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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 autoconf/make with:
125 ./configure --enable-glx=gallium-xlib --with-gallium-drivers=swrast --disable-dri --disable-gbm --disable-egl
129 but the rest of these instructions assume that scons is used.
131 For Windows the procedure is similar except the target:
134 scons platform=windows build=debug libgl-gdi
142 <p>On Linux, building will create a drop-in alternative for libGL.so into
</p>
145 build/foo/gallium/targets/libgl-xlib/libGL.so
152 <p>To use it set the LD_LIBRARY_PATH environment variable accordingly.
</p>
154 <p>For performance evaluation pass build=release to scons, and use the corresponding
155 lib directory without the
"-debug" suffix.
</p>
161 On Windows, building will create
162 <code>build/windows-x86-debug/gallium/targets/libgl-gdi/opengl32.dll
</code>
163 which is a drop-in alternative for system's
<code>opengl32.dll
</code>. To use
164 it put it in the same directory as your application. It can also be used by
165 replacing the native ICD driver, but it's quite an advanced usage, so if you
166 need to ask, don't even try it.
170 There is however an easy way to replace the OpenGL software renderer that comes
171 with Microsoft Windows
7 (or later) with llvmpipe (that is, on systems without
176 <li><p>copy build/windows-x86-debug/gallium/targets/libgl-gdi/opengl32.dll to C:\Windows\SysWOW64\mesadrv.dll
</p></li>
177 <li><p>load this registry settings:
</p>
180 ; https://technet.microsoft.com/en-us/library/cc749368.aspx
181 ; https://www.msfn.org/board/topic/
143241-portable-windows-
7-build-from-winpe-
30/page-
5#entry942596
182 [HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\OpenGLDrivers\MSOGL]
184 "DriverVersion"=dword:
00000001
185 "Flags"=dword:
00000001
186 "Version"=dword:
00000002
189 <li>Ditto for
64 bits drivers if you need them.
</li>
196 To profile llvmpipe you should build as
199 scons build=profile
<same-as-before
>
203 This will ensure that frame pointers are used both in C and JIT functions, and
204 that no tail call optimizations are done by gcc.
207 <h2>Linux perf integration
</h2>
210 On Linux, it is possible to have symbol resolution of JIT code with
<a href=
"https://perf.wiki.kernel.org/">Linux perf
</a>:
214 perf record -g /my/application
219 When run inside Linux perf, llvmpipe will create a /tmp/perf-XXXXX.map file with
220 symbol address table. It also dumps assembly code to /tmp/perf-XXXXX.map.asm,
221 which can be used by the bin/perf-annotate-jit.py script to produce disassembly of
222 the generated code annotated with the samples.
225 <p>You can obtain a call graph via
226 <a href=
"https://github.com/jrfonseca/gprof2dot#linux-perf">Gprof2Dot
</a>.
</p>
229 <h1>Unit testing
</h1>
232 Building will also create several unit tests in
233 build/linux-???-debug/gallium/drivers/llvmpipe:
237 <li> lp_test_blend: blending
238 <li> lp_test_conv: SIMD vector conversion
239 <li> lp_test_format: pixel unpacking/packing
243 Some of these tests can output results and benchmarks to a tab-separated file
244 for later analysis, e.g.:
247 build/linux-x86_64-debug/gallium/drivers/llvmpipe/lp_test_blend -o blend.tsv
251 <h1>Development Notes
</h1>
255 When looking at this code for the first time, start in lp_state_fs.c, and
256 then skim through the lp_bld_* functions called there, and the comments
257 at the top of the lp_bld_*.c functions.
260 The driver-independent parts of the LLVM / Gallium code are found in
261 src/gallium/auxiliary/gallivm/. The filenames and function prefixes
262 need to be renamed from
"lp_bld_" to something else though.
265 We use LLVM-C bindings for now. They are not documented, but follow the C++
266 interfaces very closely, and appear to be complete enough for code
268 <a href=
"https://npcontemplation.blogspot.com/2008/06/secret-of-llvm-c-bindings.html">
269 this stand-alone example
</a>. See the llvm-c/Core.h file for reference.
273 <h1 id=
"recommended_reading">Recommended Reading
</h1>
279 <li><a href=
"https://www.cs.unc.edu/~olano/papers/2dh-tri/">Triangle Scan Conversion using
2D Homogeneous Coordinates
</a></li>
280 <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>
281 <li><a href=
"http://devmaster.net/posts/6133/rasterization-using-half-space-functions">Rasterization using half-space functions
</a></li>
282 <li><a href=
"http://devmaster.net/posts/6145/advanced-rasterization">Advanced Rasterization
</a></li>
283 <li><a href=
"https://fgiesen.wordpress.com/2013/02/17/optimizing-sw-occlusion-culling-index/">Optimizing Software Occlusion Culling
</a></li>
287 <p>Texture sampling
</p>
289 <li><a href=
"http://chrishecker.com/Miscellaneous_Technical_Articles#Perspective_Texture_Mapping">Perspective Texture Mapping
</a></li>
290 <li><a href=
"https://www.flipcode.com/archives/Texturing_As_In_Unreal.shtml">Texturing As In Unreal
</a></li>
291 <li><a href=
"http://www.gamasutra.com/view/feature/3301/runtime_mipmap_filtering.php">Run-Time MIP-Map Filtering
</a></li>
292 <li><a href=
"http://alt.3dcenter.org/artikel/2003/10-26_a_english.php">Will
"brilinear" filtering persist?
</a></li>
293 <li><a href=
"http://ixbtlabs.com/articles2/gffx/nv40-rx800-3.html">Trilinear filtering
</a></li>
294 <li><a href=
"http://devmaster.net/posts/12785/texture-swizzling">Texture Swizzling
</a></li>
300 <li><a href=
"http://www.cdl.uni-saarland.de/projects/wfv/#header4">Whole-Function Vectorization
</a></li>
306 <li><a href=
"http://www.drdobbs.com/optimizing-pixomatic-for-modern-x86-proc/184405807">Optimizing Pixomatic For Modern x86 Processors
</a></li>
307 <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>
308 <li><a href=
"http://www.agner.org/optimize/">Software optimization resources
</a></li>
309 <li><a href=
"https://software.intel.com/en-us/articles/intel-intrinsics-guide">Intel Intrinsics Guide
</a><li>
315 <li><a href=
"http://llvm.org/docs/LangRef.html">LLVM Language Reference Manual
</a></li>
316 <li><a href=
"https://npcontemplation.blogspot.co.uk/2008/06/secret-of-llvm-c-bindings.html">The secret of LLVM C bindings
</a></li>
322 <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>
323 <li><a href=
"https://msdn.microsoft.com/en-us/library/gg615082.aspx#architecture">WARP Architecture and Performance
</a></li>