For a RPM-based distribution do:
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</p>
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<pre>
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yum install llvm-devel
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</pre>
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<p>
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For Windows you will need to build LLVM from source with MSVC or MINGW
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(either natively or through cross compilers) and CMake, and set the LLVM
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environment variable to the directory you installed it to.
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LLVM will be statically linked, so when building on MSVC it needs to be
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built with a matching CRT as Mesa, and you'll need to pass
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<code>-DLLVM_USE_CRT_xxx=yyy</code> as described below.
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</p>
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<table border="1">
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<tr>
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<th rowspan="2">LLVM build-type</th>
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<th colspan="2" align="center">Mesa build-type</th>
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</tr>
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<tr>
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<th>debug,checked</th>
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<th>release,profile</th>
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</tr>
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<tr>
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<th>Debug</th>
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<td><code>-DLLVM_USE_CRT_DEBUG=MTd</code></td>
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<td><code>-DLLVM_USE_CRT_DEBUG=MT</code></td>
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</tr>
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<tr>
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<th>Release</th>
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<td><code>-DLLVM_USE_CRT_RELEASE=MTd</code></td>
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<td><code>-DLLVM_USE_CRT_RELEASE=MT</code></td>
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</tr>
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</table>
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<p>
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You can build only the x86 target by passing -DLLVM_TARGETS_TO_BUILD=X86
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to cmake.
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</p>
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</li>
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<li>
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<p>scons (optional)</p>
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</li>
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</ul>
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<h1>Building</h1>
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To build everything on Linux invoke scons as:
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<pre>
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scons build=debug libgl-xlib
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</pre>
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Alternatively, you can build it with GNU make, if you prefer, by invoking it as
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<pre>
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make linux-llvm
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</pre>
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but the rest of these instructions assume that scons is used.
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For Windows the procedure is similar except the target:
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<pre>
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scons platform=windows build=debug libgl-gdi
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</pre>
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<h1>Using</h1>
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<h2>Linux</h2>
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<p>On Linux, building will create a drop-in alternative for libGL.so into</p>
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<pre>
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build/foo/gallium/targets/libgl-xlib/libGL.so
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</pre>
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or
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<pre>
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lib/gallium/libGL.so
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</pre>
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<p>To use it set the LD_LIBRARY_PATH environment variable accordingly.</p>
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<p>For performance evaluation pass build=release to scons, and use the corresponding
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lib directory without the "-debug" suffix.</p>
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<h2>Windows</h2>
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<p>
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On Windows, building will create
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<code>build/windows-x86-debug/gallium/targets/libgl-gdi/opengl32.dll</code>
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which is a drop-in alternative for system's <code>opengl32.dll</code>. To use
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it put it in the same directory as your application. It can also be used by
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replacing the native ICD driver, but it's quite an advanced usage, so if you
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need to ask, don't even try it.
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</p>
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<p>
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There is however an easy way to replace the OpenGL software renderer that comes
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with Microsoft Windows 7 (or later) with llvmpipe (that is, on systems without
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any OpenGL drivers):
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</p>
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<ul>
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<li><p>copy build/windows-x86-debug/gallium/targets/libgl-gdi/opengl32.dll to C:\Windows\SysWOW64\mesadrv.dll</p></li>
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<li><p>load this registry settings:</p>
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<pre>REGEDIT4
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; http://technet.microsoft.com/en-us/library/cc749368.aspx
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; http://www.msfn.org/board/topic/143241-portable-windows-7-build-from-winpe-30/page-5#entry942596
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[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\OpenGLDrivers\MSOGL]
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"DLL"="mesadrv.dll"
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"DriverVersion"=dword:00000001
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"Flags"=dword:00000001
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"Version"=dword:00000002
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</pre>
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</li>
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<li>Ditto for 64 bits drivers if you need them.</li>
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</ul>
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<h1>Profiling</h1>
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<p>
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To profile llvmpipe you should build as
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</p>
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<pre>
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scons build=profile <same-as-before>
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</pre>
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<p>
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This will ensure that frame pointers are used both in C and JIT functions, and
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that no tail call optimizations are done by gcc.
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</p>
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<h2>Linux perf integration</h2>
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<p>
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On Linux, it is possible to have symbol resolution of JIT code with <a href="http://perf.wiki.kernel.org/">Linux perf</a>:
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</p>
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<pre>
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perf record -g /my/application
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perf report
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</pre>
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<p>
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When run inside Linux perf, llvmpipe will create a /tmp/perf-XXXXX.map file with
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symbol address table. It also dumps assembly code to /tmp/perf-XXXXX.map.asm,
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which can be used by the bin/perf-annotate-jit script to produce disassembly of
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the generated code annotated with the samples.
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</p>
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<p>You can obtain a call graph via
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<a href="http://code.google.com/p/jrfonseca/wiki/Gprof2Dot#linux_perf">Gprof2Dot</a>.</p>
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<h1>Unit testing</h1>
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<p>
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Building will also create several unit tests in
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build/linux-???-debug/gallium/drivers/llvmpipe:
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</p>
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<ul>
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<li> lp_test_blend: blending
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<li> lp_test_conv: SIMD vector conversion
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<li> lp_test_format: pixel unpacking/packing
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</ul>
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<p>
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Some of this tests can output results and benchmarks to a tab-separated-file
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for posterior analysis, e.g.:
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</p>
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<pre>
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build/linux-x86_64-debug/gallium/drivers/llvmpipe/lp_test_blend -o blend.tsv
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</pre>
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<h1>Development Notes</h1>
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<ul>
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<li>
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When looking to this code by the first time start in lp_state_fs.c, and
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then skim through the lp_bld_* functions called in there, and the comments
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at the top of the lp_bld_*.c functions.
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</li>
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<li>
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The driver-independent parts of the LLVM / Gallium code are found in
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src/gallium/auxiliary/gallivm/. The filenames and function prefixes
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need to be renamed from "lp_bld_" to something else though.
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</li>
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<li>
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We use LLVM-C bindings for now. They are not documented, but follow the C++
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interfaces very closely, and appear to be complete enough for code
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generation. See
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<a href="http://npcontemplation.blogspot.com/2008/06/secret-of-llvm-c-bindings.html">
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this stand-alone example</a>. See the llvm-c/Core.h file for reference.
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</li>
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</ul>
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<h1 id="recommended_reading">Recommended Reading</h1>
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<ul>
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<li>
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<p>Rasterization</p>
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<ul>
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<li><a href="http://www.cs.unc.edu/~olano/papers/2dh-tri/">Triangle Scan Conversion using 2D Homogeneous Coordinates</a></li>
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<li><a href="http://www.drdobbs.com/parallel/rasterization-on-larrabee/217200602">Rasterization on Larrabee</a> (<a href="http://devmaster.net/posts/2887/rasterization-on-larrabee">DevMaster copy</a>)</li>
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<li><a href="http://devmaster.net/posts/6133/rasterization-using-half-space-functions">Rasterization using half-space functions</a></li>
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<li><a href="http://devmaster.net/posts/6145/advanced-rasterization">Advanced Rasterization</a></li>
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<li><a href="http://fgiesen.wordpress.com/2013/02/17/optimizing-sw-occlusion-culling-index/">Optimizing Software Occlusion Culling</a></li>
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</ul>
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</li>
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<li>
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<p>Texture sampling</p>
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<ul>
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<li><a href="http://chrishecker.com/Miscellaneous_Technical_Articles#Perspective_Texture_Mapping">Perspective Texture Mapping</a></li>
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<li><a href="http://www.flipcode.com/archives/Texturing_As_In_Unreal.shtml">Texturing As In Unreal</a></li>
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<li><a href="http://www.gamasutra.com/view/feature/3301/runtime_mipmap_filtering.php">Run-Time MIP-Map Filtering</a></li>
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<li><a href="http://alt.3dcenter.org/artikel/2003/10-26_a_english.php">Will "brilinear" filtering persist?</a></li>
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<li><a href="http://ixbtlabs.com/articles2/gffx/nv40-rx800-3.html">Trilinear filtering</a></li>
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<li><a href="http://devmaster.net/posts/12785/texture-swizzling">Texture Swizzling</a></li>
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</ul>
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</li>
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<li>
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<p>SIMD</p>
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<ul>
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<li><a href="http://www.cdl.uni-saarland.de/projects/wfv/#header4">Whole-Function Vectorization</a></li>
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</ul>
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</li>
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<li>
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<p>Optimization</p>
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<ul>
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<li><a href="http://www.drdobbs.com/optimizing-pixomatic-for-modern-x86-proc/184405807">Optimizing Pixomatic For Modern x86 Processors</a></li>
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<li><a href="http://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-optimization-manual.html">Intel 64 and IA-32 Architectures Optimization Reference Manual</a></li>
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<li><a href="http://www.agner.org/optimize/">Software optimization resources</a></li>
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<li><a href="http://software.intel.com/en-us/articles/intel-intrinsics-guide">Intel Intrinsics Guide</a><li>
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</ul>
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</li>
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<li>
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<p>LLVM</p>
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<ul>
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<li><a href="http://llvm.org/docs/LangRef.html">LLVM Language Reference Manual</a></li>
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<li><a href="http://npcontemplation.blogspot.co.uk/2008/06/secret-of-llvm-c-bindings.html">The secret of LLVM C bindings</a></li>
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</ul>
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</li>
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<li>
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<p>General</p>
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<ul>
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<li><a href="http://fgiesen.wordpress.com/2011/07/09/a-trip-through-the-graphics-pipeline-2011-index/">A trip through the Graphics Pipeline</a></li>
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<li><a href="http://msdn.microsoft.com/en-us/library/gg615082.aspx#architecture">WARP Architecture and Performance</a></li>
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</ul>
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</li>
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</ul>
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</div>
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</body>
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</html>
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