I first published that bug on Gentoo, because I cannot get
XvMC component using modular X on Gentoo.
http://bugs.gentoo.org/show_bug.cgi?id=112503

=== Here is the most important part of the bugreport ===

./configure is is supposed to enable XvMC fo intel arch, but it doesn't
work because ./configure tests for "x86*" instead of "i*86". The following
patch fixes that:

--- configure.orig      2005-11-14 16:27:01.000000000 +0100
+++ configure   2005-11-14 16:27:18.000000000 +0100
@@ -9333,7 +9333,7 @@
 _ACEOF

         case "$host_cpu" in
-            x86*)
+            i*86)
                 XVMC=yes ;;
             amd64*|x86_64*)
                 XVMC=yes ;;

Now, once this is fixed, it still doesn't work because now compilation
fails badly (probably some header missing)

make  all-recursive
make[1]: Entering directory
`/var/tmp/portage/xf86-video-via-0.1.32/work/xf86-video-via-0.1.32'
Making all in src
make[2]: Entering directory
`/var/tmp/portage/xf86-video-via-0.1.32/work/xf86-video-via-0.1.32/src'
Making all in xvmc
make[3]: Entering directory
`/var/tmp/portage/xf86-video-via-0.1.32/work/xf86-video-via-0.1.32/src/xvmc'
Making all in unichrome
make[4]: Entering directory
`/var/tmp/portage/xf86-video-via-0.1.32/work/xf86-video-via-0.1.32/src/xvmc/unichrome'
if /bin/sh ../../../libtool --mode=compile i686-pc-linux-gnu-gcc -DHAVE_CONFIG_H
-I. -I. -I../../..    -DIN_MODULE -DXFree86Module -I/usr/include/xorg  
-I/usr/include/drm -I/usr/include/X11/dri   -I../../../src -I../../../src/xvmc
-DTRUE=1 -DFALSE=0 -march=i686 -msse -mmmx -mfpmath=sse -Os -pipe
-fomit-frame-pointer -MT libviaXvMC_la-viaLowLevel.lo -MD -MP -MF
".deps/libviaXvMC_la-viaLowLevel.Tpo" \
  -c -o libviaXvMC_la-viaLowLevel.lo `test -f 'viaLowLevel.c' || echo
'./'`viaLowLevel.c; \
then mv -f ".deps/libviaXvMC_la-viaLowLevel.Tpo"
".deps/libviaXvMC_la-viaLowLevel.Plo"; \
else rm -f ".deps/libviaXvMC_la-viaLowLevel.Tpo"; exit 1; \
fi
mkdir .libs
 i686-pc-linux-gnu-gcc -DHAVE_CONFIG_H -I. -I. -I../../.. -DIN_MODULE
-DXFree86Module -I/usr/include/xorg -I/usr/include/drm -I/usr/include/X11/dri
-I../../../src -I../../../src/xvmc -DTRUE=1 -DFALSE=0 -march=i686 -msse -mmmx
-mfpmath=sse -Os -pipe -fomit-frame-pointer -MT libviaXvMC_la-viaLowLevel.lo -MD
-MP -MF .deps/libviaXvMC_la-viaLowLevel.Tpo -c viaLowLevel.c  -fPIC -o
.libs/libviaXvMC_la-viaLowLevel.o
viaLowLevel.c:37:25: viaXvMCPriv.h: No such file or directory
viaLowLevel.c:38:25: viaLowLevel.h: No such file or directory
viaLowLevel.c:44: error: syntax error before "CARD32"
viaLowLevel.c:44: warning: no semicolon at end of struct or union
viaLowLevel.c:45: error: `LL_PCI_CMDBUF_SIZE' undeclared here (not in a function)
viaLowLevel.c:45: warning: data definition has no type or storage class
viaLowLevel.c:54: error: syntax error before '*' token
viaLowLevel.c:54: warning: data definition has no type or storage class
viaLowLevel.c:55: error: syntax error before "hwLock"
viaLowLevel.c:55: warning: data definition has no type or storage class

[...] lots of errors.

make[4]: *** [libviaXvMC_la-viaLowLevel.lo] Error 1
make[4]: Leaving directory
`/var/tmp/portage/xf86-video-via-0.1.32/work/xf86-video-via-0.1.32/src/xvmc/unichrome'
make[3]: *** [all-recursive] Error 1
make[3]: Leaving directory
`/var/tmp/portage/xf86-video-via-0.1.32/work/xf86-video-via-0.1.32/src/xvmc'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory
`/var/tmp/portage/xf86-video-via-0.1.32/work/xf86-video-via-0.1.32/src'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory
`/var/tmp/portage/xf86-video-via-0.1.32/work/xf86-video-via-0.1.32'
make: *** [all] Error 2

!!! ERROR: x11-drivers/xf86-video-via-0.1.32 failed.
!!! Function x-modular_src_make, Line 127, Exitcode 2
!!! emake failed
!!! If you need support, post the topmost build error, NOT this status message.





Reproducible: Always
Steps to Reproduce:
1. unmask + emerge xf86-video-via

Actual Results:  
no "libviaXvMCPro.so.1" is created.

Expected Results:  
libviaXvMCPro.so.1 should be created.

NOTE: to get the driver part of XvMC on via/modular,
it is also required to #define XvExtension, but this
is covered by abother bug.