[Buildroot] How to force mesa3d to use llvmpipe?

[Romain Naour <romain.naour@gmail.com>]

Hi Nimai, All,

Le 24/12/2017 ? 17:46, Nimai Mahajan a ?crit?:
> 
> 
> On Fri, Dec 22, 2017 at 7:05 PM, Nimai Mahajan <nimaim@gmail.com
> <mailto:nimaim@gmail.com>> wrote:
> 
>     On Fri, Dec 22, 2017, 6:12 PM Adrian Perez de Castro <aperez@igalia.com
>     <mailto:aperez@igalia.com>> wrote:
> 
>         On Sat, 23 Dec 2017 01:08:43 +0200, Adrian Perez de Castro
>         <aperez at igalia.com <mailto:aperez@igalia.com>> wrote:
>         > Hello Nimai,
>         >
>         > On Fri, 22 Dec 2017 17:10:49 -0500, Nimai Mahajan <nimaim@gmail.com
>         <mailto:nimaim@gmail.com>> wrote:
>         > > On Fri, Dec 22, 2017 at 4:52 PM, Romain Naour
>         <romain.naour at gmail.com <mailto:romain.naour@gmail.com>> wrote:
>         > >
>         > > > Hi Nimai,
>         > > >
>         > > > Le 22/12/2017 ? 22:22, nimaim a ?crit :
>         > > > > Looks like BR may still not have llvmpipe support. Curious if
>         this patch got
>         > > > > anywhere?
>         > > > >?
>         http://lists.busybox.net/pipermail/buildroot/2017-July/195823.html
>         <http://lists.busybox.net/pipermail/buildroot/2017-July/195823.html>
>         >
>         > I have made those patches as part of a proof-of-concept for a project. The
>         > people involved have decided to switch over to a GPU-accelerated
>         solution, and
>         > that means that I have not been devoting time to polish the patch set for
>         > inclusion upstream. While I think it would be nice to have LLVM packages
>         > merged, so far I have been working on Buildroot using my laptop and it has
>         > been prohibitive to me to spend CPU time on side quests which don't
>         help my
>         > daily work ? sorry about that!
>         >
>         > > > This patch series is still present in the patchwork [1] but this
>         work need
>         > > > to be updated with the latest llvm/clang release (5.0.1).
>         >
>         > After Christmas I expect to have a powerful build machine and plenty
>         of disk
>         > space, and then it will be more feasible for me to try do some additional
>         > contributions to Buildroot. Let's see then whether I can get it updated.
>         >
>         > > > However, you can still test this series and you should be able to use
>         > > > llvmpipe.
>         > >
>         > > Thanks! Sounds good, I will try to merge Adrian's llvm package and
>         mesa3d
>         > > patches locally and rebuild mesa and see if I can get Qt to work
>         with the
>         > > llvm OpenGL driver. By any chance, do you know if llvm v4.0.0 will work
>         > > with mesa 17.2.x or 17.3.x or will it have to be bumped to v5? Also, not
>         > > sure how familiar with Qt you are, but do you know if Qt will require
>         > > special hooks to be able to use this with xcb?
>         >
>         > Any Mesa 17.x should work fine with LLVM 4.x; it should not be needed to
>         > update the build recipes to LLVM 5. Quoting from the Mesa website:
>         >
>         >? ??Unless otherwise stated, LLVM version 3.4 is recommended; 3.3 or
>         >? ? later is required.?
>         >
>         > There is also this note regarding PowerPC support:
>         >
>         >? ??For ppc64le processors, use of the Altivec feature (the Vector
>         Facility) is
>         >? ?recommended if supported; use of the VSX feature (the Vector-Scalar
>         >? ?Facility) is recommended if supported AND Mesa is built with LLVM
>         version
>         >? ?4.0 or later.?
>         >
>         > (See https://www.mesa3d.org/llvmpipe.html
>         <https://www.mesa3d.org/llvmpipe.html> for more details.)
> 
>         One more detail: If Mesa does not realize by itself that it should use a
>         software-based rendering driver (which can happen when there are multiple
>         drivers built into Mesa), you can force it at runtime by setting the
>         ?LIBGL_ALWAYS_SOFTWARE=1? environment variable. There is more about the
>         environment variables supported by Mesa here:
> 
>         ? https://www.mesa3d.org/envvars.html <https://www.mesa3d.org/envvars.html>
> 
>         Interesting, thanks I'll check that out. Not sure how to force it to use
>         llvmpipe if you have gallium and dri swrast both enabled as well but I
>         guess in that case you'd have to explicitly disable those, which
>         hopefully doesn't break something else. Will be interesting integrating
>         Qt into the mix here but as long as libGL.so is provided by mesa's
>         llvmpipe, it should work.
> 
> 
> 
> So I patched buildroot master with those two patches (successfully) but build
> fails. It seems to build llvm just fine, but mesa3d can't find any of the llvm
> stuff and crashes on that. I pasted a stripped buildroot build log of the llvm
> and mesa3d builds
> here:?https://gist.github.com/anonymous/6a5638bb91e4310029aaf90f43ef0d1c (the
> blank lines are merely suppressed?cmake:?/usr/local/lib/libcurl.so.4:?no?version
> information available?(required?by?cmake)?messages to make the output easier to
> read). I will have to look at this error more thoroughly at work this week. I
> believe the ./configure for mesa3d looks good now though (and should build
> llvmpipe swrast):
> 
> ? ? ? ? prefix:? ? ? ? ? /usr
> ? ? ? ? exec_prefix:? ? ?/usr
> ? ? ? ? libdir:? ? ? ? ? ${exec_prefix}/lib
> ? ? ? ? includedir:? ? ? ${prefix}/include
> 
> ? ? ? ? OpenGL:? ? ? ? ? yes (ES1: yes ES2: yes)
> 
> ? ? ? ? OSMesa:? ? ? ? ? no
> 
> ? ? ? ? DRI platform:? ? drm
> ? ? ? ? DRI drivers:? ? ?swrast?
> ? ? ? ? DRI driver dir:? ${libdir}/dri
> ? ? ? ? GLX:? ? ? ? ? ? ?DRI-based
> 
> ? ? ? ? EGL:? ? ? ? ? ? ?yes
> ? ? ? ? EGL drivers:? ? ?builtin:egl_dri2
> ? ? ? ? GBM:? ? ? ? ? ? ?yes
> ? ? ? ? EGL/Vulkan/VL platforms:? ?drm x11
> 
> ? ? ? ? Vulkan drivers:? no
> 
> ? ? ? ? llvm:? ? ? ? ? ? yes
> ? ? ? ? llvm-config:? ?
> ?/home/nimai/Desktop/buildroot/output/host/i686-buildroot-linux-gnu/sysroot/usr/bin/llvm-config
> ? ? ? ? llvm-version:? ? 4.0.0
> 
> ? ? ? ? Gallium drivers: swrast
> ? ? ? ? Gallium st:? ? ? mesa
> 
> ? ? ? ? HUD extra stats: yes
> ? ? ? ? HUD lmsensors:? ?no
> 
> 
> ? ? ? ? Shared libs:? ? ?yes
> ? ? ? ? Static libs:? ? ?no
> ? ? ? ? Shared-glapi:? ? yes
> 
> ? ? ? ? CFLAGS:? ? ? ? ? -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE
> -D_FILE_OFFSET_BITS=64 -Os -Wall -Werror=implicit-function-declaration
> -Werror=missing-prototypes -Wmissing-prototypes -fno-math-errno
> -fno-trapping-math -std=c99
> ? ? ? ? CXXFLAGS:? ? ? ? -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE
> -D_FILE_OFFSET_BITS=64 -Os -Wall -fno-math-errno -fno-trapping-math
> ? ? ? ? LDFLAGS:? ? ? ? ?
> ? ? ? ? Macros:? ? ? ? ? -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS
> -D__STDC_LIMIT_MACROS -D_GNU_SOURCE -DUSE_SSE41 -DUSE_GCC_ATOMIC_BUILTINS
> -DNDEBUG -DTEXTURE_FLOAT_ENABLED -DHAVE_XLOCALE_H -DHAVE_SYS_SYSCTL_H
> -DHAVE_ENDIAN_H -DHAVE_STRTOF -DHAVE_MKOSTEMP -DHAVE_STRTOD_L
> -DHAVE_DL_ITERATE_PHDR -DHAVE_POSIX_MEMALIGN -DHAVE_GALLIUM_EXTRA_HUD=1
> -DHAVE_LIBDRM -DGLX_USE_DRM -DGLX_INDIRECT_RENDERING -DGLX_DIRECT_RENDERING
> -DGLX_USE_TLS -DHAVE_DRM_PLATFORM -DHAVE_X11_PLATFORM -DENABLE_SHADER_CACHE
> -DHAVE_MINCORE -DHAVE_LLVM=0x0400 -DMESA_LLVM_VERSION_PATCH=0
> 
> ? ? ? ? LLVM_CFLAGS:? ?
> ?-I/home/nimai/Desktop/buildroot/output/host/i686-buildroot-linux-gnu/sysroot/usr/include
> -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS
> ? ? ? ? LLVM_CXXFLAGS:?
> ?-I/home/nimai/Desktop/buildroot/output/host/i686-buildroot-linux-gnu/sysroot/usr/include?
> -std=c++11 -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS
> ? ? ? ? LLVM_CPPFLAGS:?
> ?-I/home/nimai/Desktop/buildroot/output/host/i686-buildroot-linux-gnu/sysroot/usr/include
> -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS
> ? ? ? ? LLVM_LDFLAGS:? ?
> -L/home/nimai/Desktop/buildroot/output/host/i686-buildroot-linux-gnu/sysroot/usr/lib?
> 
> ? ? ? ? PYTHON2:? ? ? ? ?python2.7
> 
> ? ? ? ? Run 'make' to build Mesa
> 
> Any ideas that will make this compile properly? Thanks. Sorry if this gets
> posted twice, I originally pasted the log file which exceeded the mailing list
> limit.

Last time I tried this, an older version of mesa was used (17.0 or 17.1).
I don't have much time these days to work on llvm+mesa.
IIRC, mesa needs to be statically linked with llvm libraries. llvm libraries in
staging directory should be shared libraries (*.so). Try to force llvm for the
target to be build statically.

Best regards,
Romain