[Mesa-users] Trouble compiling MesaGL : llvm intrinsics seem to be missing.

[Chuck Atkins]

>
> So you should actually do (without removing anything out of files like
> I said to): --with-gallium-drivers=swrast,llvmpipe
>

Still no.  llvmpipe isn't a driver option.  --with-gallium-drivers=swrast
specifies to use the gallium software rasterizer.  This will eable softpipe
AND, if llvm is enabled (i.e.  --enable-gallium-llvm) also llvmpipe.  If
you want the fastest software render usable with osmesa then use swr.
OSMesa requires that at least swrast be enabled, hence enabling swrast and
swr.  This will give you OSMesa with softpipe, llvmpipe, and swr, with
llvmpipe being the default.



> I actually don't know terribly much about openswr I just assumed it
> would be optimized in someway for distributed systems that hinders non
> distributed ones or designed with distributed as priority leaving out
> minor optimizations or something.


Nope.  It's a common misunderstanding though since large distributed
systems without GPUs was the target as most other environments will have
GPUs.  It's developed entirely though for a single node with no awareness
to distributed systems.  Anything beyond that is the applications
responsibilty.




> And I am also not sure which version
> of OpenGL it supports or the extensions.+ the fact that it is the
> cause of a compilation error on the compilers system.


They're vary close to feature parity.  From the current git / master (just
past the 13.0 release):

llvmpipe:
OpenGL renderer string: Gallium 0.4 on llvmpipe (LLVM 3.8, 256 bits)
OpenGL core profile version string: 3.3 (Core Profile) Mesa 13.1.0-devel
(git-e3e5b1a)
OpenGL version string: 3.0 Mesa 13.1.0-devel (git-e3e5b1a)

swr:
OpenGL renderer string: Gallium 0.4 on SWR
OpenGL core profile version string: 3.3 (Core Profile) Mesa 13.1.0-devel
(git-e3e5b1a)
OpenGL version string: 3.0 Mesa 13.1.0-devel (git-e3e5b1a)

As for extensions, llvmpipe -> swr:
-GL_AMD_vertex_shader_viewport_index
-GL_ARB_copy_image
-GL_ARB_enhanced_layouts
-GL_ARB_fragment_layer_viewport
-GL_ARB_texture_buffer_range
-GL_ARB_texture_cube_map_array
-GL_ARB_texture_gather
-GL_ARB_texture_view
-GL_ARB_viewport_array
+GL_ARB_pipeline_statistics_query


For mesa 12.0.1
> swr is behind llvmpipe with extensions (at least from 4.0 core). So I
> still say llvmpipe is probably preferable but perhaps swr does have
> some performance advantage or is less buggy.
>

It's come a long way since 12.0.1.  The current 13.0.0 release is a major
step forward since the inital release.  While I'm not one of the swr
developers we do make extensive use of it in production environments.
Regarding performance diffferences, you'll likely see an increase by a
factor of 10x - 100x over llvmpipe, that's typically what we see in VTK and
ParaView.
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