I am having a hard time using apitrace on my x64 system with a 32 bits game. I
will be digging into this, but meanwhile, I can give some more information:

When I run the game from a terminal, I have those two errors repeated several
times:

EE ../../../../../../src/gallium/drivers/r600/r600_shader.c:158
r600_pipe_shader_create - translation from TGSI failed !
EE ../../../../../../src/gallium/drivers/r600/r600_state_common.c:809
r600_shader_select - Failed to build shader variant (type=1) -1

I saw in the source code that the shader can be dumped, so I will attach the
dump output to this bug ticket.