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11 <h1>The Mesa
3D Graphics Library
</h1>
14 <iframe src=
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20 The Gallium llvmpipe driver is a software rasterizer that uses LLVM to
21 do runtime code generation.
22 Shaders, point/line/triangle rasterization and vertex processing are
23 implemented with LLVM IR which is translated to x86, x86-
64, or ppc64le machine
25 Also, the driver is multithreaded to take advantage of multiple CPU cores
26 (up to
8 at this time).
27 It's the fastest software rasterizer for Mesa.
36 For x86 or amd64 processors,
64-bit mode is recommended.
37 Support for SSE2 is strongly encouraged. Support for SSE3 and SSE4.1 will
38 yield the most efficient code. The fewer features the CPU has the more
39 likely it is that you will run into underperforming, buggy, or incomplete code.
42 For ppc64le processors, use of the Altivec feature (the Vector
43 Facility) is recommended if supported; use of the VSX feature (the
44 Vector-Scalar Facility) is recommended if supported AND Mesa is
45 built with LLVM version
4.0 or later.
48 See /proc/cpuinfo to know what your CPU supports.
52 <p>Unless otherwise stated, LLVM version
3.4 is recommended;
3.3 or later is required.
</p>
54 For Linux, on a recent Debian based distribution do:
57 aptitude install llvm-dev
60 If you want development snapshot builds of LLVM for Debian and derived
61 distributions like Ubuntu, you can use the APT repository at
<a
62 href=
"https://apt.llvm.org/" title=
"Debian Development packages for LLVM"
63 >apt.llvm.org
</a>, which are maintained by Debian's LLVM maintainer.
66 For a RPM-based distribution do:
69 yum install llvm-devel
73 For Windows you will need to build LLVM from source with MSVC or MINGW
74 (either natively or through cross compilers) and CMake, and set the LLVM
75 environment variable to the directory you installed it to.
77 LLVM will be statically linked, so when building on MSVC it needs to be
78 built with a matching CRT as Mesa, and you'll need to pass
79 <code>-DLLVM_USE_CRT_xxx=yyy
</code> as described below.
84 <th rowspan=
"2">LLVM build-type
</th>
85 <th colspan=
"2" align=
"center">Mesa build-type
</th>
88 <th>debug,checked
</th>
89 <th>release,profile
</th>
93 <td><code>-DLLVM_USE_CRT_DEBUG=MTd
</code></td>
94 <td><code>-DLLVM_USE_CRT_DEBUG=MT
</code></td>
98 <td><code>-DLLVM_USE_CRT_RELEASE=MTd
</code></td>
99 <td><code>-DLLVM_USE_CRT_RELEASE=MT
</code></td>
104 You can build only the x86 target by passing -DLLVM_TARGETS_TO_BUILD=X86
110 <p>scons (optional)
</p>
117 To build everything on Linux invoke scons as:
120 scons build=debug libgl-xlib
123 Alternatively, you can build it with meson with:
127 meson -D glx=gallium-xlib -D gallium-drivers=swrast
131 but the rest of these instructions assume that scons is used.
133 For Windows the procedure is similar except the target:
136 scons platform=windows build=debug libgl-gdi
144 <p>On Linux, building will create a drop-in alternative for libGL.so into
</p>
147 build/foo/gallium/targets/libgl-xlib/libGL.so
154 <p>To use it set the LD_LIBRARY_PATH environment variable accordingly.
</p>
156 <p>For performance evaluation pass build=release to scons, and use the corresponding
157 lib directory without the
"-debug" suffix.
</p>
163 On Windows, building will create
164 <code>build/windows-x86-debug/gallium/targets/libgl-gdi/opengl32.dll
</code>
165 which is a drop-in alternative for system's
<code>opengl32.dll
</code>. To use
166 it put it in the same directory as your application. It can also be used by
167 replacing the native ICD driver, but it's quite an advanced usage, so if you
168 need to ask, don't even try it.
172 There is however an easy way to replace the OpenGL software renderer that comes
173 with Microsoft Windows
7 (or later) with llvmpipe (that is, on systems without
178 <li><p>copy build/windows-x86-debug/gallium/targets/libgl-gdi/opengl32.dll to C:\Windows\SysWOW64\mesadrv.dll
</p></li>
179 <li><p>load this registry settings:
</p>
182 ; https://technet.microsoft.com/en-us/library/cc749368.aspx
183 ; https://www.msfn.org/board/topic/
143241-portable-windows-
7-build-from-winpe-
30/page-
5#entry942596
184 [HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\OpenGLDrivers\MSOGL]
186 "DriverVersion"=dword:
00000001
187 "Flags"=dword:
00000001
188 "Version"=dword:
00000002
191 <li>Ditto for
64 bits drivers if you need them.
</li>
198 To profile llvmpipe you should build as
201 scons build=profile
<same-as-before
>
205 This will ensure that frame pointers are used both in C and JIT functions, and
206 that no tail call optimizations are done by gcc.
209 <h2>Linux perf integration
</h2>
212 On Linux, it is possible to have symbol resolution of JIT code with
<a href=
"https://perf.wiki.kernel.org/">Linux perf
</a>:
216 perf record -g /my/application
221 When run inside Linux perf, llvmpipe will create a /tmp/perf-XXXXX.map file with
222 symbol address table. It also dumps assembly code to /tmp/perf-XXXXX.map.asm,
223 which can be used by the bin/perf-annotate-jit.py script to produce disassembly of
224 the generated code annotated with the samples.
227 <p>You can obtain a call graph via
228 <a href=
"https://github.com/jrfonseca/gprof2dot#linux-perf">Gprof2Dot
</a>.
</p>
231 <h1>Unit testing
</h1>
234 Building will also create several unit tests in
235 build/linux-???-debug/gallium/drivers/llvmpipe:
239 <li> lp_test_blend: blending
240 <li> lp_test_conv: SIMD vector conversion
241 <li> lp_test_format: pixel unpacking/packing
245 Some of these tests can output results and benchmarks to a tab-separated file
246 for later analysis, e.g.:
249 build/linux-x86_64-debug/gallium/drivers/llvmpipe/lp_test_blend -o blend.tsv
253 <h1>Development Notes
</h1>
257 When looking at this code for the first time, start in lp_state_fs.c, and
258 then skim through the lp_bld_* functions called there, and the comments
259 at the top of the lp_bld_*.c functions.
262 The driver-independent parts of the LLVM / Gallium code are found in
263 src/gallium/auxiliary/gallivm/. The filenames and function prefixes
264 need to be renamed from
"lp_bld_" to something else though.
267 We use LLVM-C bindings for now. They are not documented, but follow the C++
268 interfaces very closely, and appear to be complete enough for code
270 <a href=
"https://npcontemplation.blogspot.com/2008/06/secret-of-llvm-c-bindings.html">
271 this stand-alone example
</a>. See the llvm-c/Core.h file for reference.
275 <h1 id=
"recommended_reading">Recommended Reading
</h1>
281 <li><a href=
"https://www.cs.unc.edu/~olano/papers/2dh-tri/">Triangle Scan Conversion using
2D Homogeneous Coordinates
</a></li>
282 <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>
283 <li><a href=
"http://devmaster.net/posts/6133/rasterization-using-half-space-functions">Rasterization using half-space functions
</a></li>
284 <li><a href=
"http://devmaster.net/posts/6145/advanced-rasterization">Advanced Rasterization
</a></li>
285 <li><a href=
"https://fgiesen.wordpress.com/2013/02/17/optimizing-sw-occlusion-culling-index/">Optimizing Software Occlusion Culling
</a></li>
289 <p>Texture sampling
</p>
291 <li><a href=
"http://chrishecker.com/Miscellaneous_Technical_Articles#Perspective_Texture_Mapping">Perspective Texture Mapping
</a></li>
292 <li><a href=
"https://www.flipcode.com/archives/Texturing_As_In_Unreal.shtml">Texturing As In Unreal
</a></li>
293 <li><a href=
"http://www.gamasutra.com/view/feature/3301/runtime_mipmap_filtering.php">Run-Time MIP-Map Filtering
</a></li>
294 <li><a href=
"http://alt.3dcenter.org/artikel/2003/10-26_a_english.php">Will
"brilinear" filtering persist?
</a></li>
295 <li><a href=
"http://ixbtlabs.com/articles2/gffx/nv40-rx800-3.html">Trilinear filtering
</a></li>
296 <li><a href=
"http://devmaster.net/posts/12785/texture-swizzling">Texture Swizzling
</a></li>
302 <li><a href=
"http://www.cdl.uni-saarland.de/projects/wfv/#header4">Whole-Function Vectorization
</a></li>
308 <li><a href=
"http://www.drdobbs.com/optimizing-pixomatic-for-modern-x86-proc/184405807">Optimizing Pixomatic For Modern x86 Processors
</a></li>
309 <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>
310 <li><a href=
"http://www.agner.org/optimize/">Software optimization resources
</a></li>
311 <li><a href=
"https://software.intel.com/en-us/articles/intel-intrinsics-guide">Intel Intrinsics Guide
</a><li>
317 <li><a href=
"http://llvm.org/docs/LangRef.html">LLVM Language Reference Manual
</a></li>
318 <li><a href=
"https://npcontemplation.blogspot.co.uk/2008/06/secret-of-llvm-c-bindings.html">The secret of LLVM C bindings
</a></li>
324 <li><a href=
"https://fgiesen.wordpress.com/2011/07/09/a-trip-through-the-graphics-pipeline-2011-index/">A trip through the Graphics Pipeline
</a></li>
325 <li><a href=
"https://msdn.microsoft.com/en-us/library/gg615082.aspx#architecture">WARP Architecture and Performance
</a></li>